SIBLING CONCORDANCE IN SYMPTOM ONSET AND ATROPHY GROWTH RATES IN STARGARDT DISEASE USING ULTRA-WIDEFIELD FUNDUS AUTOFLUORESCENCE.

PURPOSE: To investigate concordance in symptom onset, area of dark autofluorescence (DAF), and growth rate (GR) between Stargardt disease siblings at an age-matched time point. METHODS: In this retrospective longitudinal study of sibling pairs with identical biallelic ABCA4 variants, age at symptom onset, best-corrected visual acuity, atrophy area, and effective radius of DAF on ultra-widefield fundus autofluorescence were recorded. Absolute intersibling differences for both eyes were compared with absolute interocular differences using the Mann-Whitney test. RESULTS: Overall 39 patients from 19 families were recruited. In 16 families, age-matched best-corrected visual acuity and DAF were compared between siblings. In 8 families, DAF GR was compared. The median (range) absolute difference in age at symptom onset between siblings was 3 (0-35) years. Absolute intersibling differences in age-matched best-corrected visual acuity were greater than interocular differences ( P = 0.01). Similarly, absolute intersibling differences in DAF area and radius were greater than interocular differences ( P = 0.04 for area and P = 0.001 for radius). Differences between absolute interocular and intersibling GR were not statistically significant ( P = 0.44 for area GR and P = 0.61 for radius GR). CONCLUSION: There was significant discordance in age-matched best-corrected visual acuity and DAF beyond the expected limits of interocular asymmetry. Lack of significant intersibling differences in GR warrants further investigation.

Whole exome sequencing analysis identifies novel Stargardt disease-related gene mutations in Chinese Stargardt disease and retinitis pigmentosa patients.

OBJECTIVES: To delineate the disease-causing mutations of the Stargardt disease-related genes in Chinese patients diagnosed with Stargardt disease or retinitis pigmentosa (RP) by whole exome sequencing analysis. METHODS: A total of 123 sporadic RP or Stargardt disease patients and 2 Stargardt disease families were recruited. All sporadic patients and the probands of the families were subjected to whole exome sequencing analysis. The candidate mutations were verified by direct sequencing based on the cosegregation pattern and in 200 control subjects and by the bioinformatics analyses. RESULTS: A total of three reported ABCA4 mutations were identified in the probands of the two Stargardt disease families. The probands and the affected family members with either homozygous or compound heterozygous mutations showed typical Stargardt disease features, which was absent in their unaffected family members. The cosegregation pattern confirmed the mode of recessive inheritance. Moreover, two sporadic Stargardt disease patients were identified to carry two novel ABCA4 and one PROM1 mutations. In addition, 13 novel variants were found in 119 sporadic RP patients in 7 Stargardt disease-related genes, and 8 novel missense variants were conserved across different species and predicted to be damaging to the protein. All 15 novel variants were absent in our 200 control subjects. CONCLUSIONS: This study revealed 22.4% study subjects carrying Stargardt disease-related gene mutations with total 15 novel variants in seven Stargardt disease-related genes, assuring that targeted next-generation sequencing analysis is a high throughput strategy to facilitate the clinical diagnosis from suspicious patients and recommended as a routine examination for inherited retinal dystrophies.

Treatment and longitudinal follow-up of CNV associated with pattern dystrophy with novel PRPH2 variant.

BACKGROUND: Peripherin-2 (PRPH2) is a transmembrane glycoprotein crucial for the morphogenesis and stabilization of the photoreceptor outer segments. Variations in PRPH2 gene are associated with vision-threatening diseases. METHODS: Clinical manifestations and multimodal imaging were presented, as well as treatment history and six-year follow-up. In addition, genetic testing was performed to confirm the diagnosis. RESULTS: In this report, we present an extremely rare case of choroidal neovascularization (CNV) secondary to pattern dystrophy simulating fundus flavimaculatus (PDSFF). Multimodal imaging showed typical symmetric yellow flecks in posterior pole and choroidal neovascularization requiring timely treatment. A novel nonsense variant of c.552 C > G; p.Y184X in PRPH2 gene was detected. The patient received intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment and maintained a good vision after six years. CONCLUSION: We described a novel PRPH2 variant (Y184X) associated with PDSFF, its multimodal imaging, and long-term prognosis. Intravitreal anti-VEGF treatment can offer excellent visual prognosis in patients with PDSFF-associated CNV.

