The epidemiology of cataract in Australia.

OBJECTIVE

To describe the prevalence and risk factors for cataract in an Australian 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 visual acuity and best-corrected visual acuity, demographic details, health history, dietary intake of antioxidants, lifetime ocular ultraviolet B exposure, and clinical eye examination, including lens photography. Cortical opacities were measured in sixteenths. Cortical cataract was defined as opacity greater than or equal to 4/16 of pupil circumference. Nuclear opacities were 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 subcapsular opacity greater than or equal to 1 mm2. The worse eye was selected for analysis. Backward stepwise logistic regression was used to quantify independent 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 residents 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 ranged in age from 46 to 101 years (mean, 82 years), and 85 (21%) were men. The 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 risk factors for cortical cataract that remained in the multivariate logistic 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 Victorians aged 40 years and older had nuclear cataract including previous cataract surgery, and 11.6% (95% confidence limits, 8.61%, 14.7%) had nuclear cataract excluding previous cataract surgery. In the urban and rural cohorts, age, female gender, rural residence, brown irides, diabetes diagnosed 5 or more years earlier, myopia, age-related maculopathy, having smoked for greater than 30 years, and an interaction between ocular ultraviolet B exposure and vitamin E were all risk factors for nuclear cataract. The rate of posterior subcapsular cataract excluding previous cataract surgery was 4.08% (95% confidence limits, 3.01%, 5.14%), whereas the overall rate of posterior subcapsular cataract including previous cataract surgery was 4.93% (95% confidence limits, 3.68%, 6.17%) . The independent risk factors for posterior subcapsular cataract in the urban and rural cohorts that remained were age in years, rural location, use of thiazide diuretics, vitamin E intake, and myopia.

CONCLUSIONS

The expected increase in the prevalence of cataract with the aging of the population highlights the need to plan appropriate medical services 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.