Clinical trial of docosahexaenoic acid in patients with retinitis pigmentosa receiving vitamin A treatment

Objective: To determine whether a therapeutic dose of docosahexaenoic acid (DHA), an omega-3 fatty acid, will slow the course of retinal degeneration in adult patients with retinitis pigmentosa who are also receiving vitamin A. Design: Randomized, controlled, double-masked trial of 221 patients, aged 18 to 55 years, evaluated over a 4-year interval. Patients were given either 1200 mg/d of docosahexaenoic acid or control capsules. All were given 15 000 IU/d of vitamin A (given as retinyl palmitate). Randomization considered genetic type and baseline dietary w-3 fatty acid intake. Main Outcome Measures: The primary outcome measure was the total point score for the 30-2 program of the Humphrey field analyzer; secondary outcome measures were the total point score for the 30-2 and 30/60-1 programs combined, 30-Hz electroretinogram amplitude, and Early Treatment Diabetic Rentinopathy Study visual acuity. Results: No significant differences in decline in ocular function were found between the docosahexaenoicacid plus vitamin A (DHA+A) group and control plus vitamin A (control+A) group over a 4-year interval among all 221 randomized patients or among the 208 patients who completed all 4 follow-up visits. The mean annual rate of loss of sensitivity for the Humphrey Field Analyzer 30-2 program was 37 dB for the DHA+A group and 38 dB for the control+A group (P = .88). For the Humphrey Field Analyzer 30-2 and 30/60-1 programs combined, the mean annual rates of loss of field sensitivity were 57 dB for the DHA+A group and 60 dB (P = .73) for control+A group. No toxic adverse effects were observed. No significant differences by treatment group assignment were observed within genetic types or within the category of baseline w-3 fatty acid intake. Conclusion: In patients assigned to receive 15 000 IU/d of vitamin A, this randomized trial showed that 1200 mg/d of docosahexacnoic acid supplementation over a 4-year interval did not, on average, slow the course of disease in patients with retinitis pigmentosa.