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www.thelancet.com/lancetgh Vol 9 February 2021
e144
Articles
Lancet Glob Health 2021;
9: e144–60
Published Online
December 1, 2020
https://doi.org/10.1016/
S2214-109X(20)30489-7
See Comment page e100
*Listed at the end of the Article
†Listed online at http://www.
anglia.ac.uk/verigbd
Correspondence to:
Prof Rupert R A Bourne, Vision
and Eye Research Institute,
Anglia Ruskin University,
Cambridge CB1 1PT, UK
rb@rupertbourne.co.uk
Causes of blindness and vision impairment in 2020 and
trends over 30 years, and prevalence of avoidable blindness
in relation to VISION 2020: the Right to Sight: an analysis for
the Global Burden of Disease Study
GBD 2019 Blindness and Vision Impairment Collaborators* on behalf of the Vision Loss Expert Group of the Global Burden of Disease Study†
Summary
Background Many causes of vision impairment can be prevented or treated. With an ageing global population, the
demands for eye health services are increasing. We estimated the prevalence and relative contribution of avoidable
causes of blindness and vision impairment globally from 1990 to 2020. We aimed to compare the results with the
World Health Assembly Global Action Plan (WHA GAP) target of a 25% global reduction from 2010 to 2019 in
avoidable vision impairment, defined as cataract and undercorrected refractive error.
Methods We did a systematic review and meta-analysis of population-based surveys of eye disease from January, 1980,
to October, 2018. We fitted hierarchical models to estimate prevalence (with 95% uncertainty intervals [UIs]) of
moderate and severe vision impairment (MSVI; presenting visual acuity from <6/18 to 3/60) and blindness (<3/60 or
less than 10° visual field around central fixation) by cause, age, region, and year. Because of data sparsity at younger
ages, our analysis focused on adults aged 50 years and older.
Findings Global crude prevalence of avoidable vision impairment and blindness in adults aged 50 years and older did
not change between 2010 and 2019 (percentage change –0·2% [95% UI –1·5 to 1·0]; 2019 prevalence 9·58 cases per
1000 people [95% IU 8·51 to 10·8], 2010 prevalence 96·0 cases per 1000 people [86·0 to 107·0]). Age-standardised
prevalence of avoidable blindness decreased by –15·4% [–16·8 to –14·3], while avoidable MSVI showed no change
(0·5% [–0·8 to 1·6]). However, the number of cases increased for both avoidable blindness (10·8% [8·9 to 12·4]) and
MSVI (31·5% [30·0 to 33·1]). The leading global causes of blindness in those aged 50 years and older in 2020 were
cataract (15·2 million cases [9% IU 12·7–18·0]), followed by glaucoma (3·6 million cases [2·8–4·4]), undercorrected
refractive error (2·3 million cases [1·8–2·8]), age-related macular degeneration (1·8 million cases [1·3–2·4]), and
diabetic retinopathy (0·86 million cases [0·59–1·23]). Leading causes of MSVI were undercorrected refractive
error (86·1 million cases [74·2–101·0]) and cataract (78·8 million cases [67·2–91·4]).
Interpretation Results suggest eye care services contributed to the observed reduction of age-standardised rates of
avoidable blindness but not of MSVI, and that the target in an ageing global population was not reached.
Funding Brien Holden Vision Institute, Fondation Théa, The Fred Hollows Foundation, Bill & Melinda Gates
Foundation, Lions Clubs International Foundation, Sightsavers International, and University of Heidelberg.
Copyright © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.
Introduction
With rising sociodemographic status and life expectancy,
many countries around the world are seeing more people
live into adulthood, increases in the average age of the
population, and a shift in the disease burden towards
non-communicable diseases and disabilities. Most of the
principal causes of vision impairment, including cataract
and undercorrected refractive error,1 are subject to this
epidemiological transition2 and carry significant indi-
vidual and societal costs.3,4 Cataract surgery and the
dispensing of spectacles are among the most cost-
eective health-care interventions currently available.5–7
Addressing these reversible conditions by scaling up
existing health-care systems to provide access to cataract
surgery and spectacles is an important opportunity. To
highlight this need, the WHO and the International
Agency for Prevention of Blindness created an initiative
in 1999 called “Vision 2020: The Right to Sight”. In 2013,
the World Health Asssembly (WHA) launched a new
plan, Towards universal eye health: a global action plan
2014–2019 (GAP).8 It set a global target: to achieve by 2019
a 25% reduction from the baseline of 2010 in prevalence
of “avoidable”8 visual impairment, defined as the
aggregated crude prevalence of cataract and underc-
orrected refractive error (presenting visual acuity <6/18).
Previously, the Vision Loss Expert Group (VLEG)
reported the results of a systematic review of population-
based studies that reported the prevalence of blindness
and vision impairment dating from 1980. These studies
were compiled in a continuously updated database
Articles
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www.thelancet.com/lancetgh Vol 9 February 2021
called the Global Vision Database.1,9 WHO used these
estimates as the basis for their 2019 world report on
vision, which focused on people-centred eye care as a
means for health system strengthening,10 and cause-
specific data by region for 2015 were made available
online.
