Six-year incidence of visually significant age-related cataract: The Chennai eye disease incidence study

Background: The aim of this study is to report the 6-year incidence of age-related cataract in a population-based study. Design: The design used is a population-based cohort study. Participants: A cohort of 2484 phakic subjects, aged 40years and above at baseline, from a south Indian population was included in the study. Methods: Bilateral phakics with visual acuity of 6/12 or better and cataract less than N2, C2 and P2 on the Lens Opacities Classification System II at baseline were included. Subjects with glaucoma and corneal or retinal diseases were excluded. Incident visually significant cataract was defined as visual acuity of less than 6/18 with a corresponding one grade or greater change in Lens Opacities Classification System II or history of having undergone cataract surgery with evidence of pseudophakia or aphakia at the 6-year follow-up. Main Outcome Measures: Six-year incidence of visually significant cataract and associated risk factors data were collected. Results: Incident visually significant cataract at 6years was seen in 158 subjects (6.36%, 95% CI: 5.40-7.32, phakics:pseudophakics/aphakics 70:88). Incidence was higher in the rural cohort as compared with the urban cohort (P<0.001). Incidence increased with age and was highest in the ≥70years age group (odds ratio (OR):31.23, 95% CI: 15.20-64.16, P<0.001). Other associated risk factors included illiteracy (OR 1.75, 95% CI: 1.17-2.61, P=0.007) and smoking (OR 1.77, 95% CI: 1.08-2.88, P=0.02). Conclusions: A significant proportion of the population developed visually significant age-related cataract at 6years. Incident visually significant cataract was significantly greater for the rural cohort between 50 and 69 years old.