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Omega-3s & Vitamin A Help Preserve Vision in Retinitis Pigmentosa

Omega-3s, Vitamin A & Retinitis Pigmentosa

Retinitis pigmentosa is a group of inherited disorders affecting about 2 million people worldwide. Research suggests that the course of this condition may respond to nutrient intervention.

Three clinical trials conducted by a Harvard research team between 1984 and 2008, provided evidence that vitamin A supplementation (15,000 IU daily) alone or combined with an omega-3 rich diet could slow rate of decline in retinal function. In these trials, each lasting 4-6 years, a slower rate of decline was observed for electroretinograms (ERGs) or visual field. No significant slowing in decline of distance or retinal acuity was reported. However, Visual acuity usually declines very slowly in retinitis pigmentosa patients.

Eligibility criteria for the three trials were comparable, and test methods were the same for measuring acuity and estimating omega-3 intake. This enabled the team to combine data from all three trials to increase the statistical power and clarify whether dietary omega-3 had any effect on acuity over a 4-6 year period.

Methods

Dietary intake was calculated from questionnaires completed annually by 357 adult retinitis pigmentosa patients from the three randomized trials who were all receiving 15,000 IU vitamin A daily for 4 to 6 years. Rates of visual acuity decline were compared between those with high (> 200 mg omega-3 fatty acids/day) versus low (> 200 mg daily) intake of omega-3. The analyses took age of the participants into account.

Some patients were excluded from the ERG analyses primarily because their initial values were too low. Thus, the annual rate of decline of 163 patients with high omega-3 intake was compared with the rate of decline of 103 patients with low intake.

Results

Mean annual rates of acuity decline were slower among those with higher omega-3 intake. Mean rates of change in distance acuity (ETDRS) were -0.59 letter per year amongst the high intake group compared with -1.00 letter in the low intake group (p = .001). For retinal acuity (Snellen), a 1.5% decline per year versus a 2% yearly decline was seen with high vs. low consumers, respectively (p = .03). There was no effect of age on either distance or retinal acuity decline.

Comment

This appears to be the first report of omega-3 intake slowing, though modestly, the yearly rate of visual acuity decline in retinitis pigmentosa.

DHA / vitamin A interactions may account for the observed benefits of this combination. It’s thought rods give cones vitamin A via Muller cells, and DHA is required for releasing vitamin A from the protein (IRBP) that transports it between Muller cells. Further, rod degeneration can lead to shortages of both nutrients.

No significant difference in annual rates of decline for full-field cone ERGs was detected. Since this measure is generated predominately by mid- and far peripheral cones, this observation suggests that omega-3 benefit is limited to acuity and central field preservation.

Based on their findings, the authors estimate that the combined vitamin A and omega-3 rich diet would result in an additional 18 years of vision if the nutritional intervention begins at age 37, the average age of the participants in the combined trials.

Reference: Berson EL, et al. Omega-3 intake and visual acuity in patients with retinitis pigmentosa receiving vitamin A. Arch Ophthalmol, Published online ahead of print Feb 13, 2012.