Microvascular and metabolic alterations in retinitis pigmentosa and Stargardt disease.

PURPOSE: The aim of our study was to evaluate retinal microvascular changes recorded with optical coherence tomography angiography (OCTA) and the metabolic function measured with retinal oximetry (RO) in patients with retinitis pigmentosa (RP) and Stargardt disease (STGD). METHODS: In this prospective, noninterventional study, OCTA and RO were performed on 107 eyes (56 subjects): 53 eyes diagnosed with RP without the presence of macular oedema (no-ME-RP), 26 eyes with STGD, and 28 control eyes. Main outcome measures were the mean superficial (FAZ-S; mm2 ) and deep foveal avascular zone (FAZ-D; mm2 ) measured with OCTA as well as the mean arterial (A-SO2 ; %), venular (V-SO2 ; %) oxygen saturation, their difference (A-V SO2 ; %) and the corresponding mean diameters of the peripapillary retinal arterioles (D-A; µm) and venules (D-V; µm) determined with RO. RESULTS: Stargardt disease (STGD) patients differed from controls and no-ME-RP by an enlarged FAZ-S and reduced A-SO2 and V-SO2 (p ≤ 0.013). No-ME-RP eyes presented with attenuated vessels (p < 0.001) and increased A-SO2 and V-SO2 (p ≤ 0.012) compared to controls and STGD. The FAZ-D showed significant interactions with A-SO2 (p = 0.003) in no-ME-RP while the FAZ-S correlated with visual acuity in no-ME-RP (p = 0.007) and STGD (p = 0.034). CONCLUSION: Retinitis pigmentosa (RP) and Stargardt disease (STGD) patients suffer from microvascular and metabolic alterations, however, showing a different pattern. A combined microvascular-metabolic model may therefore allow to more precisely characterize RP and STGD as well as presumably other inherited retinal diseases.

Targeted next-generation sequencing identifies ABCA4 mutations in Chinese families with childhood-onset and adult-onset Stargardt disease.

BACKGROUND: Stargardt disease (STGD) is the most common form of juvenile macular dystrophy associated with progressive central vision loss, and is agenetically and clinically heterogeneous disease. Molecular diagnosis is of great significance in aiding the clinical diagnosis, helping to determine the phenotypic severity and visual prognosis. In the present study, we determined the clinical and genetic features of seven childhood-onset and three adult-onset Chinese STGD families. We performed capture next-generation sequencing (NGS) of the probands and searched for potentially disease-causing genetic variants in previously identified retinal or macular dystrophy genes. METHODS: In all, ten unrelated Chinese families were enrolled. Panel-based NGS was performed to identify potentially disease-causing genetic variants in previously identified retinal or macular dystrophy genes, including the five known STGD genes (ABCA4, PROM1, PRPH2, VMD2, and ELOVL4). Variant analysis, Sanger validation, and segregation tests were utilized to validate the disease-causing mutations in these families. RESULTS: Using systematic data analysis with an established bioinformatics pipeline and segregation analysis, 17 pathogenic mutations in ABCA4 were identified in the 10 STGD families. Four of these mutations were novel: c.371delG, c.681T > G, c.5509C > T, and EX37del. Childhood-onset STGD was associated with severe visual loss, generalized retinal dysfunction and was due to more severe variants in ABCA4 than those found in adult-onset disease. CONCLUSIONS: We expand the existing spectrum of STGD and reveal the genotype-phenotype relationships of the ABCA4 mutations in Chinese patients. Childhood-onset STGD lies at the severe end of the spectrum of ABCA4-associated retinal phenotypes.

Stargardt disease masquerades.

