60th Annual Symposium of the International Society for Clinical Electrophysiology of Vision (ISCEV 2023 Kyoto)

Abstract Editing Committee

Scott E. Brodie, Paul Constable, Mitchell Brigell, Mary Johnson, Omar Mahroo, J. Jason McAnany, Anne Moskowitz

Foreword In this Special 2023 Symposium Issue of Documenta Ophthalmologica, we have compiled the meeting abstracts which reflect the depth and breadth of the international community dedicated to clinical elelctrophysiology of vision. The Abstract Editing Committee has made every effort to optimize the abstracts for clarity and readability—we aimed to respect the intended meaning of the original submissions and apologise for any inadvertent misinterpretation.

O1-1-1 The electrophysiological and clinical features of CERKL-associated retinal dystrophy with genotype–phenotype associations

Anthony G. Robson^1,2, Malena Daich Varela^1,2, Samantha De Silva^1,2, Emma Duignan³, Rola Ba-Abbad⁴, Yu Fujinami-Yokokawa^5,6, Shaun Leo^1,2, Kaoru Fujinami^1,2,5, Omar Mahroo^1,2, Andrew Webster^1,2, Michel Michaelides^1,2

¹Moorfields Eye Hospital, London, UK, ²UCL Institute of Ophthalmology, London, UK, ³Royal Victoria Eye and Ear Hospital, Dublin, Ireland, ⁴Ocular Genetics Services, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, ⁵Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan, ⁶Department of Health Policy and Management, School of Medicine, Keio University, Tokyo, Japan

Purpose This multicentre retrospective study investigates the electrophysiological and clinical characteristics of a large cohort of CERKL cases in order to detail phenotypic variability and examine possible genotype–phenotype correlations.

Methods A total of 47 patients (37 probands) with likely pathogenic CERKL variants were ascertained and the clinical findings reviewed. Genotypes were divided into double null (DN) and non-double null (NDN) groups. ISCEV standard pattern and full-field ERG (PERG; ERG) were recorded in 30 subjects (age range 13–51 years) using corneal recording electrodes after mydriasis. The main ERG components were quantified and compared with age-matched control data.

Results Twenty-three different CERKL variants were detected, harboured as DN (70%) or NDN genotypes. Common fundus features included macular atrophy (57%), fine white macular dots (49%), and peripheral punctate areas of chorioretinal atrophy (45%). The relative severity of macular and peripheral retinal changes varied in both DN and NDN groups. Full-field ERGs revealed similar severity rod and cone dysfunction (53%), rod cone (27%), cone rod (10%), or macular dystrophy (10%; normal full-field ERGs). Pattern ERG P50 was undetectable in most (80%) cases in keeping with severe macular dysfunction; of the remaining cases, including 2 with macular dystrophy, PERG P50 was reduced by 45–60%. The ERG abnormalities were most severe in the majority (18 of 21) with a DN genotype, including 7 with undetectable ERGs. Of the 10 patients with normal or borderline LA30Hz ERG peak times, six harboured NDN variants including two of the three oldest individuals.

Conclusions Individuals with CERKL-retinopathy exhibit a wide range of retinal and ERG characteristics. There is overlap in phenotypes associated with DN and NDN genotypes, but with nullizygosity being mostly associated with severe retinal dysfunction. The severity and nature of retinal dysfunction cannot be inferred reliably from clinical signs or age, highlighting the importance of comprehensive phenotyping including ERG.

O1-1-2 Genetic characteristics of Korean inherited retinal disease patients: A multicenter study by the Korean Eye Gene Consortium

Se Joon Woo¹, Seok Hyun Bae¹, Jinu Han², Christopher Seungkyu Lee³, Suk Ho Byeon³, Jun Won Lee², Joo Yong Lee⁴, Min Sagong⁵, Areum Jeong⁵, Dong Ho Park⁶, Hyewon Chung⁷, Hyungwoo Lee⁷, Eun Kyoung Lee⁸, Chang Ki Yoon⁸, Seong Joon Ahn⁹

¹Seoul National University Bundang Hospital, Korea, ²Gangnam Severance Hospital, Yonsei University College of Medicine, Korea, ³Yonsei University College of Medicine, Korea, ⁴Asan Medical Center, Korea, ⁵Yeungnam University Hospital, Korea, ⁶Kyungpook National University Hospital, Korea, ⁷Konkuk University School of Medicine, Korea, ⁸Seoul National University Hospital, Korea, ⁹Hanyang University Seoul Hospital, Korea

Purpose To investigate the genetic profile of inherited retinal diseases (IRDs) in a Korean population at eight tertiary hospitals.

Methods A total of 916 Korean patients who were clinically diagnosed with IRDs and molecularly confirmed were enrolled. We performed a next-generation sequencing strategy (gene panel), followed by clinical variant interpretation. The clinical significance of each variant was classified according to the latest recommendations of the American College of Medical Genetics and Genomics standards, and we analyzed pathogenic and likely pathogenic variants.

Results Of the 916 patients, retinitis pigmentosa (48.4%) was the most common form of IRDs, followed by macular or cone dystrophy (8.0%), Leber congenital amaurosis (5.6%), and retinoschisis (4.9%). We identified pathogenic variants in 111 distinct genes in Korean patients with IRDs. The most common causative genes were EYS (10.1%), USH2A (7.6%), ABCA4 (6.6%), RP1 (6.2%), and RS1 (5.0%).

Conclusions This study provided the distribution of genetic mutations as the cause of IRDs in a large cohort in Korea. This helps to understand the ethnic differences in patients with IRDs and will provide a basis for genetic treatment.

O1-1-3 Ocular characteristics of patients with Leber Congenital Amaurosis 6 caused by pathogenic RPGRIP1 gene variation in a Chinese cohort

Shi Ying Li¹, Yumei Mao², Xiaohong Meng²

¹Xiang’an Hospital of Xiamen University (XMU), Eye Institute of XMU, Xiamen, China, ²Department of Ophthalmology, Southwest Hospital, Chongqing, China

Purpose To delineate the clinical and genetic characteristics of Chinese patients with RPGRIP1-associated Leber congenital amaurosis 6 (LCA6).

Methods After screening 352 unrelated families with clinically diagnosed RP, 5 LCA6 patients with RPGRIP1 variations from unrelated Chinese families were identified. Full ophthalmologic examinations, including best-corrected visual acuity (BCVA), fundus photography, fundus autofluorescence imaging, spectral-domain optical coherence tomography (SD-OCT), full-field electroretinography (ffERG), multifocal electroretinography (mfERG), perimetry, and flash visual evoked potential (FVEP), were performed. Target next-generation sequencing (NGS) and Sanger sequencing were performed for the 5 patients to identify and validate candidate disease-causing variants.

Results Five patients were molecularly diagnosed at an early age as the LCA6 associated with RPGRIP1 variation, with typical clinical characteristics including congenital night blindness, nystagmus, and visual defect. Interestingly, LCA6 exhibited extensive clinical heterogeneity and the changes in the morphology and function were not completely consistent in the five patients. Case 1 showed extensive inferior nasal retinal atrophy with a corresponding area of hypofluorescence in fundus autofluorescence, and the fundus photograph was nearly normal in cases 2 and 3. The ERG results showed a moderately reduced rod system response in cases 1 and 2 and a significantly reduced rod system response in case 3. Both case 4 and case 5 showed mottled pigmentation in fundi and an unrecordable rod and cone system ERG response. Moreover, we identified 8 compound variants and one homozygous variant in the five patients with RPGRIP1.

Conclusions This is the largest report focused on the clinical electrophysiological features of patients with LCA6 caused by the variation in the RPGRIP1 gene in the Chinese population. An enriched phenotypic and genotypic characterization of LCA6 may improve future gene therapies.

O1-1-4 Retinal phenotype in RNU4ATAC-related Roifman syndrome

Ajoy Vincent^1,2, Brian Ballios², Amarilla Mandola³, Alaa Tayyib^1,2, Anupreet Tumber¹, Jenny Garkaby³, Linda Vong⁴, Chaim Roifman^3,4, Elise Heon^1,2

¹Opthalmology and Vision Sciences, Hospital for Sick Children, Toronto, Canada, ²Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada, ³Division of Immunology and Allergy, The Hospital for Sick Children and the University of Toronto, Toronto, Canada, ⁴The Canadian Centre for Primary Immunodeficiency and The Jeffrey Modell Research Laboratory for the Diagnosis of Primary Immunodeficiency, The Hospital for Sick Children, Toronto, Canada

Purpose To characterize the retinal phenotype in RNU4ATAC-associated Roifman syndrome.

Methods Ten patients (8 males) with molecularly confirmed Roifman syndrome underwent detailed ophthalmologic evaluation including fundus imaging, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (SD-OCT), full-field electroretinography (ERG), and pattern electrography (PERG). Six patients had follow-up eye examinations. Patients also underwent comprehensive examination for features of extra-retinal Roifman syndrome.

Results All patients had biallelic RNU4ATAC variants. Nyctalopia was common (7/10). Visual acuity at presentation ranged from 20/20 to 20/200; age ranged from 5 to 41 years). Retinal examination revealed features of generalized retinopathy with mid-peripheral pigment epithelial changes. A para- or peri-foveal ring of hyper-autofluorescence was the most common FAF abnormality noted (6/8). The SD-OCT demonstrated relative preservation of the sub-foveal ellipsoid zone in six cases; associated features included cystoid changes (5/10) and posterior staphyloma (3/10). The ERG was abnormal in all patients; nine showed generalized rod cone dystrophy whilst one patient with sectoral retinal involvement only had isolated rod dystrophy (20 years). The PERG was abnormal in all but one case. On follow-up examination, progressive loss of visual acuity (2/6), mid-peripheral retinal atrophy (3/6), or shortening of ellipsoid zone width (1/6) was observed.

Conclusions This study has characterized the retinal phenotype in RNU4ATAC-associated Roifman syndrome. Retinal involvement is universal. Early-onset and the overall retinal and FAF features are consistent with rod cone degeneration that is slowly progressive over time. The sub-foveal retinal ultrastructure is relatively preserved at presentation in a majority of patients. Phenotypic variability, independent of age, exists. More study of allelic- and sex-based determinants of disease severity are necessary.

O1-1-5 Insights from modelling rod-driven ERG a-waves in KCNV2-retinopathy

Omar A Mahroo^1,2,3,4, Xiaofan Jiang^1,3, Shaun M Leo^1,5, Pirro G Hysi³, Thales Cabral De Guimaraes^1,3, Anthony G Robson^1,5, Christopher J Hammond³, Anthony T Moore^1,2,6, Michel Michaelides^1,2, Andrew R Webster^1,2, John G Robson^4,7

¹Institute of Ophthalmology, University College London, UK, ²Retinal Genetics Service, Moorfields Eye Hospital, London, UK, ³Department of Ophthalmology and Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, UK, ⁴Physiology, Development and Neuroscience, University of Cambridge, UK, ⁵Department of Electrophysiology, Moorfields Eye Hospital, London, UK, ⁶Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States, ⁷Gonville & Caius College, Cambridge, UK

Purpose Patients with bi-allelic pathogenic variants in the KCNV2 gene display characteristic ERG changes. In this study, we employed experimental ERG protocols to derive rod-driven a-waves in patients with KCNV2-retinopathy and in healthy controls. A mathematical model incorporating rod-photoreceptor current flows was fitted to the responses to quantitatively investigate a-wave changes in patients.

Methods Participants included patients and healthy controls. ERGs were recorded following mydriasis and using conductive fibre electrodes placed in the lower conjunctival fornix. ERGs were recorded in response to a range of white flash strengths (0.6–67 photopic cd.s/m², and, in some participants up to 200 cd.s/m²) delivered first in the dark (eliciting both rod and cone-driven responses) and then in the presence of a blue rod-saturating background (1 photopic and 30 scotopic cd/m²). Responses on the latter background were cone driven and were subtracted mathematically from the responses recorded in the dark to yield the estimated dark-adapted rod-driven a-wave. The mathematical model of Robson & Frishman (Robson JG & Frishman LJ, Prog Retin Eye Res, 2014) was applied to rod-isolated a-waves from patients and healthy controls.

Results Recordings were analyzed from over 50 healthy controls and from 6 patients with genetically confirmed KCNV2-retinopathy (mean (SD) age, 34 (15) years; range 20–54 years) from 5 unrelated families. In control participants, a sharp a-wave trough with subsequent rapid recovery was observed for strong flashes. The model provided a good fit to the rod-isolated responses to these flashes, including the initial portion of the recovery following the a-wave trough. In patients, the rod-isolated a-wave appeared to plateau. When applying the model, a reasonable fit was achieved only by substantially reducing the modelled resistivity of the outer nuclear layer (ONL) to reduce (by > 50%) the contribution to the ERG from rod-derived extra-cellular currents flowing in this layer.

Conclusions Our findings confirm that the model provides a good fit to rod-isolated a-wave responses to strong flashes in healthy subjects, also fitting the initial recovery following the a-wave trough. This is consistent with this initial recovery arising not from bipolar cell currents, but from currents derived from the photoreceptors themselves. In patients with KCNV2-retinopathy, recordings showed loss of the sharp a-wave “nose”. Responses were consistent with a substantial reduction in ONL contributions, modelled here by reducing resistivity of this layer. The changed contributions could arise from altered channel conductance or reductions in the number or diameter of rod photoreceptor axons. KCNV2 is expressed within photoreceptors, with the protein product localising proximal to the outer segment. ONL thinning has been described on optical coherence tomography imaging of patients. Our findings appear consistent with the cellular expression and with findings on structural retinal imaging.

O1-2-1 Long-term follow up of Slovene Stargardt patients determined by electrophysiology and fundus autofluorescence appearance

Martina Jarc Vidmar¹, Jana Sajovic¹, Jelka Brecelj¹, Maja Sustar¹, Andrej Meglic¹, Ana Fakin¹, Marko Hawlina¹

¹Eye Hospital, University Medical Centre Ljubljana, Slovenia

Purpose To assess ERG and fundus autofluorescence (FAF) progression rate of Slovenian Stargardt disease (STGD1) patients with the median follow-up of 17 years (range 10–27 years).

Methods A total of 15 genetically confirmed STGD1 patients (3 male, 12 female) with a median age of 42 years (range 18–72 years) were included. Minimum follow-up duration for inclusion was 10 years. Age at the first and last examinations, age at onset, Snellen decimal best-corrected visual acuity (VA), large-field PERG, full-field electroretinography (ffERG) according to ISCEV standards, and fundus autofluorescence appearance (FAF) done by Heidelberg spectralis were analysed. Based on ERG abnormalities, patients were classified into 3 groups: ERG group 1 with macular involvement, ERG group 2 with abnormal cone responses, and ERG group 3 with abnormal cone and rod responses. FAF appearance was classified according to Fishmann groups: group I has flecks inside vascular arcades, group II has flecks outside vascular arcades, group III has most diffused flecks resorbed, and group IV has diffusely resorbed flecks, atrophy of the retinal pigment epithelium, and choriocapillaris.

Results Median age of onset was 15 years (range 7–46). Age at baseline was 25 years (range 7–46) and at last examination 42 years (range 17–72). Median VA at baseline was 0.2 (range 0.05–0.9) and at the end 0.1 (range 0.0167–0.3). According to ERG, patients were classified as (number of patients at baseline; number of patient at last exam): no PERG and ffERG abnormalities (3; 0), ERG group 1 with PERG macular involvement (5; 6), ERG group 2 with abnormal PERG and ffERG cone responses (5; 4), ERG group 3 with abnormal PERG and ffERG cone and rod responses (2; 5). At baseline testing, all patients with no ERG abnormalities belonged to Fishmann group I (with flecks inside vascular arcades). In ERG group 1, there were 3 patients in Fishmann group I (with flecks inside vascular arcades) and 2 patients without any flecks at all. In ERG groups 2 and 3, there were 6 patients in Fishmann groups II and III (with flecks outside arcades and reabsorbed); interestingly, one patient in ERG group 2 had no flecks. For the course of follow-up, 46% of patients showed ERG and 67% FAF progression. At the end, in ERG group 1 there were 4 patients in Fishmann group I (with flecks inside vascular arcades), 1 was in Fishmann group II (with flecks outside vascular arcades), and 1 was in Fishmann group III (with reabsorbed flecks). All patients in ERG groups 2 and 3 were in Fishmann groups II to IV with extensive changes seen on their fundus.

Conclusions Long-term follow-up of STGD1 patients showed good concordance between ERG attributes and fundus abnormalities. In median follow-up of 17 years, 46% showed ERG progression, while FAF changes progressed in 67% of patients. For reliable detection of pathological changes at the beginning of the STGD1 disease, FAF, PERG, and ffERG should be performed to determine disease progression.

O1-2-2 Electroretinogram b:a ratio variability in the classical electronegative inherited retinal diseases

Haipha Ali¹, Chris Ovens¹, Vannessa Leung¹, Stephanie Retsas¹, Elise E Cornish^1,2, Dhimas H Sakti^1,2, Nonna Saakova¹, Peter McCluskey¹, Robyn V Jamieson^1,2, John R Grigg^1,2

¹Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia, ²Eye Genetics Research Unit, Children’s Medical Research Institute, The Children’s Hospital at Westmead, Westmead, New South Wales Australia

Purpose Inherited retinal diseases (IRD) classically associated with electronegative ERGs include X-linked retinoschisis (RS1) and complete and incomplete congenital stationary night blindness (cCSNB, iCSNB). An electronegative ERG is defined as b:a ratio ≤ 1.0. Earlier studies have shown significant heterogeneity in the ERG findings within and between these three conditions, reflecting the varying impact on inner retinal function related to genotype and specific mutation variation in the transmission cascade. Comparing the full field ERG b:a ratio phenotypes gives insights into genotype–phenotype correlations and also questions the ERG b:a ratio criteria for suspecting a classic electronegative-associated IRD.

Methods A retrospective review was performed of patients with a clinical diagnosis of iCSNB, cCSNB, or RS1 attending the Save Sight Institute Sydney, Australia. We compared ERG results for the 3 diagnostic groups. ISCEV standard ERGs were analyzed including b:a ratios calculated from both 3.0 and 12.0 stimuli. Statistical analysis was performed using 2-tailed unpaired student t tests to compare mean b:a ratios between groups. An association between electropositive b:a ratio patients and genetic diagnosis was also performed using Chi-squared tests and was assessed using thresholds of b:a > 1.0 and b:a > 1.50.

Results Fifty-four patients were included: 25 iCSNB, 13 cCSNB, and 16 RS1. Genetic confirmation was available in 8 iCSNB, 2 cCSNB, and 11 RS1 patients. There was no difference between mean b:a ratio values for DA 3.0 and DA 12.0 for any group. In sub-group analysis, genetically proven iCSNB cases had a significantly lower mean b:a ratio compared to the overall iCSNB cohort (0.62 vs 0.80, p = 0.0008), while there was no difference for cCSNB or RS1 cohorts. When comparing mean b:a ratios in genetically proven patients, cCSNB (0.52) was significantly lower than iCSNB (0.52 vs. 0.62, p = 0.042) and RS1 (1.04, p < 0.0001), and iCSNB was significantly lower than RS1 (p < 0.0001). The frequency of electropositive (b:a > 1.0) ERG traces in genetically proven patients was iCSNB 1/8, cCSNB 0/2, and RS1 7/11. When a threshold of b:a > 1.50 was used, frequencies were iCSNB 0/8, cCSNB 0/2, and RS1 2/11. An electropositive ERG was significantly more likely to be associated with RS1 than iCSNB (p = 0.026) at b:a > 1.0 threshold.

Conclusions These findings highlight the expanded variability in b:a ratios. Patients with genetically proven disease in some cases exhibited a positive b:a ratio. This work suggests that a b:a ratio up to at least 1.5 could suggest an IRD that classically has been grouped as an electronegative condition. RS1 patients were frequently found to be electropositive. All of the CSNB cases illustrated a b:a ratio of < 1.50. No cCSNB cases had a ratio > 1.0. The variation in ERG b:a ratio between the groups further assists in guiding genetic testing and interpretation.

O1-2-3 S-cone ERG: A potential biomarker for monitoring progression of Stargardt disease in genotypes conferring residual ABCA4 function

Jana Sajovic¹, Andrej Meglic¹, Marko Hawlina¹, Ana Fakin¹

¹Eye Hospital, University Medical Centre Ljubljana, Slovenia

Purpose The aim of the study was to determine which ERG response best reflects age-related disease progression in Stargardt disease (STGD1) patients with non-null genotypes.

Methods Forty-two patients with STGD1 were included. Eight patients (5 female, 3 male) in group 1 harboured 2 null mutations, while 34 patients (24 female, 10 male) in group 2 had other genotypes. Age at the time of examination, age at onset, and best-corrected visual acuity (BCVA), given as logarithm of the minimum angle of resolution (logMAR), were collected from the medical records. Full-field ERG and PERG, presented on a 30.7 × 23.6° (large field) cathode ray tube screen, were recorded according to the standards of the ISCEV. The S-cone ERG was recorded according to the ISCEV-approved extended protocol. The amplitudes of the following responses were analysed cross-sectionally with age: PERG P50 amplitude, dark-adapted (DA) 0.01 ERG b-wave and DA 3.0 ERG a-wave amplitudes, DA OPs, light-adapted (LA) 30 Hz flicker ERG and LA 3.0 ERG b-wave amplitudes, and S-cone ERG.

Results Patients in group 1 were relatively younger than patients in group 2 (median age 21 vs 39 years, respectively; p = 0.222). Group 1 had a significantly earlier age of onset than group 2 (median 8 and 18 years, respectively; p < 0.001), whereas disease duration was similar between the groups (median 13 and 12 years, respectively; p = 0.320). Group 1 patients had significantly worse VA than group 2 (1.8 vs 0.8, p < 0.001). Group 1 patients had significantly lower values of all ERG responses in comparison to group 2 patients (p < 0.001). Group 1 had no detectable macular function measured with PERG P50 amplitude, whereas it was detectable in 82% of group 2 patients. Moreover, in 24% of the group 2 patients, the PERG P50 amplitude was within normal values. A simple linear regression analysis of the correlation between age and ERG amplitudes showed different results for the two genotypic groups. In group 1, age significantly correlated with the DA 0.01 ERG b-wave (β = − 0.806, F(1, 6) = 11.134, p = 0.016, R = 0.650, R²adjusted = 0.591) and DA 3.0 ERG a-wave (β = − 0.865, F(1, 6) = 17.839, p = 0.006, R² = 0.748, R²adjusted = 0.706), while in group 2, age significantly correlated with the S-cone ERG amplitude (β = − 0.065, F(1, 32) = 25.810, p < 0.001, R² = 0.446, R²adjusted = 0.429). Other ERG parameters did not show significant correlations with age in either group.

Conclusions For double null patients, the best ERG biomarkers for follow-up were DA 0.01 and 3.0 ERG responses, representing retina rod system response. For other genotypes expected to confer residual ABCA4 function, the best ERG biomarker for follow-up was S-cone ERG, which might be included in the electrophysiological assessment of patients with STGD1. Different ERG responses may be best suited to monitor disease progression in different Stargardt genotypes. The results are especially important for designing clinical trials that require sensitive and objective biomarkers to determine disease trajectory.

O1-2-4 Dark-adapted full-field stimulus threshold in ultra-low vision patients with retinitis pigmentosa

Kaoru Fujinami^1,2,3,4, Yu Fujinami-Yokokawa^1,3,5,6, Yasutaka Suzuki¹, Jeffrey Farmer⁷, Kazushige Tsunoda⁸

¹Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan., ²Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan., ³Institute of Ophthalmology, University College London, London, UK., ⁴Moorfields Eye Hospital, London, UK, ⁵Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan, ⁶Department of Public Health Research, Yokokawa clinic, Osaka, Japan., ⁷Diagnosys LLC, MA, USA., ⁸Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan

Purpose Full-field stimulus threshold (known as full-field stimulust esting, FST) measures the minimum light stimulus required to evoke a visual response from a fully dark-adapted receptoral mechanism. FST is essential in assessing the sensitivity of the visual field, especially in patients with severe visual impairment. Recently, FST has been applied in therapeutic trials as a primary/secondary outcome for gene augmentation, gene adding (optogenetics), and other trials [NCT04516369/Japan, NCT03326336/USA, and others]. We describe the distribution of luminance thresholds in subjects with severe retinitis pigmentosa (RP), aiming to establish a deep phenotyping protocol.

Methods RP cases with ultra-low vision (ULV) showing severe visual acuity decline (counting fingers or worse) were enrolled. Comprehensive ophthalmological examinations were performed, including full-field electroretinograms (ffERGs) recorded according to the ISCEV standard. Full-field colour stimuli were generated by the Diagnosys Profile ganzfeld ColorDome (Diagnosys, LLC, MA, USA) that utilizes narrow-band LEDs of 448 nm (blue), 530 nm (green), and 627 nm (red). FST was performed based on the published method (Klein & Birch, 2009). The colour FST was performed after 40 min of dark adaptation: (i) blue, (ii) red, and (iii) white stimulus. The following settings were applied: presentation length 5 min; interstimulus interval 2.5 s; inter-trial duration 2 min; eye and test order right, left; dilated; the definition of 0 dB point 0.1 log cd.s/m²; repeat maximum four times; and audible cues. Quality assessment was conducted manually based on the traces by multiple investigators. Data with adequate quality were selected for analysis. The FST data obtained in RP patients were compared with those of 20 healthy subjects (median age 38.5, range 23–52 years) with no ocular diseases.

Results The median age of onset/examination of 40 eyes from 23 RP cases was 9.0 (range, 0–40) years/59.0 (11–82) years, respectively. The median visual acuity of 40 eyes was 2.28 (range, 1.40–3.00) logMAR. The full-field ERGs were undetectable both in dark-adapted and light-adapted conditions in all 23 cases. The median value for blue/red/white FST was − 1.71 (range, − 5.42 to 0.18)/− 0.9 (− 2.84 to 1.04)/ − 1.18 (− 4.61 to 0.96) log cd.s/m² in 40 ultra-low vision (ULV) RP eyes. The median value of thresholds for blue/red/white FST was − 7.70 (− 8.33 to − 6.93)/ − 5.32 (− 6.24 to − 4.82) − 7.11(− 7.62 to − 6.51) log cd.s/m² in the 40 healthy eyes. FST revealed a significantly different range of thresholds for each colour stimulus between ULV RP patients and healthy subjects.

Conclusions Quantitative assessment of the sensitivity of the visual field was available with FST for patients with ULV RP demonstrating undetectable ERGs, in keeping with previous reports (Roman AJ et al., Prog Retin Eye Res 2021; Klein et al., Doc Ophthalmol 2019). The broader distribution of luminance thresholds was illustrated in ULV RP patients, which was significantly higher than that of healthy subjects. These data could help monitor and counsel patients, as well as aid in the assessment of visual function in therapeutic trials.

O2-1-1 Electrophysiological and clinical characteristics of patients with positive anti-optic nerve antibodies (AONA) and suspected optic nerve dysfunction

Graham E. Holder¹, Hazel A. Lin¹, Victor T. C. Koh¹, Wendy M. H. Wong¹, Clement C. W. Tan¹

¹National University Hospital and National University of Singapore, Singapore

Purpose To investigate the clinical and electrophysiological features associated with the presence of positive anti-optic nerve antibodies (ANOA).

Methods A retrospective case review revealed 15 patients (age 33–67; 8 females, 7 males) with positive anti-optic nerve antibodies. The symptomatic presentation was often that of non-specific blurring of vision with an initial differential diagnosis usually including normal tension glaucoma (NTG) or myopic optic neuropathy (MON). Reduced monocular visual acuity (VA) was an incidental finding in 2 patients. All had comprehensive clinical investigation, including standard ophthalmological examination and MRI. All patients underwent ERG, PERG, and VEP (flash and pattern) recording. All had anti-retinal antibody (ARA) and anti-optic nerve antibody (AONA) studies performed (Casey Eye Institute, Portland, OR USA).

Results

Visual acuity was often well preserved; only both eyes of 2 patients and 1 eye of 2 patients had VA worse than 6/9. Nine patients had ≥ 5.0 dioptres of myopia and 4 were mildly hypermetropic. VEPs were delayed or undetectable in both eyes of 6 patients and one eye of 5 patients; 1 patient showed bilaterally subnormal amplitudes with no delay, and VEPs were normal in 3 patients. Five patients had delays of ≥ 15 ms without significant VA reduction. All with undetectable pattern VEPs or ≥ 10 ms delay had PERG N95 abnormalities. Three patients showed reduced PERG N95:P50 ratios, in keeping with retinal ganglion cell (RGC) dysfunction, despite normal pattern VEPs. Mild ERG abnormalities were present in both eyes of 2 highly myopic patients and cone abnormalities in one eye (probably related to anisocoria). One other patient had an unexplained mild 30 Hz flicker ERG delay, stable on longitudinal recording. The most common AONAs were 35–40-kDa and 46-kDa proteins (both present in 11 patients). ARAs were present in 9 patients, 7 with normal ERGs; the most common findings related to recoverin and enolase. One patient had metastatic disease on MRI with probable nerve involvement. MRIs were often normal, even when pattern VEPs were undetectable. When abnormal, “thinning” of the optic nerve was reported in 8/30 eyes, but there could be associated normal pattern VEP with (N = 1 eye) or without (N = 1 eye) abnormal RGC function on PERG.

Conclusions Most of these patients present challenges in diagnosis and management as there are no gold standard criteria for the diagnosis of autoimmune optic neuropathy (AON), MON, or NTG. The working diagnosis of NTG appears sustained in the three patients with RGC dysfunction demonstrated by PERG in the absence of pattern VEP abnormality (pattern VEP delays being relatively uncommon in glaucoma). Patients with substantial pattern VEP delay but good VA probably have AON in that eye, but possible NTG in the fellow eye is not excluded. Those with very poor VA could have MON or AON. The difficulty in ascribing causation to positive anti-retinal antibody studies, rather than associated epiphenomena, is emphasised by the high incidence of ARAs despite normal ERGs.

O2-1-2 Electrophysiological biomarkers of visual acuity improvement in Leber hereditary optic neuropathy (LHON)

Marko Hawlina¹, Sanja Petrovic Pajic^1,2, Maja Sustar Habjan¹, Luka Lapajne¹, Ana Fakin¹, Martina Jarc Vidmar¹, Jelka Brecelj¹, Mirella Barboni³

¹University Eye Hospital Ljubljana, Slovenia, ²Clinical Center of Serbia, Clinic for Eye Diseases, Belgrade, Serbia, ³Department Ophthalmology, Semmelweis University, Budapest, Hungary

Purpose LHON is a neurodegenerative disease characterised by deep, usually bilateral, simultaneous or sequential visual acuity (VA) loss caused by mitochondrial or autosomal recessive (DNAJC30) mutations. Visual function is severely reduced with most patients ending up legally blind. In a small number of patients, there is a spontaneous recovery of visual function, which is reflected in the reduction or fenestration of the central scotoma, resulting in an improvement in visual acuity. In this study, we analysed electrophysiological and structural characteristics in LHON patients with and without spontaneous VA improvement to explore potential structural/functional biomarkers in LHON.

Methods The 12 patients with genetically confirmed LHON included in the study were divided into two groups based on functional improvement: Group 1: 6 male patients (mean age 42.5 years) without VA improvement, and Group 2: 6 patients (4 males, mean age 35.3 years) with VA improvement. Full-field ERG with filtered OPs, large-field pattern ERG (PERG), and VEP were recorded. Segmentation analysis of retinal layers in ETDRS rings was performed using the Heidelberg Engineering Spectralis SD-OCT.

Results In the subacute phase of the disease, N95/P50 ratios were significantly (p = 0.034) lower in Group 1 compared to Group 2. The N95 amplitude was reduced in Group 1 (mean amplitude 3.37 µV), whilst in Group 2, it was relatively preserved (mean amplitude 4.37 µV). VA in the subacute phase was higher in Group 2 with a marginal significance of p = 0.05. In the chronic phase, VA differences became quite significant (p < 0.001) with an average VA of 0.75 Snellen in Group 2. VEP P100 waves were undetectable in 4/6 patients in Group 1, whilst the remaining two patients had prolonged latencies and decreased P100 amplitudes. In Group 2, all patients displayed detectable VEP P100 waves, with reduced amplitudes in two patients and normal latency values in only one case. As in the subacute phase, N95/P50 ratios were lower in Group 1 (p = 0.02) with a marginal significance (p = 0.05) for the N95 amplitudes. GCC thickness was larger in the inner ETDRS ring (p = 0.049), and the pRNFL thickness was larger in the inferior temporal segment (p = 0.034) in Group 2. Both structural and electrophysiological parameters showed significant correlations with VA. In Group 2, VA and visual field improvements were first detected 12–24 months after disease onset (mean = 17.33 months), whilst in two patients, VA improved 14 and 15 years after disease onset. In both cases, recovery of the P100 latency to normal values was observed, although the amplitudes were still reduced. The PERG N95 wave was reduced; at the level of the baseline and N95/P50 ratio was under 1. Some patients from Group 2 followed up longitudinally showed improvements of PERG, VEP, and also OP2 and OP3.

Conclusions Spontaneous VA improvement in LHON patients is associated with thicker GCC in the inner ETDRS ring and thicker inferior temporal pRNFL. P100 latency recovery as well as N95 amplitude and N95/P50 ratio increase seem to be the main functional characteristics of the spontaneous VA improvement in LHON, whilst changes in oscillatory potentials suggest a physiological remodelling of the inner retina.

O2-1-3 Comparing ERG photopic negative response (PhNR) in AQ4 + and MOG + optic neuritis

Andre Messias¹, Renata Moreto¹, Katharina Messias¹

¹University of Sao Paulo, Brazil

Purpose To compare photopic ERG results, including the photopic negative response (PhNR), in patients with optic neuritis showing positive anti-aquaporin 4 antibody (AQ4) or myelin oligodendrocyte glycoprotein antibodies (MOG).

Methods Comprehensive ophthalmological examination including best-corrected visual acuity (BCVA), automated visual field (24–2) (VF-MD), spectral-domain optical coherence tomography (OCT) to determine the peripapillary retinal fiber layer thickness (RNFL), and ERG was performed in 34 AQ4 + patients (42 ± 2 years old) and 21 MOG + patients (32 ± 7 years old), who had suffered at least one episode of neuritis (10 bilateral for AQ4, 9 for MOG) 6 months or longer prior to examination. Full-field ERG was recorded following ISCEV standard recommendations, extended by a red flash (640 nm, 2 cd.s/m²) with a blue background (460 nm, 10 cd/m²) to elicit the PhNR. Comparisons were done using a mixed-effects model.

Results No significant between-groups differences were found for mean BCVA (logMAR): AQ4: 0.17 ± 0.12 (20/29) and MOG: 0.20 ± 0.13 (20/32) (P = 0.934), or VF-MD: AQ4: − 9.73 ± 2.08 dB and MOG: − 8.40 ± 1.83 dB (P = 0.078), or RNFL: AQ4: 56.78 ± 5.05 µm and MOG: 68.84 ± 5.55 µm (P = 0.156), but a small, statistically significant difference was found for PhNR AQ4: − 17.90 ± 1.57 µm and MOG: − 11.35 ± 1.83 µm (P = 0.011). Significant correlations were found between BCVA and VF-MD (P = 0.001; r = − 0.500) but not with PhNR.

Conclusions In this cohort, with eyes showing relatively well-preserved RNFL and visual acuity after optic neuritis, we found a difference between AQ4 and MOG patients using PhNR. This might indicate that PhNR could reveal distinctive information about functional loss in these patients.

O2-1-4 Evaluation of visual evoked potential parameters in patients with hypothroidism

Manoj Mahat¹, Gulshan Bahadur Shretha¹, Pragati Gautam¹, Parash Gywali¹

¹Institute of Medicine, Tribhuvan University, Nepal

Purpose To evaluate and compare pattern reversal visual evoked potential (PRVEP) parameters between hypothyroid patients and healthy controls.

Methods We enrolled 59 female patients aged 20–60 years with a history of hypothyroidism (24 subclinical and 10 overt) and 25 healthy women of similar age (control group). All subjects had a complete ophthalmic examination. For VEP testing followed the ISCEV pattern-reversal (“PRVEP”) Standard protocol. Subjects viewed stimuli with checks subtending a visual angle of 60 and 15 min of arc using Roland Reti-Scan (Retiport 4.8.1.12).

Results The mean P100 latency of the PRVEP in the hypothyroidism group was significantly increased for both 60 min and 15 min checks (111.44 ± 7.52 ms and 112.93 ± 7.96 ms, respectively) as compared with controls (106.78 ± 3.22 and 106.96 ± 3.56, respectively) (p < 0.001). Similarly, the mean N75-P100 amplitude was reduced in the hypothyroidism group (9.03 ± 4.30 and 9.34 ± 4.80) compared with controls (12.73 ± 5.07 and 13.50 ± 5.43) (p < 0.001). Also, there was a significant correlation between thyroid stimulating hormone and P100 latency for 60 and 15 min checks (r = 0.475, p = 0.005 and 0.479, p = 0.005, respectively), but there was weak correlation between thyroid stimulating hormone and PRVEP amplitudes (r = − 0.020, p = 0.911 and r = − 0.068, p = 0.703, respectively).

Conclusions Hypothyroid patients (both overt and subclinical groups) have significantly increased P100 wave latency and reduced N75-P100 amplitude for both 60 min and 15 min checks compared to age and gender matched normal controls. Therefore, the PRVEP is a dependable marker for detection of neurological deficit in thyroid deficiency which can involve the central nervous system at an earliy stage.

O2-2-1 Evaluation of ERG abnormality in ocular hypertension and different stages of glaucoma

Maja Sustar Habjan¹, Darko Perovsek¹, Andrej Meglic¹, Barbara Cvenkel¹

¹University Medical Centre Ljubljana, Slovenia

Purpose The PERG and photopic negative response (PhNR) have been shown to be sensitive markers of retinal ganglion cell (RGC) dysfunction in glaucoma. The aim of this study was to evaluate changes in the PhNR and PERG at different stages of glaucoma, as well as a recently described PERG parameter, the P50-N95 slope, and to determine their relationship with structural changes described by spectral-domain optical coherence tomography (SD-OCT).

Methods PERG and photopic ERG traces were retrospectively analyzed from 8 patients with ocular hypertension (OHT), 15 patients with suspected glaucoma, 9 patients with early glaucoma, 16 patients with advanced glaucoma, and 24 age-matched control subjects. Thirty-three patients were followed for 5 years and divided into patients with and without progression. PERGs were elicited with a large field stimulus (21.6° × 27.8°) and photopic ERGs with a monochromatic red (635 nm) stimulus of 2.5 cd.s/m² on a blue background of 10 cd/m². The PERG signal between the P50 and N95 waves (30 ms of signal from the peak of P50) was analyzed with a linear regression y = a + bx, where the parameter b indicated the P50-N95 slope. Data from the right eyes were analyzed using ANOVA and receiver operating characteristics (ROC) curves, and correlation tests were performed to evaluate the association with peripapillary retinal nerve fiber layer (pRNFL) thickness, mean thicknesses of the macular nerve fiber layer (NFL), ganglion cell inner plexiform layer (mGCIPL), ganglion cell complex (GCC), and mean deviation of standard automated perimetry (SAP).

Results PhNR was the only parameter already significantly affected in patients with ocular hypertension (15.7 ± 7.9 vs. 25.5 ± 6.1 µV in controls, p = 0.006). N95 amplitude (5.6 ± vs. 7.3 ± µV, p = 0.007) and P50-N95 slope (− 0.14 ± 0.04 vs. − 0.19 ± 0.04, p = 0.004) were significantly reduced in patients with suspect glaucoma, while the N95/P50 ratio did not show significant changes in any of the patient groups. Of all ERG parameters, the P50-N95 slope correlated most strongly with functional abnormality, as assessed by SAP (r = 0.57, p < 0.001). Correlation with OCT parameters was highest for the N95 amplitude (r = 0.53, 0.49, 0.48 with pRNFL, NFL, and GCC, respectively, p < 0.01), while P50-N95 slope was the only ERG parameter that correlated with mGCIPL thickness (r = − 0.36, p = 0.04). None of the ERG and OCT parameters could differentiate between patients with progression and those without, but the ability to differentiate was greatest for the P50-N95 slope (AUC = 0.69).

Conclusions PhNR and PERG have different roles in the evaluation of patients with OHT and different stages of glaucoma. PhNR is affected earlier in the disease course, whereas PERG parameters correlate better with structural damage. The P50-N95 slope has been shown to be a useful additional parameter for assessing glaucomatous RGC damage.

O2-2-2 New steps to the analysis of the photopic negative response (PhNR) in Leber hereditary optic neuropathy (LHON)

Qingqing K. Zhao^1,2, Hong-An Nguyen^1,3, Alexander Svoronos⁴, Laura P. Pardon⁵, Melanie R. Lalonde^1,3, Scott H. Greenwald⁵, Alex Huang⁴, Steven S. Laurie⁵, Brandon R. Macias⁶, Stuart G. Coupland^1,3, Rustum Karanjia^1,3,7

¹The Ottawa Hospital Research Institute, Ottawa, Canada, ²University of Toronto Dalla Lana School of Public Health, Toronto, Canada, ³University of Ottawa Eye Institute, Ottawa, Canada, ⁴Shiley Eye Institute, University of California San Diego, La Jolla, United States, ⁵KBR, Houston, United States, ⁶NASA Johnson Space Center, Houston, United States, ⁷Doheny Eye Institute, University of California Los Angeles, Los Angeles, United States

Purpose The current ISCEV protocol recommends manual data cleaning by trained technologists before meaningful interpretations can be made. This process is not only time-consuming but is also prone to inter- and intra-examiner variability. The purpose of the study is to investigate the use of automated sweep rejection (ASR) and notch filters on the inter-test reproducibility of the photopic negative response (PhNR) in normal subjects and patients with Leber hereditary optic neuropathy (LHON).

Methods Data were collected at the University of Ottawa Eye Institute. Full-field photopic ERGs were recorded using 1 cd.s/m² red (640 nm) flashes on a blue (470 nm) rod-saturating background. The a-wave, b-waves, and PhNR recordings were identified using the Espion E3 software (v.6, Diagnosys LLC, Lowell, MA). Outliers were automatically removed by rejecting any tracings above + 50 µV or below -100 µV in the 80–150 ms range. A notch filter was also applied to the PhNR recordings in the 5–45 Hz range. Statistical analysis was performed using SigmaPlot (v.14.5) and R (v.4.1). One-sample t tests were performed to analyze the effect of the notch filter on the ERG recordings at a single visit and at repeated measurements.

Results The PhNR amplitude and implicit time were compared between the LHON affected (n = 60 eyes), LHON carrier (n = 64 eyes), and controls (n = 38 eyes). The ASR significantly reduced the PhNR amplitude but maintained the expected clinical difference between affected vs carrier (p < 0.001) and affected vs control (p < 0.001) with no difference in PhNR implicit time (IT) for all comparisons. Surprisingly, a significant difference was noted in the PhNR amplitude between carriers and controls (p = 0.01) which are clinically indistinguishable from each other. The application of the notch filter removed this difference, which is consistent with clinical presentation. There was no change in the clinical interpretation of the affected vs control or carrier results with the application of the notch filter. Repeated measures were evaluated in 29 affected and carrier participants who were clinically stable and had completed at least 3 sets of testing spaced ~ 6 months apart. The addition of the notch filter significantly decreased the inter-test variability in the same participant over three visits (median drop in coefficient of variation of 0.087, p = 0.0003 in PhNR amplitude; median drop in coefficient of variation of 0.021 in PhNR IT, p < 0.0001).

Conclusions The ASR provides an efficient and reliable method to clean the ERG recordings. The addition of a notch filter reduces the inter-test variability of the PhNR.

O2-2-3 Photopic negative response as an objective outcome measure in Leber hereditary optic neuropathy

Hong-An Nguyen^1,2, Melanie R. Lalonde^1,2, Qingqing Zhao^1,2, Ange-Lynca Kantungane^1,2, Stuart G. Coupland^1,2, Rustum Karanjia^1,2,3

¹University of Ottawa Eye Institute, ²Ottawa Hospital Research Institute, Ottawa, ON, Canada, ³Doheny Eye Institute, Los Angeles, CA, United States

Purpose The purpose of this study was to establish objective electrophysiological outcome measures for retinal ganglion cell (RGC) function in patients with Leber hereditary optic neuropathy (LHON). Accurate objective quantification of RGC function would provide quantifiable metrics which could be useful to evaluate the effects of therapy.

Methods This was a retrospective/prospective study at the University of Ottawa Eye Institute in collaboration with the University of California Los Angeles, involving two components: (1) quantification—the photopic negative response (PhNR) was recorded in patients with LHON, both affected and carriers, and (2) validation—the PhNR amplitude and implicit time recorded from these patients were measured against both subjective and objective functional and structural metrics that are part of standard of care to determine any correlations. Diagnostic measures included Humphrey visual fields, optical coherence tomography (OCT), and PERG. ERG testing done for this study was in accordance with ISCEV standards and following the University of Ottawa Eye Institute clinical protocols for which we have a normative database of findings.

Results Using ANOVA analysis, there was a statistically significant difference (p < 0.0001) in PhNR amplitude among LHON affected (n = 102 eyes), LHON carriers (n = 72 eyes), and the control group (n = 71 eyes). PhNR amplitudes were significantly reduced (p < 0.0001) in LHON affected (− 14.7 ± 2.87 µV at 5 cd.s/m² and − 16.7 ± 2.26 µV at 7 cd.s/m²⁾ compared to controls (− 34.2 ± 2.53 µV at 5 cd.s/m2 and − 40.2 ± 3.59 µV at 7 cd.s/m². In addition, pairwise comparison also indicated a significant difference in PhNR amplitude between LHON carriers (− 28.4 ± 2.78 µV at 5 cd.s/m² and − 25.5 ± 2.73 µV at 7 cd.s/m²⁾ and the control group at 7 cd.s/m² (p = 0.0015). PhNR metrics did not correlate with functional and structural metrics.

Conclusions Our findings show that patients who are affected by LHON have a reduced PhNR amplitude relative to the carrier and control populations. Interestingly, the patients who carry the mutation for LHON also show a reduced PhNR amplitude at certain testing parameters in comparison with the control group. The PhNR is a measure that objectively quantifies and evaluates RGC function in both the LHON affected patients and LHON carriers.

O2-2-4 Evaluation of inner retinal function of primary open angle glaucoma in different stages using the photopic negative response measured by RETeval

Takako Hidaka¹, Hideki Chuman¹, Yasuhiro Ikeda¹

¹Department of Ophthalmology, Miyazaki University, Japan

Purpose To investigate the objective function of the inner retinal layer in each stage of primary open angle glaucoma (POAG) using the photopic negative response (PhNR) with RETeval full-field ERG system and also to evaluate which PhNR parameter is most useful.

Methods There were ninety eyes of 90 POAG patients (mild stage (mean deviation (MD) ≥ − 6 dB), 30 eyes), moderate to advanced stage (MD < − 6 dB). Sixty eyes were enrolled. We compared them with 76 eyes of 76 control cases. We investigated 6 PhNR parameters: baseline to trough (BT), W-ratio, 72msPhNR, P-ratio, peak to trough (PT), implicit time (IT), MD of Humphrey 30-2 visual field test, and circumpapillary retinal nerve fiber layer (cpRNFL) thickness obtained from optical coherence tomography.

Results All PhNR parameters other than IT were significantly different in all POAG patients in moderate to advanced stages compared to the control group. In mild stage, BT and 72msPhNR were significantly different from those in the control group. Correlations between the PhNR parameters, MD, and cpRNFL thickness revealed significant correlations for all POAG patients in the moderate to advanced stage in all PhNR parameters except PT and IT. In mild stage POAG, 72msPhNR showed a weak significant correlation with cpRNFL thickness. The area under the curve value was highest in BT in mild and moderate to advanced POAG.

Conclusions The PhNR parameters measured using the RETeval were more useful than the objective visual function evaluation in moderate to advanced stages compared to mild stage of POAG. It was suggested that BT has the highest diagnostic capability.

O2-2-5 Normal tension glaucoma or non-glaucomatous optic neuropathy: Electrophysiological evaluation of a diagnostically challenging entity

Wendy Meihua Wong^1,2, Hazel Anne Lin^1,2, Clement Woon Teck Tan^1,2, Victor Teck Chang Koh^1,2, Graham Edwin Holder^1,2

¹Department of Ophthalmology, National University Hospital, Singapore, 119074, Singapore, ²Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore

Purpose To investigate the characteristics of a series of patients with a clinical diagnosis of normal tension glaucoma (NTG) but with significantly delayed peak times (≥ 7 ms) on pattern VEP testing. NTG is a diagnosis of exclusion, but detecting the masquerades of NTG can be difficult. Pattern VEP delay is generally uncommon in glaucoma, with an earlier study reporting a mean difference in P100 peak time between glaucomatous and control eyes of < 7 ms (Grippo et al., Invest Ophthalmol Vis Sci 2006;47:5331–6).

Methods Retrospective case series of patients diagnosed with NTG by a glaucoma specialist between 2018 and 2022 who underwent VEP (flash and pattern reversal), PERG, and ERG recordings to exclude other causes of visual field loss were evaluated. Inclusion criteria were a delay in the P100 peak time of ≥ 7 ms not explained by abnormalities recorded at a retinal level. The mean deviation (MD) was recorded from the SITA-standard 24-2 automated perimetry performed within 3 months of the electrophysiological test; the rate of progression of visual field (VF) loss was determined using the Guided Progression Analysis (GPA) at the most recent follow-up (Humphrey Field Analyzer II; Carl Zeiss Meditec, Inc., Dublin, CA).

