Retinitis pigmentosa is a condition that affects about one in 4,000 people, or about 2 million worldwide. The condition typically results in night blindness in adolescence before the loss of side vision in young adulthood, followed by tunnel vision as it worsens and virtual blindness by the time a patient turns 60.
Results of the new study – by researchers at Harvard University – indicates that people with the condition who consume at least 0.2 grams per day of omega-3 fatty acids have a 40% slower average annual rate of decline in distance visual acuity, compared with people with lower intakes.
The slower rate of decline would result in an additional 18 years of vision, they said.
“Vitamin A combined with an omega-3-rich diet (at least 0.20 g/d) should make it possible for many patients with typical retinitis pigmentosa to retain both visual acuity and central visual field for most of their lives,” they said.
In an email to NutraIngredients-USA, Harry Rice, VP of regulatory & scientific affairs for GOED, the omega-3 trade group, said that, until now, there has been no effective treatment for retinitis pigmentosa. "The present results suggest that this has changed.
"While it's significant to note that the combination of vitamin A and the long-chain omega-3s combo can allow the retention of both visual acuity and central visual field for most of one's life, what's really astounding is that the benefit could be upwards of 20 years.
"The potential impact on the quality of life for those afflicted with retinitis pigmentosa is amazing."
The conclusions from the Boston-based scientists are based on analysis of data from three clinical trials conducted involving 357 patients with typical retinitis pigmentosa taking 15,000 IU per day of vitamin A palmitate.
Diets containing at least 0.2 grams per day were associated with a 40% slower decline in distance visual acuity and a nearly 50% slower rate of decline in central visual field sensitivity than people with lower omega-3 intakes also receiving vitamin A.
“Since vitamin A plus an omega-3-rich diet slowed the rate of decline of distance and retinal acuity by about the same extent, we conclude that the benefit of this combination was due to an effect on preserving central retinal function.”
Commenting on the potential interaction between omega-3 and vitamin A, lead researcher Eliot Berson, MD said: “With respect to vitamin A, we and others have suggested that under daylight conditions rods give cones vitamin A via Müller cells. Interphotoreceptor retinoid binding protein (IRBP) transports vitamin A between these cells.
“Release of vitamin A from IRBP requires DHA present in oily fish. Rod degeneration leads to a deficiency of vitamin A and DHA. This could explain why vitamin A plus an oily fish diet benefits patients with retinitis pigmentosa. Patients are advised to take vitamin A to replace their rods and eat oily fish to enhance delivery of vitamin A to cones."
Source: Archives of Ophthalmology
Published online ahead of print, doi:10.1001/archopthalmol.2011.2580
“Omega-3 Intake and Visual Acuity in Patients With Retinitis Pigmentosa Receiving Vitamin A”
Authors: E.L. Berson, B. Rosner, M.A. Sandberg, C. Weigel-DiFranco, W.C. Willet