Sunlight and cataract: an epidemiologic investigation.

Cataract prevalence data from two large U.S. sources were divided according to small geographic areas for which average annual sunlight hours were determined from a map prepared by the U.S. Weather Bureau. Several non-cataract disease controls were chosen from the same geographic locations (separately for each data set). It was found that the cataract-to-control ratios for persons aged 65 years or older were significantly larger in locations with large amounts of sunlight compared to those in locations with small amounts (P less than .05). Discussion of some possible biases in the data leads to the conclusion that the biases, if they exist, are probably not large. The authors believe, however, that more research should be done before the association between sunshine and cataract is considered established.