Retinitis pigmentosa, a progressive eye disease targeting the light-collecting cells of the retina, affects one in 4,000 people worldwide and can cause vision loss. Researchers say for patients suffering from retinitis pigmentosa, the addition of docosahexaenoic acid to vitamin A therapy may not provide long-term benefits, according to a recent study.
Researchers followed 221 patients, ranging in age from 18 to 55 years, over four years. All were given 15,000 international units of vitamin A (as retinyl palmitate) along with a placebo or 1,200 milligrams of DHA, an omega-3 fatty acid. But there was no significant difference seen in the progression of the eye disease between those taking vitamin A plus a control and those taking vitamin A plus DHA over four years.
In a separate analysis of the same study, researchers investigated the effect of DHA on patients not already taking vitamin A prior to the study. It was found that patients not taking vitamin A before the study who were part of the vitamin-A-plus-DHA group had a slower decline in vision loss than those in the control group. These effects lasted over the first two years but not into years three and four of follow-up.
Researchers conclude saying that for patients with retinitis pigmentosa beginning vitamin A therapy, addition of DHA, 1,200 milligrams per day, slowed the course of the disease for two years.