An estimated 253 million people live with vision impairment: 36 million are blind and 217 million have moderate to severe vision impairment.
Globally, chronic eye diseases are the main cause of vision loss. Uncorrected refractive errors and then un-operated cataract are the top two causes of vision impairment. Un-operated cataract remains the leading cause of blindness in low- and middle-income countries.
Vision function is classified in 4 broad categories, according to the International Classification of Diseases -10: normal vision, moderate vision impairment, severe vision impairment and blindness.
Moderate vision impairment combined with severe vision impairment are grouped under the term "low vision": low vision taken together with blindness represents all vision impairment.
According to recent estimates, the major global causes of moderate to severe vision impairment are: uncorrected refractive errors 53 per cent, un-operated cataract 25 per cent, age-related macular degeneration 4 per cent, glaucoma 2 per cent and diabetic retinopathy 1 percent.
The major causes of blindness are: un-operated cataract 35 per cent, uncorrected refractive error 21 per cent and glaucoma 8 per cent.
81 percent of all people who are blind or have moderate to severe vision impairment are aged 50 years and above. With an increasing population of older people, more people will be at risk of vision impairment due to chronic eye diseases.
An estimated 19 million children are vision impaired. Of these, 12 million children have a vision impairment due to refractive error. Around 1.4 million have irreversible blindness, requiring access to vision rehabilitation services to optimize functioning and reduce disability.
Overall, the prevalence of vision impairment worldwide has decreased since early estimates in the 1990s. This decrease is associated with: overall socioeconomic development; concerted public health action; increased availability of eye care services and awareness of the general population about solutions to the problems related to vision impairment (surgery, refraction devices, etc.).
However it is estimated that the number of people with vision impairment could triple due to population growth and ageing. For example, by 2050 there could be 115 million people who are blind, up from 38.5 million in 2020 .