Incidence and progression of cortical and posterior subcapsular opacities - The longitudinal study of cataract

Objective: The purpose of the study is to estimate incidence and progression rates of cortical and posterior subcapsular (PSC) opacities in the Longitudinal Study of Cataract (LSC). Design: An epidemiologic study of the natural history of lens opacities in a clinic-based population. Participants: The LSC was based on 764 participants in an earlier case-control study of lens opacities. Main Outcome Measures: Baseline data, collected until 1988, included color slit and retroillumination photographs. The same data were collected at follow-up visits from 1989 to 1993. The Lens Opacities Classification System III (LOCS III) was used to assess lens changes between baseline and follow-up photographs. 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 rate 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 opacities was much higher, and reached 55.1% after 5 years of follow-up, The incidence of newly developed cortical or PSC opacities increased with age. The incidence of PSC opacities also increased when coexisting opacities were present at baseline. Conclusions: After 5 years, 1 in every 13 patients developed new cortical opacities, and 1 in 24 developed new PSC opacities. The 5-year progression rates for cortical and PSC opacities were much higher than the incidence rates. These results can be used to estimate the rate of cortical and PSC changes in similar populations.