Results There were 18 eyes of 14 patients. The median age was 63 years (mean 58.6 years; range 29–80 years). The median delay in P100 peak time was 18 ms (mean 21 ms; range 7–70 ms); a delay in flash VEP peak time was present in 3 eyes (16.7%). A reduced PERG N95:P50 ratio (< 1.1) suggestive of retinal ganglion cell dysfunction was noted in 13 eyes (72.2%). The median MD on VF testing was − 10.7 (4 eyes had MD < − 6, 8 eyes had MD between − 6 and − 12 MD, and 6 eyes had MD > − 12). Eleven eyes (55.6%) had sufficient serial VF tests to determine the GPA over a median follow-up of 5 years (mean 6.7 years, range 1.5–15 years); 3 eyes showed no progression, 4 eyes progressed at < 1.0% per year, and 4 eyes progressed at a rate between 1 and 2% per year. All eyes had been treated with at least one topical glaucoma medication. Neuroimaging was performed in all patients; reduced optic nerve caliber was present in 8 eyes (44.4%), of which 2 eyes (11.1%) had a concomitant increase in the T2 signal within the optic nerve.

Conclusions Non-glaucomatous optic neuropathy (NGON) may masquerade as NTG and an accurate diagnosis has implications for prognosis, the need for further diagnostic testing, and treatment. This series reports patients carrying a diagnosis of NTG in which a significant delay in pattern VEP peak time suggested that NGON should be considered. The optimal strategy to manage these patients in terms of further diagnostic work-up for inflammatory, autoimmune, or genetic causes and the cost–benefit of long-term treatment to lower their intra-ocular pressures remains to be elucidated.

O3-1-1 ISCEV standard transient pattern reversal VEPs and visual acuity

Dorothy A Thompson^1,3, John Booth², Sian E Handley^1,3, Lisanne A Horvat-Gitsels^3,4, Oliver R Marmoy^1,3,5

¹The Tony Kriss Visual Electrophysiology Unit, Great Ormond Street Hospital for Children NHS Trust, Clinical and Academic Department of Ophthalmology, London, UK., ²DRIVE, Data Research, Innovation and Virtual Environment Unit, Great Ormond Street Hospital for Children, London, UK., ³Great Ormond Street Institute for Child Health, University College London, London, UK., ⁴UKMoody’s RMS, London, UK., ⁵Manchester Metropolitan University, Manchester, UK

Purpose In this study, we explore whether a range of quantitative visual acuity (VA) may be inferred from routine clinical transient pattern reversal VEPs (prVEP).

Methods Consecutive patients attending the visual electrophysiology clinic between January 2019 and March 2021 with documented monocular logMAR VA and prVEPs were included. A bespoke algorithm extracted data from the electronic medical records including age at test, sex, monocular visual acuity, and monocular prVEP N75-P100 amplitude and P100 peak time recorded from the midline Oz or Iz referred to Fz for a range of check widths (6’, 12’, 25’, and 50’) including ISCEV large and small checks. A check width ‘threshold’ was defined as the smallest check width reported to produce a quantifiable prVEP. These include measures outside laboratory reference ranges.

PrVEPs were produced to black and white checks that reversed at 3.15/second on a plasma display panel, (82 cd/m² mean luminance, ~ 96% Michelson contrast) in a 30-degree field viewed at 1.25 m. Only one recording per patient within the sample time period was included. VA data were summarised by the median and interquartile range (IQR). Kruskal–Wallis test assessed differences in VA by check width. Quantile regression models for VA assessed associations with prVEP amplitude, prVEP peak time, and threshold check width, adjusted for age and sex as fixed effects and eye level as random effect, and stratified by check width. These models were fitted at the 2.5th, 25th, 50th, 75th, and 97.5th percentiles to investigate the estimated range of VA that can be inferred from prVEP data.

Results A total of 662 participants, 43% female (median age 8 yr), 57% male (median age 7 yr) and (range 3–17 yr for both), met the inclusion criterion and provided 772, 937, 1151, and 1232 data points for 6′, 12′, 25′, and 50′ check widths, respectively. The range of logMAR VA of the cohort was − 0.28 to 3.00, median 0.16. For threshold prVEPs to check widths grouped as 6′, 12′, 25′, and 50′, the median logMAR VAs were 0.09 (IQR, 0.00–0.30), 0.22 (0.06–0.37), 0.26 (0.10–0.46), and 0.42 (0.21—0.64), respectively. Significant differences in VA were observed in pairwise comparisons between all threshold check width groups except 25′ with either 12′ or 50′ threshold groups; Kuskal–Wallis ANOVA showed the median; logMAR VA was significantly lower (clinically better) for smaller check widths. Quantile regression models revealed that prVEP data have a nonlinear effect across the range of VA data and this pattern differs by check width. Furthermore, age was positively associated with better VA in the lower range (2.5th and 25th percentiles) and males tended to have better VA than females in the middle range (25th, 50th, and 75th percentiles).

Conclusions Preliminary analyses suggest a detectable prVEP to the ISCEV small 12′ and large 50′ check widths is evident in 75% of the population of children with logMAR letter VA better than 0.37 and 0.64, respectively. The addition of prVEPs to the smaller 6′ check width includes 75% of the population with 0.30 logMAR or better, which is the UK driving standard VA.

O3-1-2 A search for the binocular VEP

James Vernon Odom¹

¹West Virginia University Eye Institute, USA

Purpose The purpose of this presentation is to provide a selective review of efforts to detect uniquely binocular VEPs and apply them in the clinic.

Methods Visually evoked potentials (VEPs) have been employed to determine if there is a uniquely binocular response present in the VEP with the dual aims (1) to understand binocular mechanisms and (2) to assess binocularity in the clinic. Assessing binocularity in the clinic has been presumed to be of interest in the detection of amblyopia but may not be limited to that disorder. Emphasis will be placed on ISCEV members’ contributions and on assessing applicability of these efforts to evaluation of clinical patients.

Results Efforts were made to assess fusion (e.g., Kawasaki et al. 1970), summation (e.g., Spekreijse 1966; Harter et al. 1968), suppression (e.g., Wright et al. 1986), and stereopsis (e.g., Regan and Spekreijse 1970) using standard averaging techniques. Baitch and Levi (1988) introduced a frequency tagging technique whereby intermodulation components which were specifically binocular could be identified. Shortly after, Zemon et al. (1993) modeled VEPs using temporal phase differences in pattern-reversal VEPs. Odom and Chao (1995) provided a slightly more elaborated model using phases of sinusoidal flicker. Sato et al. (2002) introduced a technique using dichoptic pseudorandom binary sequences (PBRS) to study binocularity. The use of these techniques in the clinic has been very limited although theoretically they have considerable promise.

Conclusions Frequency tagging, phase analysis, and PBRS require analysis techniques beyond averaging. In the late twentieth century, technical limitations limited the wide-spread application of the required analytic procedures. At the same time, the ISCEV VEP standard emphasized a more limited set of stimulus and recording conditions. It is suggested that these factors contributed to the failure of widespread clinical utilazation of these techniques and that they deserve to be reevaluated.

O3-1-3 The effect of eye movements on the pattern reversal VEP

Herman Talsma¹, Frank Hoeben¹, Gerard de Wit¹, Wim van Damme¹, Maria van Genderen¹

¹Bartimeus, Diagnostic Centre for complex visual disorders, Zeist, Netherlands

Purpose The P100 of the pattern reversal VEP (prVEP) is often not reliably recorded in the presence of nystagmus. The nystagmus cycle comprises slow and fast phases. In the fast phase, prVEP signals deteriorate due to smearing of the retinal image. If we could restrict the recordings to the slow phases of the nystagmus, it should be possible to retrieve a more accurate prVEP. Here we explore how image motion blur due to eye movements affects the prVEP in normal subjects and how we can trigger a prVEP stimulus in the slow phase of the nystagmus with the use of an eye tracker.

Methods Electrophysiological data synchronized with eye gaze data were collected from 3 normal subjects. Eye gaze data were recorded with a Tobii Pro Spectrum eyetracker with a 600 Hz sample rate. We simulated nystagmus by having a normal subject fixate a dot moving with constant velocity in horizontal direction, from left to right and back, on a checkerboard background. The checkerboard was reversed when the fixation dot was in the central position where velocity is highest, mimicking the fast phase of nystagmus. PrVEP P100 amplitude using a 60’ check size was recorded at four different velocities. In a second condition, the subject fixated the horizontally moving fixation dot, but now the reversal prVEP was triggered the moment the eye changed direction and the velocity was at its lowest point, mimicking the slow phase.

Results P100 amplitude of prVEP, recorded at the simulated fast phase, was inversely correlated with nystagmus velocity. No correlation was found between VEP P100 latency and nystagmus velocity. When recorded at the simulated slow phase, prVEP amplitudes remained constant, regardless of the velocity of the fast phase.

Conclusions The prVEP amplitude degrades with image motion blur. This simulation shows that by using an eye tracker to trigger the reversal stimulus at low eye movement velocity, comparable to the slow phase of nystagmus, the P100 amplitude remains intact.

O3-1-4 Pulfrich and the P100: Manifestation of partial conduction delays in the VEP

Enyam Komla Amewuho Morny^1,2, Julia Haldina¹, Sven P Heinrich¹

¹Eye Center, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, ²Department of Optometry and Vision Science, University of Cape Coast, Ghana

Purpose In some cases of optic neuritis (ON), a double peak or broadening of the P100 is observed, which can confound amplitude and peak time measurement of the P100. We hypothesize that these curve shape alterations originate from conduction delays that affect only some of the fiber bundles of the optic nerve. The purpose of this study was to further the understanding of this phenomenon by inducing conduction delays in healthy eyes by manipulating stimulus luminance in analogy to the psychophysical Pulfrich effect.

Methods Checkerboard pattern reversal VEPs with check sizes of 0.8°, 0.4° and 0.2° were recorded in healthy participants. Two variants of the experiment were conducted. (1) Binocular stimulation, luminance difference between the eyes achieved by 1.8 ND filter; monocular control conditions with and without filter. (2) Monocular stimulation, hemifields with luminance difference (half of monitor covered with ND filter); single-hemifield control conditions with and without filter. In both variants, VEP responses obtained with mixed stimulation (i.e. with luminance difference) were compared to simulated VEPs that were computed from the control measurements as the summed responses recorded with and without filter. P100 characteristics were assessed.

Results There was considerable variability between participants. However, as a general pattern, in the binocular variant, VEPs from mixed recordings and simulated VEP responses were markedly different. In contrast, in the hemifield variant, both agreed quite well. At varying degrees, the expected pattern of double peaks or broadened deflections was present in many participants, albeit frequently depending on check size. Often, the nominal peak time was not indicative of a partial conduction delay.

Conclusions The present findings corroborate the hypothesis that nominal peak time does not always reflect conduction delays if only a subset of fiber bundles are affected. Peak shape might provide additional diagnostic evidence of a partial conduction delay.

O3-1-5 Correlation between oscillatory potential magnitude and the photopic negative response under different stimulus conditions

Sara Safari¹, Katherine Tsay¹, Jan Kremers², Radouil Tzekov^3,4

¹University of South Florida, Morsani College of Medicine, Tampa, USA, ²University Hospital Erlangen, Section for Retinal Physiology, Erlangen, Germany, ³University of South Florida, Department of Medical Engineering, Tampa, USA, ⁴University of South Florida, Department of Ophthalmology, Tampa, USA

Purpose An abundance of experimental and some clinical evidence has shown a potential link between the oscillatory potentials (OPs) of the full-field ERG and retinal ganglion cell (RGC) activity. The purpose of this study was to compare OP magnitude with the photopic negative response (PhNR) in a clinical data set recorded under three different stimulus conditions: standard light-adapted 3.0 ERG (LA3), red flash on blue background (RoB), and red flash on white background (RoW).

Methods A retrospective chart review and data analysis of patients aged 18 and older undergoing routine ERG testing at USF Eye Institute (Tampa, FL) was conducted. LA3 was recorded using a ~ 2.5 cd·s/m² white flash on a 30 cd/m² white background. RoB conditions were measured in three separate ways: ~ 5 cd⋅s/m² red LED flash on a 30 cd/m² blue LED background, ~ 5 cd⋅s/m² red LED flash on a 10 cd/m² blue LED background, or ~ 2.5 cd⋅s/m² red LED flash on a 10 cd/m² blue LED background. RoW was recorded under a ~ 2.5 cd⋅s/m² red LED flash on a 30 cd/m² white LED background. For OP extraction, the signal was filtered using a high-pass 8th order Butterworth filter with either 58 Hz or 100 Hz cutoff. The root means square (RMS) of the filtered signal was used to define the OP magnitude. PhNR was evaluated in two different ways: as an amplitude measured from the b-wave peak to the beginning of the i-wave (PhNR1) and as an area under the curve in a 15-ms time window starting at the b-wave peak (15 ms AUC). Linear regressions were performed on plots of the OP RMS magnitude vs other ERG parameters (a-, b-wave amplitude, PhNR1 amplitude, 15 ms AUC), and coefficients of determination (R²) were obtained.

Results The records of 70 patients/135 eyes (18 M, 52F), mean age 49.2 ± 15.3 years were evaluated. R² of regressions between OP RMS and a- and b-wave amplitudes were similar, being lowest under RoB, having intermediate values under RoW, and highest under LA3 conditions (a-wave: 0.2793, 0.5668, and 0.6872; b-wave: 0.4507, 0.6531, and 0.7036) for the 58 Hz cutoff. R² of regressions with PhNR1 and 15 ms AUC showed higher values for R² with OP RMS (PhNR1: 0.6676, 0.4698, 0.8057; 15 ms AUC: 0.7534, 0.8681, 0.8710) for the 58 Hz cutoff. The R² values between OP RMS and a-, b-waves, and PhNR1 were similar, being lowest under RoB, having intermediate values under RoW, and highest under LA3 (a-wave: 0.3210, 0.5266, 0.6948; b-wave: 0.4366, 0.5214, 0.7159; PhNR1: 0.5052, 0.5228, 0.6518) for the 100 Hz cutoff. 15 ms AUC showed higher level of correlations with OP RMS (0.4896, 0.6052, and 0.6969) for the 100 Hz cutoff; however, the difference in R² values was less than the difference noted using the 58 Hz cutoff.

Conclusions Under all recording conditions, the regression models of OP RMS and 15 ms AUC showed the strongest correlation. This indicates the potential of this new measure to serve as an alternative way to assess RGC function in clinical full-field ERG.

O3-2-1 Exploration of oscillatory potentials and their polarity in the dark-adapted ERG elicited by strong flashes

Xiaofan Jiang^1,2, Andrew R Webster^1,3, Pirro G Hysi², Christopher J Hammond², John G Robson^4,5, Omar A Mahroo^1,2,3,4

¹UCL Institute of Ophthalmology, University College London, London, UK, ²Department of Ophthalmology and Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, UK, ³Retinal Service, Moorfields Eye Hospital, London, UK, ⁴Physiology, Development and Neuroscience, University of Cambridge, UK, ⁵Gonville & Caius College, Cambridge, UK

Purpose OPs are small high frequency wavelets observed on the rising limb of the ERG b-wave. They are thought to arise from amacrine cells and are selectively affected in some diseases, including preclinical diabetic retinopathy. It is not known whether OPs reflect the addition of positive- or negative-going signals to the ERG. In this study, we investigated OP components in ERG responses to strong flashes in a largely healthy adult cohort.

Methods TwinsUK is a large cohort of adult twins (mostly female and of European ancestry) who have volunteered for research studies based at St Thomas’ Hospital in London. ERG recordings (Diagnosys ColorDome with Espion software, Diagnosys, Lowell, MA) with ISCEV standard and additional stimuli have been obtained from both eyes of more than 200 participants using conductive fiber electrodes placed in the lower conjunctival fornix. In this study, dark-adapted responses to strong white flashes (10 and 67 photopic cd.s.m²) were analyzed. Traces were first normalised, the amplitude of the ERG from the a-wave trough to a time near the peak of the b-wave (45 ms post-flash) being taken to be 100. A locally weighted smoothing (lowess) filter with a span of 120 ms was then applied, and isolated OPs were obtained by subtracting the filtered responses from the original waveforms. Despite the normalization, there was substantial variation in the peak-to-peak amplitude of the OPs. The ERG traces were sorted according to the amplitude of the OPs, and the 5% with the largest OPs and the 5% with the smallest OPs were separately averaged. The isolated OPs of these two groups were also separately averaged.

Results Responses were analyzed from both eyes of 204 participants; subject age was 62.3 (± 11.5) years. Stimuli of both strengths elicited ERGs with OPs showing 3 or more clear peaks, the second peak usually having the largest amplitude. When the averaged ERGs from participants with the largest and smallest OPs were superimposed, the waveforms were seen to be more-or-less coincident at the time of the troughs in the isolated OPs and widely divergent at the time of the peaks. This was consistently observed in both eyes for both flash strengths and can be interpreted as indicating that the amplitude of the OPs at the time of the troughs is zero and that each OP is a positive-only wavelet.

Conclusions We present a novel method of OP analysis for dark-adapted strong-flash ERGs and the results of its application to waveforms recorded from a large sample of healthy adults. Our findings are consistent with the OPs being purely positive (rather than negative or bidirectional) deflections on the rising limb of the b-wave.

O3-2-2 Electrically evoked responses elicited by transcorneal electrical stimulation in patients with retinitis pigmentosa

Yu Fujinami-Yokokawa^1,2,3,4, Oscar Onyango⁵, Yasutaka Suzuki¹, Motoshi Yamamoto^1,6, Kayoko Komatsu^1,6, Natsuki Maetani^1,6, Hisateru Tachimori⁷, Hiroaki Miyata², Jeffrey Farmer⁸, Kei Shinoda⁹, Kazushige Tsunoda¹⁰, Yozo Miyake¹¹, Kaoru Fujinami^1,4,12

¹National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center., ²Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan, ³Division of Public Health, Yokokawa Clinic, Suita, Japan, ⁴UCL Institute of Ophthalmology, London, UK., ⁵the Department of Ophthalmology, Kenyatta National and Teaching hospital, Nairobi, Kenya, ⁶Office Eye, Kyoto, Japan., ⁷Endowed Course for Health System Innovation, Keio University School of Medicine, Tokyo, Japan., ⁸Diagnosys LLC, MA, USA., ⁹Department of Ophthalmology, Saitama Medical University Faculty of Medicine, Iruma-gun, Saitama, Japan., ¹⁰Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan., ¹¹Next Vision, Kobe Eye Center, Hyogo, Japan, ¹²Moorfields Eye Hospital, London, UK

Purpose Electrically evoked response (EER) elicited by trans corneal electrical stimulation (TES) is an objective method to evaluate the visual pathway (Potts, 1968–1970; Miyake, 1980–1984; Takei, 1989–1993). This study aimed to validate EER to predict the efficacy of advanced therapies for diseases with severe photoreceptor damage. The technical studies and preliminary data were presented at ISCEV 2019/2020/2022 annual symposia. We herein describe EERs in patients with retinitis pigmentosa (RP).

Methods Twenty-six eyes of 13 patients with a clinical diagnosis of RP including potentially therapeutic target of RPE65-retinopathy and RPGR-retinopathy were enrolled. EERs were recorded under the dark-adapted condition (after 20 min dark adaptation) using DTL-Fz stimulation, Oz-Pz potential recording at current intensities of 0.5 mA, 1 mA, 1.5 mA, and 2 mA. Two ground electrodes were used: one for the stimulation and one for the recording channels. All tests were conducted using an Espion Profile electrophysiology system (Diagnosys LLC, MA, USA). The presence of EER responses for each component and each stimulus condition was evaluated by two investigators (YFY, KF). A positive peak was defined as a peak measured relative to the preceding trough with an amplitude (> 0.8 µV) (Takei 1988). The sum of EER amplitudes [30–90 ms (P1), 90–150 ms (P2), and 150–210 ms (P3)] was calculated.

Results The median age of disease onset/age at examination of the 13 patients was 16.0 (range 0–41) years/54.5 (37–76) years, respectively. The median visual acuity was 1.0 (− 0.08 to 2.8)/1.0 (− 0.08 to 2.8) in the logarithm of the minimum angle of resolution (LogMAR) unit in the right/left eye, respectively. The full-field ERG responses were undetectable. The presence of positive peaks for 0.5 mA/1.0 mA/1.5 mA/2.0 mA components was identified in 50.0%/43.6%/56.0%/66.7% in the thirteen RP patients. The median value of the sum of EER amplitudes in the 13 RP patients was 2.30 (range 0.56–9.49).

Conclusions The presence of positive responses in EERs was most commonly (> 80%) identified in 13 RP patients. The sum of EER amplitudes, reduced in the RP patients, can be a parameter to evaluate the visual pathway even when full-field ERGs are undetectable. These findings imply that EERs are derived predominantly from residual retinal ganglion cell function in RP patients, which helps in assessing the objective function in patients with severe photoreceptor damage. Further studies such as comparing EER values with the other clinical parameters would be helpful to delineate the utilities and applications of EERs.

O3-2-3 Assessment of visual function for retinal categorized medicine

Tadao Maeda^1,2, Akiko Maeda¹, Satoshi Yokota¹, Yasuhiko Hirami¹, Masayo Takahashi^1,2, Yasuo Kurimoto¹

¹Kobe City Eye Hospital, Japan, ²Vision Care Cell Therapy Inc., Japan

Purpose Clinical applications of categorized medicine, including cell transplantation and gene therapy targeting the outer or inner layer of the retina, are being attempted as new treatments for retinal degenerative diseases for which no cure has been established. Functional assessment of both outer and inner layers of the retina is required to ensure the appropriate selection of these future treatments. In this study, we evaluated the residual function of the outer and inner layers of the retina in patients with retinal degenerative disease and reported its usefulness.

Methods We tested 67 patuents with retinal degeneration (RD) (29 cases of retinitis pigmentosa (RP) and 38 cases of RD with retinal pigment epithelium (RPE) impairment (e.g., age-related macular degenerations and crystalline retinopathy etc.); mean age 65 years, range 29–95; female 31, male 36. Electrically evoked potentials (EER) were used to evaluate inner retinal layer function, full-field stimulus threshold measurement (FST) was used to evaluate outer layer function, and pupil diameter measurement (PM) was used to evaluate both outer and inner layers (melanopsin response).

Results EER was tested in 28 cases of RP and 22 cases of RD with RPE impairment. EER amplitude was markedly decreased, making it difficult to measure, and phosphenes were positive in 11/56 eyes, whereas EER amplitude was measurable in 36/44 eyes with 1.33 ± 1.35 µV of averaged amplitude and phosphenes were positive in 27/44 eyes in RD with RPE impairment. FST was tested in 22 cases of RP and 25 cases of RD with RPE impairment. The estimated threshold for blue light stimulation was − 3.67 ± 19.47 dB, and the estimated threshold for red light stimulation was 5.00 ± 11.37 dB in RP. On the other hand, that for blue light stimulation was − 41.26 ± 17.12 dB, and that for red light stimulation was − 21.13 ± 10.20 dB in RD with RPE impairment. That of RP was significantly decreased compared to those of RD with RPE impairment (Mann–Whitney Rank Sum Test: p < 0.001). PM was tested in 25 cases of RP and 17 cases of RD with RPE impairment. In RP, the response to the weak blue light stimulus was observed in 19/50 eyes (miotic width 0.08 ± 0.19 mm), to the red light stimulus in 47/50 eyes (miotic width 0.97 ± 0.60 mm), and to the strong blue light stimulus in 47/50 eyes (miosis width 1.41 ± 0.54 mm). On the other hand, in RD with RPE impairment, response to the weak blue light stimulus was observed in 34/34 eyes (miosis width 1.26 ± 0.47 mm), to the red light stimulus in 33/34 eyes (miosis width 1.38 ± 0.62 mm), and to the strong blue light stimulus in 33/34 eyes (miosis width: 1.83 ± 1.42 mm).

Conclusions Assessment of retinal function by EER, FST, and PM showed deterioration in RP cases, whereas functional maintenance was observed in some cases of RD with RPE impairment. The usefulness of these tests in assessing residual inner and outer retinal function for retinal degenerative diseases was demonstrated.

O3-2-4 The electrically inducible visual field in retinitis pigmentosa

Marten Erik Brelen¹

¹The Chinese University of Hong Kong

Purpose To investigate the size of the electrically inducible visual field in patients with retinitis pigmentosa (RP) using eyelid surface stimulation electrodes.

Methods Five RP patients with no light perception (NPL) vision in both eyes, 10 young normal-sighted subjects (19–28 years old), and 5 control subjects age matched to the RP patients (51–56 years old) were recruited. Pre-gelled self-adhesive electrodes were placed on the upper and lower eyelids of the subjects, and an anode electrode was placed on the contralateral mastoid. An asymmetric charge-balanced rectangular biphasic pulse stimulation (duration range 0.2 ms-28 ms and amplitudes 0.1 mA-24 mA) controlled by a Labview program was used to stimulate the eye electrically. Thresholds for inducing a visual sensation were estimated for each electrode and stimulation duration (the strength-duration curves). Electrical stimulations at 20% above threshold were used to individually stimulate each of the four electrodes in turn whilst the subject mapped the position of the visual sensations inside a modified Goldmann perimeter. Descriptive characteristics of the visual sensation were recorded. All visual sensations were superimposed using Matlab® Image Processing Toolbox, and the total vertical and horizontal extent of the mapped visual sensations was defined as the electrically inducible visual field.

Results The chronaxie and rheobase of the strength duration were 0.28 mA, 3.22 ms respectively, for normal sighted individuals. The threshold for eliciting visual sensations was significantly higher for all electrodes and all stimulation durations in the RP patients as compared to controls (p < 0.01). Visual sensations could not be elicited in one of the RP subjects. For normal sighted subjects, the phosphenes were localized to the same area of the visual field as the electrode position and were described as large diffuse peripherally located flashes of light. Chi-squared test showed a significant difference in the localization of the visual sensation when using different electrode configurations (p < 0.01). When stimulating RP subjects, the mapped phosphenes were smaller and located within the central 30° of the visual field. No peripheral visual sensations could be elicited in the RP subjects. The size and shape of the visual field within which visual sensations could be elicited varied in the RP subjects.

Conclusions Surface eyelid stimulation is known to generate a potential in the inner retina and is a non-invasive method to investigate the extent of inner retinal degeneration. It may be a useful test to determine the remaining viable inner retinal function for RP patients with NPL vision.

O3-2-5 Fundamental and second harmonic of the photopic flicker ERG exhibit stimulus frequency-dependent attenuation in retinitis pigmentosa

Robert Alexander Hyde¹, Jason C. Park¹, J. Jason McAnany¹

¹University of Illinois-Chicago, USA

Purpose Previous flicker ERG studies indicate a temporal frequency-dependent loss of the fundamental (F) and second harmonic (2F) response components in patients with retinitis pigmentosa (RP). However, previous work (Falsini et al., Graefes Arch Clin Exp Ophthalmol 1999;237:193–200) examining 2F amplitude losses was conducted with stimuli restricted to the macula. It is unclear how standard full-field stimulation may affect 2F responses in RP as neural generators are stimulated outside the macula. The purpose of this study was to characterize the temporal frequency dependence of F and 2F responses in patients with RP using full-field flicker stimulation.

Methods All studies were approved by the Institute Review Board. Fifteen patients with a clinical diagnosis of RP and 12 visually normal subjects participated in this study. Pupils were dilated with 1% tropicamide and 0.5% phenylephrine. ERGs were obtained under photopic conditions using DTL corneal electrodes (Diagnosys, LLC). Full-field standard ISCEV ERGs were obtained. In addition, photopic flicker ERGs were recorded across a wide range of temporal stimulus frequencies (7, 11, 15, 20, 32, 41, 62, 83 and 100 Hz).

Results The fundamental amplitude function for the controls showed a minimum near 12 Hz, a maximum near 32 Hz, and a linear decline in log amplitude at frequencies of 45 Hz and higher. The RP patients showed a reduced fundamental amplitude at the clinically relevant frequency of 31 Hz, as well as higher frequencies, with smaller reductions at low temporal frequencies. The second harmonic amplitude functions for the controls and patients were low pass in shape, with abnormalities for the patients that tended to increase with temporal frequency. For 11 Hz, 15 Hz, and 20 Hz, the 2F amplitude loss exceeded the F loss. For the 32-62 Hz range, the amplitude losses for both F and 2F were similar. 2F responses at stimulation frequencies higher than 62 Hz were low in amplitude for RP patients.

Conclusions Consistent with previous work with macular stimulation, we observed temporal frequency-dependent loss of the F and 2F response components in patients with RP. Loss of F amplitude, which is largely generated by bipolar cells, cannot completely account for the 2F loss, which likely has additional contributions from spiking neurons.

O4-1 Retinal function in HARS syndrome: A 3-year clinical trial of oral histidine supplementation in an extended Amish kindred

Daphne L. McCulloch¹, H. Albuhayzah¹, J. Andrews², R. Chakrabarti², A. Chowdhury², N. Hutchings¹, S. J. Leat¹, R. McCaughey¹, C. Parker², E. Reesor², C. A. Rupar^2,3, V. M. Siu^2,3

¹School of Optometry and Vision Science, University of Waterloo, Waterloo, ON,Canada, ²London Health Sciences Centre, London, ON, Canada, ³Children’s Health Research Institute and Division of Medical Genetics, Department of Pediatrics, Western University, London, ON, Canada

Purpose Aminoacyl tRNA synthetases are ubiquitous enzymes essential in protein translation. HARS syndrome is an autosomal recessive disorder caused by homozygous mutation in histidyl tRNA synthetase (HARS c.1361A>C, Y454S), prevalent in the Old Order Amish population in Ontario, Canada. This condition, originally described as Usher syndrome type 3B, is characterized by progressive retinopathy and hearing loss necessitating cochlear implants. There is an increased susceptibility to life threatening febrile illnesses triggered by viral or bacterial infections, with acute respiratory distress syndrome, sudden deterioration in hearing and vision, visual hallucinations, and ataxia. While vision can improve after an acute episode, the natural history is one of progressive vision loss. Based on in vitro studies, we hypothesised that supplemental oral histidine would ameliorate the symptoms and progression. We report on the impact on retinal function after a 3-year clinical trial of histidine supplementation.

Methods Fourteen participants (age 12 months to 17 years) with HARS syndrome were enrolled to receive supplemental oral histidine (50 mg/kg twice daily). Participants received comprehensive assessments including physical, neurological, hearing, and vision at baseline and had vision assessments with ocular coherence tomography and full-field ISCEV Standard dark- and light-adapted ERGs after 6 months, 12 months, and 36 months of treatment. ERGs were recorded using DTL fibre electrodes (Colordome® & Espion E3, Diagnosis LLC) or with Sensorstrip® skin electrodes in participants under 5 years of age (RetEVAL®, LKC Technologies).

Results ERGs at baseline ranged from mild abnormalities in younger children to severe amplitude reductions in the older participants with a history of acute vision loss associated with viral illness. In all cases, light-adapted 3.0 and 30 Hz flicker ERGs were more affected than dark-adapted ERGs. A-waves were relatively preserved compared with b-waves. After 3 years, all ERG waveforms were preserved; some showed larger amplitudes, but the study is not powered to distinguish between treatment effects and age-related gains (retinal maturation and test compliance).

There have been no adverse effects of histidine. Hearing also stabilised during the trial and no participant experienced a severe febrile episode with deterioration during the trial, despite documented infection with SARS-CoV-2 in 9 of the 14 children.

Conclusions HARS retinopathy is characterised by a wide range of severity that may consist of an underlying dystrophy particularly affecting the on-bipolar cell function, in combination with susceptibility to possible inflammatory retinitis and its sequelae. The retinopathy and other features of HARS (c.1361A>C, Y454S) differ from those of Usher syndrome. We propose naming the condition “HARS syndrome–Amish type”. While the long-term impact of oral histidine supplementation in HARS syndrome is not established, we recommend this treatment which we associate with stabilisation of health, hearing, and vision over a 3-year period.

O4-2 Retinal dystrophins and the retinopathy of Duchenne muscular dystrophy

Mirella Barboni^1,5, Anneka Joachimsthaler^2,3, Michel Roux⁴, Zoltan Zsolt Nagy¹, Dora Fix Ventura⁵, Alvaro Rendon⁶, Jan Kremers^2,3, Cyrille Vaillend⁷

¹Department of Ophthalmology, Semmelweis University, Budapest, Hungary, ²Section for Retinal Physiology, University Hospital Erlangen, Erlangen, Germany, ³Animal Physiology, Department of Biology, FAU Erlangen-Nurnberg, Erlangen, Germany, ⁴Department of Translational Medicine and Neurogenetics, IGBMC-ICS Phenomin, University of Strasbourg, Illkirch, France, ⁵Department of Experimental Psychology, University of Sao Paulo, Sao Paulo, Brazil, ⁶Sorbonne Universite, INSERM, CNRS, Institut de la Vision, Paris, France, ⁷Universite Paris-Saclay, CNRS, Institut des Neurosciences Paris-Saclay, 91400, Saclay, France

Purpose It has been extensively reported that dystrophin proteins are necessary for retinal integrity and proper visual performance. However, the specific role that each dystrophin plays in the retina is largely unknown. At least four dystrophins are produced in the retina from several internal promoters within the X-linked DMD gene. Duchenne muscular dystrophy (DMD) is the most frequent disease caused by DMD gene mutations and shows high prevalence of ocular symptoms.

Methods During the last years, we investigated retinal pathophysiology and visual abnormalities caused by DMD gene mutations using molecular biology, non-invasive electrophysiology, and psychophysics. The retinal expression of distinct dystrophins and their splice variants has been explored in different mouse models. Regarding non-invasive electrophysiology, we have used ISCEV standards as well as alternative ERG protocols to investigate On- and Off-bipolar cell functions and post-receptoral cone-opponent and luminance retinal pathways. We also studied the potential of gene therapy to rescue ERG abnormalities in DMD mouse models. We performed visual psychophysics to test contrast sensitivity in both DMD patients and mouse models and color vision in DMD patients. Finally, we have performed an extensive literature review and recently published a review focusing on dystrophin expression and the clinical implications of DMD gene mutations (Barboni et al., Prog Retin Eye Res 2022; (in press)).

Results As highlighted in our recent review, dystrophins are required for retinal integrity and visual function, since DMD patients and mouse models of DMD show abnormal ERGs. The DMD-related visual deficits mainly originate at the photoreceptor-bipolar cell synapse causing negative ERGs without severe visual impairment in most patients. However, DMD patients are at higher risk for development of cataract and proliferative retinopathy. The dystrophin-deficient mouse models are useful for preclinical and genotype–phenotype studies and for evaluating the effects of therapeutic intervention.

Conclusions We described the current knowledge on the putative roles of dystrophins in the retina and discussed the remaining caveats and uncertainties in our understanding of the function of retinal dystrophins. DMD patients should undergo periodic ocular examinations for early detection of more severe retinopathies. We hope the current knowledge will contribute to a better understandong of the prospects and challenges for therapeutic strategies to treat visual (and possibly other) symptoms in DMD patients.

O4-3 Clinical and electrophysiologiacal characteristics of patients with adult-onset neuronal intranuclear inclusion disease related retinopathy

Natsuko Nakamura^1,2, Kazushige Tsunoda², Akihiko Mitsutake^3,4, Shota Shibata³, Hiroyuki Ishiura^3,5, Meiko Maeda³, Masashi Hamada³, Wataru Satake³, Shoji Tsuji^3,6, Tatsushi Toda³, Hiromasa Sawamura¹

¹Department of Ophthalmology, The University of Tokyo, Tokyo, Japan, ²Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan, ³Department of Neurology, The University of Tokyo, Tokyo, Japan, ⁴International University of Health and Welfare Mita Hospital, Department of Neurology, ⁵Department of Neurology, Okayama University, Okayama, Japan, ⁶Institute of Medical Genomics, International University of Health and Welfare, Chiba, Japan

Purpose Neuronal intranuclear inclusion disease (NIID) is a slowly progressive neurodegenerative disease which is caused by expansions of the CGG repeats in the 5 UTR of the NOTCH2NLC gene (Ishiura et al., Nature Genet, 2019). Previously, we reported the clinical features of NIID-related retinopathy with rod-cone dysfunction (RCOD) (Nakamura et al., Invest Ophthalmol Vis Sci, 2020). In this study, we describe retinal examination findings including detailed ERGs in Japanese patients with NIID-related retinopathy.

Methods A total of 13 patients (9 women, 4 men; aged 60–81 years) from 12 families diagnosed with NIID using genetic analysis were studied. Ophthalmologic examinations including best-corrected visual acuity (BCVA), Goldmann perimetry (GP), ophthalmoscopy, fundus photography, optical coherence tomography (OCT), fundus autofluorescence (AF) imaging, and full-field ERG were performed.

Results The common ocular symptoms of the 11 symptomatic cases were reduced BCVA, night blindness, and photophobia. The other two cases did not have any ocular symptoms. The decimal BCVA varied from 0.15 to 1.2. The Goldmann visual field was constricted in all 11 cases tested; the physiological blind spot was enlarged in 7 cases. Ophthalmoscopic examinations showed that all 13 cases had chorioretinal atrophy (CRA) in the peripapillary region and mild retinal pigment epithelium (RPE) abnormalities in the posterior pole and midperiphery. The FAF images showed an absence of autofluorescence (AF) around the optic disc in all cases and showed mild hypo-AF or extinguished AF in the posterior pole and midperiphery. In all cases, the OCT images showed an absence of the ellipsoid zone of the photoreceptors in the peripapillary region. The full-field ERG, performed in 12 cases, showed rod-cone (RCOD) or cone-rod dysfunction (CORD).

Conclusions Fundus, FAF, and ERG findings in patients with adult-onset NIID with CGG repeat expansions in the NOTCH2NLC gene were diverse. Similarly, ERG findings were found to present not only RCOD but also CORD. The most common feature was outer retinal layer atrophy in the peripapillary region.

O4-4 Congenital posterior polar chorioretinal hypoplasia: A new disease entity or expansion of the clinical spectrum?

Caroline Atef Tawfik^1,2, Kent W. Small^3,4, Fadi S. Shaya^3,4, Nitin Udar^3,4, Uma Udar^3,4, Jessica Avetisjan^3,4, Lamia A. El-Aidy⁵

¹Ain Shams University, Egypt, ²Watany Eye Hospital, Egypt, ³Macula and Retina Institute, Glendale and Los Angeles, USA, ⁴Molecular Insight Research Foundation, Glendale and Los Angeles, USA ⁵Zagazig University, Egypt

Purpose To describe a new ocular phenotype in a single Egyptian family associated with a heterozygous noncoding mutation in the North Carolina macular dystrophy (NCMD/MCDR1) locus, likely affecting the PRDM13 gene.

Methods Eleven members of a four-generation family underwent comprehensive ophthalmic examination including visual acuity, refraction, fundus imaging, spectral-domain optical coherence tomography, and full-field ERG. Molecular genetic analysis of the MCDR1 region was performed using whole-genome and targeted sequencing. The main outcome measures were DNA sequence variants, clinical, retinal imaging, and ERG findings.

Results The 5 affected adult family members tested carried a single heterozygous mutation in a noncoding region (Chr6:100,046,783A>C) located 7.8 kb upstream of PRDM13. Visual acuity ranged from 20/200 to 20/400. All members had extensive chorioretinal absence/thinning extending outside of the macula with extensive posterior bowing of the choroid and sclera centered in the macula, giving a large macular coloboma-like appearance. Two additional members had cystoid fluid and one had macular detachment. Full-field ERG revealed reduced cone and rod responses in all affected members.

Conclusions The phenotype of this disease falls between the spectrum of progressive bifocal chorioretinal atrophy and NCMD. The findings are most consistent with progressive bifocal chorioretinal atrophy with the exception that there is no bifocal nature to the appearance nor is it a progressive disease. Another view is that the phenotype seems to be an extremely severe form of NCMD. Given that this disease falls in between progressive bifocal chorioretinal atrophy and NCMD, we propose calling it congenital posterior polar chorioretinal hypoplasia.

O4-5 Associations between ERG flicker peak times and parameters of cognitive function in a large adult cohort

Abdus Samad Ansari^1,2, Xiaofan Jiang^1,2,3, Zihe Xu^1,2, Zakariya Jarrar^1,2, Chris J Hammond^1,2, Pirro Hysi^1,2, Omar Mahroo^1,2,3,4

¹Section of Academic Ophthalmology, School of Life Course Sciences, FoLSM, King’s College London, London, UK, ²Department of Twin Research & Genetic Epidemiology, School of Life Course Sciences, FoLSM, King’s College London, London, UK., ³Institute of Ophthalmology, University College London, London, UK, ⁴Moorfields Eye Hospital NHS Foundation Trust, London, London, UK

Purpose Cognitive function is complex and multidimensional. Numerous tests have been developed to quantify different aspects. Cognitive impairment is associated with significant morbidity and mortality, and tests that can identify early cognitive impairment or predict future decline could be of major significance in enabling early intervention. Much work is currently being done exploring retinal structural biomarkers on optical coherence tomography imaging and potential for predicting cognitive impairment. The aim of this study was to explore associations between a quantitative parameter of retinal function (ERG flicker peak time) and cognitive tests in a largely healthy adult cohort.

Methods TwinsUK is a registry, based at St Thomas’ Hospital in London, of several thousand UK-based adult twins, who have volunteered for research studies. Participants were recruited for non-mydriatic photopic 30 Hz flicker ERG recordings made with a portable device and skin electrodes (RETeval, LKC Technologies, Gaithersburg, MD, USA). The device measured pupil diameter and adjusted stimulus strength accordingly to deliver retinal illuminance (85 Td s white stimuli on 850 Td white background) equivalent to that delivered by international standard light-adapted flicker stimuli. Where recordings from both eyes were available, peak times were averaged between eyes. Participants also underwent a range of tests of cognitive function, including the Useful Field of View-selective attention (UFOV), CANTAB-PAL, The Rockwood Frailty index, Contrast Sensitivity, and the Mini Mental State Examination (MMSE). ERG peak times and cognitive test scores were transformed where appropriate. Relationships were investigated using linear mixed models adjusted for age, sex, spherical equivalent, and family structure.

Results ERG recordings were available for 1802 participants (> 90% were female). Mean (SD) age was 54.7 (16.8) years. Mean (SD) flicker peak time was 25.7 (1.3) ms. Linear mixed modeling identified an association with increased peak times and worsening visuospatial cognition measured through the UFOV test (β = − 0.006, p = 0.006), Frailty (β = − 0.0474, p = 0.001) and contrast sensitivity (β = 0.0378, p = 0.001). Significant relationships were seen with age, male sex, and spherical equivalent in all models. No relationship was seen with the MMSE (β = − 0.0004, p = 0.705) and CANTAB-PAL (β = − 0.0005, p = 0.448) cognition measures.

Conclusions In this exploratory study, we found some associations between ERG flicker peak times and certain dimensions of cognitive function. Significance persisted after adjustment for age. We also found differences by sex, which invite further study. Future longitudinal studies will shed light on whether ERG peak times might have utility in predicting future cognitive decline.

O5-1 Percentage of testing performed and sensitivity of electrophysiological tests in the diagnosis of MEWDS: A multicenter study in Japan

Mineo Kondo¹, Wataru Saito², Yoshitsugu Matsui¹, Takayuki Tanaka³, Susumu Ishida³, Kazuki Kuniyoshi⁴, Shinji Ueno⁵, Takaaki Hayashi⁶, Tadashi Nakano⁶, Takuhiro Hayakawa⁷, Kazushige Tsunoda⁷, Hiroshi Keino⁸, Annabelle A. Okada⁸, Kosuke Nakamura⁹, Hideo Akiyama⁹

¹Department of Ophthalmology, Mie University, Japan, ²Department of Ophthalmology, Kaimeidou Eye and Dental Clinic, Japan, ³Department of Ophthalmology, Hokkaido University, Japan, ⁴Department of Ophthalmology, Kindai University, Japan, ⁵Department of Ophthalmology, Hirosaki University, Japan, ⁶Department of Ophthalmology, Jikei University School of Medicine, Japan, ⁷National Institute of Sensory Organs, Japan, ⁸Department of Ophthalmology, Kyorin University, Japan, ⁹Department of Ophthalmology, Gunma University, Japan

Purpose Multiple evanescent white dot syndrome (MEWDS) is a rare inflammatory retinal disease which occurs mainly in young myopic women. The fundus, fluorescein (FA) and indocyanine green (ICG) angiographic, optical coherence tomographic (OCT), and fundus autofluorescence (FAF) findings were used for the diagnosis of MEWDS. Full-field and multifocal electroretinographic tests were also performed. The purpose of this study was to determine the percentage of tests performed and the sensitivity of full-field and multifocal ERGs for the diagnosis of MEWDS in Japan.

Methods Patients diagnosed with MEWDS between 2001 and 2020 at 9 medical institutions in Japan who were followed for at least 3 months after the diagnosis were studied retrospectively. The diagnosis of MEWDS was made by experienced retinal specialists based on the classic findings and published clinical criteria. In addition to the demographic findings, the percentage of tests performed and sensitivity (abnormal/total tested) of the full-field ERGs, multifocal ERGs, OCT, and FAF was investigated.

Results The mean age of the 214 MEWDS patients was 33.3 ± 12.6 years (range 13–70 years); 76% were women. The mean refractive error (spherical equivalent) in the eyes with MEWDS was − 5.86 ± 3.67 D. Full-field ERGs were recorded in 111 of the 214 eyes (51.9%), and abnormal full-field ERGs were found in 52 of these eyes (46.8%). Multifocal ERGs were recorded from 115 of the 214 eyes (53.7%), and abnormal local responses were found in 107 of these 115 eyes (93.0%). OCT was performed in 202 of the 214 eyes (94.4%), and a disruption or irregularity of the ellipsoid zone was seen in 189 of these 202 eyes (93.6%). FAF was performed in 146 eyes of the 214 eyes (68.2%), and multiple hyperfluorescent spots were seen in 135 of these 146 eyes (92.5%).

Conclusions Currently, electrophysiologic tests are used less frequently in the diagnosis of MEWDS probably due to the time-required to perform these procedures. However, the sensitivity of multifocal ERGs was found to be as high as that of OCT and FAF in the diagnosis of MEWDS.

O5-2 Severity of ERG abnormality is associated with visual prognosis in AZOOR patients

Toshiaki Hirakata¹, Fumihiro Hara¹, Yoshimune Hiratsuka¹, Akira Murakami¹, Shintaro Nakao¹

¹Juntendo University Faculty of Medicine, Tokyo, Japan

Purpose Acute zonal occult outer retinopathy (AZOOR) is characterized by the sudden onset of subjective scotomas and photopsia due to outer retinal damage with a normal fundus appearance. Therefore, optical coherence tomography and ERGs are essential examinations for correct diagnosis. Although there have been reports of ERG characteristics in AZOOR patients, few reports have examined the relationship between ERG and visual acuity. Here, we examined the relationship between the electroretinogram and visual acuity prognosis.

Methods This is a retrospective study of AZOOR patients who had a full-field ERG or multifocal ERG (mfERG) performed at Juntendo University Hospital between April 1, 2015 and June 30, 2022. The diagnosis of AZOOR followed published guidelines (Nichigankaishi, 2019). ERGs were performed according to ISCEV standard protocol. The initial full-field ERG was classified into normal, moderately affected, or severely affected (including non-recordable) for the rod and cone responses. The initial mfERG was also classified into normal, moderately affected, and severly affected (including non-recordable), for the foveal and peripheral responses. ERG severity classification was assessed by two ophthalmologists (T.H. and F.H.). The most recent logarithm minimum angle of resolution best-corrected visual acuity (logMAR BCVA) during follow-up was used. Then, the final logMAR BCVA for each group classified by initial ERG severity was compared by statistical analysis with one-way ANOVA and Tukey’s multiple comparison test.

Results Forty-nine cases (9 male, 40 female) and 80 eyes were assessed in this study. The mean logMAR BCVA was 0.23, 0.35, and 0.70; 0.17, 0.26, and 0.60 in normal, moderate, and severely affected rod and cone full-field ERG responses, respectively: 0.19, 0.17, and 0.74; and 0.04, 0.20, and 0.37 in normal, moderate, and severely affected center and peripheral mfERG responses. In a one-way ANOVA, the severity of both cone (p = 0.01) and rod (p = 0.02) responses of the full-field ERG and central foveal response (p < 0.001) of mfERG was associated with final visual outcome. In the full-field ERG, final logMAR BCVA in the normal response group was significantly better than in the severely affected response group in both dark- (p = 0.015) and light-adapted (p = 0.01) conditions. Peripheral area responses of mfERG were associated with no difference in final vision according to mfERG severity. On the other hand, better central response of mfERG was associated with final logMAR BCVA in the normal response group significantly lower than in the severe affected response group (p = 0.003).

Conclusions These data suggest that ERGs are predictive of visual prognosis in AZOOR patients. AZOOR patients with severely affected ERG responses may have a poor visual prognosis and may benefit from early therapeutic intervention. Further study is needed.

O5-3 Antigenic regions for anti-TRPM1 autoantibodies in paraneoplastic retinopathy with retinal ON bipolar cell dysfunction

Shinji Ueno¹, Daichi Gyoten², Takahisa Furukawa²

¹HIrosaki University Department of Ophthalmology, Japan, ²Osaka University Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Japan

Purpose Cancer-associated retinal ON bipolar cell dysfunction (CARBD), which includes melanoma-associated retinopathy (MAR), has been reported to be caused by autoantibodies against the molecules expressed in ON bipolar cells, including TRPM1. The purpose of this study is to determine the antigenic regions of the autoantibodies against TRPM1 in the sera of CARBD patients, in which we previously detected anti-TRPM1 autoantibodies.