PURPOSE OF REVIEW: Stargardt disease is the most common inherited macular dystrophy but has a wide clinical spectrum, and several inherited macular dystrophies have phenotypic similarities that can make clinical diagnosis challenging. This review seeks to highlight key clinical and multimodal imaging features to aid clinicians in accurate diagnosis. RECENT FINDINGS: Multimodal imaging has provided additional information to aid in the diagnosis of Stargardt disease and its masquerades. These data from multimodal imaging are important to correlate with findings from clinical examination to help support the clinical diagnosis or guide molecular investigations. SUMMARY: This review highlights the key similarities and differences, in history, clinical examination and multimodal imaging, to help distinguish between Stargardt disease and other macular dystrophies. These findings can help direct a focused molecular analysis for accurate diagnosis, which is critical in the era of gene and stem cell therapies.

NEGATIVE VESSEL REMODELING IN STARGARDT DISEASE QUANTIFIED WITH VOLUME-RENDERED OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

PURPOSE: To quantify retinal vasculature changes in Stargardt disease1 (STGD1) with volume-rendered optical coherence tomography angiography. METHODS: Optical coherence tomography angiography volumes from healthy subjects and two subgroups of patients with STGD1 with the presence/absence of definitely decreased autofluorescence areas were compared. Optical coherence tomography angiography vessel surface area and vessel volume were measured in central zones (Z) of 1-, 2-, and 3-mm diameter. RESULTS: Twenty nine eyes of 15 patients with STGD1 (20/9 eyes with/without definitely decreased autofluorescence) and 30 eyes of 15 controls contributed data. An enlarged foveal avascular zone was found in patients with STGD1 without and even more with definitely decreased autofluorescence associated with a vessel rarefication in central and also paracentral zones with unnoticeable autofluorescence. Vessel surface area and vessel volume were reduced in both STGD1 subgroups for all zones (P < 0.0001). Stargardt disease 1 eyes when compared to without definitely decreased autofluorescence showed reduced vessel surface area and vessel volume in Z2+3 (both P < 0.05). CONCLUSION: Volume rendering of optical coherence tomography angiography in STGD1 shows a reduced retinal flow in the central macula. This is most likely secondary to loss of neurosensory tissue with disease progression and therefore not likely be favorably influenced by gene transfer and retinal pigment epithelial transplantation. Retinal blood flow assessed by 3D volume-rendered optical coherence tomography angiography could serve as surrogate marker for vascular changes of the central retina.

Long-term safety and tolerability of subretinal transplantation of embryonic stem cell-derived retinal pigment epithelium in Asian Stargardt disease patients.

BACKGROUND: Although human embryonic stem cells (hESCs) have been considered a potential therapeutic option for regenerative medicine, there are some concerns regarding tumorigenicity, immunogenicity and ethical considerations. Stargardt macular dystrophy (SMD) is the most common form of juvenile macular degeneration that causes early onset blindness. Therapeutic options for SMD remain limited, although several treatment strategies are currently under investigation. Here, we report a 3-year assessment of a phase I clinical trial involving subretinal transplantation of hESC-retinal pigment epithelium (RPE) cells in patients with SMD. METHODS: This prospective, non-randomised clinical trial included three patients with SMD. All transplant recipients had central visual acuity no better than 20/400. Trans-pars plana vitrectomy was performed in the eye with poorer vision. RPE cells were reconstituted in balanced salt solution plus, then injected into the subretinal space using a semi-automated subretinal injection method. RESULTS: No serious adverse events occurred throughout the 3-year period following the injection of hESC-RPE cells. The functional and anatomical results were favourable, compared with the natural course of SMD reported in the ProgStar study. One patient showed best-corrected visual acuity improvement, while the other patients had stable best-corrected visual acuity during the 3-year follow-up period. CONCLUSION: These results suggest the long-term safety, tolerability, and feasibility of subretinal hESC-derived RPE cell transplantation in regenerative medicine. TRIAL REGISTRATION NUMBER: NCT01625559.

Stargardt misdiagnosis: How ocular genetics helps.

Ocular Genetics at Wills Eye Hospital sees a wide range of rare disorders for accurate diagnosis. To demonstrate how focused consultation and genetic testing results in precise diagnoses, we investigated false diagnosis rates for patients referred with a diagnosis of Stargardt disease. This is a retrospective review of patients over a 3 year period referred to our Ocular Genetics clinic for possible Stargardt disease, or already holding a diagnosis of Stargardt disease. Results of diagnostic and genetic testing were compared to standard definition of Stargardt. Of 40 patients, 14 (35%) had been misdiagnosed. Four had non-Stargardt phenotype of which three had ABCA4 pathogenic variants with phenotypes inconsistent with Stargardt disease. Two of those with pathogenic ABCA4 variants were related. Nine had pathogenic variants in other different genes with overlapping features of Stargardt disease. One had Thioridazine maculopathy. Our study highlights the essential role of the subspecialty field of ocular genetics in obtaining accurate diagnoses for the delivery of correct counseling and interventional trial eligibility assessment.

