Quantifying the impact of disease severity changes on the burden of blindness: A global decomposition analysis.

Background: Despite the significant impact of blindness on the affected individuals' quality of life, its burden has not been assessed according to temporal cause-specific changes in severity, impeding our ability to evaluate the impact of blindness on population health accurately. Therefore, we aimed to comprehensively quantify the changes in cause-specific blindness burden according to changes in disease severity for 18 causes of blindness. Methods: For this cross-sectional population-based study, we derived data on prevalence, disability-adjusted life-years (DALYs), and population size between 1990 and 2019 from the Global Burden of Disease 2019 study. Using the decomposition method, we attributed changes in total DALYs to population growth, population ageing, and changes in prevalence rate and disease severity between 1990 and each subsequent year globally, regionally, nationally, and by sex, cause, and sociodemographic index (SDI). The absolute and relative contributions to the variation in blindness-related DALYs between 1990 and each year from 1991 to 2019 then served as a measure of changes in disease severity. Results: Changes in disease severity from 1990 to 2019 were associated with 15 165.11 DALYs in men and 20 639.32 DALYs in women. We observed disease severity increases in most countries/territories, with attributable DALY proportions ranging from -0.07% to 1.30% in men and from -0.06% to 1.73% in women. Notably, both attributable proportions and DALYs were greater in women than men. The largest increases in attributable DALYs were observed for cataracts, refraction disorders, and glaucoma globally; age-related macular degeneration in high-SDI countries; and trachoma and retinopathy of prematurity in lower-SDI countries. Conclusions: Growth in the burden of cause-specific blindness due to increased disease severity reflects the lag of healthy vision life behind increasing life expectancy, necessitating the implementation of preventive and long-term therapeutic measures focussed on improving visual outcomes.