Methods Antigenic regions against TRPM1 in the sera from 8 CARBD patients were examined by Western blot using HEK293T cells transfected with the plasmids expressing FLAG-tagged TRPM1 fragments. The clinical course of these patients was also documented.

Results The clinical course differed among the patients. The electroretinograms (ERGs) and symptoms recovered in 3 patients, deteriorated in 1 patient, remained unchanged for a long period in one patient, and were not followed in 3 patients. Sera in 7 of 8 patients possessed multiple antigenic regions: 2 sera contained at least 4 antigen recognition regions, and three sera had at least three regions. The antigen regions were spread over the entire TRPM1 protein: 5 sera in the N-terminal intracellular domain, 6 sera in the transmembrane-containing region, and 6 sera in the C-terminal intracellular domain. No significant relationship was observed between antigen epitope localization and the patients’ clinical course.

Conclusions Antigenic regions of anti-TRPM1 autoantibodies in CARBD patients were present not only in the N-terminal intracellular domain, which was reported in the previous report (Xiong et al., PloS One 2013;8:e69506), but also in the transmembrane-containing region and the C-terminal intracellular domain. In addition, the antigenic regions for TRPM1 were found to vary among the CARBD patients examined, and most of the sera had multiple antigenic regions.

O5-4 Electroretinogram in a leukemia patient developing bilateral progressive blindness: A case report

Cheng-Yung Lee¹, Chao-Wen Lin¹, Chang-Hao Yang¹, Yi-Ting Hsieh¹

¹National Taiwan University Hospital, Taiwan

Purpose Retinal pathologies in leukemic retinopathy rarely cause severe visual loss. However, profound visual deterioration due to central retinal artery occlusion (CRAO) or optic nerve infiltration has been reported in patients with leukemia. Precise diagnosis of the underlying causes for vision loss in patients with leukemia is sometimes challenging. Electrophysiological tests are useful in evaluating the etiology of vision loss even before structural change becomes clinically evident.

Methods We present a case with acute myeloid leukemia. The 63-year-old female patient reported sudden onset, bilateral, rapidly progressed visual loss at the end of first-round chemotherapy, when there were thrombocytopenia, neutropenia, and absence of blast cells with little chance of hemostasis.

Results The vision in both eyes deteriorated from ambulatory vision to light perception in 1 week. Initial dilated fundus examination, optical coherence tomography, and fluorescence angiography results were uncharacteristic for leukemic retinopathy, without photoreceptor disruption or inner retina edema. Profound loss of both the a-wave and b-wave in both scotopic and photopic electroretinogram (ERG) led to the suspicion of cancer associated retinopathy (CAR). The test result for anti-recoverin autoantibody was, however, negative. Serial dilated fundus evaluation also revealed gradual arterial and venous sheathing and disc pallor, which was incompatible with the disease course of CAR. Moreover, the nearly extinguished cone-specific 30 Hz flicker in ERG also made CAR unlikely, because CAR is characterized by relative preservation of the cone pathway. With the absence of the ERG a-wave, CRAO alone was also excluded. Careful review of the ERG and the clinical findings led to the suggestion of severe inner and outer retinal ischemia caused by concurrent bilateral CRAO and short posterior ciliary artery occlusion or bilateral ophthalmic artery occlusion. Rheumatological survey and repeated MRI in search for vasculitis or an organic lesion did not reveal any relevant findings. Aspirin and serial hyperbaric oxygen therapy were administered in attempt to restore the ocular circulation without success. Later examinations showed severe retinal thinning, profound disruption of photoreceptors, and extinguished ERG signals. The patient also developed hearing loss later, and inner ear circulation compromise was suggested by the otologist.

Conclusions In cases with malignancy, several visual-threatening retinal pathologies may present. In common scenarios, structural abnormalities usually accompany visual complaint. However, in atypical cases, the fundus may remain structurally intact at the early stage when visual loss has already developed. In these cases, electrophysiological tests can play an important role for timely diagnosis. Though profound ocular arterial occlusion has been reported in patients with active acute leukemia as a complication of high tumor load, it has never been reported in leukemia patients at the end of treatment, when tumor load and blood viscosity are very low. ERG in this highly atypical case provided invaluable aid to differentiate the underlying pathogenesis.

O5-5 Evaluation of changes due to hydroxychloroquine on retinal electrical activity using multifocal ERG: A retrospective study

Savitha Arun¹, Sri Ganesh¹, Rahul Roy², Kamal Thakur², J. Sachin Singh², Deepa G. K¹, Noor Zainab²

¹Nethradhama Super Speciality Eye Hospital, Bangalore, India, ²Nethradhama School of Optometry, Rguhs, Bangalore, India

Purpose To investigate the effect of hydroxychloroquine on retinal electrical activity using multifocal ERG (mfERG).

Methods A hospital-based, retrospective study was done on 55 patients who were referred for screening of hydroxychloroquine (HCQ) drug toxicity between 2018 and 2022. Data were collected on demographics, medical history, ocular history, ocular findings, visual acuity, and mfERG. A control group of 29 subjects without retinal disease and not on HCQ were selected and mfERG was performed.

Results MfERGs were recorded from 110 eyes of 55 subjects taking HCQ, with a mean age of 57.92 ± 12.26 years, and 58 eyes of 29 subjects in the control group. The Ring 1 P1 response densities were significantly lower in HCQ patients compared to the control group (P < 0.001). The Ring 2 P1 response densities and amplitude were also statistically significantly lower in the HCQ group compared to the control group (P < 0.001).

Conclusions The mfERG is an excellent tool for the early detection of HCQ drug toxicity. MfERG demonstrated depression of signals in the parafoveal and central region in patients with HCQ use. MfERG may be very useful tool in the early identification of maculopathy even in asymptomatic patients without fundus changes.

O5-6 Transient increase of flicker electroretinography amplitudes after cataract surgery: Association with postoperative inflammation

Kumiko Kato¹, Ryunosuke Nagashima¹, Hisashi Matsubara¹, Kengo Ikesugi¹, Hideyuki Tsukitome¹, Yoshitsugu Matsui¹, Takayasu Nunome¹, Masahiko Sugimoto¹, Daphne McCulloch¹, Mineo Kondo¹

¹Department of Ophthalmology, Mie University Graduate School of Medicine, Japan

Purpose To determine the characteristics and cause of the increase in the amplitude of the flicker electroretinogram (ERG) after cataract surgery.

Methods This was a prospective, observational clinical study. We studied 30 patients who underwent cataract surgery. Flicker ERGs were recorded with the RETeval system without mydriasis. Central macular thickness (CMT) was measured by optical coherence tomography, and the aqueous flare value (AFV) was measured by laser flare-cell photometry. These examinations were performed before the surgery and 1 day, 1 week, 1 month, 2 months, and 3 months after surgery. Linear regression analysis was used to compare the correlations between the relative changes in the flicker ERG amplitudes and the changes in the CMT and the AFV at different times after surgery.

Results The mean amplitude of the flicker ERGs increased significantly by 31% at 1 week after surgery (P < 0.001). The significant increase in the amplitudes was not present at 3 months after surgery. The mean AFV was significantly increased at 1 day after surgery (P < 0.001), and the CMT was significantly increased at 1–3 months after surgery (P < 0.001). The change in the flicker ERG amplitude at 1 week after surgery was significantly associated with the change in CMT at 1–3 months after surgery (P < 0.05) and was weakly associated with the change in AFV at 1 day after surgery (P = 0.05).

Conclusions These results suggest that the increase in amplitude of the flicker ERG after cataract surgery is a transient phenomenon that peaks at 1 week after the surgery. The increase in flicker ERG amplitude was associated with measures that are frequently used to evaluate postoperative inflammation.

O6-1 Studying the origins of the supernormal b-wave in cone dystrophy with supernormal rod response

Yashvi Bhatt^1,2, Livia Carvalho^1,2, David Hunt^1,2

¹University of Western Australia, Australia, ²Lions Eye Institute, Australia

Purpose Cone dystrophy with supernormal rod-response (CDSRR) is an inherited condition leading to complete blindness. CDSRR is caused by mutations within the KCVN2 gene, which encodes for the voltage-gated potassium (Kv) subunit Kv8.2. Kv8.2 pairs with the Kv2.1 subunit to form a functional heterotetrameric potassium channel. The diagnosis of CDSRR is confirmed through ERG, as CDSRR patients exhibit a unique phenotype called a supernormal b-wave response. This study utilised wildtype (WT), Kv8.2 knockout (KO), and Kv2.1 KO mouse models to probe the origins of this supernormal b-wave and how it relates to CDSRR.

Methods Five different drugs, LAP-4, BaCl2, TEA, guangxitoxin-1E, and stromatoxin, were used to modulate the b-wave temporarily. Drugs were administered directly into the eye of 6–8 I28week old WT and Kv KO mouse models, followed by ERG recordings 16–24 h later.

Results LAP-4 and TEA significantly affected the b-wave amplitude in all mouse models. BaCl2 decreased b-wave amplitude in Kv2.1 KO and WT (only at lower light intensities). The application of guangxitoxin-1E and stromatoxin did affect WT and Kv8.2 KO retinas but did not affect Kv2.1 KO.

Conclusions The results show that both bipolar cells and Muller glia contribute to the supernormal b-wave, suggesting that the absence of Kv8.2 gives rise to an altered K⁺ flux that affects both cell types. While the Kv channels play a role in generating the supernormal b-wave, further exploration is needed into the contribution of homotetrameric Kv2.1 channels to this unique phenotype.

O6-2 Novel methods for the study of cone pathophysiology in the Mongolian gerbil model

Alexander Guenter¹, Regine L. Muehlfriedel¹, Mathias W. Seeliger¹

¹Institute for Ophthalmic Research, Universitaetsklinikum Tuebingen (UKT), Germany

Purpose The cone system mediates high-acuity and color vision, and any deficiency in retinal cone function is therefore very disabling. Inferences from research in mice on human diseases affecting the cone system may be limited due to their nocturnal lifestyle, including several differences in retinal organization. Recently, we have presented basic data on the Mongolian gerbil model that features a more human-like morphology and functionality of the cone system. Here, we extend this work by novel methods to explore cone-related retinal function with a focus on the ON/OFF ERG and the high-frequency flicker response, and propose alternative ERG recording protocols for this diurnal rodent model.

Methods Data from young adult Mongolian gerbils (2–3 months postnatally) were obtained. Full-field ERG was performed including dark- and light-adapted single flash series with increasing intensities. Additionally, scotopic and photopic flicker series ranging from 0.5 to 60 Hz were recorded. Photopic series were done with 30 cd/m² or 3 cd/m² rod-suppressive backgrounds. In addition, photopic long flash ERGs were acquired to reveal retinal ON and OFF responses. Complementary morphological data were obtained in vivo via scanning-laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) imaging, and in vitro using stainings of histological sections.

Results Cone system-driven single flash responses of the Mongolian gerbils were generally larger than those in mice. This finding also extended to much larger flicker ERG amplitudes and an increased flicker fusion frequency (FFF) up to about 60 Hz in comparison to the 30 Hz typically found in mice. Further, Mongolian gerbils presented clear OFF responses, rarely observed in mice. Due to the increased sensitivity found, a reduced 3 cd/m² background was additionally tested regarding a potential reduction of photopic hill-related phenomena. While this background was still effectively rod-suppressing, there was no major improvement of the outcome of the cone-related ERG detected. Regarding retinal morphology, in vivo and in vitro imaging of the Mongolian gerbil retina confirmed the presence of a visual streak dorsal to the optic nerve head.

Conclusions In Mongolian gerbils, the visual streak analogous to the human macula is a hallmark of the morphological adaptation of the retina to a diurnal lifestyle. Regarding function, the difference between murine and gerbil data was most obvious in cone system-dependent conditions indicated by larger b-wave amplitudes. In the flicker recordings, the ranges described in Tanimoto et al. (Sci Rep: 2015;5:10731) appeared to extend to a widened frequency range in Mongolian gerbils, while cone OFF-pathway activity begins to dominate the flicker ERG above 15 Hz in mice; this threshold appears to be shifted to 30–40 Hz in gerbils. The combination of a more human-like retinal morphology, a much more distinct functional separation of the ON/OFF responses, and in particular the better flicker performance of the cone-system, makes the Mongolian gerbil a superior rodent model to investigate cone system physiology, pathophysiology, and potential therapeutic strategies.

O6-3 Effect of flicker-induced retinal stimulation on full-field electroretinography in mice

Milan Rai^1,2, Yamunadevi Lakshmanan³, Henry Ho-Lung Chan^1,2,3,4

¹School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China, ²Laboratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China, ³Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China, ⁴Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong, China

Purpose Flickering light stimulation has been found to increase retinal blood flow in response to increased metabolic demands of retinal neurons, but the effect of flickering light exposure on full-field electroretinography (ffERG) remains unclear. The purpose of this study was to investigate electrical activity of the retina by ffERG following flickering light stimulation in mice.

Methods Four experimental groups of C57BL/6 J mice (age 8–10 weeks) were used. Three groups (n = 6 per group) were stimulated under 3 levels of flickering light with 2 intensity levels; 1 group was used as a control (n = 6). After overnight dark adaptation (> 12 h), anesthetized mice were light adapted at 1 cd/m² for 10 min. Baseline ffERG was recorded, which was followed by a 60 s washout period to eliminate the aftereffect of light flashes. After the washout period, the 3 experimental groups were stimulated with either 8-Hz, 12-Hz, or 16-Hz flickering light of 0.1 cd.s/m² for 160 s. This was immediately followed by ffERG recording, which was followed by a resting period of 300 s. After the resting period, another set of pre- and post-flicker ffERG was recorded following similar procedures, except that the flickering light intensity was doubled (0.2 cd.s/m²). FfERG was recorded following similar procedures in the control group without flickering light stimulation.

Results At 0.1 cd.s/m², 12-Hz flickering light was found to induce the greatest percentage increase in b-wave amplitude, compared to 8 Hz and 16 Hz flickering light (8 Hz: 5.81% ± 1.31%, p < 0.05; 12 Hz: 8.48% ± 2.29%, p < 0.01; 16 Hz: 7.63% ± 3.11%, p < 0.05). At 0.2 cd.s/m², the greatest percentage increases in b-wave amplitude were found after 8 Hz flickering light stimulation, compared to 12 Hz and 16 Hz flickering light (8 Hz: 7.51% ± 1.86%, p < 0.05; 12 Hz: 4.31% ± 1.73%, p < 0.05; 16 Hz: 1.07% ± 2.69%, p > 0.05). However, none of the flickering lights had a significant effect on the b-wave implicit time, a-wave and a-wave implicit time. There were no significant changes in ERG responses at different time points in the control group.

Conclusions Our findings suggested that retinal stimulation by flickering light enhances the ERG responses originating from the middle retinal layer, primarily from bipolar cells, but does not have a significant effect on responses originating from the photoreceptor cells. Different flickering light frequencies and light intensities would have different effects on retino-electrical activity, which may be associated with flicker-induced hyperemia.

O6-4 Developmental changes in visual electrophysiologic correlates of intra-uterine exposure to Zika virus in a non-human primate model

James N Ver Hoeve¹, Charlene BY Kim¹, Nick Krabbe², Elaina Razo², T Michael Nork¹, Carol Rasmussen¹, Alex Katz¹, Karla Ausderau³, Emma Mohr²

¹University of Wisconsin-Madison Department of Ophthalmology and Visual Sciences, USA, ²University of Wisconsin-Madison Department of Pediatrics, USA, ³University of Wisconsin-Madison Department of Kinesiology, USA

Purpose To describe developmental changes in the ERG and flash visual evoked potential (FVEP) over the first year of life in monkeys with intra-uterine Zika virus exposure (ZVE).

Methods Pregnant rhesus macaques were inoculated with Zika virus from Puerto Rico or Africa during the first trimester. Cesarean-delivered ZVE infants were compared with sham-injected controls. Infant assessments included: neurobehavioral evaluation, ophthalmic examinations (OE), optical coherence tomography (OCT) of the anterior and posterior retinal segments, auditory evoked potentials, ERG, and FVEP. Additional details have been previously described (Koenig et al., PLOSOne 2020). Functional assessment included several classes of tests: photopic and scotopic ERG v. flash intensity series, monocular FVEP, and 30 Hz flicker. Predictor variables included standard a- and b-wave measures, Naka-Rushton (N-R) fits, and FFT harmonics of flicker ERG and oscillatory potentials (OPs). Logistic regression was used to assess the relationship between electrophysiologic measures and the probability of ZVE. Models using variables to predict exposure were evaluated within and across classes of electrophysiologic tests at postnatal ages of 45, 90, and 360 days.

Results Over the first postnatal year, marked changes occurred in ERG and FVEP waveform shape, amplitude, and implicit time in both control and ZVE infants. Striking developmental changes were evident in b-wave implicit time in the photopic intensity series. Logistic regression models showed that at 45 days of age (12 controls, 14 exposed), the likelihood of ZVE was higher in individuals with larger photopic a-wave amplitudes and longer implicit times. At 90 days of age (15 controls, 27 exposed), amplitude of the photopic b-wave, photopic negative response, and FVEP predicted ZVE. At 360 days (18 controls, 26 exposed), predictor variables from several test classes were constructed that significantly predicted ZVE. No clear abnormalities in OE or OCT were evident in ZVE infants.

Conclusions Although no structural abnormalities were noted in OCT imaging or OE, non-invasive functional measures were found that predicted ZVE status at each age. This suggests there are early and long-term sub-clinical changes in the retina and central visual pathways of ZVE infants. However, identifying visual electrophysiologic markers for ZVE necessitates comparing ZVE infants with a relatively large group of closely age-matched controls.

O6-5 Impulse response functions obtained from white noise ERGs in mice

Jan Kremers¹, Nina Stallwitz¹, Anneka Joachimsthaler¹

¹University Hospital Erlangen, Gemany

Purpose White noise ERGs (wnERGs) elicited by luminance modulating and single opsin isolating temporal white noise (TWN) stimuli can be used to obtain impulse response functions (IRFs). Components of these IRFs can be compared with flash ERGs.

Methods Mice that express a human long-wavelength sensitive L-Opsin instead of the murine M-Opsin were dark adapted overnight and all further handling was performed under dim red light. TWN stimuli contained all frequencies up to 20 Hz with equal amplitude and random phase. WnERGs were recorded to luminance (100% contrast) modulation with photopigment isolation (using the silent substitution method; 52% rod-contrast, 48% L-cone contrast, 77% S-cone contrast). Recordings of the anesthetized animals were performed at different mean luminances (MLs) between − 0.7 and 1.1 log cd/m² (luminance stimuli) and between − 0.8 and 1.0 log cd/m² (photopigment isolating stimuli). The cross-correlations between the wnERGs and the TWN stimuli resulted in the luminance or pigment-isolating IRFs. These were compared with flash ERGs.

Results The luminance and pigment isolating IRFs superficially resembled flash ERGs with an a-wave-like N1 component and a b-wave-like P1 component. The amplitudes of the N1 components in IRFs elicited by luminance stimuli increased with increasing ML, whereas the amplitude of the P1 component was minimal at a ML of − 0.4 log cd/m². The peak times of the two decreased monotonically with increasing ML. S-pigment-driven IRFs were recordable only at the highest ML (1.0 log cd/m²). L-cone-driven IRFs were recordable for MLs above − 0.2 log cd/m² and the amplitudes of the N1 and P1 increased with increasing ML, whereas their peak times decreased. N1 and P1 components of rhodopsin-driven IRFs were largest at the lowest ML (− 0.8 log cd/m²). Their peak times were larger than those of cone-pigment driven IRFs. Responses resembling oscillatory potentials were absent in all IRFs. IRFs to luminance and particularly to rhodopsin-isolating stimuli showed a pronounced late negativity (N2) at MLs below − 0.2 log cd/m².

Conclusions IRFs have N1 and P1 components with properties that resemble those of the a- and b-waves in flash ERGs. Flashes are delivered upon a background so that the ML is changed with increasing flash strength. TWN stimuli are modulated around a ML so that ML and stimulus strength are independent. The absence of OPs in IRFs indicates that they are the result of a strong nonlinearity in the flash-ERGs elicited by the unnatural compression of energy in a short time. The N2 component possibly reflects rod-driven ganglion cell activity.

O7-1 Retinal horizontal cell dysfunction in patients

Mary A. Johnson¹, Amanda Henderson², Arthur Shapiro³

¹University of Maryland, Baltimore, USA, ²Johns Hopkins University, USA, ³American University, USA

Purpose We previously have described an ERG protocol that reflects retinal horizontal cell (HC) function. The protocol, which captures changes in adaptive gain control, was validated in a horizontal cell-deficient knock-out mouse and shown to be abnormal in rats with experimental traumatic brain injury (TBI). Herein, we describe results of HC testing in patients having a variety of diagnoses. Psychophysical measures of adaptation in patients with traumatic brain injury are also presented.

Methods The ERG protocol consists of taking the ratio of b-wave amplitudes obtained by flashing a bright light (0.50 log cd.s/m²) on a dim background (1 cd/m²) to flashing a light of the same luminance (0.50 log cd.s/m²) onto a bright background (30 cd/m²). Dark-adapted psychophysical increment thresholds were measured on backgrounds of different luminance (Aguilar and Stiles, Optica Acta: Int. J. of Optics 1954; 1: 59–65) in patients with TBI and in normal subjects, and the slope of the linear segment of the function (the Weber fraction) was calculated. Brightness discrimination on 3 different background levels was measured using maximum likelihood difference scaling.

Results Although the difference in ERG background levels varies by a factor of 30, the mean ratio of the ERG recorded on the dim background to the ERG recorded on the bright background is only 1.3 in normal rats and humans. Patients with TBI, with rod dystrophies, with birdshot chorioretinopathy, or who were taking the antiepileptic drug vigabatrin, however, showed elevated ratios (reduced HC function), unlike patients with a variety of other conditions including cone dystrophy, Stargardt’s disease, MEWDS, concomitant rod-cone dystrophy, and chronic open angle glaucoma along with other optic neuropathies. Patients with TBI showed different patterns of brightness discriminability than did normal subjects, suggesting differences in their observer response functions.

Conclusions The ERG and psychophysical data in patients with traumatic brain injury suggest differences in adaptive gain control. A leading candidate for this effect is the retinal horizontal cell, which we previously have shown to be preferentially affected in experimental TBI and which is known to adjust the level of rod and cone output so that the signal is in the appropriate range for the next level of retinal processing.

O7-2 Scotopic retinal function assessed by electroretinography and pupillometry in individuals with mild or no diabetic retinopathy

Jason Park¹, J. Jason McAnany¹

¹University of Illinois at Chicago, USA

Purpose Although diabetes affects retinal function, the nature and extent of neural abnormalities under scotopic conditions remain incompletely understood. The purpose of this study was to measure dark-adapted flash ERGs and pupil responses to assess photoreceptor and post-receptor function in diabetics who have mild or no clinically-apparent retinopathy.

Methods Eleven diabetic patients with no DR (NDR), 11 patients with mild NPDR (MDR), and 11 normal control subjects participated. After dark adaptation, full-field scotopic ERG and pupillary light reflex (PLR) measurements were obtained. Achromatic flashes (luminance range: − 4 to 1 log phot cd.s/m² and long-wavelength flashes (642 nm; − 4 to 2.6 log phot cd/m²) were used for ERG and pupillometry, respectively. The a-wave, b-wave, and pupil response amplitudes were measured according to convention. The b-wave amplitudes and normalized pupil diameters were fit with Naka-Rushton functions to obtain: 1) Vmax (the maximum b-wave), Pmax (the maximum pupil response), 3) kb (b-wave sensitivity), and 4) kp (pupil response sensitivity).

Results The mean a-wave was reduced by 0.13 log units in the NDR group and 0.19 log units in the MDR group compared to the controls, which was statistically significant (F = 3.43, p < 0.05). Vmax was reduced by 0.11 log units in the NDR and 0.10 log units in the MDR groups compared to the controls, which was not statistically significant (F = 1.84, p = 0.18). kb was reduced by 0.11 log units in the NDR and 0.12 log units in the MDR groups compared to the controls, which was not statistically significant (F = 0.98, p = 0.39). Pmax was reduced by 0.01 log units in the NDR and 0.08 log units in the MDR groups compared to the controls, which was significant (F = 5.97, p = 0.01). Kp was reduced by 0.77 log units in the NDR and 0.25 log units in the MDR groups compared to the controls, which was statistically significant (F = 6.48, p = 0.01). For the diabetic subjects, neither Vmax and Pmax (r = 0.16, p = 0.51) nor kb and Kb (r = 0.39, p = 0.09) were correlated significantly.

Conclusions The modest reductions in b-wave amplitude and sensitivity observed in this group of diabetic subjects could be accounted for by the similarly modest reduction in a-wave amplitude. By contrast, there was a substantial loss of pupil response sensitivity, which suggests that additional sites of abnormality beyond the photoreceptors contribute to pupil response abnormalities in diabetics.

O7-3 Assessing functional damage with rapid and objective macular multifocal perimetry in type 1 diabetes

Ted Maddess¹, Emilie M F Rohan¹, Corinne F Carle¹, Joshua P van Kleef¹, Faran Sabeti^1,3, Christopher J Nolan^1,2, Bhim Rai^1,2

¹Australian National University, Australia, ²The Canberra Hospital, ACT Health, Australia, ³University of Canberra, School of Optometry, Australia

Purpose A growing body of evidence indicates that neuropathy and functional changes may precede classical vasculopathy in diabetes, and with rising diabetes cases,¹ we need rapid diagnostic techniques capable of detecting functional changes. Here we compare diagnostic performance of 3 variants of multifocal pupillographic objective perimetry (mfPOP) and OCT retinal thickness in young persons with type 1 diabetes (T1D).

Methods We recruited T1D patients with normal retinal photographs and visual acuity, and age- and sex-matched controls. The 3 mfPOP tests comprised a published 7-min test², P131, and two new 82-s tests, M18 and W20. P131 tested 44 regions/eye extending ± 15° from fixation. M18 and W20 tested 18 and 20 regions/eye extending to ± 10° and ± 30°, respectively. All tests assessed both eyes concurrently. Each visual-field region produced a sensitivity and a response delay. Per-region combined scores derived from pooled sensitivities and delays were also investigated. Effect sizes were measured using Hedge’s g. Partitioning subjects at 13 years provided groups with 5.03 ± 3.08 and 9.26 ± 3.43 years since diabetes onset.

Results Thirty-five patients (16 females) aged 14.9 ± 3.65 years, 19 controls aged 20.8 ± 2.30 years for P131, and 20 controls aged 20.7 ± 3.97 years for W20 and M18 were recruited. For the combined-scores, all 3 methods produced effect sizes > 2 (Huge). Receiver operating characteristic (ROC) plot areas under the curve (AUC) for M18 and W20 were between 91.7 ± 2.12% and 96.2 ± 1.89%, while P131 achieved values up to 98.0 ± 1.32%. When analysed separately, per-region delays produced better performance than per-region sensitivities. The older subjects had the greatest sensitivity changes providing Hedge’s g values of 0.79–0.87 (Large). ETDRS-grid retinal thickness and volume data produced g ≤ 0.71.

Conclusions The present results in clinically normal retina suggest that the new tests may play a role in management with drugs like fenofibrate and candesartan. The M18 stimulus provides easy structure/function comparisons with standard measures from OCT³.

References

1. Saeedi P et al.Diabetes Res Clin Pract 2019;157:107843.

2. Rai BB et al. Transl Vis Sci Technol 2021;10(13):32.

3. Rai BB et al. Ophthalmol Sci. 2022;2(2):1–9.I33.

O7-4 Correlation between OCT-angiography and multifocal electroretinogram in patients with poor visual acuity after resolution of diabetic macular edema

Marwa Abdelshafy Tabl¹, Mohamed Abdelzaher Awaad¹, Mohamed Nagy¹, Ahmed Abdelshafy Tabl¹

¹Ophthalmology, Benha University, Egypt

Purpose To assess the correlation between functional changes in multifocal electroretinogram (mfERG) and vascular changes in OCT angiography in patients with poor visual acuity (VA) after resolution of diabetic macular edema (DME).

Methods This observational case–control cohort study included 20 eyes of diabetic patients with resolved DME who were treated with multiple intravitreal injection and with normal central macular thickness (CMT) but with poor visual acuity (VA) (group 1) and 20 eyes of aged-matched diabetic patients without maculopathy (no-DME eyes; group 2). Quantitative OCT-A parameters, such as the foveal avascular zone (FAZ) area, the superficial capillary plexus vessel density (SCP-VD%), and the deep capillary plexus vessel density (DCP-VD %), were measured. The mfERG amplitude and implicit times of the N1 and P1 waves were evaluated in all participants.

Results There were no statistically significant differences between groups regarding age, gender, refraction, or intraocular pressure. The median (IQR) FAZ area was greater in group 1 compared to group 2. There was a significant correlation between increasing FAZ diameter and increasing implicit time of the innermost concentric rings. The median (IQR) vessel density in the superficial and deep capillary plexus was significantly decreased in group 1 compared with group 2 (33.4 versus 41.1, P = 0.001 and 35.9 versus 44.9, P < 0.001, respectively), whereas no significant difference in mean CMT was observed (259.8 ± 43 μm versus 260.7 ± 11 μm, P = 0.75). There was a significant positive correlation between BCVA (logMAR) with the FAZ area (r = 0.98, P < 0.001) and mfERG P1 amplitude (r = 0.97, P < 0.001). There was a significant negative correlation between BCVA (logMAR) with the SCP-VD (r = − 0.95, P < 0.0001), DCP-VD (r = − 0.96, P < 0.0001) and mf-ERG p1 implicit time (r = − 0.94, P < 0.0001) in group 1. According to the correlation analysis, the amplitude and implicit time of the N1 and P1 waves showed significant correlation with vascular density (P < 0.001). Stepwise multiple linear regression analysis demonstrated that DCP-VD in the whole area and mfERG P1 implicit time were the best predictive factors for diabetic macular ischemia.

Conclusions Despite favorable anatomic response and restoration of a CMT in the range of normal values after resolution of DME, the vascular OCT-A and functional mfERG parameters were lower than that in no-DME eyes and correlated with poor VA. These results reflect I34 macular photoreceptor disruption and the macular ischemia that may lead to visual deficiency persisting after treatment.

O7-5 Flash electroretinogram as a potential biomarker of GABAergic dysfunction in adults with autism spectrum disorder

Qiyun Huang^1,2, Claire L. Ellis^1,2, Shaun Leo³, Hester Velthuis^1,2, Andreia C. Pereira^1,2,4, Mihail Dimitrov^1,2, Francesca M. Ponteduro^1,2, Nichol M. L. Wong^1,2,5, Eileen Daly^1,2, Declan G. M. Murphy^1,2,6, Omar Mahroo^3,7, Grainne M. McAlonan^1,2,6

¹Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, UK, ²Sackler Institute for Translational Neurodevelopment, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, UK, ³Moorfields Eye Hospital NHS Foundation Trust, UK, ⁴Institute for Nuclear Sciences Applied to Health (ICNAS), Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, Portugal, ⁵Department of Psychology, University of Hong Kong, Hong Kong, ⁶MRC Centre for Neurodevelopmental Disorders, King’s College London, UK, ⁷Institute of Ophthalmology, University College London, UK

Purpose Alterations in gamma-aminobutyric acid (GABA) have been implicated in sensory differences in individuals with autism spectrum disorder (ASD). We previously combined pharmacological challenge with the GABAB agonist arbaclofen and steady-state evoked potentials measured from occipital cortex to confirm that the neural processing of visual sensory information is differentially regulated by the GABAergic system in ASD. Visual signals are initially processed in the retina and in this study; we explored the hypotheses that the retinal light response is GABA-dependent and is altered in ASD.

Methods Light-adapted ERGs were recorded from 62 adults (n = 22 ASD, right eye only) with a portable ERG device (RETeval, LKC Technologies Inc, Gaithersburg, MD, USA) using skin electrodes. Three protocols (each performed twice) were used: (i) the 2-Hz standard white flash with a luminance of 85 Td·s (850 Td background), lasting 15 s (30 flashes); (ii) the 30-Hz flickering protocol (85 Td·s on 850 Td background), lasting 5 s; (iii) the 3.4-Hz photopic negative response (PhNR) protocol (38 Td·s red flashes, 380 Td blue background), lasting 1 min. Participants were administered an oral dose of placebo, 15 mg, or 30 mg of arbaclofen (STX209) in a randomized, double-blind, cross-over order approximately 4 h before the test, and 131 study visits were completed: 42 placebo visits (18 ASD), 50 low-dose visits (18 ASD), and 39 high-dose visits (16 ASD). The a- and b-wave amplitudes and peak time, the PhNR-related parameters, and the 30-Hz ERG responses were compared to investigate any group differences or drug-induced modulations. Finally, we explored how possible GABAergic ERG associations might relate to autistic symptomatology as measured by Autism Quotient (AQ).

Results We observed that a-wave amplitudes in response to standard white single flashes were more prominent in ASD at baseline (placebo), relative to non-autistic typically developing (TD) participants. Next, we observed a significant drug-group interaction effect on a-wave amplitudes: arbaclofen was associated with decrease in a-wave amplitude in ASD, but an increase in TD, eliminating the group difference observed at baseline. We then found that both the baseline a-wave amplitude and the arbaclofen elicited shift significantly correlated with AQ scores across the whole cohort. A trend towards ‘hyper-responsivity’ in ASD was also observed at baseline in a- and b-wave amplitudes to single flashes under the PhNR protocol, but this did not reach statistical significance (a-wave: t(43) = 1.8, p = 0.08; b-wave: t(43) = − 1.8, p = 0.07). No other group differences or drug effects were observed.

Conclusions Our results suggest that autistic individuals might have basal retinal hyper-responsivity to single light flashes and that the GABAergic system might modulate this retinal response differently in autistic and non-autistic individuals. The extent of retinal response difference correlated with autistic symptomatology. Placed together with our previous findings, our work suggests that GABA-dependent differences in sensory processes might be upstream of more complex autistic phenotypes. Finally, as arbaclofen is being considered as a potential intervention for ASD, our study raises the possibility that the ERG rapidly acquired using a hand-held device could provide a pragmatic stratification tool to establish biological response pre-trial. Further studies would determine if our findings are replicated.

O7-6 Predictive Value of the Flicker ERG in Patients with Diabetes

Quentin Davis¹, Mitchell G. Brigell¹

¹LKC Technologies, Inc., USA

Purpose To assess the value of ERG, OCT-angiography (OCT-A), and ultra-wide field FA (UWF-FA) measurements obtained at baseline in predicting progression to proliferative diabetic retinopathy (PDR) and/or diabetic macular edema (DME) in eyes with mild to severe non-proliferative diabetic retinopathy (NPDR).

Methods Subjects (n = 162, 308 eyes) were followed in a longitudinal, ~ 50 site trial for 48 weeks to assess the efficacy of AKB-9778, a Tie2 activator (NCT03197870). Inclusion criteria were having an ETDRS DR severity of 20–53 (mild–severe NDPR), BCVA of 20/30 or better, and no center-involved DME. Four testing modalities (ETDRS 7-field stereo fundus photography (FP), OCT angiography (OCT-A), RETeval ERG/pupil response, and ultra-wide field fluorescein angiography (UWF-FA)) generated 56 measurements, although only photography was performed at all sites. Every 12 weeks, each eye was determined to having progressed (or not) to PDR or DME. During the trial, 84 eyes progressed. Progression prediction was performed for all individual baseline measurements (searching for the optimal cutoff) and all 1540 pairs (logistic regression). Performance measures were Kaplan–Meier analyses (and the associated relative risk (RR)) and area under the ROC curve (AUROC).

Results For individual measurements, the RETeval DR Score had the best predictive performance, with a 7.2 × RR (P < 0.0001, 81% AUCROC) for subjects having a DR Score ≥ 26.9 compared to less than 26.9. Other highly significant (P < 0.0001) measures were flicker ERG times to 16 Td·s and 32 Td·s stimuli (RR between 3.2 and 3.8). Measures with a P < 0.01 were the RETeval DR Score using only 1 eye, the OCT-A FAZ area (RR = 4.1), and 5 measures of ischemia with UWF-FA (total, disk regions 1 or 2, and macula regions 2 or 3 ischemia indices, RR between 3.9 and 5.3). FP was not a significant predictor (P > 0.05). Best pairs of measures were RETeval DR Score + any of UWF-FA macular R2 or disc R1 or disc R2 ischemia indices (AUROC all 96%). All statistically significant pairs involved RETeval and/or UWF-FA results: none used OCT-A or photography measures. Best triples used the RETeval DR Score or flicker ERG and OCT-A measures.

Conclusion Prediction of progression of NPDR is important in the management of the disease. This study showed that compared to OCT-A, UWF-FA, and photography, the RETeval DR Score was the predictor of DR worsening over 48-weeks of follow-up. Combinations of structure and function, however, provide even better results.

O8-1-1 ISCEV and the evolution of standards

Michael F. Marmor¹

¹Stanford University School of Medicine, Byers Eye Institute, USA

Purpose To review how ISCEV became the international arbiter for electrophysiological tests and how it has responded to challenges in the decades that followed.

Methods The author has participated in the evolution from ISCEV Standards from its inception.

Results The U.S. Retinitis Pigmentosa Foundation asked its Board in the 1980s to develop a standard ERG for potential clinical trials. At that time, ERG technique varied widely among labs, as did the nature of published reports. The author was on the Foundation board and argued that ISCEV should do this, not a private Foundation. The Foundation agreed, if we were quick about it….so we were.

ISCEV formed a committee of Nilsson, Zrenner, Arden and myself that first considered the available science. We knew that a Standard had to be practical if it was to be used widely by both beginning and established electrophysiologists and that some liberties had to be taken with adaptation, stimulation, and technology. Most critically, we needed to define standardized responses to make ERG reporting consistent and recognizable everywhere.

The new ERG Standard was a great success and was kept up to date by regular revisions. And it was soon joined by Standards for EOG, VEP, PERG, and mfERG. The balance of science and practicality was tested by an initial VEP document that was scientifically excellent but that had multiple electrodes and complex interpretation. This was not widely used until it was honed down to fundamental necessities in next iteration—and ISCEV learned a lesson.

These ISCEV Standards provided basic and reproducible techniques and universal reporting, but they did not address specialized tests for smaller numbers of patients, rarer diseases, and sub-specialty interests. Thus, the Extended Protocols were developed. This was not an easy undertaking, as tests developed by a small number of opinionated labs did not always lend themselves to standardization. Nonetheless, pressure to find common ground has now provided a catalogue of advice for more complex situations.

Conclusions ISCEV Standards have stabilized the quality and reporting of electrophysiological tests worldwide, and in that sense, put ISCEV on the map. We are no longer an arcane specialty society but the source and watchdog of an important category of ophthalmological testing. The Standards also register some of the highest rates of journal citation. Our committees have continually updated the Standards to incorporate new science (e.g. cone light adaptation, digital recording and stimulation, etc.), but always with awareness of what the average electrophysiology lab could perform, interpret, and report. I hope these are principles to which ISCEV will continue to adhere. I feel enormous pride that I have had the opportunity to help guide these Standards for more than 30 years, as an author and a Director of Standards. The 2022 ERG Standard is the first without my co-authorship, but I relinquish that role happily, knowing that our international enterprise is in good hands.

O8-1-2 Differences in multifocal ERG recordings between DTL and Burien-Allen (BA) corneal electrodes

Ido Perlman^1,2, Hadas Newman²

¹Technion-Israel Institute of Technology, Israel, ²Department of Ophthalmology, Sourasky Tel Aviv Medical Center, Israel

Purpose Different electrodes can be used to record ERG responses in different laboratories as well as in the same laboratory. Therefore, comparing follow-up ERGs requires information of potential differences in the recorded ERG that can be attributed to the electrode type. Here we compared multifocal ERG (mfERG) recordings between Burien–Allen (BA) bipolar electrodes and DTL electrodes.

Methods Young adult volunteers (age 25–45 years old; 3 females, 2 males) participated in the study, all having uncorrected visual acuity of 6/6 in both eyes and normal fundi. Recordings (E3 system, Diagnosys LLC, Lowell, MA, USA) were conducted in one eye, according to the preference of the volunteer, using two types of stimuli: (i) a 103 scaled hexagon stimulus covering a diameter of 48° of central retina (24° from the fovea) and (ii) 127 scaled hexagon stimulus that was adjusted to cover 85^o along the horizontal meridian and 60° along the vertical meridian. For each volunteer, 4 mfERG recordings were conducted; the first two were conducted with a DTL electrode using both stimuli patterns, and then, the same two stimuli patterns were used to record mfERG with a BA electrode. We used amplitude density and peak time measurements of P1 in different group patterns. We determined the relationship between cone system function and eccentricity from the amplitude density of rings having a constant distance from the fovea. We also calculated the total ERG response by summing the P1 of all hexagons in the stimulus.

Results Total ERG response had a smaller peak response density and a shorter time to peak when recording was made with a DTL electrode compared to BA electrode. MfERG recordings with both electrodes were characterized by a typical foveal peak of the 1st ring and a gradual decrease towards more peripheral retinal regions. However, the dependence of amplitude density of the rings upon eccentricity differed significantly between the two electrodes. The rate of response density decline with increasing eccentricity was larger with DTL recordings compared to BA recordings.

Conclusions The data presented here indicate that mfERG recording with DTL and mfERG recording withBA electrodes cannot be compared for follow-up studies. Moreover, when using amplitude density ratios between peripheral and peri-foveal retinal regions, as in hdroxychloroquine toxicity, assessment of toxicity depends upon the type of electrode used for recordings.

O8-1-3 Wireless electroretinogram recording module

Tony Man¹

¹The Chinese University of Hong Kong

Purpose To explore the wireless capacity of ERG signal acquisition and to update the hardware design of recording systems, a miniature wireless electrodiagnostic signal acquisition prototype is proposed.

Methods A wireless electroretinogram recording module was developed and tested. A clinical ERG recording system was used as reference for system evaluation. Electroretinogram signals, characteristics waveforms and their measurements, signal drift rate, and powerline noise performance between the novel module and the clinical system were compared.

Results Recorded signals by the two systems were analogous and comparable. Measurements of the characteristics points in electroretinogram waveform were indifferent between the two systems in terms of precision and dispersion. Noise performance of the two system was similar, with powerline interference minimally presented in the recorded ERG signals. Signal drift was less commonly observed in the novel electroretinogram recording module. In cases where signal drift was present, smaller drift rate of baseline potential is expected in the novel system.

Conclusions ERG signals with comparable quality recorded by the novel recording module were demonstrated in the study. The module could be further developed into an on-site recording module which could work with various portable setups, with the potential for easing clinical recording sessions and making electroretinography a more approachable practice in clinical application.

O8-1-4 Investigating ERGs recorded at high altitude

Sarah Lewis¹, Isla Petrie¹, Denisa Stroncekova¹, Shaun Leo^2,3, Omar A Mahroo^2,3, Ian MacCormick¹

¹University of Edinburgh, UK, ²Institute of Opthalmology, University College London, UK, ³Moorfields Eye Hospital, London, UK

Purpose The retina has high metabolic demands rendering it sensitive to hypoxia. Indeed, retinal hypoxia is implicated in the pathophysiology of multiple retinal conditions. Relatively little is known about retinal function during exposure to high-altitude hypoxia nor the potential changes in retinal function during acclimatisation and on return to sea level. This study aims to explore retinal function using ERG in healthy lowlanders before, during, and after exposure to high-altitude hypoxia.

Methods ERGs were recorded from 32 healthy lowlanders (mean (SD) age, 20.94 (1.77) years; 20 females, 12 males) at 4 time points: at sea level in Edinburgh (baseline), after ascent to Huayna Potosi (4775 m), Bolivia (altitude measurement 1), after 3 days acclimatisation at high altitude (altitude measurement 2), and on return to sea level (post-expedition). Full-field ERGs were recorded using a portable device (RETeval, LKC Technologies) with specialised “Sensor Strip” skin electrodes (LKC Technologies) using stimuli equivalent to ISCEV standards. Significant differences between repeat measures were identified using Friedman tests and Wilcoxon post hoc analysis using Bonferroni correction for repeat measures. Oxygen saturations, heart rate, and Lake Louise Score of acute mountain sickness were recorded at baseline and each day of the expedition.

Results Arterial oxygen saturations were significantly reduced compared to baseline following ascent to high altitude (p < 0.01) and after 3 days acclimatisation (p < 0.01). Peak time of the light-adapted 30 Hz flicker ERG was significantly increased at both altitude measurements 1 and 2 compared to baseline (p < 0.01 in both cases), and 30 Hz flicker ERG amplitude was significantly decreased (p = 0.04 and p < 0.01, respectively). The b-wave peak time of light-adapted single flash ERG was significantly increased at both altitude measurements 1 (p < 0.01) and 2 (p < 0.01) compared to baseline and b-wave amplitude significantly decreased at both altitude measurements 1 (p = 0.01) and 2 (p < 0.01). No significant differences were observed between ERGs performed before and after a 3-day period of acclimatisation to altitude. Interestingly, significant differences compared with baseline were still observed post-expedition for both the light-adapted 30 Hz peak time and the light-adapted single flash b-wave amplitude (p < 0.01 and p = 0.04, respectively). No other significant differences were observed between baseline and post-expedition light or dark-adapted ERGs. No differences were observed in dark-adapted ERG parameters across all time points.

Conclusions In this exploratory study, some changes in light-adapted ERG parameters were observed, which reached statistical significance, and invite replication in future studies. No changes were observed in dark-adapted ERGs. This could indicate that dark-adapted retinal function, as assessed with standard stimuli, is unchanged, or might reflect insufficient power to detect a difference in our analysis. It is possible that in healthy individuals, 20 min dark adaptation is sufficient time for any effects of lower arterial oxygen saturation not to be seen in ERG. Further studies of ERGs at altitude as well as dark adaptometry will be informative.

O8-1-5 Deep learning neural networks for the classification of retinal disorders using full-field electroretinography (ffERG)

Rustum Karanjia^1,2,3, Henry Liu^1,2, Hong-An Nguyen^1,2, Tara Gholamian^1,2, Daniela AbouAssali^1,2, Muhammed Anwar^1,2, Stuart G. Coupland^1,2

¹University of Ottawa Eye Institute, ²Ottawa Hospital Research Institute, Ottawa, ON, Canada, ³Doheny Eye Institute, Los Angeles, CA, United States

Purpose Deep neural networks, including convolutional neural networks (CNN), have recently been successful in tasks such as image classification and segmentation using ophthalmological images such as fundus photographs, optical coherence tomography scans, and corneal topographies. In the field of ophthalmology, there have been no studies thus far that have examined the use of deep learning neural networks utilizing full-field electroretinogram (ffERG) data. Despite the diagnostic power of ffERG, the signal can be difficult to interpret even by ophthalmologists, as there are various components to the data obtained, including waveform shapes, amplitudes, and latencies, that need to be analyzed under varying stimulus conditions. The objective of this study is to assess the diagnostic accuracy of a deep learning neural network in the detection and classification of disease using ffERG.

Methods This is a retrospective chart review of all patients who have received ffERG testing at the University of Ottawa Visual Electrodiagnostic Laboratory between the dates of 01-Jan-2011 to 01-Aug-2021. Demographics data including age, sex, diagnosis, and ERG classification as reported by a trained electrophysiologist were collected. The study was further divided into a detection phase which aimed to test the performance of a deep learning model to be able to classify between normal and abnormal waveforms trained on an ffERG dataset and classification phase which aimed to investigate the feasibility of deep learning networks for improving diagnosing of pathologies from abnormal ffERG (normal, rod dysfunction, cone dysfunction and rod-cone dysfunction). ffERG waveforms were extracted from the Espion Visual Electrophysiology System and pre-processed followed by min–max normalization of the data. The data were labelled according to the clinical classification (binary label for the detection phase and multi-class label for the classification phase). A convolutional neural network (ResNet model) was used for time series classification using our custom dataset with 80% of scans allocated as training and 20% for validation.

Results We included 1568 waveforms from 787 patients in the analysis. The mean age was 43.5 ± 22.1 years, with a female:male ratio of 1.5. Out of the 1568 waveforms analyzed, there were 1073 normal (68.4%), 13 rod dysfunction (0.8%), 112 cone dysfunction (7.1%), and 369 rod-cone dysfunction (23.5%). For the detection phase of the study, the deep learning ResNet model was able to detect normal ffERG waveforms from abnormal ffERG waveforms at an accuracy of 92.1% for training and 91.1% for validation. For the classification phase of the study, the algorithm was able to differentiate between normal, rod dysfunction, cone dysfunction, and rod-cone dysfunction at an accuracy of 89.7% for training and 88.1% validation.

Conclusions Deep learning techniques show promise in automatically detecting and classifying ffERG. The comparatively lower accuracy in the classification phase may be a result of the limited training set for the subset of isolated rod and cone dysfunctions. The results of this study may one day be applied clinically to serve as an adjunctive tool to assist clinicians in the diagnosis of various retinal disorders using ffERG responses.

O8-2-1 Effects of smoothing and adaptive filtering on amplitude and latency in mfERG

Hossein Ameri¹, Christopher Long¹

¹USC Roski Eye Institute, Keck School of Medicine, University of Southern California, USA

Purpose The mfERG can be used to assess the function of cone photoreceptors in the central retina. Diagnosys mfERG analysis software (Diagnosys LLC, Lowell, MA) has features such as “smoothing” (Sm) and “adaptive filtering” (AF) that allow modification of its waveforms. Both Sm and AF are available on a sliding scale of varying intensity from 1 to 4, with 4 being the most significant level of modification. Modification of waveforms using these features not only has an effect on the actual waveform appearances, but it also has an impact on the “normal reference” and “normal deviation” reports. The purpose of this study was to evaluate the extent of changes to the raw data by Sm and AF modifications.

