Longitudinal changes in cortical and posterior subcapsular opacities

Purpose. To estimate incidence and progression rates of cortical and posterior subcapsular (PSC) opacities in the Longitudinal Study of Cataract, an epidemiologic study of the natural history of lens opacities in a clinic based population. Methods. The LSC followed 764 participants of a case-control study of lens opacities. Baseline data, collected until 1988, included color slit, retroillumination and Scheimpflug photographs. The same data were collected at follow-up visits from 1989 to 1993. The Lens Opacities Classification System III was used to grade the lens photographs and assess lens changes between baseline and follow-up visits. The product-limit method was used to estimate the incidence and progression rates. Results. After 5 years of follow-up, the incidence rates for developing cortical and PSC opacities were 7.7% and 4.3%, respectively. The progression of pre-existing cortical opacities was 16,2% after 5 years and was twice as high as the incidence rate. The progression of pre-existing PSC was much higher and reached 55.1% after 5 years of follow-up. Older age was significantly related to higher incidence of newly developed cortical or PSC opacities The incidence and progression rates of cortical or PSC opacities were not related to the status of co-existing opacities at baseline. Conclusions. This report provides information on incidence and progression of cortical and PSC opacities in an older clinic based population. After 5 years, one in every 13 persons developed new cortical opacities and one in 24 developed new PSC opacities. Almost 85% of participants who had pre-existing cortical opacities had not progressed after 5 years In contrast, over half of those with PSC opacities had worsened after 5 years The five year progression rates for cortical and PSC were much higher than the incidence rates These results can be used to estimate the rate of cortical and PSC cataract changes in similar populations.