Incidence and progression of cataract in the Melbourne Visual Impairment Project

Purpose: To determine the 5-year incidence and progression of cataract and cataract surgery in the Melbourne Visual Impairment Project. Design Prospective cohort study. Methods: Demographic information including race, sex, age, and education level was collected at baseline. Cortical cataract was defined as 4/16 or greater opacity; progression was defined as a more than 2/16 increase. Nuclear cataract was defined as Wilmer standard grade 2 or higher; progression was defined as more than 0.5 increase. Posterior subcapsular (PSC) cataract was defined as opacity 1 mm² or greater; progression was defined as greater than 1 mm² increase. Results: Of the 3,040 participants eligible to attend follow-up examinations, 2,594 (85% of those eligible) participated. The mean age of participants at follow-up was 62.5 years, and 55% were female. The percentage of patients who had at least one lens extracted over 5 years increased from 0.5% of those aged 40 to 49 years at baseline to 35.7% of those aged 80 years or more at baseline. The overall incidence of the three types of cataract was as follows: cortical 7.7% (95% confidence limits [CL] = 5.8-9.8), nuclear 16.4% (95% CL = 12.1-20.8), and PSC 7% (95% CL = 5.3-8.7). The overall progression of cataract was cortical 14.3% (95% CL = 10.2-18.3), nuclear 19.3% (95% CL = 15.9-22.7), and PSC 20% (95% CL = 8.7-31.1). The incidence and progression rates increased significantly by age, but the rates were not significantly different by sex. Conclusions: These cataract incidence data confirm the public health importance of cataract in Australia. The data also support the need to plan both primary prevention program and adequate surgical services to meet the anticipated increase in demand with the aging population.