Novel variants of ABCA4 in Han Chinese families with Stargardt disease.

BACKGROUND: Stargardt disease (STGD1) is a common recessive hereditary macular dystrophy in early adulthood or childhood, with an estimated prevalence of 1:8000 to 1:10,000. ABCA4 is the causative gene for STGD1. The current study aims at identifying the novel disease-related ABCA4 variants in Han Chinese families with STGD1 using next-generation sequencing (NGS). METHODS: In the present study, 12 unrelated Han Chinese families (19 males and 17 females) with STGD1 were tested by panel-based NGS. In order to capture the coding exons and the untranslated regions (UTRs) plus 30 bp of intronic flanking sequences of 792 genes, which were closely associated with usual ophthalmic genetic disease, we designed a customized panel, namely, Target_Eye_792_V2 chip. STGD1 patients were clinically diagnosed by experienced ophthalmologists. All the detected variants were filtered and analyzed through the public databases and in silico programs to assess potential pathogenicity. RESULTS: Twenty-one ABCA4 mutant variants were detected in 12 unrelated Han Chinese families with STGD1, containing 14 missense, three splicing, two frameshift, one small deletion, and one nonsense variants. Base on the American College of Medical Genetics (ACMG) guidelines, 8 likely pathogenic and 13 pathogenic variants were determined. The functional consequences of these mutant variants were predicted through in silico programs. Of the 21 mutant variants in ABCA4, two novel coding variants c.3017G > A and c.5167 T > C and one novel null variant c.3051-1G > A were detected in three unrelated probands. CONCLUSIONS: By panel-based NGS, 21 ABCA4 variants were confirmed in 12 unrelated Han Chinese families. Among them, 3 novel mutant variants were found, which further expanded the ABCA4 mutation spectrum in STGD1 patients.

Genetic testing for inherited eye conditions in over 6,000 individuals through the eyeGENE network.

Genetic testing in a multisite clinical trial network for inherited eye conditions is described in this retrospective review of data collected through eyeGENE®, the National Ophthalmic Disease Genotyping and Phenotyping Network. Participants in eyeGENE were enrolled through a network of clinical providers throughout the United States and Canada. Blood samples and clinical data were collected to establish a phenotype:genotype database, biorepository, and patient registry. Data and samples are available for research use, and participants are provided results of clinical genetic testing. eyeGENE utilized a unique, distributed clinical trial design to enroll 6,403 participants from 5,385 families diagnosed with over 30 different inherited eye conditions. The most common diagnoses given for participants were retinitis pigmentosa (RP), Stargardt disease, and choroideremia. Pathogenic variants were most frequently reported in ABCA4 (37%), USH2A (7%), RPGR (6%), CHM (5%), and PRPH2 (3%). Among the 5,552 participants with genetic testing, at least one pathogenic or likely pathogenic variant was observed in 3,448 participants (62.1%), and variants of uncertain significance in 1,712 participants (30.8%). Ten genes represent 68% of all pathogenic and likely pathogenic variants in eyeGENE. Cross-referencing current gene therapy clinical trials, over a thousand participants may be eligible, based on pathogenic variants in genes targeted by those therapies. This article is the first summary of genetic testing from thousands of participants tested through eyeGENE, including reports from 5,552 individuals. eyeGENE provides a launching point for inherited eye research, connects researchers with potential future study participants, and provides a valuable resource to the vision community.

Association of Sex With Frequent and Mild ABCA4 Alleles in Stargardt Disease.

