Towards Uncovering the Role of Incomplete Penetrance in Maculopathies through Sequencing of 105 Disease-Associated Genes.

Inherited macular dystrophies (iMDs) are a group of genetic disorders, which affect the central region of the retina. To investigate the genetic basis of iMDs, we used single-molecule Molecular Inversion Probes to sequence 105 maculopathy-associated genes in 1352 patients diagnosed with iMDs. Within this cohort, 39.8% of patients were considered genetically explained by 460 different variants in 49 distinct genes of which 73 were novel variants, with some affecting splicing. The top five most frequent causative genes were ABCA4 (37.2%), PRPH2 (6.7%), CDHR1 (6.1%), PROM1 (4.3%) and RP1L1 (3.1%). Interestingly, variants with incomplete penetrance were revealed in almost one-third of patients considered solved (28.1%), and therefore, a proportion of patients may not be explained solely by the variants reported. This includes eight previously reported variants with incomplete penetrance in addition to CDHR1:c.783G>A and CNGB3:c.1208G>A. Notably, segregation analysis was not routinely performed for variant phasing-a limitation, which may also impact the overall diagnostic yield. The relatively high proportion of probands without any putative causal variant (60.2%) highlights the need to explore variants with incomplete penetrance, the potential modifiers of disease and the genetic overlap between iMDs and age-related macular degeneration. Our results provide valuable insights into the genetic landscape of iMDs and warrant future exploration to determine the involvement of other maculopathy genes.

Analysis of the Outer Retinal Bands in ABCA4 and PRPH2-Associated Retinopathy using OCT.

PURPOSE: To evaluate the outer retinal bands using OCT in ABCA4- and PRPH2-associated retinopathy and develop a novel imaging biomarker to differentiate between these 2 genotypes. DESIGN: Multicenter case-control study. PARTICIPANTS: Patients with a clinical and genetic diagnosis of ABCA4- or PRPH2-associated retinopathy and an age-matched control group. METHODS: Macular OCT was used to measure the thickness of the outer retinal bands 2 and 4 by 2 independent examiners at 4 retinal loci. MAIN OUTCOME MEASURES: Outcome measures included the thicknesses of band 2, band 4, and the band 2/band 4 ratio. Linear mixed modeling was used to make comparisons across the 3 groups. Receiver operating characteristic (ROC) analysis determined the optimal cutoff for the band 2/band 4 ratio to distinguish PRPH2- from ABCA4-associated retinopathy. RESULTS: We included 45 patients with ABCA4 variants, 45 patients with PRPH2 variants, and 45 healthy controls. Band 2 was significantly thicker in patients with PRPH2 compared with ABCA4 (21.4 vs. 15.9 µm, P < 0.001) variants, whereas band 4 was thicker in patients with ABCA4 variants than those with PRPH2 variants (27.5 vs. 21.7 µm, P < 0.001). Similarly, the band 2/band 4 ratio was significantly different (1.0 vs. 0.6 for PRPH2 vs. ABCA4, P < 0.001). The area under the ROC curve was 0.87 for either band 2 (> 18.58 µm) or band 4 (< 26.17 µm) alone and 0.99 (95% confidence interval: 0.97-0.99) for the band 2/band 4 ratio with a cutoff threshold of 0.79, providing 100% specificity. CONCLUSIONS: We report an altered outer retinal band profile whereby the band 2/band 4 ratio was able to discriminate between PRPH2- and ABCA4-associated retinopathy. This may have future clinic utility in predicting the genotype and provide further insight into the anatomic correlate of band 2. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Microperimetry and Adaptive Optics Imaging Reveal Localized Functional and Structural Changes in Asymptomatic RPGR Mutation Carriers.

