Assessment of cataracts from photographs in the Beaver Dam Eye Study. Presence and severity of age-related cataract was determined in adults 43 to 84 years of age in Beaver Dam, Wisconsin. Duplicate photograph gradings for nuclear sclerosis (n = 1160), cortical opacities (n = 1159), and posterior subcapsular cataract (n = 1137) were performed. There are five levels of nuclear sclerosis. Exact agreement occurred in 64.7% of the cases; agreement within one category in 99.8%. For cortical opacities, graders estimate involved area in nine segments of the lens. When the continuous scale is divided into 12 categories of severity, exact agreement varied between 73.5 and 82.4%; for agreement within one category, rates varied between 84.6 and 89.9%. For posterior subcapsular cataracts, exact agreement for involvement of the central circle occurred in 95.0% and agreement within one category occurred in 97.7%. Intraobserver comparisons disclosed similar concordance. These grading schemes are semiquantitative, reproducible, and can be performed for the large numbers of photographs from population-based studies. 