Sunlight Exposure and Cataract

To the Editor: There is more and earlier evidence for sunlight exposure as a risk factor for lens opacities or cataract than was cited in the article by Dr West and colleagues.¹ Hiller et al,² in an analysis of the population-based 1971-1972 National Health and Nutrition Examination Survey (NHANES), found an association between lifetime exposure to UV-B radiation in sunlight (estimated from average annual daily UV-B counts at examination sites provided by the US National Oceanic and Atmospheric Administration) and cortical cataract. In the first large-scale case-control study of risk factors for age-related cataract, Mohan et al³ found a significant association between lifetime exposure to sunlight (as estimated from residence-specific records of average cloud cover) and nuclear, cortical, and posterior subcapsular (PSC) lens opacities. Subsequently, other studies, which were to varying degrees less ecological and more refined in individual exposure estimation, have reported similar although not always consistent findings. Methods for assessing lens opacities and ocular exposure to sunlight have become increasingly objective and sophisticated. West et al, applying standardized methods for lens photography and grading together with their state-of-the-art modeling of ocular sunlight exposure, have confirmed with more credibility the emerging consensus that prevalent cortical lens opacity is associated with UV-B. Nuclear opacity and PSC lens opacities showed no association, although this study like most preceding it—Mohan et al³ being a notable exception—is underpowered to address PSC lens opacity, which is relatively rare in population-based studies.