Vitamin A and fish oils for preventing the progression of retinitis pigmentosa.

Systematic review of randomized controlled trials in children and adults with ophthalmologist-diagnosed retinitis pigmentosa, including X-linked and other inherited forms. Studies were conducted in the United States and Canada and largely excluded atypical or certain syndromic forms.

This review evaluated oral vitamin A and docosahexaenoic acid (DHA, a fish oil omega-3) regimens for retinitis pigmentosa, usually given in gelatin capsules for 4 years. Trial regimens included vitamin A 15,000 IU/day, DHA 400 mg/day, DHA titrated to 30 mg/kg/day (about 600 to 3600 mg/day), and DHA 1200 mg/day combined with vitamin A 15,000 IU/day, compared with placebo, no DHA, or vitamin A alone.

There is no clear evidence that vitamin A, DHA, or their combination slows progression of retinitis pigmentosa, and the certainty of the evidence is very low. In Berson 1993, cone ERG decline was slower with vitamin A than without vitamin A (8.3% vs 10% per year, P < 0.001; post hoc 6.1% vs 7.1%, P = 0.01), but visual field loss and visual acuity did not clearly improve. In Berson 2004a, DHA plus vitamin A did not outperform vitamin A alone for visual field decline, visual acuity, or ERG decline (for example, HFA total point score 37.95 vs 37.68 dB/year, P = 0.88; ETDRS loss 0.7 letters/year in both groups). Hoffman 2004 also found no clear benefit of DHA versus placebo, while Hoffman 2014 showed some visual field differences favoring DHA in subfields but no consistent improvement in acuity or ERG and no replicated subgroup effect; adverse events were rare, although 27 participants (34.6%) had 42 treatment-related or possibly related events in Hoffman 2014.

The evidence base was very small and of very low certainty, with heterogeneous genetic forms of retinitis pigmentosa and outcomes that were not consistently improved across trials. Some findings were based on subgroup or post hoc analyses, and adverse event reporting was limited in most studies, leaving long-term safety of high-dose vitamin A uncertain.