The Sri Lanka National Blindness, Visual Impairment and Disability Survey: rationale, objectives and detailed methodology

Abstract

Introduction Population-based data on visual impairment are required to estimate the need for services, evaluate service delivery and identify priorities that need to be addressed, as recommended in the World Health Organisation (WHO) Global Action Plan for Universal Eye Health. In the absence of national data for Sri Lanka, a nationwide survey was initiated. Objectives Determine the prevalence, distribution, magnitude and causes of blindness, visual impairment amongst adults aged ≥40 years in Sri Lanka; and to determine risk factors for blindness and visual impairment, and disability from the major causes. Methods The survey recruited a nationally representative sample of adults aged ≥40 years using proportionate-to-population size methods and ≥ 18 years to estimate the prevalence of disability. All nine provinces and 25 districts of the country were included. 100 participants aged ≥40 years were enumerated in each of the randomly selected 68 clusters, giving a sample of 6800 persons. An examination site was set up in each cluster with space for interviews, anthropometry and clinical examination. Results Fieldwork took place over a year from 2013 to 2014. Written informed consent was obtained before the examination. Overall response rate was 86.1%. Companion articles in this issue highlight the prevalence and causes of blindness, visual impairment and disability and the role of socio-demographic factors in the prevalence estimates. Conclusions The findings from the survey can be extrapolated to the entire country as the sample was representative of the demographic characteristics of Sri Lanka. Data provides sufficient evidence for program planners to identify priority regions for specific interventions to reduce the prevalence of blindness, visual impairment and disability.