Since then, the VLEG has conducted a major update of
the Global Vision Database in collaboration with
researchers from the Global Burden of Diseases,
Injuries, and Risk Factors Study (GBD study). Updated
estimates are of particular interest because of recent
rapid socioeconomic development, for example in China
and south Asia. Additionally, the progressive emergence
of causes of vision impairment such as myopic macular
degeneration (particularly in China11,12) and diabetic
retinopathy as significant contributors to the vision
impair ment burden warrants a global update. With
ageing populations, it was anticipated that two other
conditions, glaucoma13 and age-related macular degen-
era tion,14 would continue to be major causes of vision
impairment. We now have more detailed and repre-
sentative data sources from surveys of eye disease,
bolstering our ability to track changes over time in
cataract, undercorrected refractive error, macular
degeneration, diabetic retinopathy, and glaucoma.
We report global and regional estimates of the burden
of moderate and severe vision impairment (MSVI) and
blindness due to cataract, undercorrected refractive
error, glaucoma, age-related macular degeneration, and
diabetic retinopathy. We examined temporal, sex, and
age trends, with a focus on older age groups. We also
assessed progress against the WHA GAP target of
25% reduction in avoidable vision impairment between
2010 and 2019.
Methods
Estimates described here were produced in compliance
with the Guidelines for Accurate and Transparent Health
Estimates Reporting.15
Input data
Preparation of data included first a systematic review of
published population-based studies of vision impairment
and blindness by the VLEG, that also included grey
literature sources. Eligible studies from this review were
then combined with data from Rapid Assessment of
Research in context
Evidence before this study
The growing and ageing of populations have led to increasing
numbers of individuals with moderate or worse vision
impairment globally. These trends triggered WHO and the
International Agency for the Prevention of Blindness to create
an initiative in 1999 called “Vision 2020: The Right to Sight”.
This initiative set a goal to eliminate avoidable blindness.
Previous publications by the Vision Loss Expert Group, and by
the Global Burden of Diseases, Injuries, and Risk Factors Study
demonstrated that, in 2015, cataract and undercorrected
refractive error were responsible for the majority of moderate
or worse vision impairment, and case numbers continued to
rise over time.
Added value of this study
This study updates global and regional estimates of causes of
moderate and severe vision impairment and blindness
through 2020. We examined age-adjusted and sex-adjusted
differences in the contribution of these causes to vision
impairment, with a focus on older age groups. We
incorporated studies from an updated systematic review for a
total of 376 cause-specific sources. Rapid Assessment of
Avoidable Blindness studies—key sources of vision loss data
from low-income and middle-income settings—were
disaggregated from prevalence for ages 50–99 years into
5-year age groups, providing more accurate data on age
patterns. This update also allowed us 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.
Implications of all the available evidence
We 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.
For the cause-specific data by
region see http://atlas.iapb.org
For the Global Vision Database
see https://www.
globalvisiondata.org/
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Avoidable Blindness (RAAB) studies by VLEG and finally
data from the US National Health and Nutrition
Examination survey and the WHO Study on Global
Ageing and Adult Health were contributed by the GBD
team. These stages are explained in more detail as
follows. We included population-representative studies
as data sources for cause-specific vision impairment
modelling, primarily national and subnational cross-
sectional surveys. RAAB surveys, which sample
individuals aged 50 years and older, were major sources
of data for low-income and middle-income settings.
The VLEG has systematically reviewed scientific
literature published between 1980 and 2018 by com-
missioning the York Health Economics Consortium, UK,
to search Embase, SciELO, MEDLINE, WHOLIS, and
Open Grey, and additional grey literature sources. After
title and abstract screening, abstracts were sent to
regional committees of VLEG members to assess quality
and make final inclusion decisions on whether to admit
data to VLEG’s Global Vision Database. Additionally,
the VLEG commissioned the preparation of 5-year age-
disaggregated RAAB data from the RAAB repository.
To meet inclusion criteria, visual acuity data had to be
measured using a vision chart that could be mapped to
the Snellen scale; studies based on self-report of vision
impairment were excluded. We included studies that
measured either presenting vision impairment (where
visual acuity was measured using the usual corrective
lenses a person arrived wearing), or best-corrected vision
impairment (where a pinhole or lenses with power based
on refraction were used to address any refractive error),
or both. We applied WHO criteria for vision impairment
severity, categorising people according to vision in the
better-seeing eye on presentation. The categories were
moderate vision impairment (defined as visual acuity
of ≥6/60 and <6/18), severe vision impairment (visual
acuity of ≥3/60 and <6/60), and blindness (visual acuity
of <3/60 or <10° visual field around central fixation,
although the visual field definition is rarely utilised in
population-based eye surveys). We report a composite
term of MSVI that comprises people meeting either
moderate or severe visual acuity definitions. We also
report a composite term of moderate or worse vision
impairment that comprises people meeting moderate,
severe, or blind visual acuity definitions.
