Aims To quantify retinal vascular bed area (RVBA) in square millimetres on stereographically projected ultra-wide field (UWF) fluorescein angiography (FA) in eyes with diabetic retinopathy (DR). Methods A prospective, observational study. Baseline Optos 200Tx UWF FA images of 80 eyes with DR from the DAVE (NCT01552408) and RECOVERY (NCT02863354) studies were stereographically projected at the Doheny Image Reading Center to adjust for peripheral distortion. The early-phase FA frame was used to extract the retinal vasculature as a mask for calculating RVBA. The pixels of the retinal vasculature were automatically computed in square millimetres using manufacturer-provided software. Results Eighteen of 80 diabetic eyes were excluded because image quality and contrast were insufficient for automatic extraction of the retinal vasculature from the background fluorescence. The remaining 62 eyes were included in the final analysis. In comparison with age-matched and sex-matched normal controls, eyes with DR had a higher global RVBA for the entire retina (p<0.001), and RVBA correlated with DR severity (p<0.001), with a higher RVBA in eyes with proliferative DR (66.1±16.2 mm2) than in those with non-proliferative DR (56.2±16.6 mm2) or in normal controls (37.2±9.9 mm2). This tendency was also present in the posterior retina and mid-periphery but absent in the far-periphery. RVBA did not correlate with retinal ischaemia (p>0.05). Conclusions Eyes with DR harboured a larger global RVBA for the entire retina than normal controls, and RVBA appeared to indicate DR severity. However, this biomarker was not observed to be a good indicator of retinal ischaemia.

Importance Sensitive outcome measures for disease progression are needed for treatment trials of Stargardt disease. Objective To estimate the progression rate of atrophic lesions in the prospective Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study over a 12-month period. 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. Patients who were affected by Stargardt disease, aged 6 years and older at baseline, and harboring disease-causing variants of the ABCA4 gene were enrolled at 9 centers in the United States, United Kingdom, and continental Europe. Data analysis occurred from November 2016 to January 2017. Exposures Autofluorescence images obtained with a standard protocol were sent to a central reading center, and areas of definitely decreased autofluorescence, questionably decreased autofluorescence, and the total combined area of decreased autofluorescence were outlined and quantified. Progression rates were estimated from linear mixed models with time as the independent variable. Main Outcomes and Measures Yearly rate of progression, using the growth of atrophic lesions measured by autofluorescence imaging. Results A total of 259 study participants (488 eyes; 230 individuals [88.8%] were examined in both eyes) were enrolled (mean [SD] age at first visit, 33.3 [15.1] years; 118 [54.4%] female). Gradable images were available for evaluation for 480 eyes at baseline and 454 eyes after 12 months. At baseline, definitely decreased autofluorescence was present in 306 eyes, and the mean (SD) lesion size was 3.93 (4.37) mm2. The mean total area of decreased autofluorescence at baseline was 4.07 (4.04) mm2. The estimated progression of definitely decreased autofluorescence was 0.76 (95% CI, 0.54-0.97) mm2 per year (P < .001), and the total area of both questionably and definitely decreased autofluorescence was 0.64 (95% CI, 0.50-0.78) mm2 per year (P < .001). Both progression rates depended on initial lesion size. Conclusions and Relevance In Stargardt disease, autofluorescence imaging may serve as a monitoring tool and definitely decreased autofluorescence and total area as outcome measures for interventional clinical trials that aim to slow disease progression. Rates of progression depended mainly on initial lesion size.

Purpose To assess the reproducibility of retinal measurements from optical coherence tomography (OCT) in ABCA4-related Stargardt disease (STGD1). Methods The international multicenter Progression of Atrophy Secondary to Stargardt Disease (ProgStar) Study enrolled 259 STGD1 patients. OCT images were graded by the study reading center (RC). Semiautomatic segmentation with manual adjustments was used to segment the layers of retinal pigmentation epithelium, outer segments, inner segments (ISs), outer nuclear layer (ONL), inner retina, and the total retina (TR). The images were overlaid to the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. For each layer, the thickness and the intact area of the ETDRS central subfield, inner ring, and outer ring were recorded, respectively. A different set of RC graders regraded 30 independent ProgStar images to evaluate measurement reproducibility. Reproducibility was assessed graphically and using statistics including intraclass correlation (ICC) and relative absolute difference (RAD). Results Across all layers, measurements of the ETDRS central subfield had low ICC and/or large RAD. The outer-ring region was not fully captured in some images. For inner ring, good reproducibility was observed for intact area in the IS (ICC = 0.99, RAD = 4%), thicknesses of the ONL (ICC = 0.93, RAD = 6%), and TR (ICC = 0.99, RAD = 1%). Conclusions STGD1's complex morphology made outer retina segmentation challenging. Measurements of the inner ring, including the intact area of IS (i.e., the ellipsoid zone [EZ]) and ONL and TR thicknesses, had good reproducibility and showed anatomical impairment. Translational Relevance ONL and TR thicknesses and the EZ intact area in the ETDRS inner ring hold potential as structural endpoints for STGD1 trials. Structure-function relationships need to be further established.

Purpose: To describe the study design and characteristics at first visit of participants in the longitudinal Scotopic Microperimetric Assessment of Rod Function in Stargardt Disease (SMART) study. Methods: Scotopic microperimetry (sMP) was performed in one designated study eye in a subset of participants with molecularly proven ABCA4-associated Stargardt disease (STGD1) enrolled in a multicenter natural history study (ProgStar). Study visits were every 6 months over a period ranging from 6 to 24 months, and also included fundus autofluorescence (FAF). Results: SMART enrolled 118 participants (118 eyes). At the first visit of SMART, the mean sensitivity in mesopic microperimetry was 11.48 (±5.05; range 0.00–19.88) dB and in sMP 11.25 (±5.26; 0–19.25) dB. For FAF, all eyes had a lesion of decreased autofluorescence (mean lesion size 3.62 [±3.48; 0.10–21.46] mm2), and a total of 76 eyes (65.5%) had a lesion of definitely decreased autofluorescence with a mean lesion size of 3.46 (±3.60; 0.21–21.46) mm2. Conclusions: Rod function is impaired in STGD1 and can be assessed by sMP. Testing rod function may serve as a potential outcome measure for future clinical treatment trials. This is evaluated in the SMART study.