Abstract
Objective To determine whether docosahexaenoic acid will slow the course of retinaldegeneration in subgroups of patients with retinitis pigmentosa who are receivingvitamin A.
Design A cohort of 208 patients with retinitis pigmentosa, aged 18 to 55 years,were randomly assigned to 1200 mg of docosahexaenoic acid plus 15 000IU/d of vitamin A given as retinyl palmitate (DHA + A group) or control fattyacid plus 15 000 IU/d of vitamin A (control + A group) and followed upover 4 years. Seventy percent of the patients in each group were taking vitaminA, 15 000 IU/d, prior to entry. We compared rates of decline in ocularfunction in the DHA + A vs control + A groups among the subgroups definedby use or nonuse of vitamin A prior to entry. We also determined whether declinein ocular function was related to red blood cell phosphatidylethanolaminedocosahexaenoic acid level, dietary ω-3 fatty acid intake, or durationof vitamin A use. Main outcome measures were Humphrey Field Analyzer visualfield sensitivity, 30-Hz electroretinogram amplitude, and visual acuity.
Results Among patients not taking vitamin A prior to entry, those in the DHA+ A group had a slower decline in field sensitivity and electroretinogramamplitude than those in the control + A group over the first 2 years (P = .01 and P = .03, respectively);these differences were not observed in years 3 and 4 of follow-up or amongpatients taking vitamin A prior to entry. In the entire cohort, red bloodcell phosphatidylethanolamine docosahexaenoic acid level was inversely relatedto rate of decline in total field sensitivity over 4 years (test for trend, P = .05). This was particularly evident over the first2 years among those not on vitamin A prior to entry (test for trend, P = .003). In the entire control + A group, dietary ω-3fatty acid intake was inversely related to loss of total field sensitivityover 4 years (intake, <0.20 vs ≥0.20 g/d; P =.02). The duration of vitamin A supplementation prior to entry was inverselyrelated to rate of decline in electroretinogram amplitude (P = .008).
Conclusions For patients with retinitis pigmentosa beginning vitamin A therapy,addition of docosahexaenoic acid, 1200 mg/d, slowed the course of diseasefor 2 years. Among patients on vitamin A for at least 2 years, a diet richin ω-3 fatty acids (≥0.20 g/d) slowed the decline in visual fieldsensitivity.