Objective: To determine the prevalence of lens opacity among Chinese residents of Singapore.
Design: Population-based, cross-sectional survey.
Participants: Chinese men and women aged 40 years or more in Singapore.
Methods: A stratified, clustered, random sampling method, with more weights given to the older age groups, was used to initially select 2000 Chinese persons aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a comprehensive ocular examination at a centralized clinic, after which nonrespondents were examined in their homes with portable instruments.
Main outcome measures: Lens opacity, as determined clinically at the slit lamp using a modification of the Lens Opacity Classification System III. Prevalence rates were age adjusted to the 1997 Singapore census population.
Results: Of the 1232 persons examined (71.8%), 1206 (70.2%) provided lens data for this analysis. The age-adjusted prevalence of any cataract surgery was 5.1% (95% confidence interval [CI], 3.6, 6.5), with similar rates between men and women. The age-adjusted prevalence of specific types of lens opacity was 22.6% (95% CI, 19.8, 25.4) for any nuclear opacity, 23.9% (95% CI, 21.0, 26.8) for any cortical opacity, and 7.0% (95% CI, 5.3, 8.8) for any posterior subcapsular opacity. The overall age-adjusted prevalence of any cataract or cataract surgery was 34.7% (95% CI, 31.5, 38.0), increasing from 7.0% in those 40 to 49 years and to 94.3% in those 70 years and older (P < 0.001, test for trend for age). When the prevalence of distinct types of lens opacity in an eye was considered, the most common was mixed (age-adjusted prevalence, 11.5%, based on right eye data), followed by nuclear only (9.7%), cortical only (8.3%), and posterior subcapsular only (0.6%). For all cataract types, the prevalence was similar in men and women and was higher in persons examined at their homes than in those examined at the study clinic.
Conclusions: These population-based data suggest that cataract is common among adult Chinese residents in Singapore, despite ready access to cataract surgical services. Persons accepting the offer of free eye examinations were less likely to have cataract than those who did not take up this offer.