Importance: The mechanisms behind the phenotypic variability and reduced penetrance in autosomal recessive Stargardt disease (STGD1), often a blinding disease, are poorly understood. Identification of the unknown disease modifiers can improve patient and family counseling and provide valuable information for disease management. Objective: To assess the association of incompletely penetrant ABCA4 alleles with sex in STGD1. Design, Setting, and Participants: Genetic data for this cross-sectional study were obtained from 2 multicenter genetic studies of 1162 patients with clinically suspected STGD1. Unrelated patients with genetically confirmed STGD1 were selected. The data were collected from June 2016 to June 2019, and post hoc analysis was performed between July 2019 and January 2020. Main Outcomes and Measures: Penetrance of reported mild ABCA4 variants was calculated by comparing the allele frequencies in the general population (obtained from the Genome Aggregation Database) with the genotyping data in the patient population (obtained from the ABCA4 Leiden Open Variation Database). The sex ratio among patients with and patients without an ABCA4 allele with incomplete penetrance was assessed. Results: A total of 550 patients were included in the study, among which the mean (SD) age was 45.7 (18.0) years and most patients were women (311 [57%]). Five of the 5 mild ABCA4 alleles, including c.5603A>T and c.5882G>A, were calculated to have incomplete penetrance. The women to men ratio in the subgroup carrying c.5603A>T was 1.7 to 1; the proportion of women in this group was higher compared with the subgroup not carrying a mild allele (difference, 13%; 95% CI, 3%-23%; P = .02). The women to men ratio in the c.5882G>A subgroup was 2.1 to 1, and the women were overrepresented compared with the group carrying no mild allele (difference, 18%; 95% CI, 6%-30%; P = .005). Conclusions and Relevance: This study found an imbalance in observed sex ratio among patients harboring a mild ABCA4 allele, which concerns approximately 25% of all patients with STGD1, suggesting that STGD1 should be considered a polygenic or multifactorial disease rather than a disease caused by ABCA4 gene mutations alone. The findings suggest that sex should be considered as a potential disease-modifying variable in both basic research and clinical trials on STGD1.

Genotype-Phenotype Correlations in a Spanish Cohort of 506 Families With Biallelic ABCA4 Pathogenic Variants.

PURPOSE: To define genotype-phenotype correlations in the largest cohort study worldwide of patients with biallelic ABCA4 variants, including 434 patients with Stargardt disease (STGD1) and 72 with cone-rod dystrophy (CRD). DESIGN: Cohort study. METHODS: We characterized 506 patients with ABCA4 variants using conventional genetic tools and next-generation sequencing technologies. Medical history and ophthalmologic data were obtained from 372 patients. Genotype-phenotype correlation studies were carried out for the following variables: variant type, age at symptom onset (AO), and clinical phenotype. RESULTS: A total of 228 different pathogenic variants were identified in 506 ABCA4 patients, 50 of which were novel. Genotype-phenotype correlations showed that most of the patients with biallelic truncating variants presented with CRD and that these cases had a significantly earlier AO than patients with STGD1. Three missense variants are associated with CRD for the first time (c.1804C>T; p.[Arg602Trp], c.3056C>T; p.[Thr1019Met], and c.6320G>C; p.[Arg2107Pro]). Analysis of the most prevalent ABCA4 variant in Spain, c.3386G>T; p.(Arg1129Leu), revealed that is correlated to STGD1, later AO, and foveal sparing. CONCLUSIONS: Our study, conducted in the largest ABCA4-associated disease cohort reported to date, updates the genotype-phenotype model established for ABCA4 variants and broadens the mutational spectrum of the gene. According to our observations, patients with ABCA4 presenting with 2 truncating variants may first present features of STGD1 but eventually develop rod dysfunction, and specific missense variants may be associated with a different phenotype, underscoring the importance of an accurate genetic diagnosis. Also, it is a prerequisite for enrollment in clinical trials, and to date, no other treatment has been approved for STGD1.

The Effect of Attention on Fixation Stability During Dynamic Fixation Testing in Stargardt Disease.