Methods This retrospective study was performed on the mfERG data of patients who had undergone testing at our institution. For each patient, raw mfERG data were compared with the data following Sm level 4 modification and data following AF level 4 modification. Data for P1 amplitude and latency were analyzed from all 61 mfERG hexagons and compared between these 3 groups. Repeated measures ANOVA was used for statistical analysis.

Results Forty mfERG recordings from 20 patients were included; 6 males and 14 females with a mean age of 56.82 years. Twenty mfERGs (50%) were interpreted as “normal” and 20 (50%) as “abnormal”. Compared to the raw data, level 4 Sm decreased the mean P1 amplitude by 183.54 nV ± 9.12 nV (32.0% ± 0.60%, p < 0.001), while level 4 AF reduced it by 210.59 nV ± 14.58 nV (53.9% ± 3.73%, p < 0.001). Although both changes were highly significant, the effects of level 4 AF were more prominent than level 4 Sm (27.05, p < 0.001). Sm and AF modifications also affected the latency of P1. Compared to the raw data, level 4 Sm decreased the mean P1 latency by 2.18 ms ± 0.50 ms (5.78% ± 1.31%, p < 0.001), while level 4 AF reduced it by 2.39 ms ± 0.51 (6.30% ± 1.14%, p < 0.001). There were no significant differences between the effects of level 4 Sm and level 4 AF on P1 latency.

Conclusions Data modification with Sm and AF significantly lowers both P1 amplitude and P1 latency values. When interpreting a mfERG, one should be aware that data modification with Sm and AF may impact the results.

O8-2-2 Mesopic and photopic PERGs

Lisa Tucker¹, Oliver Marmoy^1,2,3, Sian Handley^1,2, Dorothy Thompson^1,2

¹The Tony Kriss Visual Electrophysiology Unit, Great Ormond Street Hospital for Children NHS Trust, Clinical and Academic Department of Ophthalmology, London, UK, ²UCL GOS Institute of Child Health, London, UK, ³Manchester Metropolitan University, Manchester, UK

Purpose The PERG ISCEV standard suggests that background room luminance is not critical, provided dim or ordinary lighting is used. The aim of this study was to compare the ISCEV standard PERG recorded in photopic (ordinary room lights on) and mesopic (dim with room lights off) conditions.

Methods PERGs and pattern reversal (PrVEPs) were recorded under two room lighting conditions. 1) Photopic, background luminance of 117 cd/m² with room lights on and 2) mesopic background luminance 4 cd/m², recorded 2 min after lights were turned off. 15 subjects (median age 34 years, range 23–51 years, 4 male) had PERGs recorded using corneal fiber electrodes referred to the ipsilateral temple. PrVEPs were recorded simultaneously from a midline electrode at Oz referred to Fz. Black and white checks of 50 min of arc width were presented at 3.15 rev/sec on a plasma display panel (82 cd/m² mean luminance, ~ 96% Michelson contrast) in a large (30 degree) and standard (15 degree) field viewed binocularly at 1.25 m. A grand average was comprised of a minimum of 300 individual trials. PERG P50 peak time, P50 amplitude, and N95 peak to trough amplitude were measured. PVEP P100 peak time and N75-P100 amplitude were also measured. Data normality was assessed using the Shapiro–Wilk test. PERG measures under the two lighting conditions were compared using Wilcoxon signed-rank tests and PVEP data using paired t tests [Origin Pro 2021 (v9.8.0.200)].

Results The P50 peak time was significantly earlier, median 3 ms (range 1–5 ms) in photopic than mesopic conditions. The median right eye P50 peak time measured (lights on/light off) 45 ms/48 ms from the large field and 47 ms/50 ms from the standard field, respectively (p < 0.01). No significant inter-ocular differences were observed in the distribution of PERG measures at 0.01 level. The median PERG amplitudes were larger in the mesopic compared with photopic conditions for the large field (p = 0.01). For P50, this showed a median increase of + 1.5 µV [8.4 µV (range 5.2–11) vs. 6.9 µV (range 4.4–9.7)], respectively] and N95 + 1.2 µV [10.6 µV (6–16) vs. 9.3 µV (5–12.9)], respectively). However, difference in median PERG amplitudes from the standard field was not consistently significant between the two lighting conditions. N95:P50 amplitude ratios were also not significantly different under the two lighting conditions. No significant differences were observed in PVEP P100 peak time and amplitude under photopic and mesopic conditions.

Conclusions Ambient room lighting can alter the PERG. We found the median P50 peak time is earlier under photopic compared to mesopic room conditions. The median amplitude of both P50 and N95 is also slightly smaller under photopic conditions in the larger, though not in the standard, field size. N95:P50 ratios did not alter significantly under the different conditions in either the large or the standard field size. These findings emphasize the PERG ISCEV standard advice that ambient lighting should be the same for all recordings and when comparing data to reference ranges.

O8-2-3 Recording PERG responses from superior and inferior peripheral fields while stimulating both fields simultaneously

Shresta Patangay¹, Priyanka Roy¹, John R. Hetling¹

¹University of Illinois at Chicago, USA

Purpose Changes in retinal structure and function in glaucoma are typically asymmetrical about the nasal-temporal axis, motivating the use of ratio-based measurements of superior vs inferior retina (e.g., the Glaucoma Hemifield Test) to improve detection of subtle changes. Here we demonstrate a method for extending this approach to peripheral retina PERG (pPERG) recording.

Methods A stimulus source designed to evoke PERG responses from peripheral retina has been developed (Patangay et al., Transl Vis Sci Technol 2018;7:8). The pPERG stimulus source consists of 4 rings of 30 checks each forming a spherical section that extends from approximately 30–60° of visual angle (half angles). The superior and inferior sectors (halves) of the stimulus source can be independently controlled for reversal rate and mean ON-luminance. All measurements were made on normally sighted subjects using DTL electrodes, recording at least two runs of 300 reversals for each experimental condition. After recording the response to the full stimulus source (superior + inferior sectors), responses to each sector were recorded separately while the pattern in the other sector was on but not reversing (luminance matched). This was done at two similar reversal rates, 4.1 and 4.6 reversals per second (RPS). Then, the two sectors were set to reverse simultaneously but at different rates (one at 4.1 RPS, the other at 4.6 RPS) and the response to the mixed stimulus was recorded. The response to each sector was recovered by windowing the mixed signal using the appropriate window (243.9 ms for 4.1 RPS, 217.4 ms for 4.6 RPS). To test the validity of this approach, the mean ON-luminance of the inferior sector was varied in successive recording runs, while holding the superior sector luminance constant.

Results Responses to superior and inferior sector stimuli presented separately produced responses of different amplitudes and waveshape, as expected based on prior experience with pPERG recording. When the superior and inferior response waveforms (recorded separately) were summed, the resulting waveform was similar in waveshape but slightly larger in amplitude than the response recorded when the full stimulus source (superior + inferior) was used. Windowing of the mixed signal yielded response waveforms very similar to those obtained when stimulating each sector separately. During mixed signal recording, amplitudes of the inferior sector responses increased with increasing inferior sector luminance, while the superior sector amplitudes decreased, even though the superior sector luminance was held constant, consistent with increasing global light adaptation.

Conclusions The simultaneous sector recording approach demonstrated here produced distinct response waveforms for each sector. The superior and inferior responses recovered from the mixed signal had signal to noise ratios greater than those recorded when each sector was recorded from separately when averaging over the same number of reversals. Recording from two retinal areas simultaneously can increase the spatial resolution of the response and support ratio-based analysis without the increase in test time that would occur if probing each sector in series.

O8-2-4 Denoising the ERG with the empirical wavelet transform to improve repeatability of the photopic negative response

Marc George Sarossy^1,2,3, Kristyna Stepnicka⁴, Alexander Sarossy⁴, Zhichao Wu¹

¹University of Melbourne, Victoria, Australia, ²Centre for Eye Research Australia, ³Royal Victorian Eye and Ear Hospital, Australia, ⁴Monash University, Australia

Purpose The Photopic Negative Response (PhNR) of the ERG is a slow negative potential following the b-wave that is reduced in glaucoma. The utility of the measure has been limited by low frequency noise including baseline drift and wander. Various signal processing techniques have been shown to enhance reliability and repeatability of the measure. In this study, we demonstrate and evaluate the use of the empirical wavelet transform (EWT), a type of adaptive filter to enhance the clinical utility of the test, and thus improve its usefulness in the management of glaucoma.

Methods Testing of both eyes of healthy participants was conducted using the Espion E2 (Diagnosis, Lowell, MA) with the ColorDome stimulator. DTL thread electrodes were applied, and eyes were dilated with tropicamide prior to 5 min of pre-adaption. Visual stimulation consisted of a 4 ms light pulse of 2.25 cd.s/m² red (peak wavelength 635 nm) on a 10 cd/m² constant homogenous blue background (peak wavelength 465 nm). Ten sweeps were recorded at a 1 kHz sampling rate, with stimuli presented at 1 Hz. The recording epoch was from -20 ms pre-stimulus to 149 ms post stimulus. The protocol was repeated once during the same session to examine the repeatability of the PhNR, which was identified as the first negative-going wave after the b-wave. EWT analysis was performed in Python. Ten wavelets were extracted with the “LocMaxMin” technique. Denoising was performed by removing the first element of the decomposition from the original signal. Coefficient of Repeatability (CoR) was used to assess the effect of the denoising on the PhNR amplitude measurements. Significance of the CoR was determined by bootstrap replication of 1000 resamples (resampling at subject level).

Results A total of 112 eyes of 56 subjects (mean age 33 years, range 20–73) without eye disease were included in the study. EWT denoising improved the CoR from 3.0 µV to 0.94 µV (p < 0.05).

Conclusions We have demonstrated that the novel EWT technique for denoising the ERG can substantially improve the repeatability of the PhNR, thereby improving the clinical utility and robustness in the management of glaucoma.

AC1-1 Expanding the FDXR-associated disease retinal phenotype and genetic spectrum in a Chinese cohort

Ruifang Sui¹, Xing Wei¹, Hui Li¹, Tian Zhu¹

¹Peking Union Medical College Hospital, China

Purpose FDXR-associated disease is a rare mitochondrial disorder, characterised by optic atrophy, acoustic neuropathy, and developmental delays. The purpose of this study was to evaluate the retinal phenotype and genetic features of Chinese patients with biallelic FDXR variants.

Methods We documented medical history and conducted systemic examinations for patients with FDXR. Detailed ophthalmic examinations, including electroretinograms (ERG), fundus photography, fundus autofluorescence (FA), and optical coherence tomography (OCT), were performed to analyze the retinal phenotype of the probands. To further evaluate the vascular abnormalities, fundus fluorescein angiography (FFA) test was performed. Whole-exome sequencing (WES) was completed to screen pathogenic variants. Sanger sequencing validation and segregation analysis were performed for confirmation.

Results Five individuals from unrelated non-consanguineous Chinese families with biallelic FDXR variants were confirmed. In addition to optic atrophy and diverse extra-ocular manifestations, all 5 patients exhibited retinal dystrophy and 4 patients who underwent ERG showed severely impaired cone and rod function in their first decades. Three of 5 patients showed vascular sheathing of the fundus and FFA further revealed the vascular abnormalities including delayed filling and retinal neovascularization, retinal vascular occlusion, and patchy fluorescence leakage presented in the macular area in the late phase, individually. Genetic analysis revealed biallelic pathogenic FDXR variants in five patients, of which variants c.383C>T (p.A128V), c.963delG (p.R322fs*7), c.1052_1053delTC (p.L351Pfs*12), c.394-11T>G, and c.1002 + 1G>A are novel.

Conclusions Retinal dystrophy with vascular sheathing was first observed in this cohort, and the retinal vascular characteristics in FFA were described. The probands with FDXR-associated disease showed severe early-onset and rapid progression ophthalmic features, indicating the significance of early diagnosis and treatment. Moreover, this is the first evidence in a Chinese cohort with novel FDXR variants, expanding the FDXR-associated disease retinal phenotype and genetic spectrum.

AC1-2 Clinical characteristics and genotyping of macular dystrophy patients in a Southeast Asian setting

Choi Mun Chan¹

¹Singapore National Eye Centre, Singapore

Purpose To analyse the genome of consecutive macular dystrophy patients presenting to an inherited retinal dystrophy clinic in Southeast Asia.

Methods Eighteen consecutive patients who had been diagnosed with macular dystrophy underwent detailed clinical phenotyping including taking a detailed history of symptoms, drawing up of a family pedigree, visual acuity, colour vision, refraction, OCT or ocular coherence scans of the maculae, colour fundus photographs, macular autofluorescence imaging, wide field colour and autofluorescence imaging, Goldmann visual field perimetry, and electrophysiology including ISCEV standard full-field electroretinogram and multifocal electroretinogram. Informed consent was obtained from patients or relatives if patients were minors. All patients underwent whole-exome genome sequencing. A multidisciplinary team consisting of geneticists, genetic counsellors, ophthalmologists, and bioinformatics specialists discussed the results, and the variants were classified according to the American College of Medical Genetics and Genomics (ACMG) standards and guidelines for variant interpretation. Segregation was performed on family members when the initial results were returned.

Results The age of the patients ranged from 16 to 72 years of age, with the age at diagnosis ranging from 8 to 61 years. Sixteen of the patients were of Chinese ethnicity, while 2 were of Indian ethnicity. Electrophysiological findings showed isolated macular dysfunction in 9 patients, macular and generalized cone dysfunction in 4 patients, and macular with generalized rod and cone dysfunction in the remaining patients. Genomic variants were identified in 14 of the 18 patients. Eight of the patients had homozygous ABCA4 mutations, while 1 had only 1 ABCA4 mutation identified. The other variants sequenced were PRPH2, CYP4V2, RP1, RP1L1, and CRX. Further analysis was performed on the 4 patients in whom no variants were found and the 1 patient in whom only 1 ABCA4 mutation was identified. This included looking for known intronic variants associated with ABCA4 dystrophy, but none were found.

Conclusions A clinical diagnosis of macular dysfunction had previously been made in these patients by clinicians. The full field and multifocal electrophysiology results showed that the dysfunction was not limited to the macula. The genotyping results had a variant return rate of more than 75%, which shows that if a stringent clinical phenotyping is done prior to genotyping, there is a high rate of return. Variants identified in this cohort are consistent with those found in other populations. Genotyping in this cohort revealed variants which were not expected for the clinical phenotype, thereby showing that genotyping plays an important role in the molecular diagnosis of macular dystrophy. Further genotyping studies should be conducted in Southeast Asian patients with retinal dystrophies—a less studied cohort—to expand our knowledge.

AC1-3 Clinical and genetic features of Korean patients with achromatopsia

Yong Je Choi¹, Kwangsic Joo¹, Hyun Taek Lim^2,3, Sung Soo Kim⁴, Jinu Han⁵, Se Joon Woo¹

¹Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea, ²Department of Ophthalmology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 05505, Korea, ³Orthopia Eye Clinic, Seoul, 06162, Korea, ⁴Institute of Vision Research, Department of Ophthalmology, Severance Hospital, Yonsei University College of Medicine, Seoul, 03722, Korea, ⁵Institute of Vision Research, Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, 06273, Korea

Purpose This study aimed to characterize Korean patients with achromatopsia.

Methods We retrospectively reviewed the patients’ genotypes and phenotypes.

Results Twenty-one patients were enrolled and followed-up for a mean of 7.3 years. Their mean age at baseline was 10.9 years. The pathogenic variants of 4 genes, CNGA3, PDE6C, CNGB3, and GNAT2, were identified by targeted gene panel or exome sequencing. Among the causative genes, CNGA3 and PDE6C were equally most prevalent: CNGA3 (N = 8, 38.1%), PDE6C (N = 8, 38.1%), CNGB3 (N = 3, 14.3%), and GNAT2 (N = 2, 9.5%). The degree of structural defects and functional deficit of the retina varied among the patients. The age of patients had no significant correlation with structural defects. The visual acuity and retinal thickness did not change significantly during the follow-up period. In CNGA3 achromatopsia patients, the proportion of patients with normal foveal ellipsoid zone on OCT was significantly higher than that of patients with the other causative genes (62.5% vs 16.7%, p = 0.023). In PDE6C achromatopsia patients, it was significantly lower than that of patients with other causative genes (0% vs 41.7%, p = 0.003).

Conclusions Korean patients with achromatopsia showed similar clinical presentations. They had higher prevalence of PDE6C variants than those of other ethnic groups. On OCT, the degree of foveal structural defects of patients with PDE6C variants were worse than those with the other causative genes.

AC1-4 Experience of enhanced S cone syndrome in South India: A multicenter case series analysis

Deepika Chennapura Parameswarappa¹, Srishti Ramamurthy^1,2, Saarang Hansraj^1,2, Srikanta Kumar Padhy³, Kiruthika Kannan¹, Munispriyan Raviselvan⁴, Dhanashree Ratra⁴, Subrat Dhal³, Isha Acharya⁵, B Poornachandra⁵, Tapas Ranjan Padhi³, Subhadra Jalali¹

¹Srimati Kanuri Santhamma Center for Vitreoretinal Diseases, Anant Bajaj Retina Institute, Kallam Anji Reddy Campus, L V Prasad Eye Institute, Hyderabad, Telangana, India, ²Standard Chartered – LVPEI Academy for Eye Care Education, L V Prasad Eye Institute, Hyderabad, Telangana, India, ³Vitreoretina and Uveitis Services, Anant Bajaj Retina Institute, Mithu Tulasi Chanrai Campus, L V Prasad Eye Institute, Bhubaneswar, India, ⁴Department of Vitreoretinal Diseases, Medical Research Foundation, Sankara Nethralaya, Chennai Tamil Nadu, India, ⁵Department of Retina, Narayana Nethralaya, Bangalore, India

Purpose To describe the clinical presentation and full-field flash electroretinogram findings of enhanced S-cone syndrome (ESCS) in a series of patients.

Methods The study includes retrospective analysis of patients with ESCS from 4 tertiary eye care centres across south India. The diagnosis of ESCS was confirmed based on full-field flash ERG findings with or without the short-wavelength-sensitive cone (S cone) ERG protocol. Flash and S cone ERGs were recorded as per standard ISCEV guidelines in all eyes.

Results Ninety eyes of 45 patients with ESCS were included in the study; 60% (27/45) were males and 40% (18/45) were females. The median age at presentation was 16 years [interquartile range (IQR);9,25]. 71% (32/45) of the patients presented with nyctalopia and 22% (10/45) presented with blurring of vision. The median best-corrected visual acuity at presentation was 0.4 logMAR [IQR 0.10, 0.17]. 71% (64/90) of the eyes had retinal pigment epithelial changes of varying size and shape along the major vascular arcades or mid periphery. A minority of the eyes also had yellow to white pigmentary dot-like changes along the major vascular arcades (24%,22/90), pallor of optic disc (13%,12/90), attenuated arteries (9%, 8/90), and in 4 of the eyes, there were no obvious retinal signs clinically. Macular retinoschisis was found in 64% (58/90) of the eyes. The flash ERG findings included unrecordable dark-adapted 0.01 responses in 84% (76/90) of the eyes. The dark-adapted 3 ERGs showed delayed peak time and reduced amplitudes in 84% (76/90) of the eyes. The light-adapted 3 ERGs showed delayed peak time and reduced amplitudes in 82% (74/90) of the eyes. The light-adapted 30 Hz flicker ERGs showed reduced amplitude in 71% (64/90) of the eyes. S cone ERG was available in 40% (36/90) of the eyes, and all these had supernormal responses.

Conclusions Enhanced S-cone syndrome eyes show varied clinical signs of retinal pigmentary abnormalities with or without atrophic changes. Despite the varied clinical signs, full-field flash ERG in the majority of the eyes is diagnostic with unrecordable dark-adapted 0.01 responses, similar looking DA 3 and LA 3 ERGs. This study highlights the role of the flash ERG as a mandatory tool in diagnosing ESCS. The S cone ERG may not always be necessary to diagnose ESCS with pathognomonic findings in the flash ERG.

AC2-1 A report of clinical features and genetic test results of Korean choroideremia patients

Woo Gyeong Jo¹, Christopher Seungkyu Lee¹, Jinu Han²

¹The Institute of Vision Research, Department of Ophthalmology, Severance Hospital, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemungu, Seoul, Republic of Korea, ²The Institute of Vision Research, Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, 211 Eonju-ro, Gangnamgu, Seoul, Republic of Korea

Purpose We aim to disclose and discuss the clinical manifestations and genetic test results of Korean choroideremia patients and female carriers.

Methods Six male patients and 3 female carriers with comprehensive ophthalmic examinations and genetic analysis were included. Detailed clinical features were identified using visual field (VF) testing and multimodal imaging including color fundus photography, fundus autofluorescence (FAF), and optical coherence tomography (OCT).

Results Six male patients showed different types of hemizygous CHM mutation, including 2 nonsense mutations (c.715C>T, p.Arg239Ter; c.799C>T, p.Arg267Ter), 2 frameshift mutations (c.1584_1587del, p.Val529HisfsTer7; c.403_404delGA, p.Asp135PhefsTer9), 1 splicing mutation (c.1511-28_1511-2del), and 1 exon duplication (2–9). The latter 3 mutations are novel findings. Widefield color fundus photography of the male patients showed diffuse yellow-whitish scleral reflex and granular pigmented lesions. FAF showed multiple patchy hypofluorescence lesions, sparing the macula. OCT showed thinning of outer nuclear layer, ellipsoid zone, retinal pigment epithelium layer, choroid thickness, and characteristic structures such as interlaminar bridges (ILBs), outer retinal tubulations (ORTs), microcysts in the inner nuclear layer. VF showed ring scotoma patterns with a small amount of remaining central field. Female carriers showed variable fundus findings and only mild changes in OCT.

Conclusions A detailed description of the genotypes and phenotypes of 6 choroideremia patients and 3 CHM mutation female carriers including 3 novel mutations is presented.

AC2-2 Visual, clinical, and electro-physiological features of gyrate atrophy patients in Indian population

Srikanta Kumar Padhy¹, Deepika C. Parameswarrapa¹, Tapas Ranjan Padhi¹

¹LV Prasad eye institute, India

Purpose To describe the visual, clinical, and full-field ERG features in patients with Gyrate Atrophy (GA).

Methods This is a retrospective study that included patients with GA presenting between March 2014 and November 2022. Data were acquired from electronic medical records and included demographic details, presenting complaints, family history, clinical findings, serum ornithine levels, macular optical coherence tomography (OCT), and ERG findings. Subgroup analysis based on zone of retinal involvement and presence of foveoschisis was done.

Results A total of 129 eyes of 65 patients were included. Average age at presentation was 26.4 ± 14.63 years, with a male preponderance (male:female ratio ~ 2:1). Nearly 10% (n = 7) presented in the first decade of life. Myopia was the commonest refractive error (117 out of 122 eyes with available refraction; mean spherical error − 6.97 ± 4.71 diopters). Nyctalopia (n = 35) was the commonest presenting complaint, followed by blurring of vision (n = 29). Twenty-one patients had positive family history. Posterior subcapsular cataract (PSC) was seen in 36.43% of eyes (n = 47). Involvement of retina was classified based on 3 zones: Zone I (n = 72; 57.14%)—atrophic patches encroaching within arcades or peripapillary or both; Zone II (n = 42; 33.33%)—atrophic patches restricted to arcades (between arcade and equator); and Zone III (n = 12; 9.52%)—atrophic patches beyond equator. Increasing age was associated with increase in Zone I involvement (100% Zone I involvement in age > 40 years); however, 10% of eyes had Zone I involvement even in the first decade of presentation. Foveoschisis (57.69%) was frequently present on OCT (n = 60 of 104 available eyes), almost in 75% of eyes by the 3rd decade of life and in Zone I involvement (72.41%). Macular hole and photoreceptor loss was seen in 6 eyes (5.7%) on OCT. Serum ornithine levels, assessed in 35 patients, were elevated in 27 and normal in 8 patients. ERG demonstrated extinguished scotopic and photopic responses in 11 out of 20 patients assessed (55%), while the rest (9 of 20) demonstrated present but non-measurable responses. The ERG involvement was independent of the zone of involvement or age at testing.

Conclusions GA commonly presents in the 2^nd and 3^rd decade of life; however, 10% cases do present in the 1^st decade of life with only zone III involvement. Therefore, it is important to differentiate GA from other causes of childhood rod cone dystrophies. Myopia and PSC are treatable causes of visual deficit in GA. Natural history of GA leads to progressive centripetal involvement (Zone I) and increased prevalence of foveoschisis with advancing age. The ERG is characterized by global decrease in recorded responses and was independent of age or zone of involvement.

AC2-3 Clinical and genetic findings of autosomal recessive bestrophinopathy

Christopher Seungkyu Lee¹, Yong Kim¹, Hae Kim²

¹Yonsei University College of Medicine, ²CHA University College of Medicine, Korea

Background Autosomal recessive bestrophinopathy (ARB) is a rare subtype of bestrophinopathy caused by biallelic mutations of the BEST1 gene. ARB is characterized by multifocal subretinal deposits accompanied by macular edema or subretinal fluid, hyperopia, co-existing narrow angle, and a marked decrease in electrooculogram. However, little is known about the genetic variants and specific clinical features of ARB. This is an observational case series of patients with a clinical and genetic diagnosis of ARB who underwent multimodal imaging.

Case report We describe 10 patients from 9 unrelated families with 6 known variants and 3 novel missense variants: c.236C>T, p.(Ser79Phe); C.452C>T, p.(Leu151Pro); and c.650C>T, p.(Trp217Met). The most common variant was c.584C>T, p.(Ala195Val), observed in 6 patients, without correlation to the severity of the phenotype. All patients manifested bilateral multifocal subretinal deposits and subretinal fluid throughout the follow-up period, while intraretinal fluid was found in approximately half of the eyes. The extent or chronicity of the fluid collection did not correlate with visual acuity. Angle closure glaucoma was present in 5 eyes. Three patients had a genetically confirmed family history of ARB, and 1 patient had a clinically suspected family history.

Conclusions This study reveals novel mutations in the BEST1 gene and adds to the spectrum of clinical presentations of ARB.

AC2-4 Autosomal dominant optic atrophy caused by novel pathogenic OPA1 variants and genotype–phenotype correlation analysis

Jinfeng Han^1,2, Ya Li², Ya You², Lei Bo^1,2

¹Zhengzhou University, ²Zhengzhou University People’s Hospital, China

Purpose To describe the genetic and clinical features of 23 patients from 13 unrelated Chinese pedigrees with OPA1-related autosomal dominant optic atrophy (ADOA) and define the phenotype-genotype correlations.

Methods Detailed ophthalmic examinations were performed. Visual acuity, optical coherence tomography (OCT), visual field, ERG, VEP, and MRI of the brain were evaluated. Targeted next-generation sequencing (NGS) was conducted in the 13 probands using a custom-designed panel PS400. Sanger sequencing and co-segregation were used to verify the identified variants. The pathogenicity of gene variants was evaluated according to American College of Medical Genetics and Genomics guidelines (ACMG).

Results Twenty-three patients from the 13 unrelated Chinese ADOA pedigrees had impaired vision and optic disc pallor. OCT showed significant thinning of retinal nerve fiber layer. The visual field showed varying degrees of central or paracentral scotoma. VEP showed reduced amplitudes and/or prolonged latencies. Onset of symptoms occurred between 3 and 24 years of age (median 6 years). Twelve variants in OPA1 were identified in the cohort and 10 novel variants were identified. AAmong the novel variants, two splicing c.984 + 1_984 + 2delGT, c.1194 + 2T>C, two stopgain c.1937C>G and c.2830G>T, and one frameshift c.2787_2794del8 were determined to be pathogenic based on ACMG. Two novel splicing variants c.1316-10T>G and c.2818 + 2_2818 + 3delGT were determined to be likely pathogenic. Also, a novel missense c.1283A>C (p.N428T) and two novel splicing variants c.2496G>A and c.1065 + 5G>C were of uncertain significance.

Conclusions Six novel pathogenic variants were identified. The findings will facilitate genetic counseling by expanding the pathogenic mutation spectrum of OPA1.

CR1-1 Pathogenicity and functional analysis of CFAP410 mutations causing axial spondylometaphyseal dysplasia with cone-rod dystrophy

Bo Lei¹, Shaoqing Yang¹, Qingge Guo¹, Ya Li¹

¹Henan Provincial People’s Hospital, People’s Hospital of Henan University, Henan Eye Institute, Henan Eye Institute, Zhengzhou, Henan, China

Purpose Axial spondylometaphyseal dysplasia (axial SMD) with cone rod dystrophy caused by mutations in CFAP410 is a very rare syndrome. The mechanisms by which the mutations cause the disease remain largely unknown. We explored the pathogenicity and performed functional analysis of two compound heterozygous CFAP410 mutations identified in an a patient with axial SMD with cone-rod dystrophy.

Methods A 4-year-old boy complained of decreased vision. He underwent ocular examinations together with systemic X-ray check. Blood sample was taken for WES gene sequencing. Pathogenicity of identified mutations was determined by ACMG guideline. Mutated plasmids were constructed and transferred to HEK293T cells. Cell cycle, protein stability and degradation, and protein ubiquitination level were measured.

Results The best-corrected visual acuity was 0.25 bilaterally. The fundi showed uneven granular pigment disorder in the periphery of the retinas. SS-OCT showed thinning and atrophy of the outer retina, residual ellipsoid bands in the fovea, and macular staphyloma. Both scotopic and photopic ERG responses severely reduced. The patient was short in stature and X-ray showed mild scoliosis. Two heterozygous missense mutations, c.319T>C (p.Tyr107His) and c.347C>T (p.Pro116Leu) in exon 4 of the CFAP410, were pathogenic by the ACMG guideline. In vitro, mutations affected a highly conserved residue which could affect cell cycle. Immunofluorescence and Western blotting showed that the mutant proteins decrease protein stability but increase protein degradation. Meanwhile, CO-IP data suggested that ubiquitination level was altered in the mutated plasmid transferred cells.

Conclusions Compound heterozygous CFAP410 mutations c.319T>C and c.347C>T in CFAP410 caused axial SMD with cone rod dystrophy. The pathogenic mechanisms may be associated with alternations of protein stability and degradation through the ubiquitin–proteasome pathway.

CR1-2 Electroretinography guides re-analysis of whole genome data to find undetected variant in CACNA1F

Mohammad Anas^1,2, Elena Schiff^2,3, Gavin Arno^2,3,4, Andrew R. Webster^2,3, Michel Michaelides^2,3, Anthony G. Robson^3,5, Omar A. Mahroo^1,2,3

¹Section of Ophthalmology, King’s College London, St Thomas’ Hospital Campus, London, UK, ²Retinal Genetics Service, Moorfields Eye Hospital, London, UK, ³UCL Institute of Ophthalmology, University College London, UK, ⁴Great Ormond Street Hospital, London, UK, ⁵Department of Electrophysiology, Moorfields Eye Hospital, London, UK

Background Whole-genome sequencing (WGS) is increasingly available for finding the molecular cause in suspected monogenic disorders and is now the first genetic investigation performed for many patients with likely inherited retinal disease in the UK. Here, we report a case in which negative primary findings were reported after WGS, but the ERG phenotype together with clinical and family history guided a targeted re-analysis to reveal the molecular diagnosis.

Case report An 18-year-old male with a history of high myopia, subnormal vision even with refractive correction, and poor night vision since a young age was reviewed in the retinal genetics clinic. Other ocular history included strabismus. In his family history, the son of his maternal aunt also had similar visual problems. Best-corrected visual acuity was 20/40 in the right eye and 20/60 in the left eye. Clinical examination and retinal imaging were largely unremarkable other than changes consistent with high myopia. An inherited disease was suspected, and a DNA sample was sent for WGS. However, the ensuing genetic report stated that no genetic cause had been found (negative primary findings). ERG reports from when the patient was 5 years old were retrieved. Although these were non-mydriatic recordings performed with skin electrodes and with only 5 min of dark adaptation, scotopic bright flash and single flash photopic ERGs were electronegative and 30 Hz flicker ERGs had a bifid shape, with the findings noted to resemble those associated with incomplete congenital stationary night blindness. The ERGs, together with the stationary nature of the patient’s symptoms, significant myopia, and the family history consistent with X-linked inheritance, pointed to CACNA1F as a particular gene of interest. The WGS results were re-analysed specifically for variants in this gene, and a frame-shifting variant was found in a region of the gene that had been designated a “filter failure”.

Conclusions In the past, the clinical phenotype was used to guide targeted, often single gene, testing. Now, it is more common in many settings to simultaneously sequence a large panel of genes, or even the whole genome, without necessarily considering specific aspects of the phenotype. However, for a range of reasons, the diagnostic yield is still far from 100%. Our case highlights the role of detailed phenotyping (including electrophysiology), in guiding re-analysis of apparently negative genetic results to reveal the genetic diagnosis.

CR1-3 Biallelic neural retina leucine zipper (NRL) gene mutations expanding the enhanced S cone syndrome (ESCS) phenotype

Stephanie Retsas¹, Elisa Cornish^1,2, Gerard Reid¹, Haipha Ali¹, Nonna Saakova¹, Peter McCluskey¹, Marium Raza¹, Jonathan Nguyen¹, Anagha Vaze^1,2, Clare L Fraser¹, Christina Petersen¹, Benjamin Nash^2,3, Julie McGaughran⁴, Robyn V. Jamieson^1,2, John R. Grigg^1,2

¹Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia., ²Eye Genetics Research Unit, Children’s Medical Research Institute, The Children’s Hospital at Westmead, Westmead, New South Wales, Australia, ³Sydney Genome Diagnostics, Western Sydney Genetics Program, Sydney Children’s Hospitals Network, Sydney NSW Australia, ⁴Genetic Health Queensland Royal Brisbane and Women’s Hospital Metro North health Service District Herston Queensland 4029 Australia

Purpose To describe the ocular phenotype in novel neural retina leucine zipper (NRL) gene mutations in 3 patients from 2 families. NRL binds directly to the promoter of NR2E3 and thus acts upstream of this transcription factor to guide the developing photoreceptor into the rod lineage. NRL is associated with autosomal dominant and recessive forms of retinitis pigmentosa. More recently, cases of autosomal recessive NRL (arNRL) mutations resulting in an enhanced S cone syndrome (ESCS) phenotype have been described.

Methods We report the clinical phenotype of 3 patients from 2 families with biallelic NRL pathogenic mutations. Investigations included electrophysiology, best-corrected visual acuity (BCVA), OCT and ultra-wide field (UWF) autofluorescence (AF), and red green (RG) retinal imaging.

Results Family 1: I1 (male) initially referred at age 15 with symptoms from age 5 years. Nystagmus was noted; best-corrected visual acuity (BCVA) was 6/120 in both eyes. Posterior subcapsular cataract (PSCC) developed during the 10-year follow-up. Genetic testing revealed a novel homozygous NRL (likely pathogenic) variant c.256G>T; p.Glu86*. ISCEV standard pERG showed no discernible response, whilst ERG and extended protocol blue ERG demonstrated responses consistent with a diagnosis of ESCS. Fundus imaging highlighted torpedo like retinal scarring with hyper- and hypo-pigmented rings and patches of atrophy along vascular arcades. Small hyperfluorescent dots were localised within the retinal arcades and posterior pole whilst small round hypofluorescent dots were noted in far temporal retina. OCT showed schitic macular changes in both eyes. Family 2: II1 and II2 (female aged 4.5 and male aged 3 years, respectively) presented with nyctalopia. BCVA was 3/6 Kay pictures both eyes. NRL pathogenic variants were reported; however, molecular details were not available at time of abstract preparation but described as novel. Abbreviated paediatric flash ERG responses recorded with skin electrodes demonstrated attenuated dim blue flash responses. Combined mix response waveforms were broadened and simplified consistent with ERG findings in patients with ESCS. Extended protocol blue ERGs were not performed due to patient ages. Fundus images were atypical ESCS. UWF-RG imaging demonstrated curved-linear yellow glistening stripes and dots scattered uniformly, particularly outside the vascular arcade. UWF-AF demonstrated hyperfluorescent spots corresponding to the centre of the yellow strips. Additionally, there were hyperfluorescent foci in a broadened circumferential elliptical ring formation within the retinal arcades, sparing the central macular. OCT through these areas of hyperfluorescence showed disruptions to the inner retina and blurring of the RPE and photoreceptor layer. These macular and peripheral fundus findings have not been previously described, thus expanding the arNRL phenotype.

Conclusions We describe the detailed electrophysiologic and multimodal phenotype in 2 families with NRL genetic variants. The electrophysiology is consistent with ESCS. Proband 1 has a more typical fundus appearance and additional nystagmus. Family 2 exhibits a distinct retinal phenotype, including curved yellow glistening stripes and hyperfluorescent dots throughout the fundus, which is atypical in ESCS. These 2 families contribute to a greater understanding of the ESCS phenotype in patients with confirmed biallelic NRL genetic variants.

CR1-4 Phenotype–genotype correlation of the first patient with a homozygous missense variant RPE65 c.499G>T, p. (Asp167Tyr)

Mirjana Bjelos^1,2,3, Ana Curic^1,3, Benedict Rak¹, Mladen Busic^1,2,3, Biljana Kuzmanovic Elabjer^1,2,3, Borna Saric¹, Damir Bosnar^1,2,3, Leon Markovic^1,3

¹University Eye Department, Reference Center of the Ministry of Health of the Republic of Croatia for Inherited Retinal Dystrophies, Reference Center of the Ministry of Health of the Republic of Croatia for Pediatric Ophthalmology and Strabismus, University Hospital “Sveti Duh”, 10000 Zagreb, Croatia, ²Faculty of Medicine, Josip Juraj Strossmayer University of Osijek, 31000 Osijek, Croatia, ³Faculty of Dental Medicine and Health Osijek, Josip Juraj Strossmayer University of Osijek, 31000 Osijek, Croatia

Background This case report aims to present the specific phenotype–genotype correlation of the first patient with pigmentary retinopathy (RP) caused by the homozygous missense variant RPE65 c.499G>T, p. (Asp167Tyr).

Case report A 66-year-old male diagnosed with a homozygous missense variant RPE65 c.499G>T, p. (Asp167Tyr) presented with light perception in the right eye (RE) and amaurosis in the left eye (LE). He had manifested nyctalopia since early childhood but completed his college education according to the regular program. Full-field stimulus testing (Metrovision, Perenchies, France) detected responses of 43 dB, 26 dB, and 53 dB to white, red, and blue light, respectively, in the RE, while in the LE, no response was evoked. The Optos® California (Optos Inc., Marlborough, MA, USA) ultra-widefield imaging depicted extensive chorioretinal atrophy with clumped nummular pigmentary changes and obliterative sclerosis of retinal vessels in the mid- and far periphery. Short-wavelength fundus autofluorescence was absent.

Conclusions In contrast with typical perivascular bone spicule clusters of relocated RPE cells, the patient presented a distinctive pattern of reactive RPE changes: rounded, heavily pigmented nummular flecks clustered against Bruch’s membrane as reported in choroideremia, RP-86, and RP-87 with choroidal involvement. We hypothesize that the lower expression level of RPE65 or the rapid degradation of the variant protein enables RPE cells to stay in situ as opposed to exhibiting migration to perivascular inner retinal sites. The observed phenotype is thus associated with less severe visual deterioration in adolescence. The melanin with its pro-oxidative potential could potentially advance chorioretinal atrophy in later stages.

CR2-1 Electrically evoked phosphenes in a patient with EYS (p.Gly843Glu)-associated retinitis pigmentosa

Akiko Maeda^1,2, Tadao Maeda^1,3, Satoshi Yokota^1,2, Yasuhiko Hirami^1,2, Masayo Takahashi^1,4, Yasuo Kurimoto^1,2

¹Kobe City Eye Hospital, Japan, ²Kobe City Medical Center General Hospital, Japan, ³Vision Care Cell Therapy, ⁴Vision Care Inc., Japan

Background Phosphenes are visual perceptions induced by stimuli other than light, such as mechanical force, eye movements, and electrical currents. Patients can recognize phosphenes if ganglion cells in the inner retina are functional. Phosphenes can be an excellent tool for selecting patients who are appropriate for photoreceptor transplantation because functional inner retina is required for such therapies. Here, a case of retinitis pigmentosa (RP) with EYS (p.Gly843Glu) homozygous variants who underwent photoreceptor transplantation after evaluation of electrophysiological tests including phosphenes is presented.

Case report Visual acuity of the patient with EYS (p.Gly843Glu) homozygous variants was hand motion (HM) in both eyes, and visual field test was not able to be performed. Phosphene detection was employed twice on different days using the Diagnosys system (LKC. Inc). Pupil diameter measurement (PM), electrically evoked response (EER), and full-field stimulus test/thresholds (FST) were also recorded. Phosphenes were recognized in both eyes and their threshold was 1.5 µV. Optical coherence tomography (OCT) showed preserved outer nuclear layer (ONL) with disappearance of ellipsoid zone (EZ) and interdigitation zone (IZ). After transplantation, slightly better visual functions were observed in some tests. Clinical phenotypes of 10 RP patients with EYS (p.Gly843Glu) homozygous variants indicated relatively milder damage to the retina compared with other RP cases.

Conclusions These observations suggest that phosphenes can be useful to evaluate visual functions in low vision patients, especially estimating inner retinal functions in RP cases who are being considered for vision sparing therapies such as photoreceptor transplantation.

CR2-2 A mysterious case with persistent serous detachment and vitelliform lesion

Mei-Chi Tsui^1,2, Yi-Ting Hsieh²

¹Tainan Municipal An-Nan Hospital-China Medical University, ²National Taiwan University Hospital, Taipei, Taiwan

Background Vitelliform lesions may present in retinal diseases such as Best disease, adult-onset vitelliform dystrophy, vitelliform exudative macular detachment, drusenoid retinal pigmented epithelium (RPE) detachment, central serous chorioretinopathy (CSC), and others. Most of them belong to inherited retinal diseases. Herein, we report a mysterious case with persistent serous detachment and vitelliform lesion in only one eye.

Case report A 16-year-old female presented with intermittent metamorphopsia in the right eye for 2 years. On examination, the best-corrected visual acuity (BCVA) was 0.7 logMAR in the right eye and 1.0 logMAR in the left eye. Intraocular pressure was within normal limits. The spherical equivalent was − 7.00 D and − 8.00 D in the right and left eyes, respectively. Fundus examination showed tessellation in both eyes and poorly demarcated yellow patch about 1 disc diameter (DD) at the fovea in the right eye. Fluorescein angiography (FA) showed about 2/3 DD-sized, donut-shaped hyperfluorescence at early phase and late staining without leakage. Fundus autofluoresence (FAF) showed donut-shaped hypefluorescence in the right eye that corresponded to the hyperfluorescence in FA. FA and FAF showed nothing particular in the left eye. Optical coherence tomography (OCT) showed a dome-shaped macula in both eyes and serous detachment and vitelliform substance at the subretinal space in the right eye. There was no choroidal neovascularization (CNV) on OCT angiography (OCTA). The electrooculogram (EOG) showed an Arden ratio of 2.28 in the right eye and 2.21 in the left eye. The ERG was normal in both eyes. Best disease and pattern dystrophy were excluded. Laboratory tests including complete blood count (CBC), differential count (DC), inflammatory factors, and autoimmune profile were within normal limits. Best disease and pattern dystrophy were not suggested. Chronic CSC was not likely because there was no pachychoroid on OCT and persistent serous detachment despite the treatments of topical dorzolamide eyedrops and oral spironolactone. During the 1-year follow-up, the BCVA fluctuated between 0.7 and 0.9 logMAR in the right eye, whereas it remained 1.0 logMAR in the left eye. The serous detachment and vitelliform substance in the right eye were stationary in shape and size on serial OCTs. Dome-shaped macula with serous detachment in the right eye was the most likely diagnosis.

Conclusions Our case presented with intermittent metamorphopsia in the right eye, and OCT and OCTA showed persistent serous detachment and vitelliform substance at subretinal space without CNV in the right eye. The corresponding lesions were early hyperfluorescence and late staining on FA and hyperautofluorescence on FAF. ERG, EOG, and laboratory tests were all within normal limits. After excluding other differential diagnosis, dome-shaped macula with serous detachment was the most likely diagnosis.

CR2-3 Visual recovery in abusive head trauma measured by VEP

Nuria Fluriach Dominguez¹, Susann Andersson^1,2, Sara Arvidsson¹, Jenny Gyllen^1,2, Gunilla Magnusson^1,2, Anders Sjostrom^1,2

¹The Queen’s Silvia Children’s Hospital. Department of Opthalmology. Sahlgrenska University Hospital, Region Vastra Gotaland, Sweden, ²Department of Neuroscience, Institute of Neuroscience and Physiology. Sahlgrenska Academy, University of Gothemburg, Sweden

Background The Queen Silvia’s University Hospital for Children in Gothemburg, Sweden, receives around 10–15 children with suspected AHT (Abusive Head Trauma) diagnosed every year. A special group of professionals has been founded to take care of these children and families at the hospital, and we represent the pediatric ophthalmology team. Basic eye examinations, reflex testing, OCT (optical coherence tomography) scan, eye/retinal photographs, and electrophysiology measurement (VEP/ERG) are performed, if possible, in every case as soon as a patient is admitted. These children are followed up for at least one year.

Case report An 8-month-old female was submitted to the eye clinic with profound bilateral eye and brain hemorrhages. She had old lesions of radiologically demonstrated cerebral atrophy and suspicious of previous AHT episodes. She did not give any visual response at our first examination, except very slow pupillary responses, and the flash VEP was largely pathologic/almost extinguished. During the follow-ups, she slowly improved in her visual responses and her hemorrhagic lesions resolved. Her recovery in general, her visual improvement, and the recovery of the retinal and neuro-radiological hemorrhages will be demonstrated. In parallel to her general recovery, she developed a responsive smile and the flash VEP indicated cortical visual potential. The patient is doing well in her new family. <b>

Despite severe brain injuries associated with AHT, we can demonstrate brain plasticity and visual recovery through flash VEP.

P1-1 Post-COVID-19 paracentral acute middle maculopathy with impending central retinal vein occlusion in a young child

Marwa Abdelshafy Tabl¹, Ahmed Abdelshafy Tabl¹

¹Ophthalmology, Benha University, Egypt

Background COVID-19 has been purported to induce inflammatory changes that predispose the patient to thrombotic disease in both the venous and arterial circulation.

Case report A 15-year-old female presented with 3-day onset of paracentral scotoma in her right eye (best-corrected visual acuity (BCVA) 6/12) while her left eye was asymptomatic (BCVA 6/6). She had recovered from a COVID19 infection (determined by PCR testing) 3 weeks prior, and her recovery was confirmed using a nasopharyngeal swab followed by detection of serum IgG antibodies against SARS-CoV-2. Funduscopic examination and fluorescein angiography in the right eye revealed scattered retinal hemorrhages, increased venular tortuosity, and a diffuse fern-like retinal whitening consistent with a diagnosis of impending central retinal vein occlusion (CRVO). Optical coherence tomography (OCT) of the right macula, OCT angiography, and enface OCT showed hyper-reflective bands in the inner nuclear layer. The perivenular pattern/fern leaves are typical of what we see in paracentral acute middle maculopathy (PAMM) by enface OCT. Flash and pattern ERG were normal in both eyes, while the mfERG in her right eye showed blunting of foveal and parafoveal responses with normal perifoveal ring responses. These areas of reduced function corresponded to areas of visual field defects. She had no history of hypertension, diabetes mellitus, or risk factors for thromboembolism. The patient underwent thorough hematological workup; all thrombotic workup was negative except for elevated D-dimer test. In particular, there was no evidence of inherited thrombophilia (protein C and S deficiencies, anti-thrombin deficiency). She also tested negative for antiphospholipid syndrome, vasculitis, and myeloproliferative neoplasms.

Conclusions The timing of COVID-19 infection, as documented by antibody testing in this patient with visual symptoms and findings, suggests an association between the two conditions. Electrophysiological tests may represent a fundamental tool in the diagnosis and follow-up evaluations of these patients.

P1-2 Retinal toxicity developed after use of hydroxychloroquine for 5.5 months without any risk factors detected at baseline screening

Soo Chang Cho¹, Ji Eun Lee¹, Kyung Eun Han¹

¹Ewha Womans University Mokdong Hospital, Korea

Background Hydroxychloroquine (HCQ) is one of the preferred drugs for treatment of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). HCQ-induced retinal toxicity involves decreased visual acuity, paracentral scotoma, and a bull’s-eye maculopathy. To the best of our knowledge, there have been a few case reports of HCQ retinopathy with short-term use. We report a case with HCQ retinopathy detected at baseline examination for a patient using HCQ for 5.5 months who had no risk factors, highlighting the potential role of baseline screening for the early detection of retinal toxicity.

Case report A 59-year-old Korean woman weighing 48 kg presented for baseline examination for HCQ retinopathy. She had taken 200 mg/day of HCQ for 5.5 months for rheumatoid arthritis. She complained of blurred vision for 3 months. She denied previous exposure to HCQ or any other medications. She had no kidney or liver dysfunction. Best-corrected visual acuity (BCVA) was 18/20 in the right eye and 16/20 in the left eye. Slit-lamp examination showed multifocal intraocular lens with mild posterior capsular opacity in both eyes. Fundus examination revealed almost normal posterior pole in both eyes. Fundus auto-fluorescence (FAF) showed parafoveal hyper-autofluorescent rings in both eyes. Optical coherence tomography (OCT) showed the ‘flying saucer sign’ with parafoveal photoreceptor (PR) loss and foveal preservation in both eyes. Humphrey visual field (HVF) with 30–2 strategy revealed central scotomas in both eyes. A diagnosis of HCQ-induced retinopathy was made, and HCQ was discontinued. Three months after the baseline screening, BCVA remained stable with similar fundus findings. HVF with 10–2 strategy showed bilateral paracentral scotomas in both eyes. MfERG revealed depression of amplitude and delayed latency in the paracentral area. After discontinuing HCQ for 3 months, partial regeneration of PR was found in the area of previous parafoveal PR loss.

