MONDAY, Sept. 13, 2004 (HealthDayNews) -- A combination treatment of vitamin A and the omega-3 fatty acid DHA (docosahexaenoic acid) do not slow the progression of retinitis pigmentosa.
The bad news comes in two articles in the latest issue of the Archives of Ophthalmology.
Rentinitis pigmentosa is a progressive eye disease that can cause vision loss. It affects about one in 4,000 people worldwide. Previous studies had found that taking vitamin A slows the decline in retinal function and vision loss.
Harvard Medical School researchers tracked 221 people with retinitis pigmentosa, aged 18 to 55, for four years. Some took 1,200 milligrams per day of DHA and others took a placebo. All the patients took 15,000 international units per day of vitamin A, according to the researchers.
The study found that, at four years, progression of the eye disease hadn't slowed in any of the patients.
In a separate analysis, the researchers did find an impact on patients who were not taking vitamin A before the study.
"Among patients not taking vitamin A prior to entry, those in the DHA+A group (30 patients) had a slower decline in (vision loss) than those in the control +A group (35 patients) over the first two years; these differences were not observed in years three and four of follow-up or among patients taking vitamin A prior to entry," the study authors wrote.
The study findings support "a previous recommendation that most adults with the typical forms of retinitis pigmentosa should continue to take 15,000 IU/d of vitamin A palmitate under medical supervision to slow the course of their condition," the authors concluded.
The U.S. National Library of Medicine has more about retinitis pigmentosa.