Purpose: Female carriers of RPGR mutations demonstrate no significant retinal dysfunction or structural change despite a characteristic tapetal-like reflex. In this study, we examined localized changes of pointwise sensitivity (PWS) and cone density (CD) using microperimetry (MP) and adaptive optics (AO) imaging in female carriers of RPGR mutations. Methods: In this cross-sectional case-control study, MP (MAIA, 10-2 test grid) and AO imaging (rtx1) were performed in female carriers of RPGR mutations and unrelated age-matched healthy controls. PWS at 68 loci located 1 degree to 9 degrees away from the preferred retinal locus and CD at 12 loci located 1 degree to 3 degrees away from the foveal center were measured. Severity of defect was defined by standard deviation (SD) from age-matched healthy control means: normal (<1 SD from normal average), moderate defect (1-2 SD from normal average), and severe defect (>2 SD from normal average). Results: Twelve patients from seven unrelated families were enrolled. Seven patients were asymptomatic, 5 of whom had visual acuity 20/20 or better in both eyes. PWS and CD were available in 12 and 8 patients, respectively. Severe PWS and CD defect in at least 1 test location was observed in 10 of 12 patients and 7 of 8 patients, respectively. Among the five asymptomatic patients who had normal visual acuity, severe PWS and CD defects were observed in three of five and four of five patients, respectively. Conclusions: MP and AO imaging revealed early functional and structural changes in asymptomatic RPGR mutation carriers and should be considered in clinical assessment of these patients.

Longitudinal Analysis of Functional and Structural Outcome Measures in PRPH2-Associated Retinal Dystrophy.

PURPOSE: To establish disease progression rates in total lesion size (TLS), decreased autofluorescence (DAF) area, total macular volume (TMV), and mean macular sensitivity (MMS) in PRPH2-associated retinal dystrophy. DESIGN: Single-center, retrospective chart review. PARTICIPANTS: Patients with heterozygous pathogenic or likely pathogenic PRPH2 variants. METHODS: Patients who underwent serial ultrawide-field (UWF) fundus autofluorescence (FAF), OCT, and Macular Integrity Assessment microperimetry with at least 1 year of follow-up were included. Linear correlation was performed in eyes of all patients to determine the rate of change over time. MAIN OUTCOME MEASURES: Outcome measures included changes in TLS, DAF area, TMV, and MMS. RESULTS: Twelve patients (mean age, 55) from 10 unrelated families attended 100 clinic visits, which spanned over a mean (SD) of 4.7 (2.0) years. Mean (SD) TLS and DAF radius expansion were 0.14 (0.12) and 0.10 (0.08) mm/year, respectively. Mean (SD) TMV change was -0.071 (0.040) mm3/year with no interocular difference (P = 0.20) and strong interocular correlation (r2 = 0.88, P < 0.01). Mean (SD) MMS change was -0.10 (1.25) dB/year. Mean macular sensitivity declined in 4 and improved in 6 patients. Mean macular sensitivity was subnormal despite a TMV within the normal range. CONCLUSIONS: Serial measurements of UWF-FAF-derived TLS and DAF showed slow expansion. Total macular volume might be a more sensitive measure than MMS in detecting disease progression.

Characterising splicing defects of ABCA4 variants within exons 13-50 in patient-derived fibroblasts.

The ATP-binding cassette subfamily A member 4 gene (ABCA4)-associated retinopathy, Stargardt disease, is the most common monogenic inherited retinal disease. Given the pathogenicity of numerous ABCA4 variants is yet to be examined and a significant proportion (more than 15%) of ABCA4 variants are categorized as splice variants in silico, we therefore established a fibroblast-based splice assay to analyze ABCA4 variants in an Australian Stargardt disease cohort and characterize the pathogenic mechanisms of ABCA4 variants. A cohort of 67 patients clinically diagnosed with Stargardt disease was recruited. Genomic DNA was analysed using a commercial panel for ABCA4 variant detection and the consequences of ABCA4 variants were predicted in silico. Dermal fibroblasts were propagated from skin biopsies, total RNA was extracted and the ABCA4 transcript was amplified by RT-PCR. Our analysis identified a total of 67 unique alleles carrying 74 unique variants. The most prevalent splice-affecting complex allele c.[5461-10T>C; 5603A>T] was carried by 10% of patients in a compound heterozygous state. ABCA4 transcripts from exon 13 to exon 50 were readily detected in fibroblasts. In this region, aberrant splicing was evident in 10 out of 57 variant transcripts (18%), carried by 19 patients (28%). Patient-derived fibroblasts provide a feasible platform for identification of ABCA4 splice variants located within exons 13-50. Experimental evidence of aberrant splicing contributes to the pathogenic classification for ABCA4 variants. Moreover, identification of variants that affect splicing processes provides opportunities for intervention, in particular antisense oligonucleotide-mediated splice correction.