Data preparation
The separation of raw data into datasets, including total
all-cause moderate vision impairment, severe vision
impairment, and blindness, has been explained in detail
elsewhere, in addition to a full list of the data sources.16
Cause-specific analyses are described below.
Presenting vision impairment was the reference
definition for each level of severity. Undercorrected
refractive error data were extracted directly from data
sources where available, and otherwise calculated by
subtracting best-corrected vision impairment from
presenting vision impairment prevalence for each level
of severity in studies that reported both measures for a
given location, sex, age group, and year. All other causes
were quantified as part of the best-corrected estimates of
vision impairment at each level of severity.
We modelled distance vision impairment and blindness
due to the following causes: cataract, undercorrected
refractive error, age-related macular degeneration, myopic
macular degeneration, glaucoma, diabetic retinopathy,
and other causes of vision impairment (in aggregate).
Minimum age for inclusion of data for these causes was
set at 20 years for cataract and diabetic retinopathy; and
45 years for glaucoma and age-related macular degener-
ation. Other vision impairment estimates were combined
with less prevalent causes of vision impairment to
create a residual category (eg, retinopathy of prematurity,
vitamin A deficiency, trachoma). Trachoma data were
extracted as a proportion, in which the numerator was
total cases of trachoma, and the denominator was total
cases of vision impairment at a given severity level.
Geographic restrictions were applied so that zero
prevalence was imputed for non-endemic locations.
Data collected using RAAB methodology were adjusted
to comprehensive surveys (reference definition) using
the same adjustment factors as for all-cause MSVI and
blindness (described in a sister paper on all-cause vision
loss).16 This approach was used because there were many
more data available for all-cause moderate vision
impairment, severe vision impairment, and blindness
than for each specific cause, allowing for more data-rich
models.
Disease modelling meta-regression 2.1 modelling
We produced location, year, age, and sex-specific esti-
mates of MSVI and blindness using Disease Modelling
Meta-Regression (Dismod-MR) 2.1, which is described
in detail elsewhere.16–18 Global estimates are first
produced with a mixed eects non-linear model using
all available data to produce a global model fit as well as
fixed and random eects. These outputs are passed to
the GBD super-region level (seven super-regions) as a
prior, and super-region fits are generated using super-
region input data and the global prior. The super-region
outputs are passed to the region level (21 regions), then
to the country level, and finally the subnational level for
21 countries. Final estimates were generated by
aggregation, for which the region final was the sum of
country estimates, etc. To location aggregate (eg, super-
regions or global estimates), we aggregated the most
granular estimates using straightforward summation of
cases, which were then used to compute all-age and
age-standardised rates. For location estimates, we used
draw-level regional estimates of regional case numbers
(“draws” from the 1000 posterior runs of the model) and
summed these to obtain super-region and global case
numbers. We then summarised the draw level estimates
by taking the mean across values. No weighting was
For the RAAB repository see
http://raabdata.info
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used in the global or regional aggregations. For avoidable
vision loss we took draw-level regional estimates of case
numbers for uncorrected refractive error and cataract
and summed these together.
During data processing, we applied data adjustments if
we knew there were potential measurement errors using
a meta-regression tool developed at Institute for Health
Metrics and Evaluation (IHME) called MR-BRT.17 For
example, our reference definition for all-cause vision loss
was presenting visual acuity systematically on the basis
of the results of a regression analysis comparing the
prevalence of the two methods. We similarly adjusted for
studies that used RAAB methodology or non-standard
severity definitions. Our estimation tool (Dismod) made
quantification of between-study heterogeneity—the part
of variance not ascribed to fixed eects or geographical
random eects–and added uncertainty based on that
finding.
Modelling and post-processing steps
Dismod-MR 2.1 models were run for all vision
impairment by severity (moderate, severe, blindness)
regardless of cause and, separately, for MSVI and
blindness due to each modelled cause of vision
impairment (eg, MSVI due to cataract and blindness due
to cataract). Then, models of MSVI due to specific causes
were split into moderate and severe estimates using the
ratio of overall prevalence in the all-cause moderate
presenting vision impairment and severe presenting
vision impairment models. Next, prevalence estimates
for all causes by severity were scaled to the models of
all-cause prevalence by severity. This produced final
estimates by age, sex, year, and location for each
individual cause of vision impairment by severity.
Models were iterated until reaching convergence, and
estimates were calculated with the final 1000 model
runs, or draws. These draws were used to produce mean
estimates and 95% uncertainty intervals (UIs), bounded
by the 25th and 975th values of the ordered 1000 draws.
To assess whether targets of the WHA GAP were
reached in the 2010–19 period, we aggregated estimates
for cataract and undercorrected refractive error to create
the “avoidable vision impairment” category used as a
metric for assessing whether the GAP target was met.
Role of the funding source
The funder of the study had no role in study design, data
collection, data analysis, data interpretation, or writing of
the report. All authors had access to all estimates
presented in the paper, and the corresponding author
had final responsibility for the decision to submit for
publication.
