Global estimates on the number of people blind or visually impaired by cataract: A meta-analysis from 2000 to 2020

Abstract Background To estimate global and regional trends from 2000-2020 of the number of persons visually impaired by cataract and their proportion of the total number of vision-impaired individuals. Methods A systematic review and meta-analysis of published population studies and grey literature from 2000-2020 was carried out to estimate global and regional trends. We developed prevalence estimates based on modelled distance visual impairment and blindness due to cataract, producing location-, year-, age-, and sex-specific estimates of moderate to severe vision impairment (MSVI; presenting visual acuity <6/18,≥3/60) and blindness (presenting visual acuity <3/60). Estimates are age-standardised using the GBD standard population. Results In 2020, among overall (all ages) 43.3 million blind and 295 million with MSVI, 17.0 million (39.6%) people were blind and 83.5 million (28.3%) had MSVI due to cataract; blind 60% female, MSVI 59% female. From 1990-2020, the count of persons blind (MSVI) due to cataract increased by 29.7%(93.1%) whereas the age-standardized global prevalence of cataract-related blindness improved by -27.5% and MSVI increased by 7.2%. The contribution of cataract to the age-standardized prevalence of blindness exceeded the global figure only in South Asia (62.9%) and Southeast Asia and Oceania (47.9%). Conclusions: Vision impairment due to cataract has risen over the past 30 years, despite a decrease in the age-standardized prevalence of cataract. This indicates that cataract treatment programs have been beneficial, but population growth and aging have outpaced their impact. Growing numbers of cataract blind indicate that more, better-directed, resources are needed to increase global capacity for cataract surgery.