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.

Genotype-Specific Lesion Growth Rates in Stargardt Disease.

Reported growth rates (GR) of atrophic lesions in Stargardt disease (STGD1) vary widely. In the present study, we report the longitudinal natural history of patients with confirmed biallelic ABCA4 mutations from five genotype groups: c.6079C>T, c.[2588G>C;5603A>T], c.3113C>T, c.5882G>A and c.5603A>T. Fundus autofluorescence (AF) 30° × 30° images were manually segmented for boundaries of definitely decreased autofluorescence (DDAF). The primary outcome was the effective radius GR across five genotype groups. The age of DDAF formation in each eye was calculated using the x-intercept of the DDAF effective radius against age. Discordance between age at DDAF formation and symptom onset was compared. A total of 75 eyes from 39 STGD1 patients (17 male [44%]; mean ± SD age 45 ± 19 years; range 21-86) were recruited. Patients with c.3113C>T or c.6079C>T had a significantly faster effective radius GR at 0.17 mm/year (95% CI 0.12 to 0.22; p < 0.001 and 0.14 to 0.21; p < 0.001) respectively, as compared to those patients harbouring c.5882G>A at 0.06 mm/year (95% CI 0.03-0.09), respectively. Future clinical trial design should consider the effect of genotype on the effective radius GR and the timing of DDAF formation relative to symptom onset.

Generation of two induced pluripotent stem cell lines from a patient with Stargardt disease caused by compound heterozygous mutations in the ABCA4 gene.

Stargardt disease (STGD1) is the most common inherited retinal dystrophy and ABCA4 c.546--10 T>C is the most commonly reported splice mutation. Here, we generated and characterized two induced pluripotent stem cell (iPSC) lines from a STGD1 patient with compound heterozygous mutations in ABCA4 (c.[5461-10 T > C;5603A > T];[4163 T > C;455G > A]). Episomal vectors containing OCT4, SOX2, KLF4, L-MYC, LIN28 and mp53DD were employed to conduct the reprogramming of patient-derived fibroblasts. Both lines had a normal karyotype, displayed iPSC morphology, expressed pluripotency markers and showed trilineage differentiation potential. These lines can provide a powerful platform for further investigating the pathophysiological consequences of mutations in ABCA4.

Clinical Evidence for the Importance of the Wild-Type PRPF31 Allele in the Phenotypic Expression of RP11.

PRPF31-associated retinopathy (RP11) is a common form of autosomal dominant retinitis pigmentosa (adRP) that exhibits wide variation in phenotype ranging from non-penetrance to early-onset RP. Herein, we report inter-familial and intra-familial variation in the natural history of RP11 using multimodal imaging and microperimetry. Patients were recruited prospectively. The age of symptom onset, best-corrected visual acuity, microperimetry mean sensitivity (MS), residual ellipsoid zone span and hyperautofluorescent ring area were recorded. Genotyping was performed using targeted next-generation and Sanger sequencing and copy number variant analysis. PRPF31 mutations were found in 14 individuals from seven unrelated families. Four disease patterns were observed: (A) childhood onset with rapid progression (N = 4), (B) adult-onset with rapid progression (N = 4), (C) adult-onset with slow progression (N = 4) and (D) non-penetrance (N = 2). Four different patterns were observed in a family harbouring c.267del; patterns B, C and D were observed in a family with c.772_773delins16 and patterns A, B and C were observed in 3 unrelated individuals with large deletions. Our findings suggest that the RP11 phenotype may be related to the wild-type PRPF31 allele rather than the type of mutation. Further studies that correlate in vitro wild-type PRPF31 allele expression level with the disease patterns are required to investigate this association.

