This study updates global and regional estimates of causes of moderate and severe vision impairment and blindness through 2020. The Vision Loss Exper Group (VLEG) examined age-adjusted and sex-adjusted differences in the contribution of these causes to vision impairment, with a focus on older age groups. They incorporated studies from an updated systematic review for a total of 376 cause-specific sources.
This update also allowed VLEG to assess the World Health Assembly 2013 Global Action Plan (WHA GAP) target to reduce avoidable vision impairment, which was specifically defined as a reduction in moderate or worse vision impairment from undercorrected refractive error and cataract by 25% between 2010 and 2019.
VLEG found that in adults aged 50 years and older there was no change in the crude prevalence of avoidable vision impairment between 2010 and 2019, and case numbers increased.
Cataract remained the largest contributor to global blindness in adults aged 50 years and older in 2020, with over 15 million individuals, approximately 45% of the 33·6 million cases of global blindness.
Undercorrected refractive error remains the largest contributor to global moderate and severe vision impairment (MSVI) in adults aged 50 years and older, with over 86 million individuals, approximately 42% of the 206 million cases of global MSVI.
Although less easily treatable, glaucoma, diabetic retinopathy, and age-related macular degeneration collectively led to more than 19 million cases of moderate or worse vision impairment in adults aged 50 years and older in 2020, making these diseases important targets for prevention and treatment.
Age-standardised prevalence was higher in women than in men for all modelled causes of moderate or worse vision impairment, with the exception of glaucoma for which age-standardised prevalence was higher in men.
Although the number of affected individuals increased for blindness due to all modelled causes, age-standardised prevalence for all modelled causes of vision except diabetic retinopathy has decreased over the past three decades. This suggests that eye care services did successfully reduce age-standardised prevalence, but they did not meet the growing need due to ageing and growth of the populations.
The Vision Loss Expert Group (VLEG) populates and curates the Global Vision Database, a continuously updated, comprehensive, online database storing worldwide ophthalmic epidemiological information. Learn more about VLEG.