PURPOSE: Sensitive, reproducible visual function biomarkers are necessary to evaluate the efficacy of emerging treatments for Stargardt disease type 1 in clinical trials. We previously demonstrated that fixation stability may serve as a secondary outcome parameter for visual function loss. However, the test duration and protocol have an unknown effect on the assessment of fixation stability. Here, we hypothesize that separate fixation testing with a single target is different from combined fixation testing using the same target with simultaneous perimetry testing. DESIGN: International, multicenter, prospective, cross-sectional study. METHODS: Microperimetry data from the international, multicenter, prospective Progression of Atrophy Secondary to Stargardt Disease (ProgStar, NCT01977846) study were analyzed. Patients underwent various types of fixation testing including static testing and dynamic testing, and a duration-corrected dynamic test was generated (30sEpoch). RESULTS: A total of 437 eyes from 235 patients were included (mean age, 33.8 ± 15.1 years; 55.3% female). The mean 1SD-BCEA (bivariate contour ellipse area), which is the smallest ellipse encompassing 1 standard deviation of all fixation events, was smaller for the static fixation test compared to the 30sEpoch (4.5 ± 6.9 deg2 vs 5.3 ± 7.0 deg2; P = .02) and the number of points within both the 2-degree and 4-degree circles was larger (P < .0001). CONCLUSIONS: Our results suggest that differences in static and dynamic assessment of fixation stability are dependent not only on different test durations but also on the testing protocol of a single fixation target vs fixation target plus simultaneous perimetry testing and provide information on the conduct of fixation testing for clinical trials.

Longitudinal Microperimetric Changes of Macular Sensitivity in Stargardt Disease After 12 Months: ProgStar Report No. 13.

Importance: Functional end points for clinical trials investigating the efficacy of emerging treatments for Stargardt disease type 1 (STGD1) are needed. Objective: To assess the yearly rate of change of macular function in patients with STGD1 using microperimetry. Design, Setting, and Participants: This multicenter prospective cohort study was conducted in an international selection of tertiary referral centers from October 21, 2013, to February 15, 2017. The study included participants with ABCA4-related STGD1 who were enrolled in the Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study at baseline. Data were analyzed from February 16, 2017, to December 1, 2019. Exposure: ABCA4-related STGD1 with a minimum lesion size on fundus autofluorescence and a minimum visual acuity. Main Outcomes and Measures: Changes in overall macular sensitivity (MS), deep scotoma count, number of points that tested normal, and location-specific sensitivity changes. Results: Among the 359 eyes from 200 patients (87 [43.5%] men; mean [SD] age, 33.3 [15.2] years) who underwent microperimetry examination graded at baseline and month 12, the mean (SD) yearly change in MS was -0.68 (2.04) dB (95% CI, -0.89 to -0.47 dB; P < .001), and deep scotoma points increased by a mean (SD) of 1.56 (5.74) points per year. The points with sensitivity of 12 dB or higher decreased in sensitivity by a mean (SD) of -3.01 (9.84) dB (95% CI, -4.03 to -1.99 dB; P < .001). The mean (SD) yearly change in MS was not significantly different between the eyes with a grading of good or fair pattern placement at both visits (-0.67 [2.1] dB) and the eyes with a poor pattern placement during at least 1 visit (-0.64 [2.2] dB) (P = .91). Conclusions and Relevance: This study showed that MS and the number of deep scotoma points had measurably changed after follow-up of approximately 1 year. Microperimetry may serve as a useful functional outcome parameter for clinical trials aimed at slowing the progression of STGD1.

Progressive Choriocapillaris Impairment in ABCA4 Maculopathy Is Secondary to Retinal Pigment Epithelium Atrophy.

Purpose: To analyze the progression of choriocapillaris (CC) impairment in recessive Stargardt disease (STGD) and compare it to the progression of retinal pigment epithelium (RPE) atrophy. Methods: Fifty-five patients with a clinical diagnosis of STGD and genetic confirmation of pathogenic biallelic variants in ABCA4 were imaged with short-wavelength fundus autofluorescence (SW-AF) and optical coherence tomography angiography (OCTA) at a single clinic visit, whereas a subset of 12 patients were imaged with the same modalities at two different clinic visits. Results: We observed three stages of CC impairment: an area of bright yet intact macular CC (11 patients), regions of vascular rarefaction and incomplete CC atrophy within an area of bright CC (10 patients), and areas of extensive CC atrophy (26 patients). These changes correlated to the degree of RPE atrophy observed in SW-AF imaging. Furthermore, 8 patients presented with early changes on SW-AF, but healthy CC. Quantitative analyses of the atrophic changes revealed that the area of RPE atrophy is larger (9.6 ± 1.7 mm2 vs. 6.9 ± 1.3 mm2, P < 0.001) and that it progresses at a faster rate (1.1 ± 0.1 mm2/year vs. 0.8 ± 0.2 mm2/year, P = 0.004) than the corresponding area of CC atrophy. Conclusions: CC impairment is progressive and OCTA imaging can be used to demonstrate the stages, which culminate in extensive CC atrophy. Furthermore, CC impairment is secondary to RPE atrophy in STGD. We further advocate the use of SW-AF and OCTA imaging in monitoring the progression of STGD.

