LOCATION AND SEVERITY OF CORTICAL OPACITIES IN DIFFERENT REGIONS OF THE LENS IN AGE-RELATED CATARACT

Purpose. To examine the distribution of cortical opacities across the lens in the Italian-American Natural History Study of Age-Related Cata ract and to study tile association between an index of sunlight exposu re and the location of cortical cataract within the lens. Methods. Len s photographs of one eye of 731 persons with cortical opacities (503 w ith pure and 228 with mixed types of opacity) were included in the ana lysis. A radial grid superimposed on the photographs was used to asses s presence, location, and severity of wedge-shaped cortical opacities. Results. Both the prevalence and the extent of cortical opacities wer e highest in the inferior-nasal quadrant and lowest in the superior-na sal quadrant of the lens. In polychotomous logistic regression, person s with the greatest excess areal involvement in the inferior half of t he lens were more likely to have high exposure to sunlight, as measure d by a sunlight index, than persons with excess involvement in the sup erior half of the lens (odds ratio, 1.73; 95% confidence interval 1.03 , 2.93). Excess areal involvement of the inferior lens also was associ ated with the pure type of cortical cataract and with the total extent of the opacity. Conclusions. Age-related cortical opacities occur mor e frequently inferiorly than superiorly and, to a lesser extent, nasal ly than temporally. Possibly higher exposure of these lens segments to sunlight may explain this preferential location of cortical opacities .