Randomized Trial for Retinitis Pigmentosa

To determine whether a nutritional supplement in addition to vitamin A will slow the course of retinitis pigmentosa.

Retinitis pigmentosa (RP) is a group of inherited retinal degenerations with a worldwide prevalence of approximately 1 in 4,000. Patients typically report night blindness and difficulty with midperipheral visual field in adolescence. As the condition progresses, they lose far peripheral visual field. Most patients have reductions in central vision by age 50 to 80 years. Based on electroretinograms (ERGs), the course of the disease can be slowed on average among adults on 15,000 IU/day of vitamin A palmitate. While conducting the trial on the effects of vitamin A on RP, it became apparent that another substance in the diet could be affecting the course of the disease. This prompted the present randomized, controlled trial.

This study is a randomized, controlled, double-masked trial with a planned duration of 5 years. Patients with the common forms of RP are assigned to either a test or a control group. All receive 15,000 IU/day of vitamin A palmitate in addition to the capsules under study. Participants will not know the contents of the supplement or the group to which they have been assigned until the end of the trial. The main outcome measurement is the total point score on the Humphrey Field Analyzer (HFA). In addition, computer-averaged 30-Hz cone ERG amplitudes and visual acuity are measured annually.

Eligible patients must be between the ages of 18 and 56, be able to see the entire face of someone sitting across the table from them without scanning, read newspaper-size print without special magnifying aids, and walk unaided in daylight. In addition, participants must have a normal fasting serum vitamin A and normal liver function profile, be in good general health, and reside in the United States. Women who are pregnant or planning to become pregnant cannot be included because of the risk of birth defects that could occur while they are on a vitamin A supplement.

No longer recruiting. Comments: Recruitment began in May 1996 and was completed in September 1997.

Completed, with results published. Comments: Completed.

Docosahexaenoic acid (DHA) supplementation at a dose of 1200 milligrams per day for four years did not, on average, slow the course of retinitis pigmentosa (RP) in adult RP patients already taking vitamin A supplements (vitamin A palmitate 15,000 IU/day), an established treatment for RP.