Results
We used 512 data sources to calculate the prevalence of
categories of distance vision impairment. 376 data sources
reported cause-specific data disaggregated to include at
least one of the following: undercorrected refractive error,
cataract, glaucoma, age-related macular degeneration,
myopic macular degeneration, or diabetic retinopathy
(appendix p 7). 230 (61%) of these 376 data sources were
RAABs.16 Many studies incorporated in the 2017 update1
have since submitted more granular levels of disaggregated
data, enabling more precise estimates of the causes of
global vision impairment in 2020 and their temporal
changes. Data sources for blindness and MSVI caused by
myopic macular degeneration were sparse globally with
the majority of sources from China. For this reason, we
reported estimates of myopic macular degeneration solely
for China. Globally, data for children and young adults
were also sparse, as were data for high-income locations.
Because of the data sparsity at younger ages, we focused
our analyses on adults aged 50 years and older.
To assess the success of the WHA GAP to reduce
avoidable vision impair ment, we calculated the change in
avoidable vision impairment over the past decade. Crude
prevalence of all moderate or worse avoidable vision
impairment between 2010 and 2019 in adults aged
Moderate and severe vision impairment Blindness
Crude prevalence Number of cases Age-standardised
prevalence
Crude prevalence Number of cases Age-standardised
prevalence
All causes 1·9% (0·8 to 3·1) 32·0% (30·5 to 33·5) 0·7% (–0·5 to 1·8) –10·0% (–11·2 to –9·1) 16·5% (15·0 to 17·8) –11·4% (–12·3 to –10·6)
Avoidable* (cataract + undercorrected
refractive error)
1·6% (0·4 to 2·8) 31·5% (30·0 to 33·1) 0·5% (–0·8 to 1·6) –14·4% (–15·9 to –13·2) 10·8% (8·9 to 12·4) –15·4% (–16·8 to –14·3)
Cataract 2·9% (1·5 to 4·2) 33·2% (31·4 to 34·9) 1·1% (–0·3 to 2·3) –14·0% (–15·5 to –12·7) 11·4% (9·5 to 13·1) –15·1% (–16·4 to –13·9)
Undercorrected refractive error 0·4% (–1·1 to 1·9) 30·0% (28·1 to 31·9) –0·1% (–1·5 to 1·3) –17·5% (–19·2 to –15·7) 6·9% (4·6 to 9·1) –17·8% (–19·5 to –16·3)
Glaucoma 10·7% (9·2 to 12·3) 43·4% (41·4 to 45·5) 8·0% (6·5 to 9·5) –8·3% (–9·8 to –7·0) 18·7% (16·9 to 20·4) –10·8% (–11·9 to –9·9)
Age-related macular degeneration 7·1% (5·2 to 9·0) 38·7% (36·2 to 41·2) 5·0% (3·2 to 6·7) –9·1% (–11·4 to –7·0) 17·7% (14·8 to 20·4) –11·7% (–13·8 to –9·8)
Diabetic retinopathy 0·8% (–0·9 to 2·6) 30·6% (28·3 to 32·8) –0·4% (–2·1 to 1·2) –6·0% (–8·4 to –3·5) 21·8% (18·7 to 25·0) –6·6% (–9·0 to –4·1)
Residual causes of vision loss 1·8% (0·7 to 3·1) 31·9% (30·4 to 33·5) 0·0% (–0·9 to 1·1) –2·4% (–4·1 to –0·8) 26·4% (24·2 to 28·5) –3·7% (–5·2 to –2·3)
Data in parentheses are 95% uncertainty intervals. Data for all ages are given in the appendix (p 6). Data presented in this table were calculated to assess the success of the World Health Assembly’s global action
plan to reduce avoidable vision impairment. *Classified as “avoidable” in the global action plan.