Conclusions We report a case with HCQ retinopathy detected at baseline examination for a patient with no risk factors, who took 200 mg/day of HCQ for 5.5 months. Although 2016 AAO guideline recommend baseline examination to rule out preexisting maculopathy, our case suggests that baseline examination is also necessary to detect early-onset toxicity with short-term use of HCQ. Our case suggests objective tests using OCT and mfERG are particularly useful for such early detection.

P1-3 Digoxin retinopathy that mimics KCNV2 retinopathy

Yuki Nagae¹, Kazuki Kuniyoshi¹, Junji Kato², Marika Ishibashi¹, Fumi Tanabe¹, Naoyuki Okamoto³, Shunji Kusaka¹

¹Kindai University, Japan, ²Kato Cardiovascular Clinic, Japan, ³Okamoto Eye Clinic, Japan

Background Digoxin retinal toxicity causes blurred vision, photophobia, central scotoma, and color vision and electroretinographic (ERG) abnormalities. Here we report a woman who showed abnormalities on transient visual, optical coherence tomographic (OCT), fundus autofluorescence (FAF), and ERG findings that mimicked KCNV2-associated retinopathy.

Case report An 89-year-old woman visited our clinic with complaints of blurred vision, night blindness, photophobia, and color vision abnormality that began on 11^th July 2022. She had atopic dermatitis, tachycardia induced by atrial fibrillation, and a history of mitral valve replacement. Her parents were not consanguineous, nor did she have any family history of visual disturbance. Her decimal best corrected visual acuity (BCVA) was 0.2 in the right eye and 0.15 in the left eye. Her fundi appeared normal, and fluoresceine and indocyanine green fundus angiography were also unremarkable. However, OCT showed a blurred and thickened ellipsoid zone, and FAF showed small ring-shaped hyperfluorescence at the fovea. A dark-adapted (DA)-30 ERG showed a reduced and “squaring” a-wave which, along with a delayed and supernormal b-wave, resulted in a high b/a-wave amplitude ratio (3.24 in the right eye and 3.36 in the left eye). Light-adapted LA-3 and flicker ERG showed severely reduced responses. We treated the patient with sub-Tenon injection of triamcinolone acetonide because an exact diagnosis could not be made at that time. One week later, she reported that she had been treated with digoxin, but its dose had been reduced 2 days before because her serum level of the digoxin had been high (3.5 ng/ml). We finally diagnosed her with digoxin retinal toxicity and observed her without any additional ophthalmic treatment. One month later, the patient’s serum digoxin level was within the normal limit, and her BCVA had improved to 0.6 in the right eye and 0.9 in the left eye. The abnormal hyperfluorescence on FAF disappeared and the thickening of the ellipsoid zone on OCT, amplitude of LA-3, and flicker ERGs were improved. However, the b/a-wave amplitude ratio on DA-30 ERG was still high (2.88 and 3.02 in the right and left eyes, respectively). Serum potassium level was within normal limits throughout the clinical course.

Conclusions The ERG/OCT/FAF abnormalities presented by the patient were similar to those observed in KCNV2 (potassium voltage-gated channel modifier subfamily V member 2)-associated retinopathy (Wu H et al., Am J Human Genet 2006;79:574–579; Robson AG et al., Doc Ophthalmol 2008; 116:79–89) and in a patient with temporal hyperkalemia (Kaizuka C et al. Doc Ophthalmol 2021;143:221–228). Digoxin retinopathy can mimic KCNV2-associated retinopathy because digoxin affects sodium–potassium ATPase and may lead to abnormal potassium levels in the retina.

P1-4 Electroretinographic evaluation of eyes with bleb-associated endophthalmitis that underwent successful vitrectomy with 0.025% povidone iodine irrigation

Koki Sakata¹, Takeshi Katsumoto¹, Yuro Igawa¹, Hirokazu Ishii¹, Tomoyuki Kumagai¹, Yu Sakaki¹, Yuji Yoshikawa¹, Masayuki Shibuya¹, Jun Makita¹, Kei Shinoda¹

¹Departments of Ophthalmology, Saitama Medical University, Faculty of Medicine, Saitama, Japan; 38 Moro-Hongo Moroyama-machi, Iruma-gun, Saitama, 350-0495, Japan

Background While vitrectomy using antibiotic perfusion is recommended for filtering bleb-associated endophthalmitis, there is only one report for two cases that uses 0.025% povidone-iodine (PI) in irrigation solution during vitrectomy. Iodine is reported to be retinotoxic depending on its concentration, raising plausible toxicity concerns with this treatment. ERGs are useful in evaluating endophthalmitis, but contact lens electrodes can interfere with filtering bleb. We performed electroretinographic evaluation in eyes with bleb-associated endophthalmitis that had a successful vitrectomy with 0.025% PI irrigation.

Case reports Case 1 was a 46-year-old male. He had atopic keratoconjunctivitis and underwent trabeculectomy after several months of starting drops in his left eye due to uncontrolled intraocular pressure. One month after the operation, mild filtering bleb-associated endophthalmitis was suspected; then, vitreal and subconjunctival injections of vancomycin (VCM) and ceftazidime (CAZ) and frequent antibiotic eye drops were started. After 3 days, the fundus became invisible and B-mode echo showed a high brightness area. Because he was diagnosed with exacerbation of the endophthalmitis, vitrectomy with VCM, CAZ, and 0.025% PI irrigation was performed. One month after surgery, the visual acuity improved from hand movements to counting fingers. Pre- and post-operative full-field ERGs (DA3.0) recorded using skin electrodes showed improved a- and b-wave amplitudes and the b/a ratio was stable at approximately 2.0. The implicit time of both waves was stable.

Case 2 was a 63-year-old male. He had a history of phacovitrectomy for proliferative diabetic retinopathy 11 years prior and trabeculectomy for glaucoma 5 years prior in the left eye. Five years after surgery, the eye developed blebitis, and frequent antibiotic eye drops and subconjunctival injections of VCM and CAZ were performed. Three days after the start of treatment, a vitreous opacity appeared, and a high brightness area was observed on B-mode echo. A diagnosis of bleb-associated endophthalmitis was made, and vitrectomy with VCM, CAZ, and 0.025% PI irrigation was performed. Preoperative visual acuity was hand movements and recovered to 0.01 logMAR 1 month after surgery. Compared with the preoperative ERG (DA 3.0), the a- and b-wave amplitudes increased, and the b/a ratio was stable at approximately 1.5 postoperatively. The implicit time of both waves was almost unchanged.

Conclusions Vitrectomy with 0.025% PI irrigation may be safe and effective for the treatment of bleb-associated endophthalmitis. Skin electrode ERG recordings were useful for evaluating perioperative retinal function of bleb-associated endophthalmitis.

P1-5 Correlation between electroretinography findings using skin electrodes for endophthalmitis and visual acuity after treatment

Shunichiro Takano^1,2, Yuro Igawa¹, Takahumi Maruyama¹, Jun Makita¹, Yuji Yoshikawa¹, Takuhei Shoji^1,3, Kei Shinoda¹, Soichi Matsumoto⁴, Yozo Miyake⁵

¹Department of Ophthalmology, Saitama Medical University school of Medicine, Japan, ²Department of Ophthalmology, Teikyo University School of Medicine, Mizonokuchi Hospital, Japan, ³Koedo Eye Institute, ⁴Matsumoto Eye Clinic, Japan, ⁵Kobe City Eye Hospital, Japan

Purpose In clinical practice, less invasive and rapid tests are desirable for functional evaluation of infectious endophthalmitis. The purpose of this study was to retrospectively examine the correlation between the pre-treatment LA3.0 and flicker ERGs, which take minimal time for recordings, and post-treatment visual acuity, and to investigate whether it is possible to predict the visual prognosis of endophthalmitis by ERG.

Methods Twenty-five cases (17 males, 8 females, age 66 ± 14 years [mean ± standard deviation]) of postoperative or endogenous endophthalmitis patients treated at Saitama Medical University Hospital from January 2015 to November 2022 and underwent ERG recordings before treatment were included. The above cases were classified into 2 groups: postoperative endophthalmitis group (S group, n = 16) and endogenous endophthalmitis group (E group, n = 9). In one case who had bilateral endophthalmitis, 1 eye had no light perception on the initial examination; therefore, only the other eye that had light perception was included for analysis. LA3.0 and flicker ERGs were recorded using RETeval® (Mayo Corporation, Inazawa, Japan). The amplitude and latency of the ERG components were measured and their correlation with best corrected visual logMAR acuity (BCVA) after treatment was examined.

Results Surgical treatment was done on 22 eyes. Pars plana vitrectomy was done in 19 eyes (13 eyes in S group and 6 eyes in E group), 2 eyes underwent enucleation (E group), and 1 eye underwent anterior chamber irrigation with intravitreal antibiotics injection (S group). Three eyes received only non-surgical treatment. The amplitude of the flicker response (ρ = − 0.6587, p = 0.0003), the cone a-wave (ρ = 0.5017, p = 0.0106), and the cone b-wave (ρ = − 0.7219, p < 0.0001) was correlated with logMAR VA after treatment. In E group, the amplitude of the flicker response (ρ = − 0.8333, p = 0.0053) was correlated with logMAR VA after treatment (Spearman’s rank correlation coefficient). The results suggest that larger amplitude was associated with better BCVA after treatment.

Conclusions The results suggest that cone and flicker responses recorded using skin electrodes can be the indicators to predict the visual prognosis in eyes with endophthalmitis.

P1-6 Early changes in photopic negative response in eyes with glaucoma with and without choroidal detachment after filtration surgery

Yuro Igawa¹, Takuhei Shoji², Jun Makita¹, Yuji Yoshikawa¹, Shunichiro Takano³, Satomi Konno¹, Kei Shinoda¹, Yozo Miyake⁴

¹Saitama Medical University, Japan, ²Koedo Eye Institute, Japan, ³Teikyo University School of Medicine, Mizonokuchi Hospital, Japan, ⁴Kobe City Eye Hospital, Japan

Purpose We presented ERG improvement of retinal function in eyes with glaucoma in the early postoperative period following glaucoma filtration surgery (ISCEV 2022, Liverpool). We have investigated the ERG changes between two groups of patients according to the presence or absence of choroidal detachment (CD).

Methods This retrospective observational single-center study included 57 consecutive patients with primary open-angle glaucoma who underwent unilateral glaucoma filtration surgery between September 2020 and June 2021. We analyzed the light-adapted ERG that had been recorded within 5.1 (2.1–8.1) (mean (95% CI)) days after surgery using the RETeval system (LKC Technologies, Gaithersburg, MD; Welch Allyn, Skaneateles Falls, New York, USA), a portable ERG device that uses skin electrodes. The stimuli consisted of a red flashing light (intensity 1.0 cd s/m², stimulus duration 4 ms) on a stable blue background light (10 cd/m²). The photopic negative responses (PhNR) were compared between eyes that developed CD (CD group) and eyes that did not (Non-CD group) after surgery.

Results There were 11 eyes in the CD group; mean (± SD) age was 72.0 ± 10.6 years, mean deviation (MD) was − 18.4 ± 7.5 dB. There were 46 eyes in Non-CD group; mean (± SD) age was 67.8 ± 11.9 years, MD was − 19.7 ± 6.5 dB. The mean (95% CI) intraocular pressure (IOP) decreased from 20.1 (15.6–24.6) to 6.4 (4.6–8.1) in CD group and from 19.3 (17.5–21.1) to 9.7 (8.6–10.7) mmHg in Non-CD group. No significant difference was found in the IOP change between the two groups (p = 0.088). While PhNR amplitude was significantly reduced (p = 0.002) in the CD group, PhNR amplitude, PhNR/b-wave amplitude ratio, and PhNR implicit time were improved significantly after surgery (p = 0.008, 0.002, and 0.039, respectively) in the Non-CD group. Postoperative IOP (p = 0.031) and postoperative presence of CD (p < 0.001) were significantly associated with change in the PhNR amplitude in the univariate models. In the multivariate analysis, severe CD (stage 3) cases tended to show more deterioration.

Conclusions Even in the early postoperative period within several days, the PhNR amplitude increased with IOP lowering following filtration surgery in the absence of CD. The presence of CD may arrest the improvement of retinal ganglion cell function. The present results enhance understanding the structural and functional recovery after glaucoma surgery and the role of postoperative CD.

P1-7 The effect of subretinal fluid reduction on macular function in age-related macular degeneration treated with anti-VEGF therapy

Tomoharu Nishimura¹, Shigeki Machida¹

¹Dokkyo Medical University Saitama Medical Center, Japan

Purpose A small amount of subretinal fluid (SRF) remaining after anti-VEGF therapy for age-related macular degeneration (AMD) has been reported to have no adverse effect on the visual prognosis evaluated by best corrected visual acuity (BCVA). The aim is to determine the SRF amount which would not influence macular function from an electrophysiological point of view.

Methods Intravitreal aflibercept injections (IVA) were made monthly for 3 months in 47 eyes of 47 AMD patients without previous treatment. The focal macular electroretinogram (fmERG) and spectral-domain optical coherence tomography (OCT) were performed before and after the treatment. In OCT images, the SRF thickness was measured from the ellipsoid zone to the retinal pigment epithelium. The fmERG b-wave amplitude was recorded by using a 15° circular stimulus spot. The correlation coefficients between the SRF thickness reduction (SRF reduction) and the b-wave amplitude improvement (b-wave recovery) after the treatments were determined.

Results The SRF disappeared in all cases after the consecutive three IVAs. The BCVA improvement did not correlate with the SRF reduction. The median values of the SRF reduction and b-wave recovery were 76.5 (5–180) μm and 0.4 (0.1–1.4) μV, respectively. These factors were non-linearly and significantly correlated (R = 0.67, p < 0.001), which was expressed by an equation of Y = 252.6*X/X + 0.754 in which X and Y represent the b-wave recovery and SRF reduction, respectively. According to the equation, when the SRF reduction was less than 29.6 μm, the b-wave recovery was less than 0.1 μV, which is the minimum measurable unit of the fmERG.

Conclusions When the AMD eyes with SRF less than 30 μm in thickness were treated with IVAs, significant improvement in the fmERG b-wave was not obtained. Therefore, macular function may not be expected to improve by anti-VEGF therapy within the initial 3 months when the SRF thickness is less than 30 μm.

P1-8 Changes in retinal function using the multifocal electroretinogram after intravitreal anti-vascular endothelial growth factor injection in chronic central serous chorioretinopathy patients

Hoon Dong Kim¹, Young-Hoon Ohn¹, Jee Yun Ahn², In Hwan Cho¹

¹Department of Ophthalmology, College of Medicine, Soonchunhyang University, Cheonan, Korea, ²Department of Ophthalmology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul, Korea

Purpose To evaluate the anatomical and functional changes in chronic central serous chorioretinopathy (CSC) patients after intravitreal anti-vascular endothelial growth factor (VEGF) injection, and to compare the functional outcomes with those who did not receive anti-VEGF injection.

Methods In a prospective interventional study, 30 eyes of 30 patients with idiopathic CSC at least 3 months in duration were included. Twenty patients (Injection Group) underwent intravitreal bevacizumab injection, and conservative treatment was applied for remaining 20 patients (Observation Group). Optical coherence tomography (OCT) was performed, and central retinal thickness (CRT) and presence of subretinal fluid (SRF) were evaluated. Multifocal electroretinogram (mfERG) was also performed to compare the changes in retinal function between the two groups. The subjects were followed up for 6 months.

Results There were no differences between the two groups in age, gender, and initial BCVA. After 6 months, 17 patients in the Observation Group and 19 in the Injection Group showed complete resolution of subretinal fluid (SRF). The mean time from baseline to initial complete resolution of SRF was 3.45 ± 2.28 months in the Observation Group, and 1.62 ± 0.51 months in the Injection Group (p < 0.001). The mean CRT was significantly thinner in the Injection Group after 1 month and 3 months (p < 0.001, p = 0.002). However, the functional status using mfERG showed no significant difference between the two groups for 6 months.

Conclusions These results suggest that intravitreal bevacizumab injection resulted in rapid resolution of serous detachment in chronic CSC patients. However, bevacizumab injection did not result in functional improvement of the retina. Further study in chronic CSC patients with various anti-VEGF agents for a long observation period is necessary.

P1-9 A case of AZOOR in a patient with multiple sclerosis: The importance of ERG for diagnosis

Fumihiro Hara¹, Toshiaki Hirakata¹, Shintaro Nakao¹

¹Department of Ophthalmology, Juntendo University Faculty of Medicine, Japan.

Background Multiple sclerosis (MS) is known to be occasionally complicated by optic neuritis. On the other hand, acute zonal occult outer retinopathy (AZOOR) is characterized by the sudden onset of subjective scotomas and photopsia due to loss of areas of the outer retina with a normal fundus aspect. Therefore, it is often important to differentiate AZOOR from optic nerve disease. Gass et al. reported that 8% of acute AZOOR patients had a past history of MS (Gass, AJO, 2022). However, to the best of our knowledge, there are few reports of cases of AZOOR and MS occurring simultaneously. Here, we report a case of AZOOR during MS treatment, in which the ERG was useful for diagnosis.

Case report A 33-year-old Japanese woman was diagnosed with MS and treated with fingolimod hydrochloride for 10 years. She had regular visits to our department to monitor for drug toxicity to the eye. At the age of 28 years, she noticed a mild loss of visual acuity and developed photophobia in the right eye. Initial best-corrected decimal visual acuity was 0.8 and 0.9 in the right and left eye, respectively. A slight reduction in central critical flicker fusion frequency (CFF) was observed in the right eye (33.67 Hz) compared with the left eye (37.67 Hz). Fundus ophthalmoscopy and fundus autofluorescence images showed no abnormalities in either eye. Because she was being treated for MS, optic neuritis was considered as a differential diagnosis. However, optic coherence tomography (OCT) images showed a slight discontinuity in the interdigitation zone in the right eye, while the left eye was normal. An ERG was performed using the ISCEV standard protocol, and abnormalities were observed only in the right eye. Multifocal ERG showed moderately reduced response in the central retina and severely reduced in the peripheral macula of the right eye. Full-field ERG showed the mixed rod-cone ERG (DA 3.0) had a moderately reduced a-wave, and the rod ERGs (DA 0.01) and the cone and 30 Hz flicker ERGs were moderately reduced only in the right eye. The a-wave elicited by long duration stimuli (300 cd/m²) were also moderately reduced in the right eye. These findings suggested the diagnosis as AZOOR. After almost 6 months, the visual acuity, IZ in OCT, and ERGs recovered spontaneously.

Conclusions We encountered a case of AZOOR during MS treatment, and the ERG was useful for the diagnosis.

P1-10 Two cases of acute zonal occult outer retinopathy (AZOOR) with selectively impaired cone function

Junya Ota¹, Yoshito Koyanagi¹, Taro Kominami¹, Koji Nishiguchi¹, Shinji Ueno²

¹Nagoya University Graduate School of Medicine, ²Hirosaki University Graduate School of Medicine, Japan.

Background Acute zonal occult outer retinopathy (AZOOR) is an idiopathic disease predominantly characterized by an acute loss of photoreceptor function. Fundus appearance shows minimal abnormalities, and mfERG indicates dysfunction of the corresponding area. Although full-field ERG basically tends to show normal or reduced amplitude in rod and cone responses, cases with lower cone response than rod response were sometimes reported. We report two severe AZOOR cases with total loss of cone response, whereas rod function was preserved.

Case report Case 1: A 37-year-old male was referred to our hospital due to visual field defect (VFD) in both eyes. The VFD was unilateral at first but it expanded to both eyes. His best-corrected visual acuity (BCVA) was 1.0, and fundus image was almost normal. Loss of ellipsoid zone (EZ) was found in optical coherence tomography (OCT), with a corresponding area of VFD and low amplitude in mfERG. The affected area expanded dramatically 2 months after the initial visit, and we diagnosed the patient with AZOOR. Central vison, which was tested with Humphrey Field Analyzer 10–2 program, gradually deteriorated in 7-year follow-up and resulted in reduction of BCVA. Full-field ERGs showed almost normal scotopic ERGs with absence of cone and 30 Hz flicker ERG.

Case 2: A 43-year-old female was referred due to visual field abnormality in both eyes. Visual acuity and Goldmann perimetry showed no abnormality, but scotomas in static visual field tests were detected in both eyes at the first visit. Blurred EZ in OCT and reduction in the amplitude of mfERG were detected in the area corresponding to scotoma. Central vision gradually decreased in both eyes, but its reduction was faster in the left eye. BCVA of left eye declined to 0.25 after 7-year follow-up. This patient also showed normal scotopic ERGs with absence of cone and 30 Hz flicker ERG.

Conclusions We encountered two cases of AZOOR with a highly reduced cone ERG response but a normal rod response. Both patients complained of a visual field abnormality at first; then, visual field loss proceeded gradually and resulted in reduction in visual acuity after several years follow-up.

P1-11 Evaluation of the macular microcirculation and function using optical coherence tomography angiography and mfERG in branch retinal artery occlusion

Haruna Amaki¹, Yuro Igawa¹, Junji Kanno¹, Yuji Yoshikawa¹, Satomi Konno¹, Ayana Hatori¹, Midori Tachibana¹, Takuhei Shoji^1,2, Kei Shinoda¹

¹Department of Ophthalmology, Saitama Medical University Faculty of Medicine, ²Koedo Eye Institute, Japan

Purpose To perform layer by layer analysis of the local retinal microcirculation and electrophysiological response by means of optical coherence tomography angiography (OCTA) and mfERG, respectively, in eyes with branch retinal artery occlusion (BRAO) and to investigate the relationship between them.

Methods Patients with BRAO who visited Saitama Medical University Hospital and underwent OCTA and mfERG examinations on the same day between October 2021 and December 2022 were included. The OCTA examinations were performed using PLEX® Elite 9000 (Carl Zeiss Meditec, Germany) within 3 mm square and 6 mm square volume scan centered on the fovea. The macular vessel density (mVD) in the superficial retinal layer (SRL) and deep retinal layer (DRL) was measured in the superior and inferior halves of the 3 mm and 6 mm diameter concentric circles, excluding 1 mm diameter circles on the 3 mm and 6 mm square images, respectively. The mfERG was recorded using an LE4100 system (Mayo Corporation, Japan) under ordinary room light with pupil dilation. The stimuli were displayed with a digital light processing projector and consisted of 9 elements arranged in a dart pattern with an overall diameter of 3.37°, 10.1°, or 20.2°; they were designed to record a focal response from the retina corresponding to the OCTA examination. The amplitude of the N1, N1-P1, and P1-N2 waves and the latency of the N1, P1, and N2 waves were measured in the superior and inferior halves of 10.1° and 20.2° diameter concentric circles, excluding the 3.37° diameter circle. The ratio of the affected side to the vertically opposite side (a/o ratio) for the mVD and mfERG parameters was calculated, and their correlations were statistically evaluated.

Results Seven eyes of 6 patients with a mean age of 71.7 ± 10.6 years (3 males, 3 females) were included in the analysis. OCTA examination showed that the mVD of the 3 mm concentric circle in DRL tended to be smaller on the affected side than on the vertically opposite side (p = 0.0781). MfERG showed that N1 amplitude of 20.2° concentric circle was significantly lower on the affected side than on the vertically opposite side (p = 0.0469) and that the N1-P1 amplitude of the 10. 1° concentric circle was significantly lower on the affected side than on the vertically opposite side (p = 0.0313). Significantly positive correlation was observed between the a/o ratio in the mVD of the 6 mm concentric circle in DRL and the a/o ratio in the P1-N2 amplitude of the 20.2° concentric circle (coefficient 0.8571, p = 0.0137).

Conclusions OCTA was able to detect deep retinal microcirculatory disturbance and mfERG was able to detect dysfunction of the middle and inner retinal layers on the affected side in the macula in eyes with BRAO. A correlation between decreased mVD in DRL and attenuation of inner retinal function was observed. Layer-by-layer analysis of local retinal microcirculation and function may be useful for understanding the pathology of BRAO.

P1-12 Impaired ERG responses in eyes with acute primary angle closure

Atsuhiro Tanikawa^1,2, Masayuki Horiguchi², Ryoko Nomura², Tadashi Mizuguchi², Yoshiaki Shimada², Yasuki Ito²

¹Fujita Health University Bantane Hospital, Japan,²Fujita Health University, Japan

Purpose To determine if ERG waveforms are altered in eyes with acute primary angle closure (APAC).

Methods Seventeen patients with unilateral APAC were examined. There were 2 males and 15 females with a mean (± SD) age of 70.0 ± 7.1 years. The photopic ERGs were elicited by red stimuli on a blue background using the RETeval system (LKC Technologies, Gaithersburg, MD) without mydriasis. The amplitudes and the implicit times of a-wave, b-wave, and photopic negative response (PhNR), and the pupil diameter were compared between affected and fellow eyes using a paired t test.

Results The mean intraocular pressure in the affected eye at the time of ERG recording was 34.2 ± 9.6 mmHg. The amplitudes of a- and b-waves in the affected eye were not significantly different from those in the fellow eye. In contrast, the amplitude of the PhNR in the affected eye was significantly reduced (p < 0.001). The implicit times of a- and b- waves were significantly prolonged (p = 0.006 and 0.002, respectively), but the implicit time of the PhNR was not significantly delayed (affected eye: 78.2 ± 12.3 ms; fellow eye: 75.0 ± 8.4 ms, p = 0.403). The mean pupil diameter during the ERG recording in the affected eye was significantly enlarged (p < 0.001).

Conclusions Pupils are moderately dilated in patients with APAC, which may have an effect on the ERG waveform, but selective attenuation of the PhNR amplitude suggests some impairments of the inner retina.

P1-13 Relationship between deep retinal macular vessel density and bipolar cell function in glaucomatous eyes

Yuji Yoshikawa¹, Takuhei Shoji^1,2, Junji Kanno¹, Yuro Igawa¹, Minami Chino¹, Hirokazu Ishii¹, Kei Shinoda¹, Yozo Miyake³

¹Saitama Medical University, ²Koedo Eye Institute, ³Kobe City Eye Hospital, Japan

Purpose To evaluate the correlation between macular retinal function and changes in macular retinal vascular structure in glaucomatous eyes.

Methods Patients with glaucoma who visited Saitama Medical University and underwent optical coherence tomography angiography (OCTA) and multifocal ERG (mfERG) examinations at the same time between February 2020 and April 2021 were included. OCTA examinations were performed using PLEX® Elite 9000 (Carl Zeiss Meditec, Germany) within a 6 mm × 6 mm (300 × 300 pixels) volume scan centered on the fovea. Macular vessel density (mVD) was measured within a 6 mm diameter circle and calculated for both the superficial and deep retinal layers. The mfERG was recorded using an LE4100 system (Mayo Corporation, Japan) under ordinary room light with a natural pupil. The stimuli were displayed with a digital light processing projector and consisted of 9 elements arranged in a dart pattern with an overall diameter of 3.37°, 10.1°, or 20.2°; they were designed to record a focal response from the retina corresponding to the OCTA examination. The amplitude and latency of the N1 wave, and the N1-P1 amplitude and latency of the P1 wave were measured in a circle at 20° in the central fovea. The correlations between mVD and mfERG parameters were evaluated using a mixed model.

Results Forty-one eyes of 24 subjects were included in the analysis. The patients had a mean age of 75.2 ± 8.3 years, and the mean deviation (MD) was − 12.4 ± 7.8 dB. The OCTA and mfERG parameters were as follows: superficial-mVD; 38.2% (quartiles 35.5, 40.5), deep-mVD; 53.3% (42.7, 56.7), N1 amplitude − 5.50 ± 2.19 nV/deg², N1-P1 amplitude 11.4 ± 4.9 nV/deg²; N1 latency 17.6 ± 2.8 ms; and P1 latency 33.1 ± 2.2 ms. There were no significant correlations for superficial-mVD and mfERG parameters. However, deep-mVD showed a significant positive correlation with P1-N1 amplitude (coefficient 0.724, p = 0.001).

Conclusions Correlation between N1-P1 amplitude and deep-mVD was observed in glaucomatous eyes, which suggests that impaired deep retinal microcirculation is associated with bipolar cell dysfunction in eyes with glaucoma.

P1-14 Correlation between the visual field test and multifocal electroretinography in early glaucoma patients

Juno Kim¹, Sang Eun Im¹, Seung Joo Ha¹, Kyung Seek Choi¹

¹Department of Ophthalmology, Soonchunhyang University Hospital, Seoul, Korea

Purpose To assess the correlation between responses of the mfERG and the visual field test in early glaucoma patients.

Methods For screening, we compared the mfERG amplitude of 22 normal subjects by separating the result of mfERG by upper and lower visual fields of each individual and found that there was no significant difference between the 2 halves. For the study, 21 eyes of 20 early glaucoma patients without any retinal diseases were included. Humphrey visual field tests (SITA 24-2) and mfERGs were performed. VF and mfERG were divided into upper and lower parts. The correlation between the damaged or intact part of visual field (upper or lower) and amplitude of the corresponding part of mfERG was assessed.

Results In early glaucoma patients, the amplitude of the mfERG was significantly lower in the half that corresponded to the damaged part in the visual field test (mean amplitude 21.47 ± 7.87) compared to the counter (intact) part (mean amplitude 25.34 ± 7.91).

Conclusions In patients with early glaucoma, visual field defects start usually in a small part of the field. We found that visual field defects and the amplitudes of the mfERG in the corresponding section were positively correlated in early glaucoma patients. With further study, abnormalities of the mfERG could be a useful detection tool for early glaucoma.

P1-15 Case of autoimmune retinopathy with negative full-field ERGs similar to melanoma-associated retinopathy

Terauchi Gaku¹, Mizuno Yoshinobu¹, Inoue Yuji¹, Mizota Atsushi¹

¹Teikyo University School of Medicine, Japan

Background Eyes with melanoma-associated retinopathy (MAR) have a characteristic negative type full-field ERG. We report a case with a negative type full-field ERG in which a primary tumor could not be found.

Case report The patient was a 63-year-old woman with a chief complaint of a disturbance of the visual field (VF) in her right eye. The best-corrected visual acuity (BCVA) was 16/20 with a concentric contraction of the VF and enlargement of optic disc cupping. The fundus findings were otherwise normal expect for the relatively large cupping of the right optic disk. The full-field ERGs in the right eye had a negative shape and those in the left eye were normal. Long-duration ERGs showed a loss of the on-response in the right eye. MAR was suspected, and 5-S-cysteinyldopa (5-SCD) and positron emission tomography (PET) were performed, but no abnormal findings were found. There were no findings suggestive of melanoma on examination by a dermatologist. The patient was followed without treatment because the cause was unknown and the signs and cymptoms non-progressive. One year later, similar signs and symptoms appeared in the left eye. The ERG changes were similar to those in the right eye. A second PET examination showed an abnormal uptake in the lumbar lymph nodes, but a primary tumor was not found. The abnormal uptake by the lymph nodes was diagnosed as being inflammatory in origin. We suspected autoimmune retinopathy, and steroid pulse therapy was performed, but it was ineffective.

Conclusions We report our findings in a case of suspected autoimmune retinopathy that had a negative type ERG similar to that in patients with MAR. Extensive examinations did not find a melanoma.

P1-16 Ketamine induced retinopathy with electronegative waveform on full field electroretinogram: A case report

Wing Yung¹, Chun Yue Mak¹, Ching Yan Noel Chan¹, Wai Kuen Yip¹, Alvin Lerrmann Young¹

¹Prince of Wales Hospital

Background Ketamine is a psychedelic anaesthetic agent that is widely used both under medical supervision and as a drug of abuse. Ketamine has myriad side effects across different body systems, but toxic retinopathy has not been reported in the literature.

Case report We report here the first case of reversible retinopathy in association with ketamine abuse. A 34-year-old female who uses ketamine regularly for recreational purpose presented with bilateral blurring of vision. Fundal examination and magnetic resonance imaging of the brain and orbits were non-revealing. Full-field electroretinogram (ffERG) showed electronegative waveforms during scotopic testing and reduced amplitude in the photopic flicker response. Furthermore, both the visual disturbance and electronegative waveforms subsided after abstinence from ketamine and recurred when ketamine was resumed.

Conclusions Ketamine can lead to a reversible toxic retinopathy. In patients with an otherwise unexplained toxic retinopathy, thorough drug history must be elicited to identify potential culprits. Early and sustained abstinence from ketamine may be curative.

P1-17 Electroretinography guides investigations leading to diagnosis of cutaneous melanoma; subsequent course following systemic and local treatments

Jit Kai Tan^1,2, Edward Bloch^1,2,3,4, Anthony G. Robson^3,5, Isabelle Chow^1,2, Gordon T. Plant⁶, Jonathan Virgo^1,2, Moin D. Mohamed^1,2, Omar A. Mahroo^1,2,3,4

¹Section of Ophthalmology, King’s College London, St Thomas’ Hospital Campus, London, UK, ²Department of Ophthalmology, St Thomas’ Hospital, London, UK, ³UCL Institute of Ophthalmology, University College London, UK, ⁴Retinal Service, Moorfields Eye Hospital, London, UK, ⁵Department of Electrophysiology, Moorfields Eye Hospital, London, UK, ⁶UCL Queen Square Institute of Neurology, University College London, UK

Background Melanoma-associated retinopathy (MAR) is associated with distinctive ERG changes that can guide diagnosis. Usually, the diagnosis of melanoma is already known. The course of visual dysfunction can be variable and challenging to treat. Here, we report a patient with visual symptoms and no known history of melanoma, in whom ERG findings guided further investigation, resulting in the discovery of metastatic melanoma and appropriate treatment. We also report the persistence of visual impairment and possible response to treatments.

Case report An 81-year-old man reported mistiness in the vision of his right eye. His medical history included cardiovascular morbidities and previous left eye cataract surgery. He underwent right cataract surgery with no improvement in symptoms. He also began to notice left eye blurring of vision and the sensation of purple bands of light paracentrally. Visual acuity was 20/40 in the right eye and 20/30 in the left eye. Visual field testing revealed right central and left centrocaecal scotomas. Clinical examination showed disc pallor, with retinal thinning seen on optical coherence tomography. Fluorescein angiography showed some non-specific late leakage and no related abnormalities were found on chest radiography, magnetic resonance imaging of brain and orbits, or on blood tests. ISCEV-standard full-field ERGs were consistent with generalised rod and cone ON-bipolar cell dysfunction bilaterally, with LA 30 Hz, LA3 and photopic ON–OFF ERG evidence of more severe ON-system dysfunction as well as additional OFF-system involvement in the left eye. The ERG findings raised the possibility of a paraneoplastic retinopathy, with ERGs noted to resemble those associated with MAR and rarely carcinoma-associated retinopathy. Pattern ERGs were undetectable in keeping with severe macular dysfunction. Positron-emission tomography (PET) scanning was arranged and revealed activity in the left axilla. Subsequent biopsy of the axillary lymph nodes was positive for metastatic melanoma. Review in the melanoma service led to the discovery and removal of an atypical cutaneous lesion, analysis of which was consistent with melanoma. The patient underwent systemic treatment, which led to complete remission of melanoma. His visual symptoms persisted and worsened (acuity dropping to 20/120 in the right eye and 20/600 in the left). Cycles of plasma exchange did not appear to help. In light of reports of possible benefit of intravitreal steroid in cases of MAR, the patient underwent intravitreal dexamethasone implants. This appeared to confer subjective and objective visual benefit in both eyes, and following multiple treatments, visual acuity appeared to be maintained with some fluctuation at around 20/80. Intraocular pressure rises were observed and these were managed effectively with topical treatment.

Conclusions This case highlights the importance of considering paraneoplastic disease when ERG abnormalities are suggestive, prompting early detection and likely promoting survival. Our case shows that MAR may be associated with asymmetrical retinal dysfunction including unilateral OFF system involvement. The visual dysfunction can persist even after oncological remission and poses challenges for treatment. Our case is consistent with a possible benefit of intravitreal steroid, but a causal relationship here is not definite.

P1-18 Multifocal electroretinography changes following L-shaped macular buckle implantation

Yolanda W. Y. Yip¹, Marten Erik Brelen¹

¹Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong

Purpose To investigate the functional improvement in the macula using multifocal electroretinography (mfERG) following L-shaped macular buckle implantation in patients with recurrent myopic macular hole retinal detachment (MHRD) or foveoschisis foveal detachment (FSFD).

Methods A total of 4 eyes from 4 patients with recurrent MHRD or FSFD underwent L-shaped macular buckling surgery. The mean amplitudes of first- and second-order kernel responses from mfERG were compared with a control group of 5 eyes, as well as preoperative and postoperative results in the MHRD/FSFD eyes. Additionally, correlation analysis was performed between mfERG response amplitudes, optical coherence tomography (OCT) parameters, and best-corrected visual acuity.

Results Prior to treatment, mfERG results from the myopic MHRD/FSFD eyes showed significant reductions in first-order kernel response amplitude of ring 1 to ring 3 (p = 0.016) and second-order kernel P1 amplitude of all rings (p ≤ 0.032) and N1 amplitude of ring 1–4 (p = 0.016) when compared to controls. Following L-shaped buckling surgery, mfERG results showed significant improvements in first-order mfERG P1 amplitude at 3 months postoperatively (p < 0.05) and first-order P1, N1, and second-order N1 amplitudes at 6 months postoperatively (p < 0.05). Correlation analysis revealed a significant correlation between visual acuity and second-order amplitudes of ring 2 (p < 0.005). No significant correlation was found between OCT parameters and mfERG responses or best-corrected visual acuity (p > 0.05).

Conclusions Functional improvement following L-shaped macular buckle implantation in patients with myopic MHRD/FSFD begins in the peripheral macula and progresses inward towards the fovea, with the inner retina recovering more slowly than the outer retina. Additionally, visual acuity was found to correlate with the severity of paracentral inner macular dysfunction as measured by mfERG.

P1-19 Relationships between vascular structure and neural function of the macula in patients with diabetes mellitus

Satoshi Ebihara¹, Shigeki Machida¹, Yuji Hara¹, Atsushi Tada¹, Masahiko Ishizuka¹, Mana Gonmori¹, Tomoharu Nishimura¹

¹Dokkyo Medical University Saitama Medical Center, Japan

Purpose To determine the significance of the correlation between the vascular structure and the neural function of the macula in patients with diabetes mellitus.

Methods Ninety eyes of 90 diabetic patients with an average age of 63.5 ± 13.8 years were studied. There were 50 eyes without clinically apparent diabetic retinopathy (non-DR) and 40 eyes with mild to moderate non-proliferative DR (NPDR). Thirty age-matched normal subjects were also studied in the same way. Swept source optical coherence tomography angiography (OCTA) was performed to obtain 3 × 3 mm enface images of the posterior pole of the eye. The vascular density (VD) of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) was determined. Focal macular ERGs elicited by a 15° circular stimulus were recorded. The amplitudes of the a- and b-waves, sum of the oscillatory potentials (ΣOPs), and photopic negative response (PhNR), and the implicit times of the OPs (OP1–OP3) were measured.

Results The VDs of the SCP and DCP were reduced in eyes with advanced DR (p < 0.01 for the SCP). The implicit times of OP1-OP3 were significantly prolonged in eyes with a lower VD of the SCP and DCP in the non-DR group (p < 0.05). The amplitudes of the ΣOPs were significantly smaller in eyes with a reduced VD of the SCP and DCP in the NPDR group (p < 0.05). The correlation coefficients were higher for the OP implicit times than for the ΣOPs amplitudes in the non-DR group.

Conclusions The OPs of the focal macular ERG are smaller with prolonged implicit times in association with capillary loss in the macula of diabetic patients. The implicit times are the most sensitive functional parameter that reflects the early changes of the microvasculature in the macula caused by diabetes.

P1-20 Comparison of the ability of the 30-Hz flicker response and oscillatory potentials of electroretinograms in discriminating eyes with diabetic retinopathy

Mana Gonmori¹, Shigeki Machida¹, Satoshi Ebihara¹, Atsushi Tada¹, Masahiko Ishizuka¹, Shinya Inoue¹

¹Dokkyo Medical University Saitama Medical Center, Japan

Purpose The implicit times of the 30-Hz flicker response and oscillatory potentials (OPs) of the electroretinogram (ERG) have been reported to be useful in detecting functional abnormalities of the retina in patients with diabetes mellitus. The aim of this study was to determine which functional indicator is better in discriminating eyes with diabetic retinopathy (DR).

Methods We studied 14 eyes of 14 normal subjects and 41 eyes of 41 diabetic patients including 21 eyes without diabetic retinopathy (without DR), 9 eyes with simple retinopathy (SDR), 6 eyes with pre-proliferative DR (PPDR), and 5 eyes with proliferative DR (PDR). The mean ages were 75.2 ± 6.2 years ranging from 59 to 83, and 68.2 ± 11.9 ranging from 33 to 92 in normal subjects and diabetic patients, respectively. The full-field ERGs were elicited by light emitting diodes that were embedded in the contact electrodes. Recordings and evaluations of the ERG were made according to the ISCEV standard. The implicit times of the 30-Hz flicker response and OPs (OP1–OP3) were measured. To compare the diagnostic abilities between implicit times of the OPs and flicker response in discriminating eyes with DR from normal eyes, we obtained the area under the curves (AUCs) of the receiver operating characteristic curves for each parameter.

Results The implicit times of the OPs were significantly prolonged with advancing stages of DR (P < 0.0001–0.005) with significant differences between normal eyes and eyes with SDR, PPDR, or PDR. The implicit times of the flicker responses were also prolonged (P < 0.05) with a significant delay in eyes with PPDR or PDR compared to normal eyes. The AUCs were 0.74 (0.56–0.88), 0.75 (0.58–0.88), 0.72 (0.54–0.86), and 0.57 (0.40–0.74) for OP1, OP2, OP3, and flicker response, respectively, with generally larger AUCs for the OPs compared to the flicker response.

Conclusions The implicit time of the OPs was a better functional indicator than that of the flicker response to detect earlier abnormalities in the retinal function of diabetic patients. The OPs implicit times may have better ability in discriminating eyes with DR than the flicker response.

P1-21 Predicting post-operative visual acuity of diabetic vitreous hemorrhage patients by using portable ERG

SangEun Im¹, Juno Kim¹, Kyung Seek Choi¹

¹Soonchunhyang University Hospital, Seoul, South Korea

Purpose To evaluate the correlations between preoperative full-field ERG (recorded with portable RETeval™) and postoperative visual prognosis in diabetic vitreous hemorrhage (DVH) patients.

Methods We investigated the medical records of patients who underwent trans pars plana vitrectomy to remove DVH resulting from PDR (proliferative diabetic retinopathy) between August 2019 and July 2022 in our clinic. We evaluated CDVA (corrected distance visual acuity) before and after the operation and full-field ERG parameters by using a portable RETeval™ with skin electrodes (LKC Technologies, Gaithersburg, MD, USA) before the operation.

Results The study included 20 eyes of 19 patients. There was significant improvement after 1 month in CDVA, from 1.91 ± 0.566 logMAR preoperatively to 0.253 ± 0.185 logMAR postoperatively (p < 0.0004). Photopic ERG parameters showed lower amplitude and longer implicit time compared to normal. Light-adapted 3.0 ERG b-wave amplitudes and flicker ERG amplitudes were positively correlated, and the flicker ERG implicit time was negatively correlated with postoperative visual acuity (correlation coefficients were − 0.683, − 0.693, and 0.695, respectively, p < 0.01).

Conclusions Preoperative full-field ERG acquired using RETeval™ with skin electrodes is helpful for predicting visual outcome in severe diabetic vitreous hemorrhage patients.

P1-22 A case of acquired night blindness with a negative type ERG

Hiromichi Kobori¹, Tomohiro Narumi¹, Shinji Ueno¹

¹Hirosaki University, Japan

Background A selective reduction in the b-wave with a normal or minimally reduced a-wave leading to a negative-type ERG or electronegative ERG often indicates dysfunction of the post-phototransduction pathways. Bilateral negative ERGs are usually detected in hereditary retinal diseases, such as complete- or incomplete-type congenital stationary night blindness (CSNB). On the other hand, melanoma-associated retinopathy is an acquired disease which presents with similar findings to complete-type CSNB, and a few case studies have reported patients with similar findings to the incomplete-type CSNB (Ueno S et al. Jpn J Ophthalmol, 2019; Hirakata T et al. Jpn J Ophthalmol, 2021). We report a case of a patient who complained of night blindness and presented with a negative ERG waveform who had the features of ERGs of both types of CSNB.

Case report A 45-year-old man with schizophrenia was referred to Hirosaki University Hospital for unexplained vision loss. At the time of initial examination, his best-corrected visual acuity was 0.2 for the right eye and 0.15 for the left eye. The fundus photography, optical coherence tomography (OCT), and fundus autofluorescence findings were essentially normal. Full-field ERGs were recorded according to the ISCEV protocol. The ERGs were essentially the same in both eyes. The dark-adapted ERGs elicited by a 0.01 cd s/m² flash (DA 0.01) were completely extinguished. The DA 10.0 ERGs had negative waveforms with normal a-waves. The amplitudes of light-adapted (LA 3.0) ERG and 30 Hz flicker ERG were reduced to 30% and 70% of those of normal ERGs, respectively. The LA 3.0 ERG did not show a square a-wave, which is usually seen in complete CSNB. Systemic screening did not detect cancer, and the symptoms have not changed over the year.

Conclusions The ERG results suggested that this patient undergoing treatment of psychiatric disorders may have bilateral acquired post-phototransductional abnormalities.

P1-23 Electrophysiological evaluations of eyes with reticular pseudodrusen by multifocal electroretinogram

Hisashi Matsubara¹, Ryunosuke Nagashima¹, Kumiko Kato¹, Shinichiro Chujo¹, Yoshitsugu Matsui¹, Taku Sasaki¹, Masahiko Sugimoto¹, Manami Kuze^1,2, Mineo Kondo¹

¹Mie University, Japan, ²Matsusaka Central General Hospital, Japan

Purpose Reticular pseudodrusen (RPD) appears as yellowish interlacing networks in color fundus photographs and has been referred to as the association of photoreceptor damage and a risk factor for progression to late stage age-related macular degeneration (Sadda SR et al., Ophthalmology 2018). We evaluated the relationship between the location of the RPD and electrophysiological function using mfERGs.

Methods We studied 7 eyes of 7 patients with RPD and without choroidal neovascularization (3 male, 4 female; age, 73.0 ± 7.5 years) and 9 eyes of 9 patients with healthy eyes (8 male, 1 female; age, 69.6 ± 6.4 years). The mfERGs were recorded according to the ISCEV Guideline using 61 hexagonal elements. The stimulus elements were grouped by four concentric circles from the center to the periphery (R1, R2, R3, and R4). The implicit time of P1 and the response density of N1-P1 of each group were analyzed. The near-infrared fundus image with the RPD locations plotted was superimposed on the mfERG array image of 61 hexagonal elements. The percentages of hexagonal elements containing at least one RPD or drusen lesion were calculated for each concentric circle.

Results The range of decimal visual acuity was 0.7 to − 1.2 in the RPD group and 1.0–1.5 in the normal group. The percentage of hexagonal elements containing RPD or drusen was did not differ significantly between each group of concentric circles. The median implicit times and response densities were, respectively, 30.83 ms and 20.20 nV/deg² for R1, 30.00 ms and 15.70 nV/deg² for R2, 30.00 ms and 12.20 nV/deg² for R3, and 30.00 ms and 10.60 nV/deg² for R4 in the RPD group. The median implicit times and response densities for the normal group were, respectively, 29.17 ms and 18.70 nV/deg² for R1, 27.50 ms and 13.50 nV/deg² for R2, 26.67 ms and 10.20 nV/deg² for R3, and 27.50 ms and 8.80 nV/deg² for R4. The implicit times of the RPD group were not significantly different from the normal group for R1 and R4, but were significantly prolonged for R2 and R3 (R1, p = 0.11; R2, p < 0.01; R3, p = 0.02; R4, p = 0.065: Mann–Whitney U -test). There were no significant differences in the response density between the normal and RPD groups. The prolongation of the implicit times was not correlated with the percentage of hexagonal elements containing RPD or drusen lesions.

Conclusions The retina with RPD may have subtle functional damage as detected by the prolongation of the implicit times of the mfERG. Further studies are needed regarding the relationship between the location of RPD and functional abnormalities detected by mfERGs.

P2-1 Longitudinal evaluation of retinal electrophysiology in C57BLKsJ-db/db (db/db) mice

Christie Hang-I Lam^1,2, Henry Ho-Lung Chan^1,2, Dennis Yan-Yin Tse^1,2,3

¹School of Optometry, The Hong Kong Polytechnic University, ²Centre for Eye and Vision Research Limited, Hong Kong, ³Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong

Purpose Diabetic retinopathy (DR) is one of the leading causes of blindness and vision impairment. Although DR is commonly associated with microvascular abnormalities, emerging evidence has suggested that functional and structural changes in the retinal neurons may be one of the earliest manifestation of DR and could be used to predict the progression of angiopathy. Numerous rodent models have been used to study in the context of vasculopathy and to test treatment effect on pinpoint vascular lesions in DR. However, the characterization of the early DR phenotype, in particular neurodegeneration, is limited. This study aimed to investigate the longitudinal characteristics of retinal function in db/db mice during the early stage of DR.