Generation of an induced pluripotent stem cell line from a patient with Stargardt disease caused by biallelic c.[5461-10T>C;5603A>T];[6077T>C] mutations in the ABCA4 gene.

Mutations in ABCA4 gene are causative for autosomal recessive Stargardt disease (STGD1), the most common inherited retinal dystrophy. Here, we report the generation of an induced pluripotent stem cell (iPSC) line from a STGD1 patient carrying biallelic c.[5461-10T>C;5603A>T];[6077T>C] mutations in the ABCA4 gene. Episomes carrying OCT4, SOX2, KLF4, L-MYC, LIN28 and mp53DD were employed for the reprogramming of patient-derived fibroblasts. This iPSC line expressed comparable pluripotency markers as in a commercially available human iPSC line, displayed normal karyotype and potential for trilineage differentiation, and were negative for both reprogramming episomes and mycoplasma test.

CLASSIFYING ABCA4 MUTATION SEVERITY USING AGE-DEPENDENT ULTRA-WIDEFIELD FUNDUS AUTOFLUORESCENCE-DERIVED TOTAL LESION SIZE.

PURPOSE: To establish a mutation-specific age-dependent ultra-widefield fundus autofluorescence (UWF-FAF) trajectory in a large Stargardt disease (STGD1) cohort using total lesion size (TLS) and to develop a clinical method for variant classification. METHODS: A retrospective study of patients with biallelic ABCA4 mutations that were evaluated with UWF-FAF. Boundaries of TLS, defined by stippled hyper/hypoautofluorescence, were outlined manually. Pathogenicity was assessed according to ACMG/AMP criteria, and mutation severities were classified based on the current literature. Age-dependent trajectories in TLS were examined in patients with nullizygous, mild, and intermediate mutations. Mutations of uncertain severities were classified using a clinical criterion based on age of symptom onset and TLS. RESULTS: Eighty-one patients with STGD1 (mean age = 42 ± 20 years and mean visual acuity = 20/200) were recruited from 65 unrelated families. Patients with biallelic null/severe variants (n = 6) demonstrated an increase in TLS during their second decade reaching a mean ± SD of 796 ± 29 mm2 by age 40. Those harboring mild mutations c.5882G>A or c.5603A>T had lesions confined to the posterior pole with a mean ± SD TLS of 30 ± 39 mm2. Intermediate mutations c.6079C>T or c.[2588G>C;5603A>T] in trans with a null/severe mutation had a mean ± SD TLS of 397 ± 29 mm2. Thirty-two mutations were predicted to cause severe (n = 22), intermediate (n = 6), and mild (n = 5) impairment of ABCA4 function based on age of symptom onset and TLS. CONCLUSION: Age-dependent TLS showed unique ABCA4 mutation-specific trajectories. Our novel clinical criterion using age of symptom onset and TLS to segregate ABCA4 mutations into three severity groups requires further molecular studies to confirm its validity.

Generation of two induced pluripotent stem cell lines from a retinitis pigmentosa patient with compound heterozygous mutations in CRB1.

Two human iPSC lines were generated from dermal fibroblasts derived from a patient with retinitis pigmentosa caused by CRB1 mutation using episomal plasmids containing OCT4, SOX2, LIN28, KLF4, L-MYC and mp53DD. These clonal iPSC lines carry compound heterozygous mutations in CRB1 (c.2555 T > C and c.3014A > T). Both lines expressed pluripotency markers, displayed a normal karyotype and demonstrated the ability to differentiate into the three primary germ layers, as well as retinal organoids.