Table 1: Percentage change in crude prevalence of moderate and severe vision impairment and blindness in adults aged 50 years and older between 2010 and 2019
See Online for appendix
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Cases (thousands) Age-standardised prevalence (per 1000)
2020 Percentage change from
1990 to 2020
2020 Percentage change from
1990 to 2020
Cataract
Global 15 200 (12700 to 18000) 55·7% (51·4 to 59·9) 8·38 (7·04 to 9·93) –31·7% (–33·2 to –30·1)
Central Europe, eastern Europe, and
central Asia
266 (211 to 332) –4·3% (–7·3 to –1·4) 1·88 (1·50 to 2·33) –36·1% (–37·5 to –34·6)
High income 456 (367 to 566) 56·0% (48·2 to 64·6) 0·877 (0·702 to 1·08) –22·6% (–24·2 to –21·3)
Latin America and Caribbean 1010 (826 to 1210) 78·4% (73·2 to 83·7) 7·85 (6·42 to 9·48) –43·8% (–44·7 to –42·7)
North Africa and Middle East 756 (593 to 941) 30·0% (24·9 to 35·4) 9·06 (7·13 to 11·4) –53·7% (–55·3 to –52·0)
South Asia 5910 (4990 to 6970) 51·1% (44·7 to 57·6) 22·3 (18·9 to 26·1) –46·4% (–48·1 to –44·5)
Southeast Asia, east Asia, and Oceania 5540 (4620 to 6590) 67·2% (62·5 to 72·5) 9·72 (8·14 to 11·5) –43·8% (–45·6 to –41·6)
Sub-Saharan Africa 1240 (1030 to 1490) 54·4% (51·3 to 57·7) 14·9 (12·4 to 17·8) –30·5% (–31·7 to –29·2)
Undercorrected refractive error
Global 2290 (1790 to 2800) 54·4% (48·7 to 60·6) 1·22 (0·960 to 1·50) –28·7% (–31·1 to –26·0)
Central Europe, eastern Europe, and
central Asia
16·8 (12·8 to 21·1) 9·0% (5·7 to 12·0) 0·121 (0·0912 to 0·150) –17·0% (–19·2 to –14·6)
High income 46·1 (35·7 to 56·9) 35·1% (29·9 to 40·5) 0·103 (0·079 to 0·128) –23·1% (–24·8 to –21·4)
Latin America and Caribbean 126 (97·5 to 153) 97·3% (91·3 to 103·0) 0·943 (0·731 to 1·14) –31·2% (–32·9 to –29·6)
North Africa and Middle East 84·2 (63·8 to 103) 68·3% (61·5 to 74·7) 0·875 (0·673 to 1·07) –36·1% (–38·5 to –33·9)
South Asia 976 (762 to 1190) 25·8% (19·9 to 32·0) 3·30 (2·59 to 4·00) –52·3% (–54·0 to –50·5)
Southeast Asia, east Asia, and Oceania 933 (728 to 1140) 91·5% (82·8 to 101·5) 1·47 (1·16 to 1·79) –27·9% (–31·0 to –24·3)
Sub-Saharan Africa 111 (84·5 to 136) 91·4% (85·3 to 98·0) 1·14 (0·881 to 1·41) –15·0% (–17·2 to –12·8)
Glaucoma
Global 3600 (2800 to 4410) 61·8% (57·2 to 66·8) 2·04 (1·59 to 2·49) –31·9% (–33·0 to –30·6)
Central Europe, eastern Europe, and
central Asia
178 (139 to 219) 5·5% (1·9 to 9·3) 1·25 (0·972 to 1·53) –31·4% (–32·8 to –30·0)
High income 785 (622 to 964) 60·3% (53·0 to 69·0) 1·41 (1·12 to 1·74) –23·2% (–24·5 to –21·9)
Latin America and Caribbean 334 (256 to 411) 105·5% (98·4 to 113·6) 2·63 (2·01 to 3·23) –36·2% (–37·6 to –34·8)
North Africa and Middle East 463 (354 to 578) 64·8% (57·6 to 72·3) 5·69 (4·37 to 7·10) –40·9% (–43·0 to –39)
South Asia 577 (439 to 726) 75·7% (65·1 to 86·7) 2·26 (1·71 to 2·83) –38·7% (–41·0 to –36·1)
Southeast Asia, east Asia, and Oceania 754 (575 to 957) 52·4% (44·5 to 61·3) 1·34 (1·02 to 1·67) –48·6% (–51·3 to –45·6)
Sub-Saharan Africa 510 (398 to 628) 70·1% (65·1 to 75·2) 6·64 (5·20 to 8·09) –23·5% (–25·5 to –21·5)
Age-related macular degeneration
Global 1840 (1340 to 2420) 69·8% (64·4 to 75·3) 1·03 (0·755 to 1·36) –28·0% (–30·0 to –25·6)
Central Europe, eastern Europe, and
central Asia
62·5 (43·2 to 84·0) 21·8% (17·2 to 27·5) 0·437 (0·305 to 0·587) –16·8% (–18·5 to –14·9)
High income 595 (455 to 768) 48·3% (40·8 to 56·3) 1·08 (0·828 to 1·39) –28·6% (–30·0 to –27·3)
Latin America and Caribbean 71·1 (49·1 to 97·1) 142·1% (131·5 to 152·5) 0·550 (0·379 to 0·747) –21·2% (–23·3 to –18·8)
North Africa and Middle East 194 (136 to 264) 105·1% (95·0 to 115·8) 2·23 (1·55 to 2·99) –23·3% (–26·5 to –20·1)
South Asia 296 (199 to 421) 53·4% (42·4 to 65·4) 1·05 (0·717 to 1·47) –41·0% (–44·1 to –37·5)
Southeast Asia, east Asia, and Oceania 492 (340 to 673) 104·0% (91·8 to 116·5) 0·835 (0·578 to 1·14) –27·3% (–31·3 to –22·9)
Sub-Saharan Africa 130 (91·4 to 178) 78·5% (70·2 to 86·5) 1·50 (1·05 to 2·04) –19·1% (–23·0 to –15·7)
Diabetic retinopathy
Global 861 (592 to 1230) 150·9% (143·3 to 159·0) 0·459 (0·316 to 0·658) 14·9% (11·4 to 18·4)
Central Europe, eastern Europe, and
central Asia
11·9 (7·96 to 17·3) 26·6% (17·8 to 36·4) 0·0842 (0·0565 to 0·121) –6·1% (–11·8 to –0·2)