Methods Male db/db mice (n = 11) and their normoglycemic heterozygous littermates (db/+, n = 14) were used. The diabetic phenotype of the db/db mice was confirmed by testing the blood glucose levels with a digital blood glucometer after overnight fasting. Those with fasting blood glucose levels ≥ 13.9 mmol/L at 9 weeks of age were included in the experiment. Scotopic full-field ERGs were performed at 9, 13, 17, and 25 weeks of age after at least 16 h of dark adaptation, with white LEDs delivered by a ganzfeld bowl. Stimulation and data recording were performed using the RETI-Port system® according to a customized protocol with stimulus intensities varying from − 4.32 log cd s/m² to + 1.3 log cd s/m². The signals were amplified and band-pass filtered from 1 to 1000 Hz for a- and b-waves. OPs were isolated by digital filtering the raw signal recorded at + 0.3 log cd s/m² in the free software environment R.

Results Our results showed that while both the amplitude and implicit time of scotopic a-waves were not statistically different between the db/db and db/ + mice from 9 to 25 weeks of age, the b-wave amplitude declined with the duration of diabetes. At 25 weeks, the b-wave amplitudes of db/db mice at all tested stimulus intensities were significantly reduced compared to their non-diabetic littermates (p < 0.05). The implicit times of the 4 major OPs, amplitudes of OP1–OP3, and the ∑OPs at 9 weeks were not statistically different between the two groups of mice. However, the amplitude of OP4 in db/db mice was significantly larger than that of the db/ + mice (p = 0.013). At 25 weeks, the amplitudes of the first two major OP wavelets (p ≤ 0.006) and the ∑OPs amplitude (p = 0.009) were significantly reduced in db/db mice compared to db/ + mice. Also, the implicit time of all OPs wavelets of db/db mice was significantly delayed compared to their normoglycemic littermates (p < 0.05).

Conclusions Our data suggest diabetes-induced functional deterioration in the neuroretina, particularly the inner retina (i.e., reduced b-wave and OP amplitudes), of the db/db mice in the early stage of retinopathy. While the mechanistic cause leading to this change remains elusive, the db/db mice could be a useful animal model for testing potential treatment regimens that target the neurodegeneration of DR.

P2-2 Drinking hydrogen water improves photoreceptor structure and function in retinal degeneration 6 mice

Shuhei Kameya^1,2, Tsutomu Igarashi^2,3,4, Ikuroh Ohsawa⁵, Maika Kobayashi³, Kai Miyazaki⁶, Toru Igarashi⁷, Asaka Lee Shiozawa⁴, Yasuhiro Ikeda⁸, Yoshitaka Miyagawa⁴, Mashito Sakai⁴, Takashi Okada⁹, Iwao Sakane¹⁰, Hiroshi Takahashi³

¹Kameya Eye Clinic, ²Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Japan ³Department of Ophthalmology, Nippon Medical School, Japan, ⁴Department of Biochemistry and Molecular Biology, Japan, ⁵Biological Process of Aging, Tokyo Metropolitan Institute of Gerontology, Japan, ⁶Faculty of Medicine, Nippon Medical School, Japan ⁷Department of Pediatrics, Nippon Medical School, Japan, ⁸Department of Ophthalmology, Miyazaki University School of Medicine, Japan, ⁹Division of Molecular and Medical Genetics, Center for Gene and Cell Therapy, Institute of Medical Science, Japan, ¹⁰Central Research Institute, ITO EN, LTD., Japan

Purpose Retinitis pigmentosa (RP) is a genetically heterogeneous group of inherited retinal disorders involving the progressive dysfunction of photoreceptors and the retinal pigment epithelium (RPE) for which there is currently no treatment. Those afflicted with RP inevitably progress to blindness. Over 100 gene mutations have been implicated in the development of this disease. Mutations of the MFRP gene are known to be associated with microphthalmia and RPE atrophy, and the rd6 mouse is a natural model of autosomal recessive retinal degeneration caused by a 4-bp deletion in a splice donor site in Mfrp. Given the known contributions of oxidative stress caused by reactive oxygen species (ROS) and selective inhibition of potent ROS peroxynitrite and OH· by H₂ gas we have previously demonstrated, we hypothesized that ingestion of H₂ water may delay the progression of photoreceptor death in rd6 mice.

Methods Both rd6 mice and C57BL/6J mice were used in the present study. Optical coherence tomography (OCT) imaging, electroretinogram readings, histology and thickness of the outer retina, immunohistochemistry, and RNA-seq and analysis of differentially expressed genes (DEG) were performed, and results were compared between control and H₂ mice.

Results Notably, on OCT, H₂ mice at postnatal age of 21 weeks showed significantly higher retinal thickness as compared to controls. Histopathologic and morphometric analyses revealed greater thickness of the outer nuclear layer for H₂ mice than controls, as well as higher counts of opsin red green-positive cells. RNA-seq analysis of DEG in the H₂ group versus control group revealed 1996 genes with significantly different expression, and gene and pathway ontology analysis showed substantial upregulation of genes responsible for phototransduction in H₂ mice.

Conclusions Our results show that drinking water high in H₂ (1.2–1.6 ppm) had neuroprotective effects and inhibited photoreceptor death in mice, and we suggest the potential of using H₂ for the treatment of RP.

P2-3 Glibenclamide/glyburide retinal neuroprotection: Importance of electroretinographical assessment

Marianne Berdugo¹, Kimberley Delaunay¹, Lolita Radet¹, Cecile Lebon¹, Marie-Christine Naud¹, Gabrielle Polak¹, Emilie Picard¹, Alejandra Daruich¹, Michel Polak², Patricia Crisanti¹, Francine Behar-Cohen^1,3

¹Physiopathology of Ocular Diseases: Therapeutic Innovations, Centre de Recherche des Cordeliers, Sorbonne Universite, Inserm, Universite Paris Cite, F-75006 Paris, France, ²AP-HP, Hopital Necker-Enfants Malades, 75015 Paris, France, Universite Paris Cite, 75006 Paris, Institut Imagine, 75015 Paris France, ³Assistance Publique, Hopitaux de Paris, Hopital Cochin, OphtalmoPole, 75014 Paris France

Purpose In the Goto-Kakizaki (GK) rat model of diabetic retinopathy (DR), reduction in retinal vascular perfusion, blood retinal barrier breakdown, and ERG alteration have been documented. We previously repeatedly showed in this model that treatment by glibenclamide/glyburide (a known hypoglycemic Sulfonylurea) is an efficient therapeutic approach to improve retinal vascular perfusion and visual function (reduction of mixed rod-cone and rod scotopic b-wave implicit times (IT) following blue/white flashes, reduction of OPs IT) and to protect the outer blood retinal barrier (Berdugo M et al., Transl Res:2021;229:83–99; Berdugo M et al., Pharmaceutics:2021;13(7):1095). In this study, we evaluated the feasibility of administering glibenclamide through an intravitreal injection of a novel biodegradable sustained release formulation based on PLGA/PLA microparticles (GLI-MP) in the GK rat model of DR to improve treatment adherence.

Methods Old diabetic GK rats received one intravitreal injection of GLI-MP or empty MP. At t = 2w, in a first group of animals, dextran-FITC was injected intravenously. When the urine was colored, the animals were killed, eyes were enucleated, and neuroretinas were flat-mounted. Confocal microscopy pictures were taken to quantify intratissular dextran-FITC as a representation of the blood retinal barrier status. Semi-quantitative quantification was performed following a blind scoring process: score 1 = poor to score 4 = normal vascular perfusion. On the same whole neuroretina pictures, the number of vascular walls infiltrated with dextran-FITC was counted. At t = 28d, in a second group, tolerability of the formulation was assessed in vivo by scotopic and photopic full-field ERG.

Results GLI-MP intravitreal injection very significantly improved vascular perfusion in the neuroretina of old diabetic GK rats (mean semi-quantitative score = 3.86 ± 0.14 in the GLI-MP group vs. 2.33 ± 0.42 in the empty-MP group, p = 0.0041); the number of vascular walls infiltrated with dextran-FITC was significantly reduced (mean = 1.64 ± 1.25 in the GLI-MP group vs. 18.4 ± 1.5 in the empty-MP group, p = 0.005). At 28 days, ERG parameters were either unchanged or deteriorated: scotopic b-wave IT to white flashes were mostly unchanged (p = 0.032 at 0.03 cd s/m² and NS otherwise); scotopic 3rd OP IT was significantly delayed (mean IT =  + 1.62 ± 0.53 ms in the GLI-MP group vs. − 0.37 ± 1.12 ms in the empty-MP group, p = 0.047); photopic 3rd OP implicit time was significantly delayed (mean IT =  + 1.89 ± 0.73 ms in the GLI-MP group vs. − 1.16 ± 0.84 ms in the empty-MP group, p = 0.03). Clinical inflammation was observed following microparticles intravitreal injection that could explain discrepancies between ERG and ex vivo results, reinforcing the value of performing an ERG test, a sensitive procedure, in order to identify a discrete poor tolerance.

Conclusions Glibenclamide/glyburide retinal protective effects during DR in old GK rats are confirmed. Our work pinpoints 1) the sensitivity of ERG testing in such studies, as compared to other examinations, 2) the deleterious effect of non-optimized microparticles that masks the beneficial effect of glibenclamide, and 3) the need to improve such MP slow-release system to deliver glibenclamide to the diabetic retina without exacerbating underlying inflammation.

P2-4 Effects on the electrically evoked cortical potentials by one-month suprachoroidal transretinal stimulation using anodic-first current pulses

Yasuo Terasawa¹, Yukari Nakano¹, Hiroyuki Tashiro²

¹NIDEK CO., LTD., ²Kyushu University, Japan

Purpose Charge-balanced biphasic current pulses are commonly used in neural prostheses in order to prevent net charge injection into the stimulated tissue. Previous studies on retinal prostheses suggested that anodic-first (AF) pulses, biphasic pulses with their first phase positive, more efficiently excite retinal neurons than cathodic-first (CF) pulses when electrodes were placed subretinally or suprachoroidally. On the other hand, the long-term safety of AF pulses to retinal neurons is not well studied. This study aims to investigate the long-term safety of suprachoridally applied AF pulses.

Methods Three Japanese white rabbits were used in this study. An electrode array with two 0.5-mm-diameter platinum electrodes was implanted inside the sclera of the rabbit eye. A 1.4-mm-diameter platinum recording electrode was fixated on the visual cortex of the rabbit (8 mm anterior, 7 mm lateral from lambda). AF current pulses with 1.5 mA amplitude and 0.5 ms width at 50 Hz were applied for 8 h per day for 1 month. Visually evoked cortical potentials (VECPs) and electrically evoked cortical potentials (EECPs) were recorded before and after the 1-month stimulation.

Results No significant differences were observed in either waveforms or amplitudes of VECPs before and after 1-month stimulation. In EECPs, no difference was observed when high-intensity electrical stimulation was applied (1 ms, 1 mA) in EECP measurement; however, when low-intensity stimulation was used (1 ms, 0.6 mA), different waveforms were observed in some cases.

Conclusions The fact that neural responses to optical and electrical stimulation were observed after 1-month stimulation suggested safety of AF suprachoroidal chronic stimulation. As the current study is limited to 1-month stimulation, further investigation with a more extended stimulation period is necessary to prove the long-term safety of AF suprachoroidal stimulation.

P2-5 Inter-pulse interval of paired-pulse stimulation in suprachoroidal-transretinal stimulation in retinal prosthesis

Yukari Nakano¹, Yasuo Terasawa¹, Hajime Sawai²

¹Artificial Vision Institute, R&D Div., Nidek Co., Ltd., ²Department of Health Sciences, School of Nursing, Osaka Metropolitan University, Japan

Purpose We have been developing a retinal prosthesis based on suprachoroidal-transretinal stimulation (STS) and have demonstrated in a previous study that collicular field responses to a train pulse of STS at 20 Hz rapidly decrease in acute animal experiments. This finding suggested that elevation of stimulus threshold and fadeout of phosphenes may occur quickly when using STS. This highlighted the need to elucidate a more efficient frequency for STS than 20 Hz with 50 ms of inter-pulse interval (IPI). Therefore, we first considered IPI and investigated its effect in paired pulse STS on the amplitude of the second response and compared it with the amplitude of the first response.

Methods In the left eye of urethane-anesthetized healthy adult rats (Long-Evans, n = 8), a platinum monopolar stimulating electrode (0.5 mm in diameter and 0.3 mm in height) was placed and a biphasic current pulse was energized between the electrodes (22 G needle) under the nasal skin. Evoked potentials (EPs) produced by retinal electrical stimulation were recorded from the right superior colliculus with a microelectrode (0.5 MΩ tungsten). Stimulation was paired pulses and the IPI between the first and the second pulses varied between 20 and 200 ms. For each stimulation pulse, the first positive peak of EP was defined as P1 and the subsequent negative peak as N1, and the amplitude of EP was analyzed through the following method: (1) baseline-N1: the mean amplitude before electrical train stimulation was set as a baseline and the differences between the baseline and N1 was determined. (2) P1-N1: the difference between P1 and N1 was calculated. All experiments were conducted in accordance with the approval of the institutional Animal Care and Use Committee of Nidek Co., Ltd.

Results The second EPs were significantly suppressed (p < 0.05, paired t test) by 44% (baseline-N1) and 51% (P1-N1) of the first EPs with an IPI of 50 ms, 37% (baseline-N1) and 67% (P1-N1) with an IPI of 60 ms, and 76% (baseline-N1) and 72% (P1-N1) with an IPI of 100 ms. We observed a trend toward recovery as IPIs increased to > 100 ms.

Conclusions A strong suppression of the second response to paired-pulse stimulation with an IPI of approximately 50 ms was found. Similar results have been reported for paired-pulse stimulation using mouse retinal patches and rat optic nerves. It can be said that the IPI length affects the EPs of the second pulse in the visual nerve, which may explain the reduced STS efficiency measured at a frequency of 20 Hz in our previous study. In the future, we propose to study the stimulation interval optimization in continuous stimulation.

P2-6 Circadian rhythms of the electroretinogram of ipRGC and the chronotype in humans

Manami Kuze^1,2, Moto Kataoka¹, Hisashi Matsubara², Yumi Fukuda³, Takeshi Morita⁴

¹Matsusaka Central General Hospital, Japan ²Mie University School of Medicine, Department of Ophthalmology, Japan, ³University of Kitakyusyu, Faculty of Environmental Engineering, Japan, ⁴Fukuoka Women’s University, Japan

Purpose The biological clock regulates circadian rhythms, and intrinsically photosensitive retinal ganglion cells (ipRGCs) play an important role. It is known that every human being has their own chronotype. We recorded electroretinograms (ipRGC-ERG) and investigated the diurnal variation of ipRGC function and chronotype.

Methods Eighteen eyes of 18 normal subjects (mean age 22.4 years) had their ERGs recorded with ipRGC stimulating light using a four-primary-color stimulator. Peak wavelengths (nm) of the stimuli were 633, 593, 508, and 468. After light adaptation, the stimulus for ipRGC was given additional 40% increase and stimulus duration was 250 ms. Five responses were averaged. Recording was performed at 4 times: 8:00, 12:00, 16:00, and 20:00, and daily rhythm was managed from a few days before and until the end of recording. Chronotype was determined by the Morning and Evening Questionnaire (MEQ).

Results Two negative waves were recorded after stimulation and were termed N1 and N2 in order. 8:00/12:00/16:00/20:00 amplitudes (μV) were N1: 19.9 ± 12.0/11.4 ± 15.3/11.4 ± 8.1/15.6 ± 12.8; N2: 11.8 ± 7.5/11.8 ± 8.7 /11.1 ± 8.9/10.6 ± 8.4. Latencies (ms) were N1: 147.0 ± 58.2/158.6 ± 47.2/152.8 ± 38.2/164.3 ± 47.8; N2: 488.2 ± 135.7/475.1 ± 142.7/445.0 ± 151.3/452.7 ± 158.7. N1 amplitude was significantly larger at 8:00 (p < 0.05). N2 amplitude and N1 and N2 latencies did not change significantly.

Conclusions The ipRGC-ERG showed a maximum N1 amplitude at 8:00, indicating that ipRGC function may fluctuate within the day. IpRGC N1 and N2 amplitudes increased with higher MEQ scores.

P2-7 The influence of attention on the pattern electroretinogram and visual evoked potentials

Maja Sustar Habjan¹, Ziga Korent²

¹University Medical Centre Ljubljana, Eye Hospital, Ljubljana, Slovenia, ²University of Ljubljana, MEi:CogSci, Ljubljana, Slovenia

Purpose The aim of the study was to examine if the pattern electroretinogram (PERG) and visual evoked potentials (VEP) might be affected in healthy subjects when the subject’s cooperation and fixation appear appropriate, but their attention to their visual task is distracted during the recording.

Methods The study was performed on 10 healthy volunteers, in which PERG and VEP were recorded simultaneously from one eye. Ten different sets of recordings were made. First, a test recording was made, which was not further analyzed. Subsequently, 9 different recordings were made in a random order—1 with optimal attention and 8 with simultaneous performance of several disturbances (disturbances of focus, mental and sensory disturbances), during which the patient’s fixation remained stable. The values of PERG P50 and N95 waves and VEP P100 wave were analyzed and compared between different sets of recordings with one-way ANOVA and Dunnet post-hoc test.

Results PERG and VEP amplitudes varied between the recordings obtained with optimal attention (P50: 5.8 ± 0.2 µV, P100: 17.9 ± 1.7 µV) and those with distracted attention. A notable deviation of both PERG and VEP amplitude was observed when subjects simulated blurred focus (P50: 4.7 ± 0.3 µV, p < 0.05; P100: 14.9 ± 1.4 µV, p < 0.001), indicating an important influence of optical factors during the recording. A notable deviation of the VEP, without simultaneous PERG reduction, was detected during auditory disturbance (P50: 5.6 ± 0.4 µV; P100: 15.9 ± 1.2 µV, p < 0.001) and mental disturbance with mathematical task (P50: 5.8 ± 0.5 µV; P100: 16.3 ± 1.2 µV, p < 0.01). PERG and VEP peak times showed no difference between recordings obtained with optimal and distracted attention.

Conclusions Even when the patient’s cooperation appears adequate, a lack of attention can significantly affect electrophysiological responses at both the macular and cortical level. This finding indicates the importance of optimal environmental conditions during electrophysiological testing and the need to carefully monitor and encourage the patient’s attention toward the visual stimulus.

P2-8 The consequence of modulating background on the luminance-response function of the human photopic electroretinogram

Avinash J. Aher¹, Jan Kremers¹, Cord Huchzermeyer¹

¹University Hospital Erlangen, Germany

Purpose To study the consequences of modulating background on the luminance response function of the human photopic electroretinogram.

Methods Five healthy subjects (age 29–63 years; two females) participated in the study. First, we measured the response to flashes (9 flash strengths in total ranging from 0.12 to 30.72 cd s/m² while doubling the strength at each step; 5 ms flash duration) on a steady background (24 cd/m²) as a control (1). Second, the responses to a 1 Hz sinusoidally modulating stimulus (24 cd/m² mean luminance; 100% contrast) were recorded (2). Third, the responses to the same flashes as in (1) were recorded on the modulating background as in (2). The flashes were presented at 6 different phases during the sine wave (0°, 90°, 180°, 225°, 270°, and 315°). The responses to the control sine wave (1 Hz) were subtracted from the responses to the combined flash plus sine-wave stimuli to obtain the flash ERGs at different phases. The dependency of a-wave and b-wave amplitudes on flash strength and on flash phase relative to the sinusoidally modulating background was studied.

Results With a steady background and a modulating background at 0° and 180°, the a-wave amplitudes increased with increasing flash strength. The b-wave reached a maximal response at 1.9 cd s/m², above which it decreased again, showing the signature of the “photopic hill effect.” The photopic hill effect was observed for all phases relative to the sinusoidally modulating background; however, the maximal amplitude was higher at phase 270° as compared to other phases. The b-wave amplitude difference for the different flash phases was large for flashes that were weaker than those needed for the photopic hill. For flash strengths beyond the photopic hill, there was no substantial difference in b-wave amplitudes at different flash phases. The amplitudes of the components could be described by the Weber fraction plus saturation and a delay.

Conclusions The present study assesses the effects of dynamic background on the processing of flash stimuli. The b-wave response showed the photopic hill in both steady and dynamic backgrounds; however, the dynamic background enhanced the flash response when presented at the phases where the Weber fraction is higher. Weber fraction of the flashes is an adequate quantification of stimulus strength to describe the amplitudes of the flash ERGs. The ascending limb of the photopic hill was substantially influenced by the Weber fraction of the flash, whereas the effect was very small or absent on the descending limb, suggesting that the Weber fraction of the flash might be processed differently in the ON and OFF post-receptoral pathways that are responsible for the photopic hill.

P2-9 A comparison of alternative methods for the clinical assessment of oscillatory potentials

Laura Milner¹, Lawrence Brown¹, Katherine Pearson¹

¹Sheffield Teaching Hospitals NHS Foundation Trust, UK

Purpose The ISCEV ERG standard advises that the qualitative analysis of OPs and the reporting of the presence of OP peaks and their normality relative to appropriate reference data are adequate for most clinical applications. It states quantification is optional and provides examples of three alternative measurement indices [Robson et al. Doc Ophthalmol 2022;144:165–177]. Current local practice is the former approach. This project aims to determine if this reporting method correlates with the suggested quantitative assessment methods and investigates if there are any differences between the three indices. OPs derived from both the DA 3 and the DA 10 stimuli are analysed to examine if there is any benefit to using either stimulus for OP assessment.

Methods ERG data were exported, and in-house software was used to derive the three alternative measurements proposed by ISCEV: Method 1—individual peak amplitudes measured from their preceding troughs; Method 2—sum of amplitudes of specified peaks; Method 3—integrated root-mean-square amplitude of the OP waveforms. These values were calculated for the local adult ERG reference range (n = 16). All clinical reports that mentioned OPs from 2020 to 2022 were identified. Values were calculated for a cohort of patients where OPs had been clearly reported as bilaterally normal (n = 7) and a cohort where they were reported as bilaterally abnormal (n = 24). If the report referred only to abnormal OP implicit timing and not amplitude, the data were excluded. These three cohorts were compared for each of the three measurement techniques for both the DA 3 and DA 10 stimuli.

Results All three quantitative measurement methods for both stimuli supported current local reporting practices with statistically significant differences identified between the reported abnormal cohort and the reference data. There were no significant differences found between the reference data and the reported normal cohort, although mean OP index values for the reported normal cohort were generally lower than those from the reference data. When considering the current qualitative reporting as ‘gold standard’ and comparing the ability of the different calculation methods and stimuli to determine normality or abnormality of patient OPs, all methods provided high specificity (0.93 for DA 3 using method 1 and 1.00 for all other methods/stimuli). However, sensitivity was more variable, with the DA 3 stimulus performing better at identifying abnormality (sensitivity: method 1 = 0.81, method 2 = 0.73 and method 3 = 0.71) than the DA 10 stimulus (sensitivity: method 1 = 0.54, method 2 = 0.46 and method 3 = 0.44).

Conclusions Quantitative methods of OP analysis broadly correlate with the current local practice of qualitative reporting. There does not appear to be a significant difference between the three indices proposed in the ISCEV standard, although these preliminary findings recognise small numbers and a heterogenous cohort as limitations of this study. Initial results indicate that the DA 3 flash stimulus may provide greater accuracy in detecting OP abnormality compared to the DA 10, and further investigation of this could be warranted.

P2-10 Age-dependencies of the ERG

Ronja Jung¹, Melanie Kempf^1,2, Krunoslav Stingl^1,2, Katarina Stingl^1,2

¹University Eye Hospital, Center for Ophthalmology, University of Tuebingen, 72076 Tuebingen, Germany, ²Center for Rare Eye Diseases, University of Tuebingen, 72076 Tuebingen, Germany

Purpose The ERG of healthy individuals is known to undergo multiple changes with advancing age. However, previous studies on the age dependencies of ERG components have mostly used customized protocols, yielding incomplete and inconsistent findings that are not easily comparable with the commonly used standard tests. Therefore, we reassessed the effects of aging on the amplitudes and implicit times of rod and cone full-field ERGs, including ISCEV standard protocols.

Methods Full-field ERG was conducted in 72 healthy participants in the age range between 14 and 73. The examination protocol comprised different flash stimuli in dark-adapted (DA) and light-adapted (LA) states, with light intensities ranging from 0.001 to 10 cd s/m². Flicker ERGs were performed with 9 and 31 Hz stimuli to assess the function of rod and cone channels, respectively. S-cone responses were isolated with a blue flash stimulus. The activity in ON and OFF channels was separated with a long-duration stimulus. Age dependencies were calculated via correlation analysis.

Results Both scotopic and photopic ERGs displayed significant age-dependencies. Reductions of the a-wave could be detected across all flash intensities, which were accompanied by significant delays in implicit times. The b-wave amplitudes and implicit times were most strongly correlated with age in the rod-driven ERGs with low-intensity flashes. B-waves of either mixed rod-cone or pure cone origin showed amplitude reductions but usually no significant increase in implicit time. In contrast, isolated ON and OFF bipolar cell responses displayed detectable changes in their implicit times, but no significant amplitude reductions. S-cone responses were not significantly correlated with age. Notably, a- and b-wave amplitudes were poorly correlated with one another, especially in rod-mediated conditions. The 31-Hz flicker protocol remained rather stable across all participants, whereas the 9-Hz flicker displayed strong age effects in both amplitude and implicit time.

Conclusions The ERG of healthy individuals undergoes significant changes with advancing age. These alterations are most likely caused by an interplay between diverse processes of retinal and non-retinal origin. A weakening of the signals may, in general, be attributed to changes of the optical media. However, the age-dependencies were more pronounced in the scotopic, rod-driven conditions, pointing to a specific reduction in rod function or number over time. Bipolar cells also displayed significant amplitude reductions with age, which were not correlated with the preceding attenuation of the a-wave. This suggests that bipolar cells themselves also undergo functional changes.

P2-11 Effect of short-term exposures to near work environments on photopic electroretinography

Natalie Yu Yan Chan¹, Kai Yip Choi¹, Henry Ho-lung Chan¹

¹The Hong Kong Polytechnic University

Purpose To investigate the changes in photopic retinal electrophysiological responses after near work under different environments in terms of scene defocus profiles based on the dioptric uniformity hypothesis.

Methods Eighteen healthy myopic Asian young adults age 19–24 years (mean ± SD: 20.99 ± 1.5 years) were recruited. In each of the 3 visits, participants viewed a 30-min video under exposure to one of 3 simulated near work visual scenes with low, mid, and high level of scene defocus dispersion (SDd); these were anticipated to impose an increasingly myopiagenic stimulus to the participant. Photopic standard full-field flash and the 30-Hz flicker ERG were measured before and after scene exposure. Normalized percentage changes in amplitude and implicit time of a- and b-waves and flicker responses were extracted for analysis.

Results The spherical equivalent refraction of subjects ranged from − 1.00 D to − 5.38 D (− 3.20 ± 1.39 D; 8 had low myopia of lower than − 3.00 D and 10 had moderate myopia greater than or equal to − 3.00 D). There was no significant difference in the percentage change in either the amplitude or implicit time of the a- or b-wave under different SDd. The percentage change in amplitude of the 30 Hz flicker ERG was stratified by myopia severity, and statistically significant reduction was obtained under high SDd exposure in moderate myopes (mixed ANOVA, SDd*myopia severity: F_2,32 = 3.68, p = 0.04) but not in low myopes.

Conclusions Significant reduction in the 30-Hz flicker ERG, representing post-receptoral function of the cone pathway, was found in moderate myopes after 30 min of near work under high SDd conditions. Our results implied that dispersed defocus profile in the environment may weaken inner retinal activity in moderate myopes and may relate to myopiagenic risks.

P2-12 Evaluation of retinal function in advanced RP patients using a combination of transcorneal electical stimulation (TES) test and localization test

Takeshi Morimoto¹, Takao Endo², Masakazu Hirota³, Hiroyuki Kanda⁴, Takashi Fujikado.⁵

¹Department of Advanced Visual Neuroscience, Graduate School of Medicine, Osaka University, Japan ²Department of Ophthalmology, Graduate School of Medicine, Osaka University, Japan ³Department of Orthoptics, Faculty of Medical Technology, Teikyo University, Japan ⁴Department of Applied visual Science, Graduate School of Medicine, Osaka University, Japan ⁵Graduate School of Frontier Biosciences, Osaka University, Japan

Purpose Evaluation of visual function in patients with advanced retinitis pigmentosa (RP) to determine their candidacy for a retinal prosthesis is difficult to perform by conventional ophthalmologic examinations. On the contrary, we have developed the TES test to evaluate residual inner retinal function in patients with advanced RP and have also developed a square localization test to evaluate visual function in patients with ultra-low vision. In the present study, we examined the usefulness of combining these tests to evaluate visual function in advanced RP patients.

Methods Eighteen patients with advanced RP participated in this study. Patients included 10 men and 8 women of mean age 64.4 ± 11.5 years (± SD). All subjects were right-handed and the visual acuity ranged from hand motion to bare light perception. A signed written informed consent was obtained from all patients. This study was approved by the Ethics Committee of the Osaka University Hospital. The procedures used conformed to the tenets of the Declaration of Helsinki. TES was performed with a contact lens stimulating electrode. Phosphene determination was subjective. The electrical current threshold for initial phosphene was determined. A square localization tester had white square targets with a visual angle of 10° that were projected randomly on a computer monitor screen. Patients were instructed to touch the center of the target. Each patient was tested 20 times. The distance between the touched point and the center of the target (the absolute deviation) were averaged. Tests were performed on one eye at a time, with the other eye occluded. Both eyes of the patient were measured, and the results of the right eye were used in the analysis unless the patient’s right eye could not perceive the phosphene; in that case, the results of the left eye were used. Correlations among the patient’s visual acuity, phosphene threshold, and results of localization test were calculated.

Results The mean threshold of the initial phosphene was 1.25 ± 0.6 mA (± SD). The mean absolute deviation was 16.0 ± 6.7°. There were no statistically significant correlations between visual acuity, TES results, and localization test results. Patients were divided into 4 groups based on a threshold of 1 mA and 15° of deviation, and the deviation group of less than 1 mA and more than 15° was considered to be the patient group most likely to achieve improvement in visual function with a retinal prosthesis.

Conclusions The combination of TES test and localization test may be useful in evaluating visual function to select candidates for retinal prosthesis in patients with advanced RP who cannot be evaluated with conventional ophthalmologic tests.

P2-13 Full-field pupillary light responses in patients with retinitis pigmentosa and healthy subjects

Natsuki Maetani^1,2, Yu Fujinami-Yokokawa^1,3,4,5, Oscar Onyango^6,7, Yasutaka Suzuki¹, Motoshi Yamamoto^1,2, Kayoko Komatsu^1,2, Jeffrey Farmer⁸, Kazushige Tsunoda^9,10, Kaoru Fujinami^1,3,6,10,11

¹Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan., ²Office Eye, Kyoto, Japan., ³UCL Institute of Ophthalmology, University College London, London, UK., ⁴Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan, ⁵Department of Public Health Research, Yokokawa clinic, Osaka, Japan., ⁶Department of Ophthalmology, Nairobi University, Nairobi, Kenya., ⁷Department of Ophthalmology, Kenyatta National and Teaching hospital, Nairobi, Kenya, ⁸Diagnosys LLC, MA, USA., ⁹Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan., ¹⁰Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan., ¹¹Moorfields Eye Hospital, London, UK

Purpose Pupillary light responses (PLR, alternatively named pupillometry) have been applied in assessing visual function, especially in patients with ultra-low vision (ULV). We describe PLRs in ULV patients with retinitis pigmentosa (RP) and healthy subjects aiming to establish a comprehensive deep phenotyping protocol.

Methods Three patients with a clinical diagnosis of RP (age 49, 72, 73) and 7 healthy participants (mean age 29 years, range 23–45) with no ocular diseases were enrolled. The RP patients showed severe visual acuity decline (counting fingers or worse) and undetectable full-field electroretinograms (ERGs) both in dark-adapted and light-adapted conditions. Full-field colour stimuli were generated by the Diagnosys Profile ganzfeld ColorDome (Diagnosys, LLC, MA, USA), which utilizes narrow-band LEDs of 448 nm (blue), 530 nm (green), and 627 nm (red). PLRs were measured with an infrared camera-based pupillometry module incorporated into the Profile system. Three PLR steps were performed according to parameters similar to a previously published method (Collison 2015): (i) rod response was elicited by blue light (0.001 cd/m², duration 1000 ms) after 10 min of dark adaptation; (ii) cone response was elicited by red light (10 cd/m², duration 1000 ms) on a blue background (0.1 cd/m²); (iii) mixed rod- and cone-mediated response was elicited by white light (3 cd/m², 4 ms flashes) on a white background (1 cd/m²). All steps were completed four times, and an average of at least two trials for each step was used for analysis. Baseline diameter and constriction rate (the difference between baseline diameter and minimum diameter divided by the baseline diameter) were obtained as clinical parameters, and these data were compared between the RP eyes and the healthy eyes.

Results The mean baseline diameter/constriction rate of six ULV RP eyes for PLR-rod, PLR-cone, and PLR-mixed was undetectable/unavailable, 6.62 mm (range, 4.46–7.94)/0.18 (range, 0.07–0.36), and 6.32 mm (4.43–7.86)/0.14 (0.06–0.24), respectively. The mean baseline diameter/constriction rate of 14 healthy eyes for PLR-rod, PLR-cone, and PLR-mixed was 6.82 mm (range, 5.92–8.12)/0.35(0.17–0.44), 4.45 mm (2.74–6.88)/0.32 (0.13–0.45), and 4.21 mm (2.86–5.95)/0.31 (0.13–0.37), respectively. Larger baseline pupil size and lower baseline diameter/constriction rate was found in RP eyes compared to those of healthy eyes.

Conclusions PLRs were documented in ULV RP eyes and healthy eyes. Quantitative data were available in UVL RP patients for PLR-cone and PLR-mixed, although responses were undetectable for PLR-rod. Characteristic features of larger baseline pupil size and lower constriction rate in UVL RP patients were identified compared to the healthy eyes; meanwhile, the distribution/variation of PLR was also noted in healthy participants. The potential use of PLR for monitoring ULV RP patients was suggested, although further data from additional affected and healthy participants are required to validate.

P2-14 Detection of subtle retinal function with full-field stimulus testing in inherited retinal degenerations: A case report

Qingge Guo¹, Changgeng Liu¹, Ya Li¹, Ya You¹, Bo Lei

¹Henan Eye Hospital, Henan Eye Institute, Henan Provincial People’s Hospital, China

Purpose To detect subtle retinal function with full-field stimulus testing (FST) in a case of early onset inherited retinal degeneration (IRD) in which no ERG responses were recordable.

Methods A 9-year-old girl complained of visual impairment in both eyes for 5 years. Detailed ophthalmology examinations, including best-corrected visual acuity (BCVA), color fundus photography, autofluorescence (AF), swept-source optical coherence tomography (SS-OCT), static visual field thresholds, full-field electroretinogram (ff-ERG), and full-field stimulus threshold (FST), were performed. Peripheral blood sample was collected, and the whole-genome DNA was extracted. An Inherited Retinal Disease Panel PS400 was used for DNA sequencing. Sanger verification was performed to verify the pathogenic mutations. The pathogenicity of the suspected mutations was analyzed according to the American College of Medical Genetics and Genomics (ACMG) guidelines.

Results The BCVA was 0.6 in the right eye and 0.7 in the left eye. There was no abnormality in the anterior segment and vitreous body. The retina was pale without bone spicule pigmentation. AF showed annular hyperfluorescence and peripheral hypofluorescence in the macular area. SS-OCT showed atrophy of the outer layers of parafoveal retina, as well as disappearance of light reflection in the ellipsoid zone and chimera zone. ERGs were extinguished in both eyes. FST indicated 14 dB higher sensitivity to the blue light stimulus than the red. Compared with the rod system, the cone system function was better preserved. Although a variant in an FEVR associated gene FZD4 was detected, it appeared not linked with the phenotype.

Conclusions When the ERG is not detectable, it is challenging to assess residual retinal function in advanced IRDs. FST may be a supplementary assessment to the analysis of visual function in these patients and for evaluating the effects of therapeutic interventions.

P3-1 Evaluation of the Diagnosys ColorFlash device

Hong-An Nguyen^1,2, Jeffrey Matthew Mah^1,2, Rustum Karanjia^1,2,3, Stuart G. Coupland^1,2

¹University of Ottawa Eye Institute, ²Ottawa Hospital Research Institute, Ottawa, ON, Canada, ³Doheny Eye Institute, Los Angeles, CA, United States

Purpose The ColorFlash (Diagnosys LLC, Lowell, MA, USA) is a new stimulator for full-field ERG testing that can be used as a handheld or tabletop mounted device. This flexibility makes it ideal for pediatric patients, patients in wheelchairs, and operating room testing. The objectives of this study were to perform ERG testing using the ColorFlash on control subjects and build a normative database of findings and to evaluate the effect of dilation on ColorFlash recordings.

Methods We conducted a prospective, non-interventional study. The inclusion criteria were best corrected visual acuity (BCVA) of 20/25 or better and a normal dilated eye exam. Exclusion criteria included poor compliance with the standard of care ERG testing protocol and previous intraocular surgery in the last 6 months. Patients underwent testing of both eyes with the ColorFlash using the following protocols, both before and after dilation: light-adapted 3.0 cd s/m², light-adapted 30 Hz flicker, dark-adapted 0.01 cd s/m², dark-adapted 3.0 cd s/m² and dark-adapted 10 cd s/m². The outcomes were the component amplitudes and implicit times. Eyes were analyzed independently. Summary statistics were used to define normative ranges for the ColorFlash. Amplitudes and implicit times were compared for before dilation versus after dilation using independent sample T tests.

Results Twenty patients (40 eyes) were included. Patients were predominantly female (65%) with a median age of 25 years (range 20–35). Normative ranges for the component amplitudes and implicit times for dilated ColorFlash testing were calculated. In general, waveform amplitudes were smaller and implicit times were longer for undilated compared to dilated testing.

Conclusions The ColorFlash-specific normative database generated by this study will allow for the interpretation of future ColorFlash results. Establishing new normative data for undilated patients would expand the utility of the ColorFlash in patients in whom dilation is contraindicated or when testing is challenging, such as in children.

P3-2 Effect of transcranial alternating current stimulation (tACS) electrode montage on visually evoked occipital responses: A pilot study

Kai Yip Choi¹, Jingying Wang¹, Benjamin Thompson^2,3, Henry HL Chan^1,3, Allen MY Cheong^1,3

¹School of Optometry, The Hong Kong Polytechnic University, Hong Kong, ²School of Optometry and Vision Science, University of Waterloo, Canada, ³Centre for Eye and Vision Research, 17W Hong Kong Science and Technology Parks

Purpose Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that can modulate neural activity in human visual cortex. However, the optimal tACS electrode array for visual cortex stimulation is unknown. We compared the effects of two electrode montages and sham stimulation on pattern-reversal visual evoked potentials (PVEPs).

Methods TACS (10 Hz, 2 mA, 20 min) was delivered to 10 healthy adults. Two electrode montages, Oz-Cz and Oz-cheek, were tested along with sham (placebo) stimulation in separate randomly sequenced sessions. PVEPs (0.25° and 1.0° check size) were measured at pre-stimulation baseline (BL), immediately post-stimulation (T0), and 20 min post-stimulation (T20) in each session. Time-domain features (i.e., N75, P100 amplitude and P100 latency) were extracted and analyzed. Subjective sensations during tACS were evaluated by questionnaire.

Results The effect of stimulation on P100 amplitude differed across conditions (p = 0.03). At T20, P100 amplitude following stimulation with the OZ-CZ montage was significantly reduced, while the sham and OZ-cheek conditions did not vary from baseline. No significant effects of active tACS on other time-domain features were observed. Subjective sensations were similar in all montages.

Conclusions The OZ-CZ montage induced a sustained reduction in P100 amplitude indicating a larger effect on visual cortex function than the OZ-cheek montage and sham stimulation.

P3-3 Assessment of factors affecting flicker ERGs recorded with RETeval from data obtained from health checkup screening

Taiga Inooka¹, Taro Kominami¹, Shunsuke Yasuda¹, Yoshito Koyanagi^1,2, Junya Ota¹, Satoshi Okado¹, Ryo Tomita¹, Yasuki Ito³, Takeshi Iwase⁴, Hiroko Terasaki¹, Koji M. Nishiguchi¹, Shinji Ueno⁵

¹Nagoya University Graduate School of Medicine, Japan, ²Kyushu University Graduate School of Medical Sciences, Japan, ³Fujita Health University School of Medicine, Japan, ⁴Akita University Graduate School of Medicine, Japan, ⁵Hirosaki University Graduate School of Medicine, Japan

Purpose To determine the factors associated with the amplitudes and implicit times of flicker ERGs recorded with the RETeval system by analyzing the comprehensive data obtained during a health checkup screening.

Methods Flicker ERGs were recorded with the RETeval system from over 330 individuals who had a normal fundus and optical coherence tomography images. Sex, age, anthropometric, ophthalmologic, and hematologic data were collected from all participants (40–89 years of age). Univariate and multivariate linear mixed effects regression analyses were performed to identify factors that were significantly associated with the amplitude and implicit time of the RETeval flicker ERGs.

Results Univariate linear mixed effects regression analysis showed significant correlations between the implicit times and best-corrected visual acuity, age, axial length, blood sugar level, and blood urea nitrogen level. Multivariate linear mixed effects regression models identified axial length (regression coefficient (β) = 0.28), age (regression coefficient (β) = 0.24), and blood sugar level (regression coefficient (β) = 0.092) as three independent factors that were significantly correlated with the implicit times of the RETeval flicker ERGs. Univariate linear mixed effects regression analysis also showed significant correlations between the amplitudes of the RETeval flicker ERGs and age, platelet count, and creatinine level. Multivariate linear mixed effects regression models identified age (regression coefficient (β) = − 0.092), platelet count (regression coefficient (β) = 0.099), and creatinine level (regression coefficient (β) = − 0.12) as three independent factors that were significantly correlated with the amplitudes of the RETeval flicker ERGs. However, smoking habits, body mass index, and blood pressure were not significantly correlated with either implicit times or amplitudes of the RETeval flicker electroretinograms.

Conclusions Our results indicate that age and some ophthalmologic and hematologic findings, but not the anthropometric findings, were significantly associated with the amplitudes and implicit times of the RETeval flicker ERGs. Thus, clinicians should remember these correlations when analyzing RETeval flicker ERGs.

P3-4 Reproducibility of ERGs recorded with Sensor Strip electrodes and electrocardiography skin electrodes

Ryunosuke Nagashima¹, Kumiko Kato¹, Daisuke Kurose¹, Iroha Fujimoto¹, Hisashi Matsubara¹, Kengo Ikesugi¹, Mineo Kondo¹

¹Department of Ophthalmology, Mie University Graduate School of Medicine, Japan

Purpose The development of electroretinography (ERG) devices that use skin electrodes has enabled clinicians to record ERGs less invasively. In Japan, ERGs can be recorded with either the Sensor Strip electrodes (LKC Technologies) or the Red Dot electrocardiography electrodes (3M, USA). The purpose of this study was to determine whether the reproducibility of the ERGs differed for the two types of skin electrodes.

Methods Eleven subjects (5 male, 6 female) were studied. The RETeval (LKC Technologies) was used to elicit and record the ERGs, and the Sensor Strip or the Red Dot 2330 (Red Dot) electrodes were used. The Sensor Strip is a single adhesive tape electrode containing the active, reference, and ground electrodes. It was placed 2 mm from the lower eyelid margin. Red Dot is an adhesive seal electrode. We used three Red Dot electrodes; two were placed 2 mm from both lower eyelid margins and one was placed at the temple. Flicker ERGs were recorded under natural pupillary conditions. Three different examiners recorded the cone flicker ERGs from the 11 subjects to determine the inter-rater reliability. To test the intra-rater reliability, one examiner recorded the ERGs 3 times on different days from each subject. The implicit times and amplitudes of the flicker responses were analyzed using a one-way variate of the number of intraclass correlations for intra-rater reliability and a two-way variate of the number of intraclass correlations for inter-rater reliability.

Results The intra-rater reliability ranged from 0.778 to 0.866 for the Sensor Strip and 0.792–0.874 for the Red Dot electrodes, indicating that both types were highly reliable. Inter-rater reliability was slightly lower for the amplitude of the flicker ERGs at 0.474 (p = 0.080) and the amplitude of the cone response at 0.633 (p = 0.064) when recorded with the Sensor Strip. When recorded with the Red Dot, the implicit time of the cone response was significantly less reliable at 0.764 (p = 0.032).

Conclusions The intra-examiner reliability was high for both types of electrodes, but examination of the inter-examiner reliability showed that the amplitudes of the ERGs tended to be less reliable when the Sensor Strip was used, and the implicit time of the cone ERGs tended to be less reliable when the Red Dot was used. To obtain good reproducibility even with different examiners, it is necessary to pay attention and have less variation in the position of the skin electrodes.

P3-5 Investigation of the effect of posture on the electroretinogram in half-gas-filled eyes

Saori Yamaguchi¹, Minami Chino¹, Jun Makita¹, Yuro Igawa¹, Satomi Konno¹, Takashi Matsushima², Yuji Yoshikawa¹, Yu Sakaki¹, Takeshi Katsumoto¹, Masayuki Shibuya¹, Kei Shinoda¹, Soiti Matsumoto^1,3

¹Departments of Ophthalmology, Saitama Medical University, Faculty of Medicine, Saitama, Japan, ²Departments of Ophthalmology, Tokai University, Japan, ³Matsumoto Eye Clinic, Japan

Purpose We previously investigated the effects of vitrectomy with gas tamponade on ERG recordings in eyes with rhegmatogenous retinal detachment (RRD). We presented at ISCEV 2019 in Seoul that the ERG response recorded when the size of the tamponade gas was approximately one-half of the vitreous cavity was correlated with that before the surgery (baseline) and when the gas had been completely resorbed. In this study, ERGs were recorded using skin electrodes with the patient in a sitting position. The aim was to investigate the effect of the patient’s posture on the ERG in 50% gas filled eyes.

Methods Twenty-one eyes of 21 patients who underwent vitrectomy and gas tamponade at Saitama Medical University Hospital between August and December 2022 and had skin electrode ERG recordings performed postoperatively were included in the study. Flicker ERG under light adaptation was recorded using RETeval® (Mayo Corporation, Inazawa, Japan) when the volume of intraocular gas reached approximately 50% of the vitreous cavity. ERG recordings were performed in two postures, sitting and supine, and the order was reversed between the right and left eyes. Comparison of the values from the two positions was analyzed using the Wilcoxon signed rank test.

Results The subjects were 65 (62, 73) (median [quartiles]) years of age, 8 female and 13 male. Vitreoretinal diseases that were indications for surgery were epiretinal membrane or macular hole in 7 eyes, rhegmatogenous retinal detachment (RRD) in 13 eyes, and ruptured retinal microaneurysm in 1 eye. Tamponade materials were room air in 10 eyes, 12% C3F8 in 2 eyes, and 20% SF6 in 9 eyes. The time from surgery to postoperative ERG recordings was 5 (4, 8) (median [quartiles]) days. The amplitude was 14 (8.15, 25.85) (median [quartiles]) µV in the sitting position and 16.2 (7.6, 24.5) µV in the supine position, and the latency was 28.35 (26.53, 30.15) ms in the sitting position and 28.4 (26.75, 30.65) ms in the supine position. No significant differences were observed between the sitting and supine positions for either amplitude and latency (p = 0.4487 for amplitude; p = 0.5206 for latency).

Conclusions ERG responses in 50% gas-filled eyes were similar in the sitting and supine positions.

P3-6 Effect of 50-Hz filters on pattern electroretinogram

Ungsoo Samuel Kim^1,2

¹College of Medicine, Chung-Ang University, Korea, ²Department of Ophthalmology, Chung-Ang University Gangmyeong Hospital, Korea

Purpose The pattern electroretinogram (PERG) is used to evaluate the function of retinal ganglion cells. However, the amplitude of the PERG is relatively small and sensitive to examination. To minimize noise in the waveform, various filters can be applied. We aimed to investigate the effect of 50 Hz filters on the results of PERG.

Methods Pattern electroretinograms were recorded using RETI-scan (Roland-Consult, Germany) according to ISCEV guidelines. Three types of 50 Hz filters (soft, middle, and hard) were applied. The difference in parameters (N35 latency, P50 latency, N95 latency, P50 amplitude, N95 amplitude, and N95/P50 ratio) was analyzed. Based on the provided normal range, the case of changing from the normal range to the abnormal range or from the abnormal range to the normal range was investigated.

Results A total of 24 waveforms were obtained and analyzed. After filtering, the amplitude of P50 and N95 showed a significant reduction of about 8–15% (P50 amplitude; without filter 5.1 ± 2.7 μV, 50 Hz soft 4.6 ± 2.3 μV, 50 Hz middle 4.3 ± 2.1 μV, 50 Hz hard 4.3 ± 2.1 μV, N95 amplitude; without filter 7.2 ± 4.2 μV, 50 Hz soft 6.6 ± 3.8 μV, 50 Hz middle 6.3 ± 3.6 μV, 50 Hz hard 6.1 ± 3.6 μV). All latencies, except N35 latency, and the N95/P50 ratio also had no difference among the tests. Based on the normative data, it was rare for normal and abnormal results to switch.

Conclusions Although the latency was not significantly affected, the amplitude is significantly reduced after 50 Hz filtering. Thus, using the 50-Hz filters has the effect of smoothing out the waveform. However, we should be careful with the reading.