Multimodal Retinal Imaging and Microperimetry Reveal a Novel Phenotype and Potential Trial End Points in CRB1-Associated Retinopathies.

Purpose: Biallelic crumbs cell polarity complex component 1 (CRB1) mutations can present as Leber congenital amaurosis (LCA), retinitis pigmentosa (RP), or cystic maculopathy. This study reports a novel phenotype of asymptomatic fenestrated slit maculopathy (AFSM) and examines macular volume profile and microperimetry as clinical trial end points in CRB1-associated retinopathies. Methods: Twelve patients from nine families with CRB1 mutation were recruited. Ultra-widefield (UWF) color fundus photography and autofluorescence (AF), spectral-domain optical coherence tomography (SD-OCT), microperimetry, and adaptive optics (AO) imaging were performed. Macular volume profiles were compared with age-matched healthy controls. Genotyping was performed using APEX genotyping microarrays, targeted next-generation sequencing, and Sanger sequencing. Results: We identified one patient with LCA, five patients with RP, and four patients with macular dystrophy (MD) with biallelic CRB1 mutations. Two siblings with compound heterozygote genotype (c.[2843G>A]; [498_506del]) had AFSM characterized by localized outer retinal disruption on SD-OCT and parafoveal cone loss on AO imaging despite normal fundus appearance, visual acuity, and foveal sensitivity. UWF AF demonstrated preserved para-arteriolar retinal pigment epithelium (PPRPE) in all patients with RP. Microperimetry documented preserved central retinal function in six patients. The ratio of perifoveal-to-foveal retinal volume was greater than controls in 89% (8/9) of patients with RP or MD, whereas central subfield and total macular volume were outside normal limits in 67% (6/9). Conclusions: AO imaging was helpful in detecting parafoveal cone loss in asymptomatic patients. Macular volume profile and microperimetry parameters may have utility as CRB1 trials end points. Translational Relevance: Macular volume and sensitivity can be used as structural and functional end points for trials on CRB1-associated RP and MD.

Deep clinical phenotyping and gene expression analysis in a patient with RCBTB1-associated retinopathy.

Background: Mutations in the RCC1 and BTB domain-containing protein 1 (RCBTB1) gene have been implicated in a rare form of retinal dystrophy. Herein, we report the clinical features of a 45-year-old Singaporean-Chinese female and her presymptomatic sibling, who each possesses compound heterozygous mutations in RCBTB1. Expression of RCBTB1 in patient-derived cells was evaluated.Materials and Methods: The natural history was documented by a series of ophthalmic examinations including electroretinography, fundus autofluorescence imaging, spectral-domain optical coherence tomography, visual field, microperimetry, and adaptive optics retinal imaging. Patient DNA was genetically analysed using a 537-gene Next Generation Sequencing panel and targeted Sanger sequencing. Expression of RCBTB1 in lymphocytes, fibroblasts, and induced pluripotent stem cells (iPSC) derived from the proband and healthy controls was characterized by quantitative PCR, Sanger sequencing, and western blotting.Results: The proband presented with left visual distortion at age 40 due to extrafoveal chorioretinal atrophy. Atrophy expanded at 1.3 (OD) and 1.0 (OS) mm2/year. Total macular volume declined by 0.09 (OD) and 0.13 (OS) mm3/year. Microperimetry demonstrated enlarging scotoma in both eyes. Generalised cone dysfunction was demonstrated by electroretinography. A retinal dystrophy panel testing revealed biallelic frameshifting mutations, c.170delG (p.Gly57Glufs*12) and c.707delA (p.Asn236Thrfs*11) in RCBTB1. The level of RCBTB1 mRNA expression was reduced in patient-derived lymphocytes compared to controls. RCBTB1 protein was detected in control fibroblasts and iPSC but was absent in patient-derived cells.Conclusions: Atrophy expansion rate and macular volume change are feasible endpoints for monitoring RCBTB1-associated retinopathy. We provide further functional evidence of pathogenicity for two disease-causing variants using patient-derived iPSCs.

