The epidemiology of cataract in Australia

PURPOSE: To describe the prevalence and risk factors for cataract in an Aus tralian population aged 40 years and older. METHODS: Participants were recruited by a household census and stratified, random cluster sampling to represent residents of Victoria, Australia, aged 40 years and older. The following information was collected: initial visua l acuity and best-corrected visual acuity, demo graphic details, health his tory, dietary intake of antioxidants, lifetime ocular ultraviolet B exposur e, and clinical eye examination, including lens photography. Cortical opaci ties were measured in sixteenths. Cortical cataract was defined as opacity greater than or equal to 4/16 of pupil circumference. Nuclear opacities wer e graded according to the Wilmer cataract grading scheme, and cataract was defined as greater than or equal to nuclear standard 2.0 of four standards. The height and width of any posterior subcapsular opacity was measured and recorded. Posterior subcapsular cataract was defined as posterior subcapsu lar opacity greater than or equal to 1 mm(2). The worse eye was selected fo r analysis. Backward stepwise logistic regression was used to quantify inde pendent risk factors for cataract. RESULTS: A total of 3,271 (83% of eligible) of the urban residents, 403 (90 % of eligible) nursing home residents, and 1,473 (92% of eligible) rural re sidents participated. The urban residents ranged in age from 40 to 98 years (mean, 59 years), and 1,511 (46%) were men. The nursing home residents ran ged in age from 46 to 101 years (mean, 82 years), and 85 (21%) were men. Th e rural residents ranged in age from 40 to 103 years (mean, 60 years), and 701 (47.5%) were men. The overall weighted rate of cortical cataract was 11 .3% (95% confidence limits, 9.68%, 13.0%) excluding cataract surgery and 12 .1% (95% confidence limits, 10.5%, 13.8%) including cataract surgery. The r isk factors for cortical cataract that remained in the multivariate logisti c regression model were age, female gender, diabetes duration greater than 5 years, gout duration greater than 10 years, arthritis diagnosis, myopia, use of oral beta-blockers, and increased average annual ocular ultraviolet B exposure. Overall, 12.6% (95% confidence limits, 9.61%, 15.7%) of Victori ans aged 40 years and older had nuclear cataract including previous catarac t surgery, and 11.6% (95% confidence limits, 8.61%, 14.7%) had nuclear cata ract excluding previous cataract surgery. In the urban and rural cohorts, a ge, female gender, rural residence, brown irides, diabetes diagnosed 5 or m ore years earlier, myopia, age-related maculopathy, having smoked for great er than 30 years, and an interaction between ocular ultraviolet B exposure and vitamin E were all risk factors for nuclear cataract. The rate of poste rior subcapsular cataract excluding previous cataract surgery was 4.08% (95 % confidence limits, 3.01%, 5.14%), whereas the overall rate of posterior s ubcapsular cataract including previous cataract surgery was 4.93% (95% conf idence limits, 3.68%, 6.17%). The independent risk factors for posterior su bcapsular cataract in the urban and rural cohorts that remained were age in years, rural location, use of thiazide diuretics, vitamin E intake, and my opia. CONCLUSIONS: The expected increase in the prevalence of cataract with the a ging of the population highlights the need to plan appropriate medical serv ices and public health interventions for primary and secondary prevention. Many of the identified risk factors for cataract in the population have the potential for being modified through public health interventions. (Am J Op hthalmol 1999;128:446-465. (C) 1999 by Elsevier Science Inc. All rights res erved.).