Visual Acuity Loss in the Retrospective Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar-1) Study

Abstract

Purpose: The multi-center ProgStar studies aim to characterize the natural history of Stargardt disease in order to develop new outcome measures to test efficacy of forthcoming therapy trials. The objective of this presentation is to estimate the yearly rate of visual acuity (VA) loss in participants of the ProgStar-1 study.

Methods: Participants were enrolled at nine clinical sites in the Unites States and Europe. Their VA measures (best or presenting with correction) were obtained from retrospective review of medical records. VA measurements at the first visit were categorized into four groups according to WHO criteria: 1. no or mild visual impairment (VI): better or equal to 20/70; 2. moderate VI: 20/70-20/200; 3. severe VI: 20/200-20/400; 4. blindness: less than 20/400. VA values were converted to LogMAR scale, and linear mixed effects models were used to assess the average rate of VA loss.

Results: VA of 286 study eyes of 150 molecularly confirmed Stargardt patients with available VA data were evaluated. The mean age at the baseline (first) visit was 32.1 years (SD 15.2). Median observation period was 2.7 years (range 1.1 to 8.6). Median visual acuity at baseline was 20/125 (range 20/500 to 20/16) both in right and left eyes, respectively. Overall the rate of VA loss was 0.036 (95% CI 0.022, 0.045) LogMar units per year in the right (n=205) and 0.033 (0.026, 0.045) per year in the left eye (n=211). In group 1, VA loss was 0.085 (95% CI 0.061, 0.109) in right (n=54) and 0.077 (0.051, 0.102) lines per year in left eyes (n=55); in group 2, the rate was 0.020 (0.009, 0.031) in right (n=70) and 0.022 (0.011, 0.035) units per year in left eyes (n=70); and in group 3 and 4 combined, the rate was -0.025 (-0.044, -0.005) in right (n=19)and -0.019 (-0.037, 0.000) units per year in left eyes (n=18).

Conclusions: Visual acuity measures showed only a small yearly decline (an overall estimated decline of 1/3 line per year) and are not suitable as primary outcome measures in clinical trials for Stargardt disease that aim to slow down disease progression. More sensitive measures are needed and will be evaluated in the ProgStar-studies.