High income 139 (97·2 to 196) 53·2% (44·2 to 62·2) 0·307 (0·215 to 0·433) –13·7% (–17·6 to –9·7)
Latin America and Caribbean 203 (142 to 283) 130·7% (121·7 to 140·5) 1·50 (1·05 to 2·09) –17·9% (–20·5 to –15·2)
North Africa and Middle East 61·0 (40·1 to 91·8) 169·3% (149·2 to 193·1) 0·621 (0·413 to 0·928) 0·9% (–6·2 to 9·3)
South Asia 152 (101 to 225) 190·7% (162·6 to 222·9) 0·487 (0·330 to 0·708) 17·9% (7·8 to 30·1)
Southeast Asia, east Asia, and Oceania 261 (171 to 387) 286·7% (257·9 to 316·2) 0·406 (0·269 to 0·602) 44·5% (33·1 to 56·3)
Sub-Saharan Africa 33·9 (23·0 to 49·2) 177·4% (162·4 to 192·3) 0·341 (0·234 to 0·498) 25·7% (19·4 to 32·3)
(Table 2 continues on next page)
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50 years and older did not change (percentage change
of –0·2% [95% UI –1·5 to 1·0]); 2019 prevalence 95·8
cases per 1000 people [85·1 to 108·0], 2010 prevalence
96·0 cases per 1000 people [86·0 to 107·]), but it increased
in all ages by 9·1% (7·6 to 10·7). Total cases of moderate
or worse avoidable vision impairment increased in people
aged 50 years and older by 29·2% (27·6 to 30·9) and in all
ages by 20·8% (19·2 to 22·6) for a composite 211 million
cases of moderate or worse vision impairment in 2010 to
254 million cases in 2019. Crude prevalence by cause and
severity in 2020 is given in the appendix (pp 4–5).
Underlying the overall lack of change in crude
prevalence of all moderate or worse avoidable vision
impairment in people aged 50 years and older, avoidable
MSVI showed little change between 2010 and 2019, with
an increase of 1·6% (0·4 to 2·8), whereas avoidable
blindness decreased by –14·4% (–15·9 to –13·2; table 1).
Similarly, age-standardised prevalence of avoidable MSVI
showed no change (0·5% [–0·8 to 1·6]), but blindness
decreased (–15·4% [–16·8 to –14·3]). By contrast, the
number of cases increased markedly for both avoidable
MSVI (31·5% [30·0 to 33·1]) and avoidable blind-
ness (10·8% [8·9 to 12·4]).
We then looked at the contribution of individual causes
to global visual impairment in 2020. Among the global
33·6 million adults aged 50 years and older who were
blind in 202016 the leading causes of blindness (table 2)
were cataract (15·2 million cases [95% UI 12·7–18·0]),
followed by glaucoma (3·6 million cases [2·8–4·4]),
undercorrected refractive error (2·3 million cases
[1·8–2·8]), age-related macular degeneration (1·8 million
cases [1·3–2·4]), and diabetic retinopathy (0·9 million
cases [0·6–1·2]). For the estimated 206 million aged
50 years and older adults with MSVI in 2020,16 the leading
causes of MSVI (table 3) were undercorrected refractive
error (86·1 million cases [74·2–101·0]), followed by
cataract (78·8 million cases [67·2–91·4]), age-related
macular degeneration (6·2 million cases [5·0–7·6]),
glaucoma (4·1 million cases [3·2–5·2]), and diabetic
retinopathy (2·9 million cases [2·1–3·9]).
In terms of relative contribution to age-standardised
prevalence of total blindness in adults aged 50 years and
older (table 4), cataract caused 45·5% (41·7–49·0) of all
global blindness, followed by glaucoma (11·0% [9·3–12·8]),
undercorrected refractive error (6·6% [5·6–7·8]), age-
related macular degenera tion (5·6% [4·3–7·0]) and
diabetic retinopathy (2·5% [1·7–3·7]). The leading
contributor to global age-standardised prevalence of adult
MSVI was under corrected refractive error (table 4; 41·0%
[38·0–44·1]), followed by cataract (38·9% [35·6–42·4]),
age-related macular degeneration (3·0% [2·5–3·5]),
glaucoma (2·1% [1·7–2·5]), and diabetic retinopathy (1·4%
[1·0–1·9]).
Overall, prevalence of vision impairment increased
with age, although the pattern of age-specific prevalence
varied by cause and severity (figure 1). MSVI prevalence
was consistently higher than blindness for all causes,
with the exception of glaucoma and age-related macular
degeneration at the oldest ages. MSVI due to most causes
increased from age 50 years onward, although MSVI due
to undercorrected refractive error increased up to the age
of around 80 years and decreased thereafter.
Of the explicitly modelled causes of global blindness,
cataract was the principal cause of global blindness in all
10-year age groups for ages 50 years and older (figure 2).
