To evaluate whether a diet high in long-chain ω-3 fatty acids can slow the rate of visual acuity loss among patients with retinitis pigmentosa receiving vitamin A palmitate.

We calculated dietary intake from questionnaires completed annually by 357 adult patients from 3 randomized trials who were all receiving vitamin A, 15 000 IU/d, for 4 to 6 years. Rates of visual acuity decline were compared between those with high (≥0.20 g/d) vs low (<0.20 g/d) ω-3 intake. Analyses took age into account.

Mean rates of decline of acuity were slower among those with high ω-3 intake: Early Treatment Diabetic Retinopathy Study distance acuity: high intake = 0.59 letter per year, low intake = 1.00 letter per year, P = .001; Snellen retinal acuity: high intake = 1.5% per year, low intake = 2.8% per year, P = .03.

We conclude that mean annual rates of decline in distance and retinal visual acuities in adults with retinitis pigmentosa receiving vitamin A, 15 000 IU/d, are slower over 4 to 6 years among those consuming a diet rich in ω-3 fatty acids. To our knowledge, this is the first report that nutritional intake can modify the rate of decline of visual acuity in retinitis pigmentosa.