Introduction There is paucity of data on the epidemiology of visual impairment in Sri Lanka. Objectives Estimate the prevalence and determine causes and risk factors of visual impairment among adults aged ≥40 years in Sri Lanka. Methods Multistage, stratified, cluster random sampling was used to select a nationally representative sample aged ≥40 years. All participants underwent vision testing, autorefraction and a basic eye examination. Participants with a presenting acuity of <6/12 in either eye underwent detailed eye examination, assessment of best-corrected acuity if required, and a cause of visual loss assigned. Results 5,779 of those enumerated (6,713) were examined (response rate 86.1%). The prevalence of blindness was 1.7% (95% confidence interval [CI]: 1.3-1.99%) and low vision was 17% (95% CI: 16.0-18.0%). Cataract (66.7%) and uncorrected refractive errors (12.5%) were the commonest causes of blindness. Uncorrected refractive errors (62.4%) and cataract (24.2%) were the commonest causes of low vision. Blindness was significantly higher in older age groups (OR 132.4: 95% Cl 11.7-149.3), those residing in the North Central (OR-12.5), North (OR-12.0), North West (OR-7.3), Eastern (OR-6.7), Western (OR-5.3) and Uva provinces (OR-5.3) compared to the Southern, and in those educated up to and including secondary school (OR 2.3: 95% CI 1.5- 3.17). Gender and socio-economic status were not significant after adjusting. Conclusions The prevalence of blindness in Sri Lanka is lower than in other South Asian countries and most causes are avoidable. Access to eye care needs to improve amongst the aged, those less educated and those in provinces with higher blindness risk.