The Global Burden of Disease Study recently assessed the extent of the global vision loss burden for 2020 and forecasted vision loss up to 2050 as part of the VISION 2020: the Right to Sight Joint WHO and International Agency for the Prevention of Blindness initiative. By examining temporal change from 1990 to 2020, they found that the age-adjusted prevalence of blindness has decreased over the study period, but because of population growth, the progress made hasn’t kept pace with needs.

Here are some of the investigators’ findings for 2020:

• 43.4 million people worldwide were blind (23.9 million, or 55%, female)
• 295 million people experienced moderate and severe vision impairment (163 million, or 55%, female)
• 258 million had mild vision impairment (142 million, or 55%, female)
• 510 million had visual impairment due to uncorrected presbyopia (280 million, or 55%, female)

Globally, the investigators found that between 1990 and 2020, the age-standardized prevalence of blindness among adults aged 50 and older decreased by 28.5% (-29.4 to -27.7) and the prevalence of mild vision impairment decreased slightly (-0.8 to -0.2). On the other hand, the prevalence of moderate and severe vision impairment increased slightly (1.9 to 3.2). “This slight increase is probably due to resources for cataract being directed to more severe disease,” the researchers noted. They added that there was insufficient data to calculate this statistic for vision impairment due to uncorrected presbyopia.

During the three decades in question, the number of people who went blind increased by 50.6% and those with moderate and severe vision impairment increased by 91.7%. The researchers predict that by 2050, 61 million people will be blind, 474 million will have moderate and severe vision impairment, 360 million will have mild vision impairment and 866 million will have uncorrected presbyopia.

“The increase in prevalence is determined by at least two variables: the need and the provision of services,” the researchers wrote. “Factors contributing to the extent of provision of services include the extent of services available (dependent on the availability of limited resources allocated to blindness alleviation vs. other competing priorities), awareness of the population that the services are available, perceived need for services among the population (including assurance of quality) and the extent to which barriers such as cost of travel, fees and fears can be overcome.”

“Sustainability of the efforts put into provision of these services is one of many long-term needs,” they noted. “Although the observed decrease in age-adjusted burden of vision impairment suggests systematic improvements are occurring, more improvements are needed to alleviate the problem of vision impairment to the extent envisioned in the global action plan. These measures would need to address both the supply of services and factors affecting demand for the services.”

“Between 2020 and 2050, the proportion of the world's population aged 65 years or older is expected to double, from approximately one billion to two billion,” they added. “The aging of the world's population will have critical ramifications on age-related diseases, including age-related blindness from cataract, uncorrected refractive error, age-related macular degeneration and glaucoma.”

They said, however, “We should be mindful that although the regions undergoing development with increasing life expectancies face the challenge of age-related vision impairment, the most under-developed and economically disadvantaged regions, particularly sub-Saharan Africa, still have the highest prevalence of blindness in older adults.”

The investigators concluded that this study highlights a large burden of mild, moderate and severe vision impairment that could become overwhelming as the global population increases and ages.