P4-1 Clinico-electrophysiological and genetic correlation in a case of autosomal recessive Bestrophinopathy

Srikanta Kumar Padhy¹, Deepika C. Parameswarrapa¹, Tapas Ranjan Padhi¹, Anand Singh Brar¹

¹LV Prasad eye institute, India

Purpose A 35-year-old male fire officer, who had been treated as having central serous chorioretinopathy (CSC) at various places for the past 5 years, visited our OPD for further management. He was addicted to tobacco and was treated elsewhere with oral eplerenone for a period 1 year. He stated a history of nyctalopia and colour vision difficulty (Ishihara 17/23 plates). Electrophysiological evaluation was performed based on clinical symptoms and imaging features.

Methods Case report.

Results Best-corrected visual acuity was 20/40 and 20/20 in right eye and left eye, respectively. There was no family history of visual dysfunction or any systemic illness or drug use (apart from eplerenone). The anterior segment and dilated fundus examination was essentially unremarkable; however, fundus autoflurosence imaging revealed the presence of subtle granular hyper-autofluorescent lesions in the posterior pole bilaterally. Optical coherence tomography macular line scan images showed intraretinal cystic spaces in the outer nuclear and plexiform layer with a subretinal hyporeflective space at the macula. Full-field ERG revealed reduced amplitude of the b-wave for the scotopic 0.3 and 10.0 responses as well as for the photopic responses. EOG showed an absence of the light rise bilaterally. Genetic testing revealed an autosomal recessive homozygous mutation in the BEST1 gene (intron 4, variant- c.456 + 1G>C).

Conclusion This case emphasizes the importance of looking for a condition mimicking CSC and the indications for going ahead with specialized electrophysiological investigations.

P4-2 BEST1 gene associated bestrophinopathies and angle closure glaucoma with risk of postoperative malignant glaucoma

Deepika Chennapura Parameswarappa¹, Sirisha Senthil², Saarang Hansraj¹, Ramya Natarajan³, Jeyapoorani Balasubramnian⁴, Srikanta Kumar Padhy⁵, Venkatesh Pachaboina⁴, Brijesh Takkar¹, Tapas Ranjan Padhi⁵, Subhadra Jalali¹

¹Srimati Kanuri Santhamma Center for Vitreoretinal Diseases, Anant Bajaj Retina Institute, Kallam Anji Reddy Campus, L V Prasad Eye Institute, Hyderabad, Telangana, India, ²VST Center for Glaucoma Care, Kallam Anji Reddy Campus, L V Prasad Eye Institute, Hyderabad, Telangana, India., ³Department of Ophthalmic Biophysics, L V Prasad Eye Institute, Hyderabad, Telangana, India, ⁴Department of Ocular Genetics, L V Prasad Eye Institute, Hyderabad, Telangana, India, ⁵Vitreoretina and Uveitis Services, Anant Bajaj Retina Institute, Mithu Tulasi Chanrai Campus, L V Prasad Eye Institute, Bhubaneswar, India

Purpose To describe the clinical and genetic characteristics of autosomal recessive bestrophinopathy (ARB) associated with refractory angle closure glaucoma (ACG).

Methods The study includes 6 patients with ARB who had coexisting ACG with risk of post glaucoma filtration surgery malignant glaucoma (MG) in at least one eye. ARB was diagnosed with multimodal imaging features and appropriate electrodiagnostic tests (ERG and EOG). The genomic DNA samples from the patients were used for library preparation after obtaining written informed consent. The patients’ exomes were sequenced using Next-generation Sequencing-based Illumina MiSeqSequencer to identify the mutations.

Results The study included 12 eyes from 6 patients who had ARB and ACG. EOG in all 12 eyes with ARB had severe reduction of the light-peak to dark-trough ratio (< 1.30). Flash ERG showed abnormality of both dark-adapted and light-adapted responses in all eyes. All 12 eyes were treated with NdYag laser peripheral iridotomy (LPI) for angle closure. Fifty-eight % (7/12) of the eyes had progression of glaucoma despite patent LPI and required surgical management of glaucoma. All 7 eyes that underwent glaucoma filtration surgery developed postoperative malignant glaucoma. The malignant glaucoma was intractable and was relieved only by irido-zonulo-hyaloido-vitrectomy (IZHV) and core pars plana vitrectomy (PPV). Twenty-five % (3/12) of the eyes that were prophylactically managed with IZHV and PPV did not develop postoperative malignant glaucoma. Genomic DNA analysis of all 6 patients showed BEST1 gene affection. The common genetic characteristics found were homozygous autosomal recessive (83%, 5/6), missense mutation (67%, 4/6) and a pathogenic variant (67%, 4/6).

Conclusions ARB patients with ACG are at risk of intractable malignant glaucoma post any glaucoma filtration surgery. EOG, ERG, and genomic analysis of patients with ARB and ACG is crucial to establish the accurate diagnosis. IZHV and core pars plana vitrectomy is a safe alternative to glaucoma filtration surgery in eyes with ARB and ACG.

P4-3 Bacillary layer detachment in Best vitelliform macular dystrophy

Srikanta Kumar Padhy¹

¹LV Prasad eye institute, India

Purpose Bacillary layer detachment (BCD), an optical coherence tomography finding, represents an accumulation of intraretinal fluid within a space created by a split in the photoreceptor layer at the level of the inner segment myoid. Two main factors are required to form a BCD: 1) the potential space associated within the anatomic plane of weakness of the photoreceptor inner segment myoid bounded by the external limiting membrane and ellipsoid zone, and 2) a hydrostatic force from the choroid strong enough to split the photoreceptors (in the choroidal neovascular membrane).

Methods Case report.

Results An 11-year-old boy presented with gradual blurring of vision OU in the last 6 months. The best-corrected visual acuity was 20/40 and 20/30 in the right and left eye, respectively. Anterior segment examination was essentially normal. Dilated fundus examination revealed the presence of yellowish subretinal vitelliform deposits in the macula that were coalesced inferiorly in the right eye and scattered in the left eye. There was absence of the light rise on electrooculography. Optical coherence tomography (OCT) of the right eye showed subretinal hyperreflective material with adjacent splitting of ellipsoid zone, suggestive of a BCD. OCT and fundus fluorescein angiography ruled out an underlying choroidal neovascular membrane.

Conclusion This case highlights a novel observation of BCD in Best vitelliform macular dystrophy in the absence of a coexistent choroidal neovascular membrane.

P4-4 Harel Yoon syndrome: A novel mutation in the ATAD3A gene and expansion of the clinical spectrum

Caroline Atef Tawfik¹, Aliaa Farag², Raghda Zaitoun³

¹Watany Eye Hospital, Ain Shams University, ²Department of Ophthalmology, Cairo University, Egypt, ³Department of Neurology, Ain Shams University, Egypt

Purpose Harel–Yoon syndrome (HAYOS) is a recently described neurodevelopmental disorder characterized by psychomotor delay, truncal hypotonia, appendicular spasticity, and peripheral neuropathy. It is caused by mutations in ATAD3A gene which is a mitochondrial gene whose functions include mitochondrial DNA stabilization, the regulation of mitochondrial fission/fusion, and cholesterol homeostasis.

Methods An 11-year-old male patient of consanguineous Egyptian parents who presented with neuroregression and ptosis along with progressive impaired vision underwent complete ophthalmological and neurological examination. Additionally, color fundus photography, fundus autofluorescence (FAF), spectral domain optical coherence tomography (SD-OCT) of both the macula and optic nerve head, full-field electroretinogram (ERG), and visual field perimetry were obtained. Whole-exome sequencing and mitochondrial genome sequencing were done in a commercial laboratory from a peripheral blood sample.

Results A novel mutation in ATAD3A gene (c.624_644del) was identified by whole-exome sequencing, consistent with a diagnosis of HAYOS. The 11-year-old boy had characteristic features of neurodevelopmental delay, hypotonia, and peripheral neuropathy. However, we documented some novel features including fatiguable ptosis, facial weakness, progressive bulbar palsy, and obsessive–compulsive disorder (OCD), in addition to cone system dysfunction.

Conclusions Our study reports a novel mutation in the ATAD3A gene and expands the clinical spectrum of Harel–Yoon Syndrome. Future research aiming at better understanding of gene function will lead to better genotype–phenotype correlations and could pave the way to better treatment options.

P4-5 Can electrophysiological and clinical findings confirm ESCS in an 11 year old girl?

Jelka Brecelj¹, Andrej Meglic¹, Martina Jarc-Vidmar¹

¹Eye Hospital, University Medical Centre Ljubljana, Slovenia

Background

An 11-year-old girl with esotropia, normal visual acuity, and normal night and colour vision had PERG and VEP recordings in April 2022 due to mild bilateral optic nerve oedema. She began visiting the Orthoptic and Stabismus department of the University Eye hospital at an early age due to squinting. Visual electrophysiology demonstrated subnormal macular function (large-field PERG was abnormal) and normal visual pathway function (VEP was normal). Additional visual electrodiagnosis revealed ERG abnormalities consistent with enhanced S-cone syndrome (ESCS). The aim of this case report is to discuss whether her electrodiagnostic and clinical features could already confirm the diagnosis of ESCS, although we are still waiting for the genetic results.

Case report Mild bilateral optic disk oedema in an 11-year-old girl led to unexpected but characteristic full-field ERG and S-cone ERG findings that demonstrated ESCS. Electrophysiology testing was done in accordance with ISCEV standards. Autofluorescence imaging and optical coherence tomography (OCT) were done using Heidelberg Spectralis. Visual fields were done using Goldmann kinetic perimetry. The rod dark-adapted 0.01 ERG was undetectable; brighter flash dark-adapted 3.0 was of simplified and delayed waveform and was of a similar waveform to the light-adapted 3.0 ERG; 30-Hz flicker ERG was delayed and was of lower amplitude. S-cone ERG was of high amplitude. Normal central ring mfERG response was in concordance with normal visual acuity in both eyes. While On–Off ERG had a normal b wave, the presence of the d-wave was, due to blinking artefacts, not reliable to study. Ophthalmological examination showed normal visual fields. On fundus examination, yellow white dots were seen along the vascular arcades and nasally to the optic discs; on autofluorescence imaging these spots were hyperautofluorescent. OCT showed normal foveal structure without oedema and numerous hyperreflective spots in the inner retina along the vascular arcades. Genetic results are not known yet.

Conclusions Electrophysiological studies of children with ESCS are few, and all genetic testing demonstrated mutations in the NR2E3 gene and ERG findings that were defined as pathognomonic for ESCS. Definitely, this 11-year-old girl showed typical ophthalmological findings and pathognomonic ERG findings for hyperactivity of S cones. Diagnosis can be established by molecular confirmation of the disease causing mutation in NR2E3 gene or by diagnostic full-field electroretinography.

P4-6 Deep phenotyping of NR2E3 G56R-retinopathy in a Japanese patient

Kayoko Komatsu^1,2, Yu Fujinami-Yokokawa^1,3,4,5, Oscar Onyango^6,7, Yasutaka Suzuki¹, Gavin Arno^1,3,8,9, Nikolas Pontikos^1,3,8,10, Motoshi Yamamoto^1,2, Natsuki Maetani^1,2, Kazushige Tsunoda^11,12, Kaoru Fujinami^1,3,6,8,12

¹Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan., ²Office Eye, Kyoto, Japan., ³Institute of Ophthalmology, University College London, London, UK., ⁴Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan, ⁵Department of Public Health Research, Yokokawa clinic, Osaka, Japan., ⁶Department of Ophthalmology, Nairobi University, Nairobi, Kenya., ⁷Department of Ophthalmology, Kenyatta National and Teaching hospital, Nairobi, Kenya, ⁸Moorfields Eye Hospital, London, UK., ⁹Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK., ¹⁰Phenopolis, London, UK, ¹¹Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan, ¹²Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan

Purpose We present a detailed clinical and molecular study of a patient with childhood-onset retinal dystrophy with autosomal dominant inheritance caused by a monoallelic pathogenic variant in the NR2E3 gene.

Methods This was an observational case study. Detailed phenotyping was performed, including full clinical evaluation, fundus photography, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (OCT), ISCEV standard full-field electroretinograms (ffERGs), dark-adapted full-field stimulus threshold (D-FST), and electrically evoked response (EER) elicited by trans corneal electrical stimulation (TES). Comprehensive genetic testing with next-generation sequencing-based panel profiling covering 935 retinal disease-associated genes was performed for the proband.

Results A 65-year-old female was examined with complaints of progressive visual impairment in both eyes. There were two affected family members in the pedigree (mother and daughter). She had poor visual acuity since the age of 5 years and was first described as having retinitis pigmentosa in her early teens. Her best corrected visual acuity was 0.8 in decimal in each eye at 16 years. She has noticed visual decline, especially since the age of 55. Her best-corrected visual acuity was light perception in the right and left eyes. The anterior segments were normal. Fundus photography and FAF imaging showed atrophic changes with pigmentations of the entire retina in both eyes. OCT showed photoreceptor layer loss of the entire retina and relatively preserved inner retinal layers.The ffERG demonstrated undetectable responses for DA0.01, DA10.0, LA3.0, and LA3.0 30 Hz flicker in both eyes. The median value for blue/red/white FST was 0.18/− 0.44/0.47 log10 cd.s.m² in the right eye and − 0.77/− 0.11/− 0.18 log10 cd.s.m² in the left eye. EER by TES revealed positive responses in both eyes. Genetic testing revealed one NR2E3 variant: NM_014249.4:c.166G > A, (p.Gly56Arg). This variant was classified as pathogenic in an autosomal dominant inheritance.

Conclusions To our knowledge, this report is the first to describe the detailed phenotypic characterization by utilizing ffERG, FST, and TES-EER in an ultra-low vision (ULV) patient caused by a monoallelic pathogenic NR2E3 variant. The features of early-onset progressive photoreceptor/RPE damage are in keeping with those of the European case series (Blanco-Kelly et al. PLoS One 2016;11(2):e0149473). In addition, a quantitative assessment of highly elevated FST was available and residual inner retinal function was revealed by EER. Such deep-phenotyping data would help monitor and counsel patients and also aid in designing therapeutic trials such as RNA therapies (Naessens et al. Genes (Basel) 2019;10(5):363).

P4-7 Long-term ERG changes in Bietti’s crystalline dystrophy

Masakazu Takayama¹, Kaoruko Torii¹, Kentaro Kurata¹, Yoshihiro Hotta¹

¹Hamamatsu University School of Medicine, Japan

Background Bietti’s crystalline dystrophy (BCD) is a degenerative retinal disease characterized by crystalline deposits in the retina that is caused by CYP4V2 gene abnormalities. The condition generally develops after the age of 30 and causes slow and progressive visual dysfunction. As the disease progresses, visual field defects increase. However, few reports have evaluated the progression of electrophysiological changes over a long period of time. In this study, we report a case of BCD observed for a period of 28 years.

Case report A 75-year-old woman was aware of her vision loss since the age of 47. At the time of initial examination, her best-corrected visual acuity was 1.2 in the right eye and 0.4 in the left eye. There were no glistening limbic crystals in the superficial corneal stroma. Funduscopy revealed multiple crystalline deposits on the posterior pole in both the eyes, and Goldmann perimetry showed a paracentral dark spot. The full-field ERG showed a slight decrease in amplitude in the rod and cone responses. Based on these findings, we diagnosed the condition as BCD. We followed up with ongoing visual acuity testing, visual field tests, and fundus examinations. ERG showed a decrease in amplitude over time that almost disappeared within 10 years of the initial diagnosis. Visual acuity decreased slowly and at a steady rate. After 28 years, her corrected visual acuity was 0.4 in the right eye and 0.15 in the left eye. The visual field defect gradually expanded from a paracentral dark spot to a central dark spot. Further, the rate of progression of the visual field defect was largely steady after the initial examination but progressed rapidly during the last 2 years. Funduscopy revealed progressive atrophy of the retinal pigment epithelium and crystalline deposits became less prominent. Optical coherence tomography showed loss of retinal pigment epithelium and thinning of the retina, including the macula of both the eyes. The choroidal thickness was reduced and outer retinal tubulation was also seen. Genetic analysis revealed compound heterozygous mutations i.e., c.802-8_810delinsGC and c.1199G>A in the CYP4V2 gene.

Conclusions To our knowledge, there are few reports of long-term progression from the early stage of disease at a single institution. Long-term follow-up revealed that the patient’s visual acuity worsened slowly and at the same rate. Further, the visual field deteriorated rapidly in later years. ERG worsened preceding deterioration of visual function.

P4-8 Phenotypic spectrum of the founder deletion-insertion variant in CYP4V2 patients with inherited retinal dystrophy

Kensuke Goto¹, Yoshito Koyanagi^1,2, Taro Kominami¹, Hanae Iijima³, Mikiko Endo³, Shinji Ueno^1,4, Chikashi Terao², Yukihide Momozawa³, Koji M. Nishiguchi¹

¹Department of Ophthalmology, Nagoya University Graduate School of Medicine, Japan, ²Laboratory for Statistical and Translational Genetics, RIKEN Center for Integrative Medical Sciences, Japan, ³Laboratory for Genotyping Development, RIKEN Center for Integrative Medical Sciences, Japan, ⁴Department of Ophthalmology, Hirosaki University Graduate School of Medicine, Japan

Purpose The founder deletion–insertion variant, c.802-8_810del17insGC, in CYP4V2 has been reported as the pathogenic variant in Bietti crystalline dystrophy (BCD) in the East Asian population. It has also been reported as a pathogenic variant in a Chinese pedigree with retinitis pigmentosa (RP). The purpose of this study was to detect c.802-8_810del17insGC in CYP4V2 using next-generation sequencing (NGS) data and a bioinformatic approach, and to elucidate the phenotypic spectrum in patients with inherited retinal dystrophy (IRD).

Methods We collected DNA samples from 790 patients with IRD at the Nagoya University Hospital. Multiplex PCR-based target sequencing was performed on the coding region of the transcripts and the boundary region between intron 6 and exon 7 including c.802-8_810del17insGC in CYP4V2. The detected variants on the coding region were interpreted according to the ACMG guidelines. To detect c.802-8_810del17insGC, we developed the grep search program with fastq format files in NGS data.

Results We ultimately enrolled 773 probands with IRD, including 600 with non-syndromic RP and 73 with macular dystrophy (MD), 16 with cone-rod dystrophy (CRD), and 7 with BCD. The c.802-8_810del17insGC in CYP4V2 was detected in a total of 17 patients: 9 heterozygous and 8 homozygous. The allele frequency of c.802-8_810del17insGC in CYP4V2 was 1.62% in the total IRD patient sample and 0.78% in IRD patients excluding BCD. The heterozygous c.802-8_810del17insGC in CYP4V2 was detected in 5 patients with non-syndromic RP, 1 with BCD, 1 with MD, and 2 with other IRDs. However, there were no patients who had another pathogenic variant as compound heterozygous in CYP4V2. Of the 8 patients with homozygous c.802-8_810del17insGC in CYP4V2, 6 patients were diagnosed with BCD and 2 patients were diagnosed with CRD and MD. The patient with CRD showed reduced amplitudes of both photopic and scotopic ERGs. The macular retina was more atrophic than the peripheral retina, and a central scotoma was observed in Goldmann visual fields. The patient with MD showed macular atrophy and relatively preserved amplitudes of photopic and scotopic ERGs. The distinctive glistening yellow–white crystalline deposits were not observed in the retina of either patient.

Conclusions Our analysis revealed that 1.2% of IRD patients were genetically solved by homozygous c.802-8_810del17insGC in CYP4V2 and 20% of the solved patients showed atypical fundus findings without the distinctive glistening yellow–white crystalline deposits, suggesting a wide phenotypic spectrum of this founder variant in CYP4V2.

P4-9 Recovery of ERG in patients with RPE65-related Leber congenital amaurosis following gene replacement therapy

Wayne Tschetter¹, Alessia Amato¹, Paul Yang¹, Lesley Everett¹, Andreas Lauer¹, Steven Bailey¹, Timothy Stout², Mark Pennesi¹

¹Oregon Health and Science University Casey Eye Institute, USA, ²Baylor College of Medicine Cullen Eye Institute, USA

Purpose Leber congenital amaurosis (LCA) caused by biallelic RPE65 mutations is considered treatable with gene therapy. A notable finding in early research involving experimental animal models was a marked improvement of ERG after sub-retinal delivery of the RPE65 gene. This finding was not reported in patients treated with Voretigene Neparvovec (Luxturna), despite improvements in vision. Here we present a series of patients with improved ERGs following gene replacement therapy.

Methods Records of 17 patients treated with Luxturna between 2018 and 2022 at the Casey Eye Institute were reviewed. Dark-adapted (DA) ERGs in response to a flash strength of 0.01 cd s/m² (scotopic) and light-adapted (LA) ERGs in response to 3.0 cd s/m² (photopic) were analyzed and b-wave amplitude as a percentage of lower normal are reported. Factors that could influence outcomes such as age and pre-treatment ERGs were also reviewed.

Results Five eyes of 3 bilaterally treated patients showed a partial ERG rescue following treatment. Patient 1 showed a dramatic ERG improvement 4 months after treatment. The scotopic b-wave amplitude increased from 8 to 52% in OD and from 4 to 96% in OS. Similarly, photopic b-wave amplitude increased from 30 to 63% in OD and from 22 to 60% in OS. Over a 50-month follow-up, ERG responses remained stable in OD. In OS, the scoptopic response decreased to 70% while the photopic increased to 77%. Patient 2 exhibited an improvement after 14 months from treatment. Scotopic response increased from 29 to 54% in OD and from 24 to 40% in OS. Similarly, photopic response amplitude increased from 21 to 32% in OD and from 19 to 25% in OS. One year later, the scoptopic amplitude slightly decreased in both eyes to 41% and 32% of lower normal amplitude, respectively. Photopic responses also decreased to 7% in OD and 11% in OS. In patient 3, one eye showed a transient improvement after 52 months from treatment. The scotopic response increased from 5 to 17% and the photopic increased from 6 to 17%. However, 2 years later responses in both eyes were unrecordable. Preliminary results indicate there is no association between ERG improvement and age at time of treatment or pre-operative ERG amplitudes.

Conclusions This is the first series of patients treated with Luxturna showing a partial ERG rescue. The mechanisms underlying the electrophysiological recovery of function in some patients are not well understood, but the extensive work in animal models may provide useful insights on using ERG in combination with other psychophysical and imaging modalities to better determine treatment outcomes.

P4-10 Bilateral macular edema associated with Fahr’s disease

Yoshiaki Shimada¹, Masayuki Horiguchi¹, Atsuhiro Tanikawa¹, Yasuki Ito¹

¹Fujita Health University, Japan.

Background Fahr’s disease is a rare neurological condition characterized by abnormal idiopathic calcification of basal ganglia and commonly has an autosomal dominant inheritance. Four causative genes have been reported i.e., SLC20A2 (40%), PDGFB (11%), PDGFRB (2%), and XPR1 (2%); 46% of cases have an unknown gene mutations (Amisha & Munakomi, StatPearls [Internet]: 2022 PMID: 32809692). Fahr’s disease can present with a variety of symptoms of brain involvement. However, to our knowledge, there are no reports of ocular involvement.

Case report A 39-year-old female noticed distorted vision in both eyes and visited a local ophthalmologist, where she was found to have bilateral macular edema (ME). Five years before that, she had developed left oculomotor nerve palsy, and a brain CT scan revealed calcifications in the bilateral basal ganglia and thalamus without biochemical abnormalities, infection, poisoning, or history of trauma. While her family history was unremarkable, the diagnosis of Fahr’s disease was made. The oculomotor nerve palsy resolved spontaneously, and no neurological symptoms appeared thereafter. During examinations at our clinic, her corrected visual acuity was 1.2 and intraocular pressure was 12 mmHg in both the eyes. No field losses were found in static perimetry. Microcystic ME was observed bilaterally on optical coherence tomography (OCT). Subsequent measurement of aqueous humor protein concentration using a laser flare cell meter showed a high concentration of 100.2 ± 0.2 and 96.3 ± 0.9 photon counts/ms in the right and left eyes, respectively. Full-field ERGs recorded according to the ISCEV standard protocol were only slightly reduced, whereas the attenuation of mfERGs was more distinct. Genetic analysis revealed two variants i.e., ADAR c.1785 + 5G > A;p.? het. rs17843866 0.12%, and CTC1 c.663T>C; p. = het. rs138725914 0.23%, but their clinical significance is not clear.

Conclusions We present an unusual case of Fahr’s disease, with development of bilateral ME. Although the cause of cerebral calcification in Fahr’s disease is unknown, it has been postulated that it may be a microvascular or capillary disorder. The ME and elevated aqueous humor protein concentration seen in this case may also share the same pathophysiology as the brain calcification.

P4-11 The role of S-cones in oscillatory potentials: Analysis of achromats and S-cone monochromats

Giulia Righetti¹, Katarina Stingl^1,2, Bernd Wissinger³, Krunoslav Stingl^1,2

¹Center for Ophthalmology, University Eye Hospital, University of Tuebingen, 72076 Tuebingen, Germany, ²Center for Rare Eye Diseases, University of Tuebingen, 72076 Tuebingen, Germany, ³Molecular Genetics Laboratory, Center for Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany

Purpose We investigated the possible effect of blue cones on the creation of oscillatory potential (OPs) in two congenital stationary dysfunctional cone syndromes: achromatopsia (ACHM) and blue cone monochromacy (BCM). The major difference between the two syndromes is S-cone functionality in BCM. This difference can also be observed in full-field electroretinography (ERG). In ACHM, there is a complete absence of cone function with an almost normal signal from the rods, whereas in BCM there is a profoundly reduced but present signal under photopic conditions with preservation of rod responses. Retinal layers appear normal on fundus examinations, although foveal atrophy can be observed in adult patients. The aim of the study is to examine whether the presence of S-cones in BCM patients plays a key role in the generation of OPs.

Methods OP power (dB) from both the left and right eyes was extracted in 39 ACHM (mean age 35.6 ± 11), 19 BCM (mean age 36.5 ± 18), and 26 healthy subjects (mean age 40.1 ± 11). Additionally, the effect of morphological differences between the groups in foveal thickness (µm) was measured as a cofactor. Full-field ERG (ColorDome, Espion E2/E3, Diagnosys) was used to record the mixed cone rod signal according to ISCEV standards under mesopic conditions at 3 cd·s/m², and OPs were extracted by filtering the traces [70–300 Hz]. Subsequently, time–frequency analysis was performed by convolving a complex Morlet wavelet to extract the power. Foveal thickness values were extracted from OCT examinations (Heyex, Heidelberg Engineering).

Results One-way ANOVA conducted to compare OP power in the 3 groups showed a significant effect on both left [F(2) = 17.05, p < 0.001] and right [F(2) = 28.45, p < 0.001] eyes. Tukey HSD test for multiple comparisons confirmed the significant reduction of OP power in the ACHM and BCM groups compared with the healthy subjects, while no differences were found between ACHM and BCM groups. Spearman’s rank correlation computed to assess the relationship between foveal thickness and OP power indicated a different trend among the groups (NORM left eye: R(21) =  − 0.26, p = 0.24, right eye: R(22) =  − 0.17, p = 0.42; ACHM left eye: R(38) = 0.11, p = 0.49, right eye: R(39) = 0.22, p = 0.16; BCM left eye: R(17) = 0.16, p = 0.53, right eye: R(19) = 0.38, p = 0.10).

Conclusions This evidence suggests that the OP components are not functionally different from ACHM by the presence of only the S-cones in BCM, indicating that S-cones alone no not contribute to their generation. Foveal thickness appears to have no effect on the generation of the OPs; however, there are different trends among the groups.

P4-12 Longitudinal clinical course of two siblings with KCNV2-associated retinopathy

Tomoko Sato¹, Kazuki Kuniyoshi¹, Takaaki Hayashi², Hirokazu Nishiwaki³, Yoshikazu Hatsukawa⁴, Kei Mizobuchi², Ryota Tomemori⁵, Takao Endo⁴, Tadashi Nakano², Shunji Kusaka.¹

¹Department of Ophthalmology, Kindai Universtiy Faculty of Medicine, ²Department of Ophthalmology, Japan, The Jikei University School of Medicine, Japan, ³Department of Ophthalmology, Tenri Hospital, Japan, ⁴Department of Ophthalmology, Osaka Women’s and Children’s Hospital, Japan, ⁵Department of Ophthalmology, Tomemori Eye Clinic, Japan.

Background Potassium voltage-gated channel modifier subfamily V member 2 (KCNV2)-associated retinopathy is a rare cone dysfunction syndrome that is congenital and progresses gradually. KCNV2-associated retinopathy was first reported as “cone dystrophy with nyctalopia and supernormal rod responses,” showing pathognomonic ERG findings (Gouras P et al. Arch Ophthalmol 1983). This paper aims to report the longitudinal clinical courses of two siblings with KCNV2-associated retinopathy.

Case reports Case 1 A 3-year-old boy with intermittent exophoria was brought to our hospital. His parents were not consanguineous but were from the same village. No family history of visual disturbance was reported. His decimal best-corrected visual acuity (BCVA) was 0.9 and 0.5 in the right and left eyes, respectively. The fundi appeared normal. Both photophobia and night blindness were noted at age 12 years. Subsequently, ERG was performed, demonstrating delayed and supernormal b-wave with “squaring” of the a-wave in the flash ERG (DA-30) and reduced flicker ERG in both eyes. His vision gradually decreased, and his BCVA at the age of 27 years was 0.05 in both eyes, when a faint bull’s eye maculopathy was noticed bilaterally. Fundus autofluorescence (FAF) images showed ring-shaped hyperfluorescence in the macula, and optical coherence tomography (OCT) showed atrophy of the outer layer of the retina in the macula. ERG at the age of 27 years showed similar waveform and amplitude to those at age 12 years. We suspected KCNV2-associated retinopathy because of the pathognomonic ERG waveforms and performed a genetic examination on him. Consequently, a homozygous missense mutation of c.529T>C (p.Cys177Arg) was detected in the KCNV2 gene.

Case 2 Another patient was Case 1’s younger sister, who was brought to our hospital when she was age 3 years. She had exotropia and nystagmus and reported photophobia, night blindness, and color vision abnormality. Her near visual acuity was 0.8 and 0.6 in the right and left eyes, respectively. Her BCVA gradually decreased and were 0.15 and 0.1 in the right and left eyes, respectively, at age 22 years. The fundi were unremarkable. FAF showed slight hyperfluorescence in the macula, and OCT showed interruption of the ellipsoid zone at the macula and thinning of the outer nuclear layer in the parafoveal region. ERGs at ages 7 and 22 years showed similar findings as those of her brother, and genetic examination revealed the same homozygous missense mutation in the KCNV2 gene as that of her brother.

Conclusions Although the siblings’ fundi appeared normal, KCNV2-associated retinopathy demonstrated pathognomonic ERG waveforms even in childhood. ERGs were not reduced until their twenties. Therefore, a genetic examination was needed for the final diagnosis.

P4-13 Electrophysiological features of occult macular dystrophy in 10 patients heterozygous for the prevalent RP1L1 (p.Arg45Trp) variant

Shaun M. Leo¹, Antonio P. Calcagni^1,2, Magella M. Neveu^1,2, Omar A. Mahroo^1,2,3,4, Michel Michaelides^1,2, Andrew R. Webster^1,2, Anthony G. Robson^1,2

¹Moorfields Eye Hospital, London, United Kingdom, ²UCL Institute of Ophthalmology, London, United Kingdom, ³Section of Ophthalmology, King’s College London, St Thomas’ Hospital Campus, London, United Kingdom, ⁴Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, United Kingdom

Purpose To describe the phenotype in 10 patients with RP1L1-related occult macular dystrophy (Miyake disease), consequent to the same missense variant.

Methods The retinal phenotype in 10 patients with occult macular dystrophy related to the same p.Arg45Trp variant was reviewed, prompted by the findings in a recently examined adolescent patient with some atypical clinical features. Investigations included optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging, and ISCEV-standard pattern, full-field, and multifocal ERG (PERG; ERG; mfERG).

Results A male patient presented at the age of 16 years with an 8-year history of worsening central vision (20/120 bilaterally) and reported nyctalopia. Fundus autofluorescence (FAF) imaging showed paracentral rings of increased signal (approximate diameter 12°), similar to that reported commonly in retinitis pigmentosa. OCT of the macula showed a large area of inner segment ellipsoid zone irregularity, typical for occult macular dystrophy. PERG and ERG were consistent with severe dysfunction confined to the macula (normal ERG). The findings in 9 other unrelated patients harbouring the same heterozygous variant were ascertained (mean age 38 years; range 19–77). Fundus autofluorescence was normal or near-normal (6 eyes of 4 subjects), showed paracentral rings of high density (4 eyes of 2 subjects), concentric areas of increased signal surrounding foci of increased macular signal (4 eyes of 2 subjects; mottled in 1 subject), and 3 eyes showed a high-density foveal signal, including a subject with well-demarcated macular atrophy in the other eye. There was no correlation between PERG P50 and age. PERG P50 was bilaterally undetectable (2 eyes of 1 subject; age 32 years), subnormal (16 eyes of 8 subjects; median amplitude 1.2 µV), and bilaterally normal in a 28-year-old patient with central mfERG reductions. The ERGs were normal in 17 of 18 eyes; there was cone system dysfunction in 1 eye of 1 patient, tested after cataract surgery. Follow-up recordings in 3 cases after 3, 4 and 10 years revealed stable macular dysfunction.

Conclusions Patients with RP1L1-related occult macular dystrophy harbouring the prevalent p.Arg45Trp missense variant show a range of fundus autofluorescence and pattern ERG phenotypes, including cases of severe macular dysfunction. The severity of macular dysfunction was unrelated to age, suggesting variable expressivity owing to genetic or environmental modifiers.

P4-14 An elderly case of butterfly-shaped pattern dystrophy

Rina Shikura¹, Takaaki Hayashi², Kei Mizobuchi¹, Ryo Taguchi³, Toshikatsu Kaburaki³, Tadashi Nakano⁴

¹The Jikei University Kashiwa hospital, Japan, ²The Jikei University Katsushika hospital, Japan, ³Saitama Medical Center, Jichi Medical University, Japan, ⁴The Jikei University, Japan

Background Pattern dystrophy (PD) is a rare inherited retinal disorder (IRD) characterized by retinal pigment epithelium abnormalities at the macula, classified as one of the macular dystrophies, and is diagnosed based on characteristic fundus findings. Although butterfly-shaped PD (BPD) has been reported to account for approximately 30% of all PD, BPD is an extremely rare IRD in the Japanese population, except for BPD seen in a subset of myotonic dystrophy patients. Here, we report a case of an elderly Japanese male diagnosed with BPD unassociated with myotonic dystrophy.

Case report An 81-year-old male was referred to the Jikei University Hospital for suspected macular dystrophy. There were few subjective symptoms and no family history of IRD. Decimal corrected visual acuity was 1.0 in each eye. Fundus photography showed discoloration of the macular region in both eyes. Fundus autofluorescence imaging revealed a butterfly-shaped autofluorescence pattern, consistent with BPD. Optical coherence tomography showed macular subretinal fluid in the left eye, in addition to bilateral irregular retinal pigment epithelial lines. Full-field ERGs were recorded according to the protocol of the International Society of Clinical Electrophysiology of Vision. The amplitudes of dark-adapted (DA) 0.01 and DA 200 (strong flash) were preserved, but the amplitudes of light-adapted (LA) 3.0 and LA 30 Hz flicker peak-to-trough amplitudes were slightly reduced in both eyes. Multifocal ERGs showed reduced responses in the central areas. We conducted genetic testing to identify pathogenic gene variants. Whole-exome sequencing was performed for genetic testing, but no pathogenic variant was found in PRPH2, BEST1 or CTNNA1 genes, which are known to be responsible for BPD. The fundus findings were unchanged during the subsequent follow-up period.

Conclusions We report a case of BPD, which is a rare IRD in Japan. Although no pathogenic variant was found in whole-exome sequencing, a pathogenic variant might exist in gene(s) not registered on the Retinal Information Network or in deep introns of known genes because the characteristic findings of BPD on the fundus autofluorescence images were observed.

P4-15 Deep phenotyping of RBP3-retinopathy; inherited pathological myopia and retinal dystrophy

Motoshi Yamamoto¹, Yu Fujinami-Yokokawa^1,3,4,5, Oscar Onyango^6,7, Yasutaka Suzuki¹, Gavin Arno^1,3,8,9, Nikolas Pontikos^1,3,8,10, Kayoko Komatsu^1,2, Natsuki Maetani^1,2, Kazushige Tsunoda^11,12, Michel Michaelides^1,3,8, Kaoru Fujinami^1,3,6,8,12

¹Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, ²Office Eye, Kyoto, Japan, ³UCL Institute of Ophthalmology, University College London, London, UK, ⁴Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan, ⁵Department of Public Health Research, Yokokawa clinic, Osaka, Japan., ⁶Department of Ophthalmology, Nairobi University, Nairobi, Kenya., ⁷Department of Ophthalmology, Kenyatta National and Teaching hospital, Nairobi, Kenya, ⁸Moorfields Eye Hospital, London, UK., ⁹Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK., ¹⁰Phenopolis, London, UK., ¹¹Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan., ¹²Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan

Purpose We present a detailed clinical and molecular study of a patient with childhood-onset pathological myopia and retinal dystrophy caused by multiple pathogenic variants in the retinol-binding protein 3 (RBP3) gene.

Methods This was an observational case study. Detailed phenotyping was performed, including full clinical evaluation, fundus photography, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (OCT), and ISCEV standard electroretinography. Comprehensive genetic testing with next-generation sequencing-based panel profiling covering 935 retinal diseases-associated genes was performed for the proband.

Results A 45-year-old male was examined with complaints of progressive visual impairment and night blindness in both eyes. There was no family history of ocular disorders or consanguinity. He had poor visual acuity from birth and was first described as having high myopia at the age of 3. His best recorded visual acuity was 0.6 in decimal in each eye at the age of 6. He described visual decline, especially since the age of 40. His best-corrected visual acuity in decimal was 0.5 with a correction of − 16.50 DS/− 1.00 DC × 150° in the right eye and 0.15 with − 16.75 DS/− 0.75 DC × 20° in the left eye. The anterior segments were normal. Fundus photography and FAF imaging showed atrophic changes at the posterior pole and the peripheral retina, with myopic and pigmentary changes along the vessels in both eyes. OCT detected photoreceptor layer loss at the posterior pole with relatively preserved retinal structure at the fovea in both eyes. Full-field electroretinogram (ERG) demonstrated undetectable responses for DA0.01, DA10.0, LA3.0, and LA 30-Hz flicker in both eyes. Genetic testing revealed two RBP3 variants; NM_002900.3: c.632G>A, (p.Trp211Ter) and c.345_349delCTGGC, (p.Trp116AlafsTer7). The former variant was classified as pathogenic and the latter as likely-pathogenic.

Conclusion To our knowledge, this report is the first to describe inherited pathological myopia and retinal dystrophy caused by multiple pathogenic RBP3 variants in the East Asian population. The detected early-onset features of high myopia and retinal dystrophy are in keeping with those of the four British case series (Arno et al. Invest Ophthalmol Vis Sci. 2015;56(4):2358–65.), although fundus changes were clearly identified in our case unlike the British cases. RBP3-related disease should be considered in children with high myopia and retinal dystrophy. Such deep-phenotyping data would help monitor and counsel patients, as well as in designing therapeutic trials.

P4-16 The clinical and genetic features of Korean patients with rhodopsin-associated retinitis pigmentosa (RHO-associated RP)

Younghoon Jung¹, Jiyong Kwak², Kwangsic Joo¹, Minseok Kim¹, Eunkyoung Lee¹, Kyuhyung Park¹, Suk Ho Byeon³, Jinu Han⁴, Junwon Lee⁵, Sejoon Woo¹

¹Department of Ophthalmology, Seoul National University College of Medicine, Korea, ²Department of Ophthalmology, The Institute of Vision Research, Yonsei University College of Medicine, Korea, ³Department of Ophthalmology, The Institute of Vision Research, Severance Eye Hospital, Yonsei University College of Medicine, Korea, ⁴Department of Ophthalmology, The Institute of Vision Research, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea, ⁵Department of Ophthalmology, The Institute of Human Barrier Research, Gangnam Severance Hospital, Yonsei University College of Medicine, Korea

Purpose To investigate the clinical features, natural course, and genetic characteristics of Korean patients with rhodopsin-associated retinitis pigmentosa (RHO-associated RP).

Methods This was a retrospective, multicenter, observational cohort study of 21 probands with RHO-associated RP who visited Seoul National University Bundang Hospital, Seoul National University Hospital, Severance Eye Hospital and Gangnam Severance Hospital. Targeted next-generation sequencing or whole-exome sequencing was performed, and patients with a molecular confirmation of a pathogenic variant in the RHO gene were included in this study. Medical records were retrospectively reviewed, and the subjects were divided into two subgroups: generalized RP and sector RP. A central visual field of the better seeing eye less than 10° and the best-corrected visual acuity (BCVA) of less than 20/40 were considered as progression of RP. Main outcome measures were genotype–phenotype correlation, clinical features, disease progression analysis of BCVA, and visual field (VF).

Results The mean age of onset of symptom was 27.1 years (range, 8–76 years), and mean follow-up period was 56.1 months (range, 6–196 months). At the last follow-up, the generalized RP group showed a significantly higher rate (60.0%, 9/15) of visual field impairment (central visual field < 10°) than the sector RP group (0%, 0/6, p = 0.019). The generalized RP group showed a higher rate of visual acuity deterioration than the sector RP group without statistical significance (26.7% (4/15) and 0% (0/6), respectively, p = 0.281). We identified 10 known RHO mutations, and 3 novel RHO mutations including two missense mutations (p.T108P and p.G121R) and one deletion (p.P347_A348del). All of the patients had single heterozygous variants in the RHO gene. The major RHO-associated RP mutation was found in exon 1 (57.1%, 12/21). RHO p.G101E (19.0%, 4/21) and was the most common pathogenic variant. RHO p.T17M (14.3%, 3/21) and p.R135W (14.3%, 3/21) were the second most common pathogenic variants. Seventeen patients (81.0%) showed autosomal dominant inheritance while 4 patients (19.0%) with the p.G101E variant showed sporadic inheritance. There were genetic differences in the variants in the RHO gene between generalized and sector RP groups.

Conclusions This multicenter cohort study provides the clinical and genetic features of RHO-associated RP in Koreans. It has clinical importance in expanding the genetic spectrum and understanding genotype–phenotype correlations, ultimately facilitating the development of gene therapy.

P4-17 Unilateral pigmentary retinopathy: A 36-year follow-up

Marita Andersson Gronlund^1,2, Fahad Razooqi², Ebtisam Yaseen², Alexandra Lind², Susann Andersson²

¹Deparment of Ophthalmology, Faculty of Medicine and Health, Orebro University, Orebro, Sweden., ²Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden

Purpose Retinitis pigmentosa (RP) is a group of inherited, heterogeneous, progressive retinal dystrophies, primarily affecting photoreceptors and retinal pigment epithelium function. RP may occur alone or as part of various syndromes, and may be inherited as a dominant, recessive, or x-linked trait or may occur sporadically. RP manifests as night blindness, constricted visual fields, and marked visual impairment in some patients. Ophthalmoscopically, bone-spicule pigmentary changes, optic disc pallor, arteriolar narrowing, and atrophy of the retinal pigment epithelium are found. RP usual manifests bilaterally and symmetrically, but unusual manifestations have been described. Unilateral pigmentary retinopathy is a rare condition. Several cases have been reported in the literature. Only a few of these cases were found to be unilateral with no discernible alternative aetiology, especially those cases that were reported prior to the advent of electrophysiology. The Francois & Verriest criteria for unilateral pigmentary retinopathy are: 1. Clinical signs of disease present in one eye; 2. The fellow eye has no clinical sign of disease; 3. All infectious, vascular, inflammatory, or other aetiologies of pigmentary retinopathy have to be ruled out; 4. The case must be followed for a minimum of five years.

Methods Case report.

Results This man first presented in 1984 at the age of 30 years with pigmented retinal changes confined to one eye. The patient had no history of trauma, carcinoma, systemic medication with known retinal toxicity, previous retinal inflammatory or vascular diseases, or hereditary retinal disorders. The visual acuity (VA) was 0.0 logMAR bilaterally. Ophthalmological examination of right eye (RE) showed pale disc, narrowed arterioles with obvious pigmentation in the periphery of the retina without pigment clumping or bone spicules, while the fundus examination of the left eye (LE) was completely normal. The ff-ERG was almost extinguished in the RE but normal in the LE, and this has been repeated over years. The patient presented again at age 43 with a significant decrease in VA in the RE (0.4 log MAR). The anterior segment showed a mild posterior subcapsular cataract. On fundus examination, a pale disc, narrowed arterioles, and extensive pigmentation in the form AV bone spicules in the periphery was seen. At age 53, the patient presented with a progressive deterioration of VA in the RE (0.80 logMAR); VA in the LE was still 0.0 logMAR. Follow-up examinations of the RE at age 63 and 66 showed a continued decrease in vision with progression of subcapsular cataract and macular edema. Fundus examination of the fellow eye did not reveal any abnormalities over the years. Visual fields of the RE have become more and more constricted; LE stayed normal. Blood test for anti-retinal antibodies and lues was negative. Genetic testing with whole-exome sequencing (WES) showed no mutations related to RP.

Conclusions We present a rare case of RP that has been followed for an exceptionally long time, 36 years, where retinal function has decreased over time in one eye while in the other eye, no signs of retinal dystrophy have been found. Differential diagnosis of other conditions of pigmentary retinopathy that mimic RP has been ruled out. Thus, this patient fulfills all criteria for diagnosis of unilateral RP.

P4-18 Analysis using the microperimeter MP-3 for a case with suspected unilateral retinitis pigmentosa

Yoshito Koyanagi¹, Hideki Kawai¹, Taiga Inooka¹, Junya Ota¹, Kensuke Goto¹, Taro Kominami¹, Koji M. Nishiguchi¹

¹Department of Ophthalmology, Nagoya University Graduate School of Medicine, Japan

Purpose The purpose of this study was to evaluate a case with suspected unilateral retinitis pigmentosa (URP) using the microperimeter MP-3 (Nidek Co. LTD, Aichi, Japan) and to compare the results with those of the Humphrey field analyzer (HFA) 10-2 (HFA10-2) and the left–right difference between the eyes.

Methods A 70-year-old woman with suspected URP with a follow-up period of less than 5 years was evaluated. The ophthalmoscopic findings (e.g., bone spicule-like pigment clumping in the mid-peripheral and peripheral retina and attenuation of retinal vessels) and severe rod-cone dysfunction in the electroretinogram (ERG) were observed only in the right eye. There were no abnormal findings in the fundus of the left eye and the ERG was normal. The retinal sensitivity was measured with HFA10-2 and the MP-3, which was set up with 68 points coinciding with the measurement points of HFA10-2, and the results of both analyses were compared. The 68 points were divided into 5 regions (regions 1–5) from the periphery to the centre, and the results of MP-3 and HFA10-2 were compared in each region. The results were also compared with fundus autofluorescence (FAF) images.

Results The maximum retinal sensitivity in MP-3 was 25 dB in the right eye and 31 dB in the left eye, while in HFA10-2 it was 33 dB in the right eye and 31 dB in the left eye. The difference in maximum retinal sensitivity between the right and left eyes was greater in MP-3 than in HFA10-2. By region, MP-3 detected a more pronounced trend towards reduced retinal sensitivity from region 3 to the periphery compared to HFA10-2. In the right eye, there were scattered 0 dB regions around 10° coinciding with hypofluorescent areas in the FAF image. In addition, there was a localized hypofluorescent area near the macula in the right eye, and the retinal sensitivity of that area measured by MP-3 was 0 dB. Overlaying the images assuming that the 68 points correspond one-to-one to the MP-3 visual field area showed a discrepancy between retinal sensitivity in the HFA10-2 and the hypofluorescent regions of FAF. The HFA10-2 did not detect the hypofluorescent regions of FAF near the macula, suggesting that the fixation point may have been shifted.

Conclusions Our analysis suggested that MP-3 detects the reduced retinal sensitivity more accurately in a case of suspected URP compared with HFA10-2.

P4-19 The role of history-taking in assessment of inherited retinal diseases

Susann Andersson¹, Sara Arvidsson¹, Nuria Fluriach Dominguez¹, Marita Andersson Gronlund^1,2

¹Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden, ²Department of Ophthalmology, Faculty of Medicine and Health, Orebro University, Orebro, Sweden

Purpose To present the ophthalmological, electrophysiological, and genetic assessment of retinal dysfunction in two siblings who were examined separately from each other. The family came from the Middle East to Sweden approximately 25 years ago. The parents were cousins and had no ophthalmological disorders. The siblings have a good contact with each other but have no tradition of talking about diseases.

Methods Case report.

Results The brother, who was first examined at the age of 26 years, had low visual acuity in one eye due to optic neuritis and multiple sclerosis. However, retinal pathological findings in the mid-retinal periphery were also noted and a rod-cone dystrophy was suspected. The ff-ERG showed no detectable rod responses, decreased cone amplitudes, and a prolonged implicit time. iGenetic analyses could not confirm the diagnoses at that time. He was followed at the Unit for inherited retinal disease at the Eye Clinic in Gothenburg, Sweden. The sister was diagnosed at the age of 22 with uveitis. Her visual acuity was normal but she had difficulty seeing in the dark. She was suspected of having an inflammatory/autoimmune retinal disease, as she had retinal fundus abnormalities as well. Ff-ERG showed no detectable rod responses and reduced amplitudes of the cones. There was no genetic explanation found for this phenotype at this early stage. She was followed at the Uveitis unit at the same eye clinic as her brother for many years with recurrent uveitis and suspected Bechet´s disease. In both siblings, retinal function decreased over the years. The sister was regularly examined due to recurrence of uveitis and the brother underwent ff-ERGs and ophthalmological examinations every 4–5 years. When the brother was genetically tested again (NGS, Next-Generation Sequencing) at 35 years of age, he was confirmed as having autosomal recessive retinitis pigmentosa (RP45). When the siblings finally talked about their retinal disease with each other, the sister was also genetically tested and she was found to have the same variant as her brother, RP45.

