Distribution of Cataract Types in the Italian-American Case-control Study and at Surgery in the Parma Area

Purpose: To compare the distribution of cataract types at surgery with the distribution detected in an ophthalmology clinic-based case-control study in the same geographic area (Parma, Italy). Methods: The distribution of cataract type assessed according to the Lens Opacities Classification System I in 284 consecutive patients 45 years of age or older, who were admitted for cataract surgery to the Institute of Ophthalmology in Parma during 1994, was compared with the distribution assessed in 1008 participants in the Italian-American case-control study of age-related cataract in the Parma metropolitan area from 1987 to 1989. Results: Analysis of cataract distribution indicates in the surgical group, compared with the case-control population, a significant increase of nuclear (N) and posterior subcapsular (PSC) opacities (any), a reduction of pure forms of cortical and N cataracts, and a marked increase of mixed types of opacities with a simultaneous N and PSC component. Conclusion: Although cortical opacities are probably the most prevalent type of age-related lens change in the general population of Parma metropolitan area, the type of cataract most frequently responsible for the decision of patients to undergo cataract surgery is a mixed type of opacity with an N-PSC component.