Basic research studies suggest that oxidative mechanisms may play an important role in the pathogenesis of cataract and age-related macular degeneration, the two most important causes of visual impairment in older adults. These findings raise the possibility that vitamins and trace minerals with antioxidant properties can be of benefit in preventing the onset or progression of disabling eye disease. Results from observational epidemiological studies in humans, however, are inconclusive. Although findings from several studies, primarily cross-sectional and case-control, are generally compatible with a possible protective role for micronutrients in disease development, the data for specific nutrients or specific disease types are inconsistent. The imprecision of dietary exposure data and the likely effects of uncontrolled confounding further limit these observational studies. Well-designed, large-scale, randomized trials are required to evaluate definitively the potentially important benefit of vitamin supplementation in eye disease.