The contribution of glaucoma and age-related macular
degeneration were greatest in the oldest age group, while
the contributions of diabetic retinopathy to blindness
decreased with age. For global MSVI, undercorrected
refractive error was the principal contributor in the age
groups 50–59 and 60–69 years, and cataract was the
principal cause in those aged 70 years and older.
We compared age-standardised prevalence between
men and women aged 50 years and older for each
Cases (thousands) Age-standardised prevalence (per 1000)
2020 Percentage change from
1990 to 2020
2020 Percentage change from
1990 to 2020
(Continued from previous page)
Residual causes of vision loss
Global 9840 (8200 to 11500) 69·3% (62·0 to 76·5) 5·33 (4·46 to 6·24) –24·2% (–27·3 to –21·3)
Central Europe, eastern Europe, and
central Asia
647 (545 to 754) 11·7% (8·7 to 14·9) 4·63 (3·92 to 5·38) –22·5% (–23·9 to –21·1)
High-income 551 (461 to 650) 48·5% (43·1 to 54·9) 1·22 (1·03 to 1·44) –16·5% (–18·5 to –14·4)
Latin America and Caribbean 1140 (940 to 1350) 125·2% (117·5 to 133·1) 8·69 (7·16 to 10·3) –25·8% (–27·6 to –24·1)
North Africa and Middle East 788 (631 to 959) 73·7% (65·1 to 82·5) 8·48 (6·79 to 10·4) –35·6% (–38·8 to –32·8)
South Asia 1670 (1370 to 2010) 23·4% (12·1 to 36·5) 5·93 (4·84 to 7·10) –54·2% (–58·5 to –49·7)
Southeast Asia, east Asia, and Oceania 3850 (3230 to 4500) 117·0% (108·1 to 125·6) 6·35 (5·33 to 7·40) –23·0% (–26·2 to –19·8)
Sub-Saharan Africa 1200 (973 to 1440) 54·7% (49·4 to 60·0) 12·9 (10·4 to 15·3) –30·0% (–32·1 to –27·8)
Data in parentheses are 95% uncertainty intervals. Data for all ages are given in the appendix (p 2).
Table 2: Cases and age-standardised prevalence in 2020 for blindness and percentage changes from 1990 to 2020 in adults aged 50 years and older,
by cause of blindness
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cause of vision impairment and found that age-
standardised prevalence of blindness was greater in
women for cataract (dierence between means: 0·19%
[0·16 to 0·24]), undercorrected refractive error (0·006%
[0·003 to 0·01]), age-related macular degeneration
(0·037% [0·028 to 0·047]), and diabetic retinopathy
(0·008% [0·005 to 0·001]), and greater in men for
glaucoma (–0·072 [–0·086 to –0·058]. The same patterns
were found for sex dierences in causes of MSVI (data
not shown).
When looking at geographical trends, in 2020, cataract
was the largest contributor to blindness in adults
aged 50 years and older in all super-regions except for the
high-income super-region, where the largest contributor
was glaucoma (table 4). This was primarily driven
by two regions, western Europe (glaucoma: 32·5%
[27·3 to 37·3] vs cataract: 11·4% [9·4 to 34·9]) and high-
income Asia Pacific (glaucoma: 33·7% [29·4 to 37·7] vs
cataract: 20·5% [17·7 to 23·9]). For MSVI (table 4),
cataract was the leading contributor in western and
Cases (thousands) Age-standardised prevalence (per 1000)
2020 Percentage change from
1990 to 2020
2020 Percentage change from
1990 to 2020
Cataract
Global 78 800 (67200 to 91400) 175·2% (170·9 to 179·5) 43·4 (37·1 to 50·2) 19·2% (17·8 to 20·5)
Central Europe, eastern Europe, and
central Asia
3050 (2490 to 3620) 49·7% (46·2 to 53·0) 21·3 (17·5 to 25·2) 0·4% (–1·1 to 1·9)
High income 7880 (6660 to 9230) 100·2% (94·0 to 106·5) 14·6 (12·2 to 17·1) –1·8% (–2·8 to –0·7)
Latin America and Caribbean 4350 (3650 to 5090) 208·6% (201·8 to 215·7) 33·9 (28·5 to 39·6) –1·2% (–2·4 to 0·14)
North Africa and Middle East 5020 (4230 to 5920) 181·0% (172·6 to 189·6) 58·1 (49·2 to 68·0) 0·6% (–2·1 to 3·6)