HOMOZYGOSITY FOR A NOVEL DOUBLE MUTANT ALLELE (G1961E/L857P) UNDERLIES CHILDHOOD-ONSET ABCA4-RELATED RETINOPATHY IN THE UNITED ARAB EMIRATES.

PURPOSE: Stargardt disease (On-Line Mendelian Inheritance In Man 242000, STGD1) is the most common inherited macular dystrophy. STGD1 is typically a young-adult-onset disease that is recurrently associated with the ABCA4 mutant allele G1961E in homozygosity or compound heterozygosity. The genetics of ABCA4-related retinopathy in the Arabian Gulf region have not been well-studied. This report reviews the experience of the Ocular Genetics Service at Cleveland Clinic Abu Dhabi with clinically diagnosed ABCA4-related retinopathy in Emirati patients who underwent genetic testing. METHODS: Retrospective case series (2016-2018, inclusive). RESULTS: All 22 identified patients (19 families; 11 males, 11 females; first visual symptoms 5-33 years old) were found to harbor biallelic ABCA4 pathologic variants. There were 14 childhood-onset cases (onset before 18 years of age; 12 families; 7 males, 7 females; first visual symptoms from 5 to 12 years old, median 8)-all were homozygous, 11 for the same novel double mutant allele G1961E/L857P. Those who underwent electroretinography (8) had cone-rod rather than isolated macular dystrophy. There were 8 adult-onset cases (onset at or after 18 years of age; 7 families; 4 males, 4 females; first visual symptoms from 18 to 33 years old, median 22)-all were compound heterozygous, seven harboring the common G1961E mutant allele. CONCLUSION: The molecular yield for biallelic ABCA4 pathogenic variants is high for clinically diagnosed ABCA4-related retinopathy in Emiratis (100% in this case series). Homozygosity for a novel complex allele G1961E/L857P causes a childhood-onset cone-rod dystrophy rather than the young-adult-onset macular dystrophy that is associated with G1961E alone. This G1961/L857P complex allele likely represents a founder effect for the region.

Prospective Cohort Study of Childhood-Onset Stargardt Disease: Fundus Autofluorescence Imaging, Progression, Comparison with Adult-Onset Disease, and Disease Symmetry.

PURPOSE: To determine the reliability and repeatability of quantitative evaluation of areas of decreased autofluorescence (DAF) from fundus autofluorescence (FAF) images and track disease progression in children with Stargardt disease (STGD1), and to investigate clinical and genotype correlations, disease symmetry, and intrafamilial variability. DESIGN: Prospective cohort study. METHODS: Children and adults with molecularly confirmed STGD1 (n = 90) underwent longitudinal FAF imaging with subsequent semiautomated measurement of the area of DAF and calculation of the annual rate of progression. The age of disease onset was recorded for all subjects, as well as the electroretinography (ERG) group at baseline (n = 86). Patients were grouped for analysis based on the age at baseline and age of onset, into children (n = 56), adults with childhood-onset STGD1 (n = 15), and adults with adult-onset (n = 19). Fifty FAF images were selected randomly and analyzed by 2 observers to evaluate repeatability and reproducibility. Differences between groups, interocular symmetry, genotype-phenotype correlations, and intrafamilial variability were also investigated both for baseline measurements as well as progression rates. We measured visual acuity, molecular genetics, ERG group, FAF metrics, and their correlations. RESULTS: The mean age of onset ± SD was 9.6 ± 3.4 years for childhood-onset (n = 71) and 28.3 ± 7.8 years for adult-onset STGD1 (n = 19). The intra- and interobserver reliability of DAF quantification was excellent (intraclass correlation coefficients 0.995 and 0.987, respectively). DAF area was symmetric between eyes and the mean rate of progression (SD) was 0.69 (0.72), 0.78 (0.48), and 0.40 (0.36) mm2/year for children, adults with childhood-onset, and adults with adult-onset disease, respectively. Patients belonging to a group 3 ERG phenotype (generalized cone and rod dysfunction) had a significantly greater progression rate. Limited intrafamilial variability was observed. CONCLUSIONS: This is the first large prospective study of FAF in a cohort of molecularly confirmed children with STGD1. DAF area quantification was highly reliable and may thereby serve as a robust structural endpoint. A high rate of progression was observed in childhood-onset disease, making this subtype of STGD1 ideally suited to be considered for prioritization in clinical trials.