Conclusion The sibling’s slightly different phenotype and the reluctance of talking about their diseases probably prolonged the time to make the correct diagnosis. This shows the importance of taking a thorough history. A thorough history is a very important piece of the puzzle, together with fundus appearance/visual fields, electrophysiology, and genetic testing, in diagnosing inherited retinal diseases.

P4-20 Assessments of macular function by focal macular ERG and static perimetry in eyes with retinitis pigmentosa

Satoshi Okado¹, Yoshito Koyanagi¹, Taiga Inooka¹, Taro Kominami¹, Hiroko Terasaki¹, Koji M Nishiguchi¹, Shinji Ueno²

¹Nagoya University Graduate School of Medicine, Japan, ²Hirosaski University Graduate School of Medicine, Japan

Purpose To assess macular function by focal macular ERG (FMERG) and static perimetry in eyes with retinitis pigmentosa (RP).

Methods Eighty-eight eyes of 88 RP patients were analyzed. The relationships between the FMERG components and the mean deviations (MDs) of the Humphrey Field Analyzer (HFA) 10-2 were determined. Spectral-domain optical coherence tomography (SD-OCT) was used to determine the integrity of the ellipsoid zone (EZ) and the interdigitation zone (IZ).

Results The MDs were significantly correlated with the amplitudes of the a-waves (r = 0.65, p < 0.01), the b-waves (r = 0.70, p < 0.01), the OPs (r = 0.61, p < 0.01), and the implicit times of the b-waves (r = − 0.47, p < 0.01) of the FMERGs. However, forward–backward stepwise regression analyses showed that only the amplitudes (r = 0.45, p < 0.01) and implicit times (r = − 0.29, p < 0.01) of the b-waves were significantly correlated with the MDs. Some of the eyes with early stage of RP (≥ − 10.0 dB) had reduced b-wave amplitudes (< 1.0 µV) with intact EZ but disrupted IZ in OCT images. Subgroup analyses of the eyes with early stage of RP (≥ − 10.0 dB) showed that the EZ width was correlated with the MDs but not with the b-wave amplitude. The thickness of the EZ-retinal pigment epithelium (EZ-RPE thickness) as an alternative indicator of IZ was correlated with the b-wave amplitude (r = 0.32, p = 0.04) but not with the MDs (r = − 0.10, p = 0.53).

Conclusions The fact that the FMERG amplitudes are reduced before the shortening of the EZ width in the early stage of RP indicates that the FMERG amplitudes are an earlier indicator of macular dysfunction than the HFA 10-2 findings.

P4-21 Pigmented paravenous retinochoroidal atrophy with confusing electrophysiological findings

Randa Abdelgawad^1,2

¹Ain Shams University, Egypt, ²Electrophysiology consultant Watany Eye Hospital, Egypt

Background Pigmented paravenous retinochoroidal atrophy (PPRCA) is a rare disorder characterized by pigment accumulation along the distribution of retinal veins. The findings are usually incidental with minimal effect on vision. The etiology is still not fully understood. Diagnosis is made by peculiar retinal findings.

Case report A 33-year-old male complaining of night blindness came for electrophysiological assessment. Having a negative ERG, electrophysiological findings were confused with congenital stationary night blindness (CSNB), the incomplete form. Fundus examination was performed revealing the characteristic retinal perivenous pigments of PPRCA. Fundus imaging and OCT were performed.

Conclusions PPRCA is a disease with variable electrophysiological findings. This case represents one of its variable electrophysiological presentations in the form of negative ERG. Correlation with clinical examination and imaging is crucial.

P4-22 Characterization of POMGN1 retinopathy with late onset and intrafamilial phenotypic heterogeneity

Monique Leys¹, Lingo Lai¹, Brian Ellis¹, Grace Levy-Clarke¹, Cassidy Pinion¹, J. Vernon Odom¹

¹WVU Eye Institute, USA

Purpose Recessive loss of function POMGNT1 mutations can cause early onset muscle–eye–brain disease (MEB, OMIM no. 253280), but also have more recently been associated with non-syndromic retinitis pigmentosa. We describe 3 sisters affected by non-syndromic autosomal recessive POMGNT1 retinopathy with report of a new variant.

Methods The proband was seen for cataract evaluation at age 42 and her fundus examination was suggestive of retinitis pigmentosa. Her oldest sister had been treated for acute anterior uveitis with retinal vasculitis since age 40. Another sister was diagnosed with multiple sclerosis (MS) at age 50 and peripheral retinal degeneration at age 54. We reviewed ERG records, imaging files, and visual fields and obtained DNA samples for a next-generation sequencing panel of 330 genes in 5 family members.

Results The 3 siblings had constricted fields with preserved central vision. Posterior subcapsular cataracts were diagnosed between age 42 and 55. In the oldest sibling, the ERG was normal at age 40 and reduced and delayed at age 61 in the eye with a prior diagnosis of vasculitis and was delayed in the fellow eye. The electroretinogram was delayed and reduced but recordable for all conditions in the younger siblings. In the 3 siblings, we identified a pathogenic POMGNT1 variant, c.751 + 1G>A (splice donor), leading to a loss of protein function, in trans with a likely pathogenic missense change, c.1010T>C (p.Ile337Thr). The impact of this on POMGNT1 protein function, as well as the the clinical and electrophysiological findings in the 3 siblings, is very suggestive of pathogenicity of the second variant.

Conclusions The cases emphasize the need for thorough family history and genetic testing. A detailed family history and examination of the siblings with genotyping might have led to an earlier diagnosis of retinal inherited disease and avoidance of immunomodulatory treatment in the oldest sibling.

P4-23 How much retinal loss causes an ERG to become flat?

Jasleen Kaur Jolly^1,2, Archith Kamath³, Rafee Ahmed², Deepika Kommanapalli¹, Saoud Al-Khuzaei², Susan M Downes^2,3

¹Vision and Eye Research Institute, Anglia Ruskin University, Cambridge, UK, ²Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK, ³Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK

Purpose With the increase in potential treatment options for inherited retinal diseasess (IRDs), we are seeing more patients with these conditions in our clinics. Many patients with measurable visual function have flat line ERGs. This study attempts to use clinical data to establish whether there is a link between the degree of retinal loss and an unmeasurable ERG.

Methods Patients underwent ISCEV standard ERG testing as part of NHS routine care.

Results We present results from a series of patients with IRDs, with associated ocular coherence tomography (OCT) scans and Goldmann visual fields.

Conclusions There is a relationship between the degree of retinal loss and ERG loss, but there is a range of loss over which unmeasurable ERG responses occur.

P4-24 Dark-adapted oscillatory potentials in retinal and optic nerve disease

Enid Chelva¹, Monika Dolliver¹, Sarina Laurin¹, Jessica Munster¹, Jonathan Stafford¹, Chee Cheng¹

¹Sir Charles Gairdner Hospital, Australia

Purpose The dark-adapted 3.0 oscillatory potentials (DA 3 OPs) of the ISCEV ERG are thought to reflect inner retinal activity of amacrine and retinal ganglion cells and are known to be affected in retinal vascular disease. However, there has been little published data relating to other ocular disease. This study investigates the diagnostic value of recording DA 3 OPs across the major diagnostic groups to provide further insight into the retinal aetiology of these signals.

Methods A retrospective study of all patients referred to the state Visual Electrophysiology Clinic in Western Australia for ISCEV ERGs over the past 10 years was conducted. Results for each eye were categorised into 4 groups based on the summed amplitude (peak to succeeding trough) of the initial 4 individual wavelets. Interval classifications using the ratio of the summed amplitude divided by the age-related lower normal limit of (1.0, 0.7], (0.7, 0.3] and (< 0.3) defined mild, moderate, and gross abnormalities, respectively, the remainder being normal. In cases with asymmetric findings, the result from the more severely affected eye was used. Relative frequencies for the predominant diagnoses within each group were calculated.

Results Successful DA 3 OPs were recorded in 2723 patients (1523female, 1200 male) with an age range of 3 months to 96 (mean 43.2 ± 22.8) years. Of these, 1570 (58%) were bilaterally normal. Mild, moderate, and gross abnormalities were found in 387 (14%), 519 (19%) and 247 (9%) patients, respectively. Those with gross abnormality were predominantly affected with retinitis pigmentosa (87, 35%) and rod-cone dystrophy (30, 12%). Most of the remainder comprised various unspecified retinopathies, night blindness, Usher syndrome, and autoimmune retinopathy, each constituting approximately 7%. Moderate abnormalities were mainly found in retinitis pigmentosa-like disease (122, 24%), optic nerve dysfunction (69, 13%), other inherited retinal diseases (55, 11%), unexplained visual loss (51, 10%), ocular toxicity (39, 8%), and maculopathy (30, 6%). There were only 2 cases of retinal ischemia, both of which were moderately abnormal.

Conclusions This study suggests that recording the DA 3.0 OP can be of value in the diagnosis of various disorders including inherited retinal disease, optic nerve disorders, unexplained visual loss, autoimmune retinopathy, and ocular toxicity. This preliminary work will form the basis of further detailed analysis of individual oscillatory potential wavelets and their relationship with each other within specific diagnostic categories, which may elucidate a better understanding of the aetiology of these retinal signals.

P4-25 Bardet-Biedl syndrome caused by a novel homozygous variant in the ARL6 gene, initially diagnosed with retinitis punctata albescens

Keitaro Mizumoto^1,2, Kumiko Kato², Kaoru Fujinami^3,4, Tadasu Sugita⁵, Iichiro Sugita⁴, Ayako Hattori⁶, Shinji Saitoh⁶, Shinji Ueno⁷, Kazushige Tsunoda⁸, Takeshi Iwata⁹, Mineo Kondo²

¹Department of Ophthalmology, Okanami General Hospital, Japan ²Department of Ophthalmology, Mie University Graduate School of Medicine, Japan ³Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, ⁴UCL Institute of Ophthalmology, University College London, London, United Kingdom, ⁵Department of Ophthalmology, Sugita Eye Hospital, Japan ⁶Department of Pediatrics and Neonatology, Graduate School of Medical Sciences, Nagoya City University, Japan ⁷Department of Ophthalmology, Hirosaki University Graduate School of Medicine, Japan ⁸Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Japan ⁹Division of Molecular and Cellular Biology, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Japan.

Background Bardet-Biedl Syndrome (BBS) is an autosomal recessive systemic disorder characterized by retinitis pigmentosa, polydactyly, obesity, intellectual disability, renal impairments, and hypogonadism. The purpose of this study was to determine the ocular characteristics of a boy with BBS caused by a novel homozygous variant in the ARL6 (alternative name BBS3) gene who had been originally diagnosed with retinitis punctata albescens.

Case report A 7-year-old boy was examined in our hospital with complaints of a progressive reduction of his visual acuity and night blindness in both eyes. There was no family history of eye diseases and no consanguineous marriage. Fundus examinations showed numerous white spots in the deep retina and retinal pigment epithelium. Fundus autofluorescence (FAF) showed hypofluorescence consistent with these spots. Both the scotopic and photopic components of the full-field ERGs were non-detectable. Based on these clinical findings, this boy was suspected to have retinitis punctata albescens. Subsequent genetic testing using WES revealed a novel homozygous variant in the ARL6/BBS3 gene [NM_001278293.3:c.528G>A, (p.Trp176Ter)]. A systemic examination by the pediatric department revealed that this boy had a history of a surgical excision of polydactyly on his left foot when he was born, and that he was mildly obese. There was no obvious intellectual impairment, gonadal dysfunctions, craniofacial or dental abnormalities, congenital heart disease, or hearing impairment. He was then clinically and genetically diagnosed with BBS.

Conclusions In children with night blindness and progressive visual dysfunction, it is important for eye care practitioners to consult clinical geneticists and pediatricians to rule out the possibility of systemic diseases such as BBS.

P4-26 Electroretinographic abnormalities in X-linked Alport syndrome with a novel COL4A5 variant

Kei Mizobuchi¹, Takaaki Hayashi^1,2, Ryo Ohira¹, Tadashi Nakano¹

¹The Jikei University School of Medicine, Japan, ²Katsushika Medical Center, Japan, The Jikei University School of Medicine, Japan

Background Alport syndrome comprises a heterogeneous group of inherited multiorgan diseases characterized by hematuria, progressive renal failure, hearing loss, and ocular complications. Approximately 85% of patients with Alport syndrome have an X-linked pattern caused by variants in COL4A5 localized on Xq22.3. Several ocular complications are associated with Alport syndrome, such as corneal opacities, posterior polymorphous corneal dystrophy, anterior lenticonus and cataract, central and peripheral fleck retinopathies, temporal macula thinning, and giant macula hole. However, little is known about retinal function in these patients, including electroretinographic findings and retinal disease progression. In this study, we describe a male patient with a novel COL4A5 variant of X-linked Alport syndrome who had previously unreported electroretinographic findings.

Case report We performed genetic testing to identify a disease-causing variant of Alport syndrome and a comprehensive ophthalmic examination including full-field electroretinography (FF-ERG). For genetic testing, we employed a hybridization capture-based target enrichment method for next-generation sequencing (NGS), revealing a novel hemizygous variant [c.51_52delGA (p.Trp20GlyfsTer19)] in exon 1 of COL4A. The patient underwent cataract surgery in both eyes because of decreased visual acuity and photophobia. The best-corrected visual acuity improved from 0.9 and 0.7 in the right and left eyes, respectively, to 1.5 in both eyes. Anterior-segment optical coherence tomography (OCT) revealed anterior and posterior lenticonus. Fundus photographs showed central and peripheral fleck retinopathy. Wide-field fundus autofluorescence imaging showed mottled hyper-autofluorescence (AF) and hypo-AF at the peripheral retina, which was consistent with peripheral fleck retinopathy. OCT also revealed thinning of the inner retinal layers, especially at the temporal macula, whereas the outer retinal layers were preserved. Ganglion cell analysis showed no progression for 5 years. FF-ERG was performed at the age of 41 (phakia) and 46 (pseudophakia). Dark-adapted (DA) response showed that the b-wave amplitude of DA 0.01 was reduced to 50% and that the a- and b-wave amplitudes of DA 3.0 were reduced to 70% and 50%, respectively, compared with those in the controls. The b/a-wave ratio of DA 3.0 was 1.22 and 1.16 in the right eye and left eye, respectively. The amplitude of DA 3.0 oscillatory potentials (OP) was reduced. Light-adapted (LA) response showed that the a- and b-wave amplitudes of LA 3.0 were reduced to 70% and 30%, respectively, and that the peak-to-trough amplitudes of LA 30-Hz flicker were also reduced to 40% compared with those in the controls. Five years later, the amplitudes of DA and LA responses revealed no remarkable changes compared with those at the initial examination except for the DA 3.0 OP wave, which was nonrecordable.

Conclusions We described a patient with X-linked Alport syndrome who carried a novel truncated COL4A5 variant (p.Trp20GlyfsTer19). Our results revealed electroretinographic abnormalities in a patient with Alport syndrome, indicating impairment predominantly of the inner retina. Notably, no short-term progression was observed in this patient.

P4-27 A case of X-linked retinoschisis mimicking “idiopathic” cystoid macular edema

Sophia Ling Li¹, Noel Chan¹, Andrew Mak¹

¹The Prince of Wales Hospital, Hong Kong

Purpose X-linked retinoschisis (XLRS) is a relatively common cause of macular dysfunction in young males. It is a hereditary disease characterized by the presence of schitic changes at the fovea and internal splitting of the retina, affecting primarily males with a juvenile onset. The disease course and severity are highly variable.

Methods This study presents a case of XLRS with the disease course, diagnostic challenges, and the role of full field ERG illustrated.

Results A 28-year-old male patient with good past health presented with a painless drop in vision in both eyes during the previous 6 months. Presenting visual acuity was 20/80 for both eyes. Initial fundus examination showed sequential cystoid macular edema in the right eye followed by the left eye. There was no significant intraocular inflammation, retinal pigmentary changes, or vascular occlusion. He had no prior history of ocular surgery. Blood workup for the autoimmune panel and syphilis was negative. The patient was labelled as idiopathic cystoid macula edema. Further investigation including optical coherence tomography (OCT) showed foveoschitic changes with cystoid macula edema which gradually subsided with foveal thinning. Visual fields showed a central scotoma in both eyes. The patient was treated with topical nonsteroidal anti-inflammation drugs and topical Brinzolamide. The diagnosis was then revised to suspected inherited maculopathy with no prior family history identified. The full-field ERG showed selective scotopic loss of b-wave amplitude with relative preservation of the a-wave in both eyes (low b:a ratio); this was ratio was below 1 (electronegative waveform) in the left eye. The finding was in keeping with inner-retinal dysfunction, and the electronegative waveform of the left eye is a characteristic, but not universal, finding in XLRS.

Conclusions The case report illustrated the diagnostic value of ffERG in managing XLRS patients with atypical clinical features.

P4-28 Photoreceptor malfunction in a cohort of X-linked juvenile retinoschisis patients

Qingge Guo¹, Bo Lei¹, Ya Li¹

¹Henan Provincial People’s Hospital, China

Purpose X-linked juvenile retinoschisis (XLRS), caused by RS1 gene mutations, presents with high phenotypic heterogeneity. Previous studies have shown that defects of RS1 protein mainly affected the inner retina. We explored whether decreased vision in these patients was associated with morphological and functional alterations in the photoreceptors.

Methods Twenty-two eyes of 11 patients with XLRS confirmed by genetic testing were divided into two groups according to the severity of visual impairment. Best-corrected visual acuity (BCVA) greater than or equal to 0.1 was group A, and BCVA less than 0.1 was group B. Visual acuity less than 0.01 was counted as 0.001. The retinal fovea thickness, outer nuclear layer (ONL) thickness, and photoreceptor inner segment and outer segment (IS/OS) thickness were detected by swept source optical coherence tomography (SS-OCT). Retinal function was assessed by ERG. ERG amplitude and b-wave to a-wave ratios were obtained. The relationships between the BCVA and ERG amplitudes, thickness of the fovea, ONL, and IS/OS were evaluate with linear regression.

Results In B-scan SS-OCT, the light reflection of the foveal macula ellipsoid zone (EZ) was reduced to various degrees or even disappeared in both groups. The ERG amplitudes correlated with the severity of the phenotype. The BCVA, thickness of IS/OS, and b-/a-wave ratio of group A were significantly higher than that of group B (p = 0.002, 0.001, and 0.038, respectively). There were no significant differences in retinal fovea thickness and ONL thickness between the two groups (p = 0.9334 and 0.5242). The BCVA was significantly associated with the thickness of IS/OS (p = 0.0003, r = 0.7599).

Conclusions Visual acuity in XLRS patients was closely associated with the ERG a-wave amplitude and the thickness of IS/OS. Our data suggested that photoreceptor degeneration might be a key factor affecting vision in these patients. Given the fact that RS1 protein is abundantly expressed in the photoreceptor, its role in the progression and outcome of the diseases should not be overlooked.

P4-29 ERG changes in eyes with familial exudative vitreoretinopathy with or without Wnt signaling gene mutations

Takuma Futami¹, Sho Naruse¹, Itsuka Matsushita¹, Tastuo Nagata¹, Hiroyuki Kondo¹

¹University of Occupational and Environmental Health, Japan

Purpose Familial exudative vitreoretinopathy (FEVR) is an inherited retinal disease caused by a deficiency of the retinal vascular development. Mutations in the Wnt signaling genes are known to be associated with FEVR. The mutations account for about 50% of FEVR patients, but the genetic causes in the rest of the families are unknown. Few studies have addressed ERG changes of FEVR. In this study, we compared ERG changes in FEVR patients with and without mutations in the Wnt signaling genes.

Methods FEVR patients treated at the University of Occupational and Environmental Health Hospital from 2014 to 2022 participated in this study. We measured full-field ERGs: rod, dark-adapted maximal response, cone, flicker, and long flash ERGs for 65 eyes of 33 patients (19 males, 14 females, mean age 5.6 years) in accordance with the ISCEV protocols. Based on the report by Yaguchi et al., the severity of FEVR was classified into stage 1, peripheral retinal abnormalities only; stage 2, macular traction; stage 3, falciform retinal folds; and stage 4, falciform retinal folds with extensive retinal degeneration. The ERG recordings were compared between eyes with mutations in the Wnt signaling genes (Wnt group) and patients without mutations (no mutation group).

Results Of the 33 patients, 24 had mutations in the Wnt signaling genes. Of the 65 eyes, 47 and 18 eyes were in the Wnt group and no mutation group, respectively: 19 and 8 eyes in stage 1, 12 and 0 eyes in stage 2, 11 and 6 eyes in stage 3, and 5 and 4 eyes in stage 4. Consistent with the previous report, the amplitude of each ERG tended to decrease as the severity of the stage increased (p < 0.020). In eyes in the Wnt group, the b/a ratios of the dark-adapted maximal response and the b/d ratios in the long flash ERG were higher than in eyes in the no mutation group (p < 0.001 and p = 0.021, respectively). In stage 1, the amplitudes of a-wave in the maximal response and the d-wave in the long flash ERG were lower in the Wnt group than in the no mutation group.

Conclusions FEVR may show different ERG characteristics between eyes with and without mutations in the Wnt signaling genes.

P4-30 Electroretinograms of eyes with Stickler syndrome

Sadamitsu Nishimura¹, Hiroyuki Kondo¹, Kazushi Fujimoto¹, Mamika Imagawa¹, Kazuma Oku¹, Itsuka Matsusita¹, Tatsuo Nagata¹, Takaaki Hayashi¹

¹University of Occupational Environmental Health, Japan

Purpose To determine the characteristics of the full-field electroretinograms (ERGs) in eyes with Stickler syndrome.

Methods Twenty-two eyes of 14 Japanese patients from 9 families with Stickler syndrome were studied. All of the patients were found to have mutations in the COL2A1 gene and had undergone ERG recordings. The ERGs from one of the two eyes were compared to 11 eyes of 11 normal control subjects who were matched by age, sex, and refractive error.

Results One patient had non-recordable ERGs under both scotopic and photopic conditions. For the remaining 13 patients, the amplitudes of the b-waves of the scotopic combined, rod, and cone responses were significantly smaller than those of the control subjects (p = 0.0001, p = 0.015, p = 0.0006, respectively). The implicit times of the b-wave of the scotopic combined and photopic responses were significantly prolonged (p = 0.0037, p = 0.0126, respectively). Age was inversely and significantly correlated with the amplitudes of the scotopic combined a-wave (p = 0.0184) and b-wave (p = 0.0076) in 13 eyes. The amplitudes of the scotopic combined b-wave were not significantly correlated with the refractive error.

Conclusions The reduced or absent full-field ERGs in eyes with Stickler syndrome indicate that the physiology of the entire retina was negatively altered. The greater reduction of the ERGs with increasing age suggests that the physiological alterations of the retina are progressive.

P5-1 Pattern VEP and retinal nerve fiber thickness in a Japanese girl with anti-myelin oligodendrocyte glycoprotein (MOG) antibody seropositive optic neuritis

Midori Tachibana¹, Shunichirou Takano^1,2, Aya Hanabusa³, Yuri Ohta¹, Yuji Yoshikawa¹, Kaori Sassa⁴, Takuhei Shoji^1,3, Kei Shinoda¹, Hideo Yamanouchi⁴

¹Departments of Ophthalmology, Saitama Medical University, Faculty of Medicine, Japan, ²Department of Ophthalmology, Teikyo University School of Medicine, Mizonokuchi Hospital, Japan, ³Koedo Eye Institute, Japan, ⁴Departments of Pediatrics, Comprehensive Epilepsy Center, Saitama Medical University, Faculty of Medicine, Japan

Purpose To describe a Japanese girl with unilateral optic neuritis (ON) who was seropositive for the anti-myelin-oligodendrocyte glycoprotein (MOG) antibody. Functional and microstructural changes were assessed by means of serial recordings of the pattern visual evoked potentials (PVEPs) and optical coherence tomography (OCT).

Methods Case Report.

Results A 5-year-old girl developed sudden vision loss and a deep ocular pain in her right eye. On examination at Saitama Medical University Hospital, the best-corrected visual acuity (BCVA) was light perception. Swelling of the optic disc and surrounding tortuous vessels were observed in the right eye. MRI showed that her right optic nerve was hyperintense on a short TI inversion recovery (STIR) sequence. She was diagnosed with right papillitis and treated with 450 mg of intravenous methylprednisolone pulses for 3 days (days 3–5) followed by a gradual tapering of oral prednisolone. The visual acuity decreased to no light perception and plasmapheresis combined with high-dose intravenous immunoglobulin therapy was performed. The visual acuity rapidly improved to 1.0 on day 13 and no recurrence was observed for at least 4 years. On day 19, she was found to be anti-MOG antibody-positive and anti-aquaporin 4 antibody-negative. The implicit time of N75, P100, and N145 in PVEPs and circumpapillary retinal nerve fiber (cpRNFL) thickness in OCT was measured during the course of the disease. PVEPs showed dynamic changes of the physiology of the visual pathways. The cpRNFL thickness of the right eye decreased rapidly and was less than half within 1 year and then stabilized. On the other hand, optic nerve function improved, i.e. the implicit times of the N75 and P100 components in the right eye were shortened and stabilized after approximately 1 year. However, the implicit times in the right eye were still prolonged compared to the left eye.

Conclusions Our findings illustrate the disease course with respect to microstructure and function in an eye with anti-MOG antibody-positive optic neuritis. This information may be useful for understanding the pathology and prognosis of this disease, and further analysis of PVEP and structural changes in more cases is awaited.

P5-2 Visual evoked potentials in cases of acute optic neuritis in AQP4-IgG positive NMOSD, MOGAD, double seronegative disease and MS

Ayano Enomoto^1,2,3, Namie Kobayashi^2,3, Kazuo Fujihara⁴, Kentaro Kobayashi², Yuji Inoue¹, Yutaka Isono^1,2,3, Atsushi Mizota¹

¹The University of Teikyo, Japan, ²Southern TOHOKU Eye Clinic, Japan, ³Southern TOHOKU General Hospital, Japan, ⁴Department of Multiple Sclerosis Therapeutics, Fukushima Medical University, Japan

Purpose Because of recent advances in antibody testing and imaging of the optic disc by optical coherence tomography (OCT), new diagnostic criteria and new classifications of optic neuritis are needed. We reviewed visual evoked potential (VEP) findings in aquaporin 4 (AQP4)-IgG positive neuromyelitis optica spectrum disorders (NMOSD), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), double seronegative disease, and multiple sclerosis (MS).

Methods We analyzed the VEP responses of 33 eyes with a diagnosis of acute optic neuritis, including 7 with AQP4-IgG positive NMOSD, 13 with MOGAD, 9 with double seronegative disease, and 4 with MS seen at the Departments of Ophthalmology and Neurology of Southern TOHOKU General Hospital.

Results Abnormal VEPs were recorded from 33 of the 33 eyes (100%). Of these, 19 (57.6%) had prolonged P100 latency and 14 (42.4%) had nonrecordable VEPs. The VEP response was absent more frequently in AQP4-IgG positive NMOSD than in MOGAD, double seronegative disease, and MS (6/7 vs 4/13 vs 3/9 vs 1/4, respectively).

Conclusions Our cooperative study by ophthalmologists and neurologists suggests that VEP findings appear to be different in various types of optic neuritis. The VEP may help guide decisions on the therapeutic strategy.

P5-3 Photopic ERG waveforms of patients with Werner syndrome

Gen Miura¹, Hirotaka Yokouchi¹, Masaya Koshizaka², Yoshiro Maezawa², Koutaro Yokote², Takayuki Baba¹

¹Department of Ophthalmology and visual science, Chiba University Graduate School of Medicine, Japan, ²Department of Endocrinology, Hematology and Gerontology, Chiba University Graduate School of Medicine, Japan

Purpose To investigate the waveform of the ERG and the correlation between the photopic negative response (PhNR) and the peripapillary retinal nerve fiber layer thickness (RNFLT) in patients with Werner syndrome.

Methods Photopic ERGs using 2 Hz and 28.3 Hz flash stimuli were recorded with the RETeval system without mydriasis. The RNFLT was measured by optical coherence tomography. The amplitude and peak time of ERGs and PhNR waveforms were evaluated. The PhNR waveform was measured at 72 ms and at the negative trough following the b-wave. The ratio of PhNR voltage at 72 ms to b-wave peak and the ratio of the b-wave peak voltage to the PhNR trough voltage to b-wave amplitude were also analyzed. Other data analyzed included age, gender, and logMAR visual acuity.

Results A total of 12 eyes of 6 patients (2 female) with Werner syndrome were studied. The mean age and logMAR visual acuity were 56.0 ± 10.8 years and − 0.22 ± 0.14, respectively. The mean peak time and amplitude of a- and b-waves were 13.7 ms, 9.55 µV, 31.6 ms, and 18.3 µV, respectively. The mean peak time and amplitude of flicker ERG were 28.8 ms and 28.7 µV, respectively. A-wave peak time in 6 eyes, b-wave peak time in 1 eye, and flicker ERG peak time in 2 eyes were increased from normal values. Eight eyes of 4 patients showed thinning of the RNFLT. The amplitude of the PhNR and the PhNR/b-wave ratio tended to decrease with a decrease in RNFLT.

Conclusions Non-mydriatic portable ERG with skin electrodes enables electrophysiological evaluation of Werner’s syndrome patients. Further investigation of retinal function in more patients is needed.

P5-4 Meridional anisotropy of visual-evoked potentials and contrast sensitivity in young adults with high astigmatism

Siu Sang Anthony Wu¹, Tsz Wing Leung¹

¹The Hong Kong Polytechnic University

Purpose Refractive (or manifest) astigmatism, a common refractive error among the Native American and Asian Chinese population, influences visual development if not appropriately corrected in early life. Unless the circle of least confusion falls precisely at the retina, the orientation-dependent optical feature of astigmatism leads to visual deficits that often degrade one meridian more than the others. This meridional anisotropy has been consistently reported in contrast sensitivity at high spatial frequencies and for grating acuity. However, previous electrophysiology studies that have primarily determined the electrophysiological response of the primary visual cortex to a low spatial frequency (3–4 cycles per degree [cpd]) stimulus have yielded conflicting results. This study aimed to investigate the effect of astigmatism on meridional anisotropy using contrast sensitivity (CS) and steady-state visual evoked potentials (ssVEP) over a broad spectrum of spatial frequency.

Methods Thirty-two healthy young adults (18–35 years) with best-corrected distance visual acuity (BCDVA) of logMAR 0.0 or better were recruited and divided into two refractive-error groups: (1) Highly astigmatic group (HAS, n = 14): spherical-equivalent error (SE) ≥ − 6.00D, cylindrical error (cyl) ≥ 2.00DC, with negative cylindrical axis 180° ± 20°; (2) Non-astigmatic group (NAS, n = 18): SE ≥ − 00D, cyl ≤ 0.50DC. The ssVEP measured the electrophysiological response of the primary visual cortex for sinusoidal gratings oriented horizontally and vertically. Grating spatial frequencies (SF) of 0.6, 1.3, 3, 6, and 12 cpd were used as stimuli. For each grating orientation and spatial frequency, the first harmonic response extracted by a Fourier transform was analyzed. The CS for horizontal and vertical gratings was assessed psychophysically through a spatial four-alternative forced-choice procedure with a 3-down-1-up modified staircase protocol at 0.6, 1.4, 3, 6, and 12 cpd. Both ssVEP and CS were measured with full optical correction.

Results The grating orientation significantly affected the VEP amplitude (ANOVA repeated measures, p = 0.04) and CS (p = 0.002) in the HAS group; both were generally lower for the horizontal than vertical gratings. However, the effect was non-significant in the NAS group (p ≥ 0.17). When comparing the two refractive-error groups, the VEP amplitudes showed significant interactions between refractive error groups and SF for both horizontal and vertical gratings (mixed model ANOVA, p < 0.001), but pairwise comparisons for individual SF were not significant after Bonferroni’s correction. For CS, there was a significant interaction between refractive error groups and SF for horizontal gratings (mixed model ANOVA, p = 0.02) but not for vertical gratings (p = 0.51). Bonferroni’s post hoc test revealed significantly lower CS at 12 cpd in the HAS group than in the NAS group (p = 0.03). No significant group effect or interaction was found for the vertical grating.

Conclusions Highly astigmatic subjects exhibited significantly lower VEP and CS for horizontal than vertical gratings, even though their BCDVA were clinically normal. In addition, their CS for horizontal gratings at high spatial frequency was significantly lower than that in non-astigmatic subjects. The pattern of meridional anisotropy matches the orientation-dependent optical blur created by their astigmatism when uncorrected.

P6-1 Follow-up of disease process with visual electrophysiology in a pediatric age group

Azza Abdelfattah Shehab^1,2, Randa Elmofty^2,3

¹Minia University, Egypt, ²Al Watany Eye Hospital, Egypt, ³Cairo University, Egypt

Purpose Follow-up of pediatric patients with retinal dystrophies or neurological disorders with visual electrophysiology.

Methods Fifty-four pediatric patients were included in this retrospective study, with ages ranging from 6 months to 10 years. They represented different types of retinal dystrophies and neurological disorders. The period of follow-up was from January 2016 until November 2022. Only patients with complete data were included in the study. Ophthalmological, electrophysiological, and multimodal imaging were assessed. MRI was obtained for neurological cases.

Results Retinal dystrophies showed stable or mild progression. Neurological cases showed improvement or were stable in cerebral palsy cases and stable to progressive in cases with shunts.

Conclusions The application of electrophysiology as a method of establishing the diagnosis, following the disease, and determining stability versus progression was very helpful and crucial in most of the cases.

P6-2 Pediatric visual electrophysiology in Slovenia: Early and recent approaches and diagnostics

Jelka Brecelj¹, Branka Stirn-Kranjc¹, Manca Tekavcic-Pompe¹, Martina Jarc-Vidmar¹, Maja Sustar-Habjan¹, Eva Lenassi¹, Katarina Likar¹, Alma Kurent¹

¹Eye Hospital, University Medical Centre Ljubljana, Slovenia

Purpose We were fortunate to be able to establish pediatric electrophysiology in a clinical setting in 1989 at the University Medical Centre Ljubljana, first at the Institute of Clinical Neurophysiology and from 2002 onwards at the Eye Clinic. With the support of Prof. Tine S Prevec in his laboratory of Sensory Electroencephalography, with excellent technical capabilities, we were able to develop and apply pediatric electrophysiology in clinical practice. Our mentor was Dr. Anthony Kriss, from Great Ormond Street Hospital in London, with his approach of simultaneous skin electrode ERG and VEP recording in babies and small children (GOSH protocol). Research, mentorships, and presentation of studies at the ISCEV, Pediatric Ophthalmology, and other conferences were all equally important. The aim is to present some of our early and subsequent approaches for electrophysiological diagnostics in babies and children with retinal or visual pathway disorders.

Methods In babies and children, recordings are performed with the patient in an alert state with an effort to maintain their happy emotions and good performance. From newborn to around the age of 3 years, simultaneous recordings of skin ERG to flash stimuli and VEP to flash, reversal, and onset stimuli (GOSH) are used. From age 4–7 years, ISCEV full-field ERG with skin electrodes is performed, while after this age, HK electrodes are used. From 7 years onwards, we use HK electrodes for large-field PERG as well as for ISCEV mfERG, S-cone ERG, and On–Off ERG. EOG and large-field PERG in younger children are recorded with skin electrodes. VEP half-field reversal is performed from early age onwards.

Results Some of our pediatric electrophysiological studies, using different recording techniques for different age groups, are demonstrated. (1) Maturation of the visual system and ERG and VEP age group normative data; (2) Colour VEPs for paediatric use; (3) ERG and VEP characteristics in babies with congenital nystagmus; (4) Follow-up in childhood optic neuritis with pattern-reversal VEP; (5) Evaluation of the crossed and uncrossed fibre function with reversal half-fields VEP in children with chiasmal tumours; (6) Specific flash and onset VEP asymmetries in achiasmia and ocular albinism; (7) Childhood retinal disorders with specific ERG abnormalities (full-field ERG, PERG, MFERG, On–Off ERG, S-cone ERG). Our clinical practice is increasing in pediatric patients (e.g. in 2002, 165 children; in 2012, 307 children; in 2022, 433 children, with a population of 2 million in Slovenia).

Conclusions Pediatric visual electrophysiology tests are performed non-invasively, which can be relevant for pediatric ophthalmology, e.g., when it is necessary to define the cause of unexplained poor vision, or confirm the diagnosis by assessing retinal or visual pathway function, or monitor stability or deterioration of visual function. For clinical pediatric electrophysiology, normative data for different ages are mandatory, as well as experienced staff for recording, evaluating, and differentiating valid signals from artefacts in restless children. We conclude that in the future of clinical pediatric visual electrophysiology, studies with different ERG and VEP recording approaches for different age groups are expected.

P6-3 Optimal age for flash VEP investigation of chiasmal crossing in infants and young children

Ruth Hamilton¹, Manaim Shah¹, Fadi R. Ghazala¹

¹Royal Hospital for Children, Glasgow, UK

Purpose Monocular lateral VEPs are highly diagnostic for excessive chiasmal decussation of optic nerve fibers in albinism. In children under 3 years of age, pattern-onset VEPs are insensitive and flash VEPs should be used. Infants suspected of having albinism may present at very young ages due to nystagmus and/or very fair skin and hair. However, VEPs in infants can be inconclusive: Identification of excessive decussation using flash VEPs requires suitably mature lateral VEPs to identify the ‘mirrored’ inter-ocular asymmetry. We sought to establish an optimal age for first undertaking flash VEP assessment in infants to avoid inconclusive results and repeat testing.

Methods Infants and children who had undergone flash VEP assessment of chiasmal crossing because of possible albinism were identified from a clinical database and notes were reviewed. VEPs were typically part of a more extensive test procedure. Presence of foveal hypoplasia, nystagmus, fundal pallor, fair hair/skin, positive family history, or molecular diagnoses were noted. Monocular flash VEPs were recorded from three active electrode sites (Oz, right occiput, left occiput, and a difference channel). A handheld, diffuse white flash (42 cd s/m²) was used to evoke VEPs. VEPs were analysed by visual inspection, by calculation of cross-correlation between 60 and 300 ms of monocular difference channels (< − 0.3 considered positive for excessive crossing), and by calculation of the ‘Apkarian’ coefficient from amplitudes (> 0.7 considered positive for excessive crossing). VEPs were categorised as clear (all analyses agreed) or equivocal (analyses disagree).

Results Of 503 children assessed from 2002 to 2022, 25 (10 female) were tested twice, two of whom were tested three times. Nine children were diagnosed with albinism, 9 had albinism excluded, 7 had no diagnosis or insufficient data were available. Median age at first test was 10 months (range 12 weeks to 33 months); 11/25 (44%) had a clear result at first test (8 positive, 3 negative). Median age at second test was 30 months (range 5 months to 6 years); 24/25 (96%) had a clear result at second test (10 positive, 14 negative); the 25th child had a clear, negative result at a third test at age 4 years. Ages at the 36 clear tests had a lower limit (5th percentile) of 7 months (90% bootstrapped confidence interval 5–10 months). Ages at the 15 equivocal tests had an upper limit (95th percentile) of 19 months (90% bootstrapped confidence interval 13–24 months).

Conclusions We found equivocal flash VEP findings in infants up to 19 months, while clear results were evident as early as 7 months. The disparity may partially reflect the challenge of identifying and selecting peaks/troughs against a background of rapidly maturing and already variable flash VEP waveforms. A first test at 7–9 months, while infant cooperation is likely with feeding or a pacifier, is recommended. In case of equivocal findings, a repeat test within 6 months is likely to produce clearer findings. A clinical guideline developed by expert users may improve diagnostic reliability.

P6-4 Normative photopic electroretinogram data in Hong Kong preschool children

Sonia S. H. Chan¹, Kai Yip Choi^1,2, Henry H. L. Chan^1,2,3

¹Centre for Myopia Research, School of Optometry, the Hong Kong Polytechnic University, Kowloon, Hong Kong, ²Laboratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University, Hong Kong, ³Centre for Eye and Vision Research, Hong Kong

Purpose This cross-sectional study aimed to determine the reference normative values of photopic ERG responses in preschool children in Hong Kong using the RETeval system.

Methods A total of 506 preschool children between 3 and 7 years of age from 11 local kindergartens were examined. ERG measurements were performed using RETeval (LKC Technologies), a handheld full-field ERG/VEP device using non-invasive Sensor Strip skin electrodes without mydriasis. Full-field flash electroretinogram (ffERG) with ISCEV photopic flash and flicker protocols was adopted. Data were obtained from one eye selected at random. The mean values (presented as mean ± SD) and normal range of the ERG measurements including photopic a- and b-wave responses and 30-Hz flicker responses expressed as amplitudes and implicit times were reported. The measurements were also compared to age by using the Pearson correlation test.

Results The mean age of the preschool children was 4.92 ± 0.91 years; 46.2% were female. The mean values of a-wave amplitude and implicit time, b-wave amplitude and implicit time, 30-Hz flicker amplitude and flicker implicit time were − 10.85 ± 3.48 uV, 11.75 ± 0.89 ms, 37.7 ± 8.88 uV, 28.18 ± 1.06 ms, 38.60 ± 8.32 uV, and 24.79 ± 0.75 ms, respectively. The b-wave amplitude (r = 0.116; p = 0.011) and 30-Hz flicker amplitude (r = 0.139; p = 0.003) under photopic conditions statistically significantly increased with increasing age, while flicker implicit time (r = 0.139; p = 0.003) decreased with increasing age. No correlation was found between age and a-wave amplitude, a-wave implicit time, or b-wave implicit time.

Conclusions A normative data set of photopic ffERG in Hong Kong preschool children was established using RETeval. The b-wave amplitude, flicker amplitude, and implicit time of photopic ffERG were statistically correlated with age. The normative data set can be used as a reference for future clinical studies.

P6-5 Initial retinal electrophysiologcal responses and subsequent myopia progression in children wearing Defocus Incorporated Multiple Segments (DIMS) lenses (myopia control intervention)

Vivian Wai Ying Lo¹, Kai Yip Choi¹, Henry Ho Lung Chan¹

¹The Hong Kong Polytechnic University

Purpose To investigate the relationship between the initial retinal electrophysiological response (as measured by global flash multifocal electroretinogram [MOFO mfERG]) and progression in spherical equivalent refraction (SER) and axial length (AL) in children wearing Defocus Incorporated Multiple Segments (DIMS) lenses (which is an intervention for myopia control), retrospectively compared with those wearing single-vision (SV) spectacle lenses.

Method Twenty-eight subjects age 7–12 years were prescribed with DIMS and underwent 1 year follow-up. The changes in SER and AL as well as the initial MOFO mfERG were compared to twenty-seven subjects wearing SV spectacles from a previous study. MOFO mfERG was measured at baseline before intervention at a 49% contrast. Responses from the 61 hexagons were averaged into 5 concentric rings (Rings 1–5) to investigate the localized responses at different retinal eccentricities, from which the direct component (DC) and induced component (IC) were extracted. SER and AL were measured at baseline and at 1 year to monitor refractive changes.

Results The baseline SER for the DIMS group and the SV group were − 2.74 ± 1.06 D and − 1.74 ± 0.71 D, respectively. The baseline AL for the DIMS group and SV group were 24.75 ± 0.88 mm and 24.09 ± 0.74 mm, respectively. In the 1-year follow-up, multiple linear regression revealed a significant positive relationship in the DIMS group between initial MOFO mfERG responses and change in AL (e.g., Ring 1 IC amplitude: B = 0.004, p = 0.015), as well as a negative relationship for change in SER (e.g., Ring 1 IC amplitude: B = − 0.014, p = 0.002). The results were different when retrospectively compared with those wearing single-vision (SV) spectacle lenses in which a negative relationship was noted between the initial MOFO mfERG and the change in AL, as well as a positive relationship for the change in SER in the SV group.

Conclusions Unlike the SV controls, a stronger retinal response was associated with faster myopic progression with DIMS intervention. An ERG screening protocol is advised to identify ideal candidates for prescribing DIMS spectacle lenses to reduce the likelihood of an unfavorable treatment response.

P6-6 Hand-held electroretinography in infants treated with vigabatrin

Sota Mitsui¹, Toshiaki Hirakata¹, Mitsuru Ikeno², Shinpei Abe², Takashi Negishi¹

¹Department of Ophthalmology, Juntendo University Faculty of medicine, Japan, ²Department of Ophthalmology, Juntendo University Faculty of medicine, Japan

Purpose The antiepileptic drug vigabatrin (VGB, Sabril; Lundbeck, Deerfield, IL) is associated with VGB-induced retinal toxicity, which is manifested by visual field loss. Therefore, ophthalmological assessments, including ERGs, are necessary to monitor retinal health during vigabatrin treatment. Although performing visual field testing on infants is difficult, ERGs are very important to detect retinal toxicity caused by VGB. RETeval™ (LKC Technologies, Gaithersburg, MD) is a hand-held ERG device and a noninvasive system that is easy to use in children. However, to our knowledge, there are few reports of ERG recordings using the RETeval™ for infants treated with VGB. Here, we determined whether the RETeval™ is useful for infants treated with VGB.

Methods This study design was retrospective. Two infants (female, < 1-year-old) treated with VGB from January 2022 to November 2022 were included in this study. Full-field ERGs were recorded with RETeval™ using the ISCEV standard protocol and skin electrodes. Infants had their eyes dilated before examination and were under sedation with intravenous thiopental sodium during examination. ERGs were recorded before treatment (baseline) and every 3 months after treatment.

Results One patient had tuberous sclerosis and West syndrome; the other had agenesis of the corpus callosum and West syndrome. Under sedation with intravenous thiopental sodium, ERGs in both the light- and dark-adapted conditions could be recorded without any problems using RETeval™. The response of full-field ERGs after VGB administration showed no reduction compared to baseline, in both light- and dark-adapted conditions during follow-up. RETeval™ was able to safely record full-field ERGs for infants under one year old.

Conclusions The handheld RETeval™ system can be a useful tool for obtaining full-field ERGs in infants treated with VGB. Since the number of cases is still small, continued research is required.

P6-7 Flicker electroretinogram recorded with a portable ERG device in pediatric patients with retinal disease and amblyopia

Hyuna Kim¹, Song-hee Park²

¹Soonchunhyang University, Korea, ²Nune Eye Hospital, Korea

Purpose To evaluate the characteristics of electroretinographic recordings in pediatric patients with retinal disease and amblyopia.

Methods A total of 29 patients age 3–18 years with retinal disease or amblyopia were included in this study. Subjects were further subdivided according to best corrected visual acuity of better or worse than logMAR 0.5. We obtained 30-Hz flicker ERG responses and compared implicit times and amplitudes between the groups.

Results The mean implicit time in the low visual acuity group was 31.23 ± 0.3 ms, whereas in the relatively good visual acuity group, the implicit time was 28.16 ± 1.2 ms. The amplitude did not show significant differences.

Conclusions Pediatric retinal disease and amblyopia patients with low vision (worse than log MAR 0.5) showed longer implicit time of the 30-Hz flicker ERG response compared to those who had normal retinal structure. The portable ERG could be a good functional evaluator in pediatric patients.

P6-8 ERG flicker responses in retinopathy of prematurity

Christina Gerth-Kahlert¹, Aylin Taner¹, James V. M. Hanson¹

¹University Hospital Zurich, Switzerland

Purpose Retinopathy of prematurity (ROP) affects retinal maturation and retinal sensitivity, in rod more than cone photoreceptors (Fulton et al. Invest Ophthalmol Vis Sci. 2008; 49:814–819). The aim of this study was to record and evaluate non-invasive flicker ERGs in preterm infants with type 1 ROP.

Methods Flicker ERGs were recorded in preterm infants with type 1 ROP before and after treatment. ERGs were recorded in both eyes through closed eyelids while the infants were asleep using the portable RETeval® device and small size proprietary skin electrodes. Flicker stimuli were presented at 28.3 Hz with stimulus levels of 3, 6, 12, 30, and 50 cd s/m² as described previously (Hanson et al. Doc Ophthalmol: 2022; 145:175–184). Infants were tested on the day of intervention prior to the treatment (Test 1) and again 5 days (Test 2) and approximately 1 month (Test 3) after treatment. Response amplitudes and peak times were analysed. Results were compared with those from 10 healthy term-born neonates [gestational ages (GA) 37 to 39 + 5] recorded on the 3rd day of life using identical electrodes.

Results Three infants (two males, one female; GA 24 + 3, 25 + 1, and 25 + 4 weeks) received treatment at the ages of 35 + 3, 37 + 4, and 39 + 4 weeks postmenstrual age with an intravitreal injection (IVI) of ranibizumab in both eyes. One infant was additionally treated with peripheral laser photocoagulation in one eye 2 weeks after the initial IVI. It was not possible to acquire data at Test 2 for a single infant due to unstable health status. Responses for the 30 cd s/m² were analysed. From a total of 16 measurements at this stimulus strength, 2 were of insufficient quality for analysis. At Test 1, 5 of 6 eyes had higher amplitudes than normal, with the remaining eye being at the upper limit of the normal range. At Test 2, amplitudes were higher in 1 eye of 1 infant, and stable in both eyes of the other. At Test 3, the eye that had required a second treatment exhibited a larger response amplitude relative to Test 1, with all other eyes being approximately stable. Peak times were variable at all tests.

Conclusions Type 1 ROP may be associated with increased flicker ERG responses, which normalize after successful treatment. Hypoxia-mediated inflammation may contribute to enhanced ERG responses. The utility of flicker ERG peak times in this population remains unclear.