A novel phenotype in a family with autosomal dominant retinal dystrophy due to c.1430A > G in retinoid isomerohydrolase (RPE65) and c.37C > T in bestrophin 1 (BEST1).

PURPOSE: The c.1430A > G (Asp477Gly) variant in RPE65 has been reported in Irish and Scottish families with either an autosomal dominant retinal dystrophy (adRD) that resembles choroideremia, a vitelliform macular dystrophy or an isolated macular atrophy. We report novel features on multimodal imaging and the natural history of a family harbouring this variant in combination with the BEST1 c.37C > T (Arg13Cys) variant. METHODS: Members of a family with an adRD were examined clinically to ascertain phenotype and underwent genetic testing. Multimodal imaging included widefield colour fundus photography, quantitative autofluorescence (qAF) and spectral domain optical coherence tomography. Electrophysiology and microperimetry were also performed. RESULTS: Vision loss was attributed to foveal atrophy in the proband and choroidal neovascularisation and a vitello-eruptive lesion in one affected son. Peripheral retinal white dots corresponding to subretinal deposits were seen in three patients. The median qAF8 values in the proband (I:1) were low (40 and 101 in OD and OS) at age 79. Similarly, the qAF8 values for the middle son (II:2) were also low (100 and 87 in ODS and OS) at age 60. Electrophysiology showed disproportionate reduction in Arden ratio prior to the gradual loss of full-field responses. Microperimetry demonstrated an enlarging scotoma in the proband. CONCLUSIONS: The coexistence of the pathogenic BEST1 c.37C > T variant may modify clinical features observed in RPE65 adRD. This study expands our understanding of RPE65 adRD as a retinoid cycle disorder supported by the reduced qAF, fine white retinal dots and corresponding subretinal deposits on OCT in affected members.

Gene correction of the CLN3 c.175G>A variant in patient-derived induced pluripotent stem cells prevents pathological changes in retinal organoids.

BACKGROUND: Mutations in CLN3 cause Batten disease, however non-syndromic CLN3 disease, characterized by retinal-specific degeneration, has been also described. Here, we characterized an induced pluripotent stem cell (iPSC)-derived disease model derived from a patient with non-syndromic CLN3-associated retinopathy. METHODS: Patient-iPSC, carrying the 1 kb-deletion and c.175G>A variants in CLN3, coisogenic iPSC, in which the c.175G>A variant was corrected, and control iPSC were differentiated into neural retinal organoids (NRO) and cardiomyocytes. CLN3 transcripts were analyzed by Sanger sequencing. Gene expression was characterized by qPCR and western blotting. NRO were characterized by immunostaining and electron microscopy. RESULTS: Novel CLN3 transcripts were detected in adult human retina and control-NRO. The major transcript detected in patient-NRO displayed skipping of exons 2 and 4-9. Accumulation of subunit-C of mitochondrial ATPase (SCMAS) protein was demonstrated in patient-derived cells. Photoreceptor progenitor cells in patient-NRO displayed accumulation of peroxisomes and vacuolization of inner segments. Correction of the c.175G>A variant restored CLN3 mRNA and protein expression and prevented SCMAS and inner segment vacuolization. CONCLUSION: Our results demonstrate the expression of novel CLN3 transcripts in human retinal tissues. The c.175G>A variant alters splicing of the CLN3 pre-mRNA, leading to features consistent with CLN3 deficiency, which were prevented by gene correction.

Generation of two induced pluripotent stem cell lines from a patient with recessive inherited retinal disease caused by compound heterozygous mutations in SNRNP200.

