Most vision loss in the world is avoidable: preventable or treatable with cost-effective interventions, chiefly cataract surgery and spectacles
About 90% of people with vision impairment live in low- and middle-income countries (Lancet Global Health Commission on Global Eye Health, 2021)

## Definitions: ICD-11

Vision impairment is graded by the visual acuity in the better eye. Global surveys use presenting acuity (with any correction the person already wears), so uncorrected refractive error counts as a cause

Category	Presenting distance acuity, better eye
0: No vision impairment	6/12 or better
1: Mild	Worse than 6/12, down to 6/18
2: Moderate	Worse than 6/18, down to 6/60
3: Severe	Worse than 6/60, down to 3/60
4: Blindness	Worse than 3/60, down to 1/60 (counting fingers at 1 m)
5: Blindness	Worse than 1/60, down to light perception
6: Blindness	No light perception
Near vision impairment	Worse than N6 (or M0.8) at 40 cm with existing correction

A central visual field of less than 10° radius around fixation in the better eye also counts as blindness, whatever the acuity
Moderate and severe vision impairment (MSVI) = categories 2 and 3, worse than 6/18 down to 3/60. Blindness = worse than 3/60

## How many people? (GBD/VLEG estimates for 2020)

Category	2020	Projected 2050
Blind	43.3 million	61 million
Moderate and severe vision impairment	295 million	474 million
Mild vision impairment	258 million	360 million
Near vision impairment from uncorrected presbyopia	510 million	866 million
Total	About 1.1 billion	About 1.8 billion

Source: GBD 2019 Blindness and Vision Impairment Collaborators and the Vision Loss Expert Group (VLEG), Lancet Global Health, 2021
From 1990 to 2020, the age-standardised prevalence of blindness in adults aged 50 and over fell by 28.5%, but the number of blind people rose by 50.6%, and those with MSVI by 91.7%. Population growth and ageing outpace the gains
The WHO World Report on Vision (2019) gives a broader figure: at least 2.2 billion people have a near or distance vision impairment, of whom at least 1 billion have one that was preventable or has not been addressed
About 55% of people who are blind or visually impaired are women (VLEG, 2021), reflecting longer life expectancy and, in many places, poorer access to cataract surgery
Distance vision impairment is about four times more prevalent in low- and middle-income regions than in high-income regions (WHO fact sheet, 2026)

## Causes (adults aged 50 and over, 2020)

Rank	Blindness	Moderate and severe vision impairment
1	Cataract: 15.2 million	Undercorrected refractive error: 86.1 million
2	Glaucoma: 3.6 million	Cataract: 78.8 million
3	Undercorrected refractive error: 2.3 million
4	Age-related macular degeneration: 1.8 million
5	Diabetic retinopathy: 0.86 million

Source: GBD 2019 Blindness and Vision Impairment Collaborators (VLEG), Lancet Global Health, 2021
The pattern varies by region. In low-income regions (e.g. South Asia and sub-Saharan Africa) cataract and refractive error dominate, with infectious causes still present. In high-income regions, where cataract services are accessible, AMD, glaucoma and diabetic retinopathy make up a larger share
The burden of the chronic, non-communicable causes (glaucoma, diabetic retinopathy, AMD) is growing with ageing and the global rise of diabetes

Cataract: the leading cause of blindness. Undercorrected refractive error: the leading cause of MSVI. Glaucoma: the leading cause of irreversible blindness
Absolute numbers rise even as age-standardised prevalence falls

## Infectious and nutritional causes

Trachoma: Chlamydia trachomatis (serovars A–C), spread by contact and flies. Repeated infection causes scarring, trichiasis and corneal opacity

About 1.9 million people are blind or visually impaired from trachoma, and 92 million live in endemic areas (WHO, 2026)
Controlled by the SAFE strategy: Surgery for trichiasis, Antibiotics (mass azithromycin), Facial cleanliness, Environmental improvement (water and sanitation)
33 countries had been validated by WHO as having eliminated trachoma as a public health problem by September 2026

Onchocerciasis (river blindness): Onchocerca volvulus, transmitted by Simulium blackflies near fast-flowing rivers, mainly in sub-Saharan Africa. Controlled by community-directed mass treatment with ivermectin
Vitamin A deficiency (xerophthalmia): night blindness, Bitot's spots, corneal xerosis and keratomalacia in young children, often precipitated by measles. Prevented by vitamin A supplementation and measles vaccination

## Childhood blindness

Fewer children than adults are blind, but each child lives with blindness for many more years
Causes vary with national income:

Low-income: corneal scarring (vitamin A deficiency, measles, harmful traditional remedies), cataract
Middle-income: retinopathy of prematurity, as neonatal care improves survival of preterm babies without adequate oxygen monitoring and screening
High-income: cerebral visual impairment, optic nerve disease and inherited retinal disease

## Global initiatives

VISION 2020: The Right to Sight was launched in 1999 by WHO and the International Agency for the Prevention of Blindness (IAPB) to eliminate avoidable blindness by 2020. It focused on disease control, human resources and infrastructure
The WHO Universal Eye Health: Global Action Plan 2014–2019 set a target of a 25% reduction in the prevalence of avoidable vision impairment from the 2010 baseline by 2019

It was not met: the age-standardised prevalence of avoidable blindness fell by about 15%, and avoidable MSVI did not change (VLEG, 2021)

The World Report on Vision (2019) called for integrated people-centred eye care (IPEC), built into primary health care and universal health coverage
The 74th World Health Assembly (2021) endorsed two global targets for 2030:

Effective refractive error coverage (eREC): an increase of 40 percentage points
Effective cataract surgical coverage (eCSC): an increase of 30 percentage points
"Effective" means the person not only received the service but has a good outcome: presenting acuity of 6/12 or better
eCSC = people who have had cataract surgery with a good outcome ÷ all people who need or have had cataract surgery

## Measuring eye health in populations

Rapid Assessment of Avoidable Blindness (RAAB): a standardised population survey of people aged 50 and over, where most blindness occurs

Two-stage cluster random sampling, with about 50 people examined per cluster
Measures the prevalence and causes of vision impairment, cataract surgical coverage, eREC and eCSC, surgical outcomes and the barriers to using services

Cataract surgical rate (CSR): cataract operations per million population per year, a measure of service output
Cataract surgical coverage (CSC): the proportion of people with operable cataract who have had surgery, a measure of access

Vision impairment is estimated to cost about US$411 billion a year in lost productivity worldwide (WHO fact sheet, 2026)
Common barriers to cataract surgery: cost, distance, fear, lack of awareness and lack of an escort. Poor surgical outcomes in a community also deter others

Sources: GBD 2019 Blindness and Vision Impairment Collaborators / Vision Loss Expert Group, Lancet Global Health 2021 (two papers: trends in prevalence, and causes); Burton et al., Lancet Global Health Commission on Global Eye Health, 2021; WHO World Report on Vision, 2019; WHO fact sheets on vision impairment (February 2026) and trachoma (September 2026); WHA74 2030 eye care targets, 2021; WHO Universal Eye Health Global Action Plan 2014–2019; ICD-11 9D90