RESUMO
PURPOSE: Activity limitations, which induce loss of autonomy in the elderly, are a major public health problem. We investigated the associations between objectively determined visual impairments and activity limitations and assessed the visual acuity thresholds associated with these restrictions. METHODS: The study sample consisted of 1887 people aged 63 years and over from a population-based cohort. Moderate to severe visual impairment was defined as presenting visual acuity lower than 20/70, according to the World Health Organization (WHO) definition. In addition, we studied mild visual impairment, defined as visual acuity [20/70-20/40]. Multivariate logistic regressions were used to estimate the associations between vision and instrumental activities of daily living (IADL) limitations. Using receiver-operating characteristic (ROC) curves, we identified visual acuity thresholds that maximized the Youden index ([sensitivity + specificity]-1) for predicting IADL limitations. RESULTS: After adjustment for potential confounders, moderate to severe visual impairment and mild visual impairment were strongly associated with IADL limitations (odds ratio [OR] = 3.49; 95% confidence interval [CI] = 1.93, 6.32 and OR = 1.77; 95% CI = 1.07, 2.91, respectively). Visual acuity was a strong predictor of IADL limitations, with an area under the ROC curve of 0.72 (95% CI = 0.68, 0.76). The best discrimination between subjects with or without IADL limitations (global, physical and cognitive) was obtained for visual acuities around 20/40-20/50. CONCLUSION: This study confirms major increased risk for IADL limitations in subjects with moderate to severe visual impairment. In addition, it suggests that milder visual impairments (in particular below 20/40) may also be related to an increased risk for IADL limitations and should be considered for early medical intervention, before the decline of the subject autonomy.