The human induced pluripotent stem cell (iPSC) lines LEIi015-A and LEIi015-B were derived from a patient with inherited retinal disease caused by compound heterozygous mutations in the SNRNP200 gene (c.[1792C>T];[3341T>C]). Dermal fibroblasts were transfected with episomal plasmids carrying transgenes encoding OCT4, SOX2, KLF4, L-MYC, LIN28, mir302/367 microRNA and shRNA for P53. The clonal iPSC lines LEIi015-A and LEIi015-B expressed iPSC markers, were free from genomic alterations and demonstrated trilineage differentiation potential.

Atrophy Expansion Rates in Stargardt Disease Using Ultra-Widefield Fundus Autofluorescence.

Purpose: To investigate atrophy expansion rate (ER) using ultra-widefield (UWF) fundus autofluorescence (FAF) in Stargardt disease (STGD1). Design: Retrospective, longitudinal study. Participants: Patients with biallelic ABCA4 mutations who were evaluated with UWF FAF and Heidelberg 30° × 30° and 55° × 55° FAF imaging. Methods: Patients with atrophy secondary to STGD1 were classified into genotype groups: group A, biallelic severe or null-like variants with early-onset disease; group B, 1 intermediate variant in trans with severe or null-like variant; and group C, 1 mild variant in trans with severe or null-like variant or late-onset disease. The boundaries of definitely decreased autofluorescence (DDAF) were outlined manually and areas (in square millimeters) were recorded at baseline and follow-up. Bland-Altman analysis was conducted to examine agreement between observers and devices. Linear mixed modeling was used to evaluate predictors of ER in DDAF area and square root area (SRA). Main Outcome Measures: Patient and ocular predictors of DDAF area ER and DDAF SRA ER included age at onset, duration of symptoms, genotype group, baseline visual acuity, and baseline atrophy size. Results: A total of 138 eyes from 69 patients (33 men [47%]; mean age ± standard deviation, 41 ± 20 years; range, 10-83 years) carrying 61 unique ABCA4 variants were recruited. Ultra-widefield FAF measurements were equivalent to Heidelberg 30° × 30° imaging. Baseline DDAF area was the only significant predictor of DDAF area ER (P < 0.001). Age at baseline and genotype group were predictors for DDAF SRA ER. Definitely decreased autofluorescence area ER ranged from 4.65 mm2/year (group A) to 0.62 mm2/year (group C). Conclusions: Ultra-widefield FAF is a feasible and reliable method for assessing atrophy ER in STGD1. The value of ABCA4 mutation severity in predicting atrophy ER warrants further investigation.

Progressive sector retinitis pigmentosa due to c.440G>T mutation in SAG in an Australian family.

BACKGROUND: Heterozygous c.440 G > T mutation in the S-antigen visual arrestin (SAG) gene has been described as a cause of autosomal dominant retinitis pigmentosa (adRP) in a series of patients of Hispanic origin. This study presents the early and late clinical features and disease progression rates in an Australian family with SAG adRP. MATERIALS AND METHODS: An observational case series of four family members with adRP. They were examined clinically, with multi-modal retinal imaging and electroretinography (ERG) to ascertain phenotype. Disease progression rate was measured using optical coherence tomography (OCT) and fundus autofluorescence (FAF). A retinal dystrophy panel was used for the proband and cascade testing with targeted Sanger sequencing was conducted in other available family members. RESULTS: The proband presented at 36 years of age with profoundly reduced full-field ERG responses despite a sector RP phenotype. This progressed to a classic RP pattern over several decades leaving a small residual island of central visual field. The horizontal span of the residual outer nuclear layer and the area of hyperautofluorescent ring contracted at a rate of 8-11% and 9-14% per year, respectively. DNA sequencing confirmed the segregation of SAG c.440 G > T mutation with disease. CONCLUSION: SAG adRP presents with a reduced full-field ERG response consistent with a rod-cone dystrophy in mid-life despite a sector RP phenotype. Centripetal progression of the disease into the macula can be tracked by OCT and FAF imaging.