Fluorescence Lifetime Patterns of Retinal Pigment Epithelium Atrophy in Patients with Stargardt Disease and Age-Related Macular Degeneration.

PURPOSE: To investigate whether autofluorescence lifetime patterns within retinal pigment epithelium (RPE) atrophy differ between age-related macular degeneration (AMD) and Stargardt disease (STGD). METHODS: Mean retinal autofluorescence lifetimes were measured in a short and a long spectral channel (SSC: 498-560 nm; LSC: 560-720 nm). Mean retinal fluorescence lifetimes were analyzed with corresponding clinical features, fundus images, fundus autofluorescence intensity images, and optical coherence tomography. Mean fluorescence lifetime values of atrophic areas were compared between the two cohorts and within the same patient to adjacent nonatrophic regions. RESULTS: Mean fluorescence lifetimes within areas with RPE atrophy of 13 patients with STGD (mean age ± SEM 43.7 ± 5 years) and 30 patients with geographic atrophy (mean age: 78 ± 2 years) were analyzed and compared to age-matched healthy participants. The mean area of RPE atrophy in STGD and AMD was 6.6 ± 2.3 mm2 (range: 0.66-33.17 mm2) and 17.5 ± 3.8 mm2 (range: 0.58-50.02 mm2), respectively. In patients with AMD, atrophic areas revealed significantly longer mean fluorescence lifetime values as compared with patients with STGD (SSC: 997 ± 60 vs. 363 ± 26 ps; LSC: 880 ± 46 vs. 393 ± 23 ps; p < 0.0001). CONCLUSIONS: This study established that RPE atrophy in patients secondary to STGD and AMD display distinctive mean fluorescence lifetime characteristics. As retinal fluorescence lifetimes within areas of RPE atrophy were significantly longer in AMD patients, the analysis of specific lifetime patterns may provide additional insight into the disease processes and the pathogenetic mechanisms in the development of atrophic patches in AMD and STGD.

Peripapillary Sparing With Near Infrared Autofluorescence Correlates With Electroretinographic Findings in Patients With Stargardt Disease.

Purpose: To evaluate the correlation between the quantification of peripapillary sparing and electroretinogram (ERG) outcomes in autosomal recessive Stargardt disease (STGD1). Methods: Near infrared fundus autofluorescence (NIR-FAF) images of 101 eyes of 101 patients were retrospectively reviewed. Peripapillary sparing was assessed both qualitatively and quantitatively. The area of spared tissue (AST) was calculated in a 1-mm-wide ring around the optic disc after binarization of the 55° NIR-FAF. These measurements were correlated with the presence of normal ERG (group I), abnormal photopic responses (group II), or abnormal photopic and scotopic responses (group III). Results: AST showed significant correlations with ERG groups (R = -0.802, P < 0.001). While qualitative assessment of peripapillary sparing (i.e., present or not) also showed a significant correlation with ERG groups (R = -0.435, P < 0.001), it was weaker than by AST quantification. The ordinal regression analysis showed that the increase in AST was associated with a decrease in the odds of belonging to ERG groups II and III, with an odds ratio of 0.82 (95% confidence interval [CI] 0.78-0.87), P < 0.001. Conclusions: The AST around the optic disc in eyes with STGD1 correlates with the impairment of photoreceptors as shown in the ERG. If replicated in future longitudinal studies, the quantification of peripapillary sparing may prove to be a useful parameter for evaluating the visual prognosis of these eyes.