Docosahexaenoic acid (DHA) is an omega-3 fatty acid found in high concentrations in the retina, particularly in the photoreceptor outer segments. This anatomical evidence has led to the hypothesis that DHA may play a protective role in retinal health and, by extension, in conditions like age-related macular degeneration (AMD). Several observational studies have suggested a correlation between higher dietary intake of DHA (and other omega-3 fatty acids) and a reduced risk of developing AMD. However, randomized controlled trials have provided mixed results. Notably, the Age-Related Eye Disease Study 2 (AREDS2), a large, well-designed clinical trial, found that supplementation with DHA (and EPA) did not significantly reduce the progression to advanced AMD when added to the original AREDS formulation.

Despite this, some meta-analyses of observational studies indicate a potential modest protective association, but causality has not been conclusively established. Therefore, while the biological plausibility and epidemiological data suggest a possible benefit, the current body of clinical trial evidence does not strongly support DHA supplementation as an effective intervention for AMD. As a result, the scientific justification for using DHA in this context is weak to moderate, and major guidelines do not currently recommend DHA supplementation specifically for the prevention or treatment of macular degeneration.