Prevalence and the risk factors for visual impairment in age-related macular degeneration

Purpose To characterize the type, and the causes of visual impairment (VI) in various stages of early and late age-related macular degeneration (AMD) and the factors associated with visual impairment in subjects with AMD Methods 6617 subjects >= 60 years were enumerated; 5495 (83.04%) participated in eye examination. Of which, 4791 subjects had gradable fundus images. AMD was graded per International ARM Epidemiological Study Group. Subjects underwent detailed ophthalmic exam. VI was defined per the WHO classification. Mild VI was defined as VA less than 6/12 to 6/18, moderate VI-VA less than 6/18 but up to 6/60, severe VI-VA less than 6/60 but up to 3/60 and legal blindness-VA worse than 3/60. Factors associated with VI in AMD was analyzed with univariate and logistic regression analysis. Results Nine hundred and eighty-eight subjects were identified as having AMD (893 with early AMD and 95 with late AMD); 85% of the subjects (95% CI: 82.7-87.1) had no VI, 13.1% had mild VI (95% CI: 11.1-15.3), 0.8% had severe VI (95% CI: 0.4-1.6), 1.1% had legal blindness (95% CI: 0.6-1.9). Prevalence of any VI was 13.7% in early AMD and 27.4% in late AMD, P= 0.0004; age group 65-70 years (OR= 1.89, 95% CI: 1.16-3.08, P= 0.011), and those >= 75 years (OR= 3.67, 95% CI: 1.956.91, P= 0.0001) had greater odds of VI compared with age group 60-64 years. Male gender was a protective factor for VI (OR= 0.57, CI: 0.36-0.90, P= 0.016). Cataract (31.8%) and refractive error (28.4%) accounted for a majority of the VI. Conclusions Cataract and refractive error account for a significant proportion of VI in the south Indian population with AMD. Early AMD is the third leading cause of VI. Greater age and female gender are associated with VI in subjects with AMD.