PURPOSE: To describe progression of best-corrected visual acuity (BCVA), full-field stimulus thresholds (FST), and electroretinography (ERG) over 4 years in the DESIGN: Prospective natural history study. PARTICIPANTS: Participants (n = 105) with biallelic disease-causing sequence variants in USH2A and BCVA letter scores of ≥54 were included. METHODS: BCVA, FST, fundus-guided microperimetry, static perimetry, and spectral domain OCT were performed annually and ERG at baseline and 4 years only. Mixed effects models were used to estimate annual rates of change with 95% confidence intervals. Associations of change from baseline to 4 years between BCVA, FST, ERG, and other metrics were assessed with Spearman correlation coefficients (r MAIN OUTCOME MEASURES: Best-corrected visual acuity, FST, and ERG. RESULTS: The annual rate of decline in BCVA was 0.83 (95% confidence interval: 0.65-1.02) letters/year. For FST, the change was 0.09 (0.07-0.11) log cd.s/m CONCLUSIONS: Best-corrected visual acuity was not a sensitive measure of progression over 4 years. Full-field stimulus threshold was a more sensitive measure
however, additional information on the clinical relevance of changes in FST is needed before this test can be adopted as an endpoint for clinical trials. FINANCIAL DISCLOSURES: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.