South Asia 27200 (23200 to 31800) 180·7% (171·8 to 189·6) 94·6 (81·1 to 109) 1·7% (–0·3 to 3·6)
Southeast Asia, east Asia, and Oceania 26 800 (23000 to 30900) 235·5% (228·3 to 242·7) 47·1 (40·4 to 54·1) 13·5% (11·7 to 15·3)
Sub-Saharan Africa 4440 (3780 to 5160) 150·8% (146·1 to 156·1) 51·4 (44·0 to 59·3) 11·4% (9·7 to 13·4)
Undercorrected refractive error
Global 86 100 (74200 to 101000) 101·8% (98·9 to 104·9) 45·8 (39·6 to 53·7) –6·9% (–8·0 to –5·9)
Central Europe, eastern Europe, and
central Asia
6340 (5400 to 7480) 25·8% (23·2 to 28·3) 45·1 (38·5 to 53·1) –4·4% (–5·5 to –3·3)
High income 8940 (7680 to 10400) 69·6% (66·3 to 72·9) 19·4 (16·7 to 22·5) –4·6% (–5·6 to –3·6)
Latin America and Caribbean 5780 (4950 to 6780) 162·3% (158·5 to 165·8) 42·8 (36·8 to 50·0) –7·7% (–8·8 to –6·6)
North Africa and Middle East 4680 (3960 to 5550) 140·5% (134·2 to 147·2) 47·3 (40·2 to 55·4) –10·7% (–13·2 to –8·0)
South Asia 32 100 (27500 to 37900) 94·1% (89·6 to 99·7) 103 (88·2 to 121) –23·4% (–24·9 to –21·9)
Southeast Asia, east Asia, and Oceania 25 000 (21500 to 29300) 143·7% (138·4 to 148·7) 39·4 (33·9 to 45·6) –8·8% (–10·6 to –7·1)
Sub-Saharan Africa 3210 (2730 to 3800) 131·7% (126·7 to 136·4) 31·6 (27·3 to 37·0) 2·4% (0·6 to 4·1)
Glaucoma
Global 4130 (3240 to 5170) 151·2% (147·2 to 155·3) 2·29 (1·80 to 2·86) 8·3% (6·8 to 9·9)
Central Europe, eastern Europe, and
central Asia
213 (167 to 270) 43·6% (40·0 to 47·6) 1·47 (1·15 to 1·86) –3·0% (–4·7 to –1·4)
High income 596 (467 to 762) 103·2% (95·7 to 111·5) 1·09 (0·853 to 1·39) –0·2% (–1·5 to 1·0)
Latin America and Caribbean 498 (390 to 623) 191·7% (185·2 to 199·2) 3·86 (3·02 to 4·84) –4·7% (–6·1 to –3·1)
North Africa and Middle East 325 (251 to 419) 148·1% (139·1 to 157·7) 3·76 (2·87 to 4·85) –9·7% (–12·8 to –6·5)
South Asia 952 (745 to 1200) 145·2% (136·4 to 154·5) 3·38 (2·66 to 4·21) –12·8% (–15·0 to –10·6)
Southeast Asia, east Asia, and Oceania 1160 (916 to 1450) 251·5% (242·0 to 262·0) 2·01 (1·58 to 2·52) 21·4% (18·3 to 24·8)
Sub-Saharan Africa 391 (306 to 493) 111·9% (107·1 to 116·8) 4·57 (3·61 to 5·69) –4·3% (–6·3 to –2·2)
Age-related macular degeneration
Global 6220 (5030 to 7570) 150·2% (145·9 to 154·8) 3·39 (2·75 to 4·12) 10·6% (8·7 to 12·6)
Central Europe, eastern Europe, and
central Asia
228 (182 to 282) 51·1% (47·8 to 54·3) 1·57 (1·26 to 1·95) 4·8% (3·13 to 6·51)
High income 738 (584 to 917) 76·8% (70·5 to 83·3) 1·39 (1·11 to 1·72) –9·4% (–11·2 to –7·5)
Latin America and Caribbean 333 (269 to 407) 202·2% (193·0 to 212·2) 2·55 (2·07 to 3·13) 1·5% (–1·2 to 4·5)
North Africa and Middle East 493 (390 to 613) 166·0% (156·5 to 175·6) 5·48 (4·36 to 6·77) –0·5% (–4·0 to 2·8)
South Asia 1220 (968 to 1510) 121·4% (112·8 to 130·2) 4·18 (3·36 to 5·11) –20·5% (–23·0 to –18·0)
Southeast Asia, east Asia, and Oceania 2760 (2210 to 3380) 214·6% (204·7 to 224·4) 4·61 (3·73 to 5·61) 13·8% (10·7 to 17·1)
Sub-Saharan Africa 453 (359 to 565) 132·2% (124·6 to 140·3) 4·96 (3·98 to 6·14) 5·6% (2·3 to 9·0)
(Table 3 continues on next page)
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Cases (thousands) Age-standardised prevalence (per 1000)
2020 Percentage change from
1990 to 2020
2020 Percentage change from
1990 to 2020
(Continued from previous page)
Diabetic retinopathy
Global 2950 (2140 to 3950) 129·5% (123·2 to 135·9) 1·59 (1·15 to 2·12) 3·3% (0·4 to 5·8)
Central Europe, eastern Europe, and
central Asia
134 (94·2 to 183) 21·7% (17·3 to 25·9) 0·942 (0·661 to 1·28) –11·3% (–13·9 to –8·7)
High income 386 (277 to 522) 68·4% (63·5 to 74·1) 0·802 (0·578 to 1·08) –7·7% (–9·7 to –6·0)
Latin America and Caribbean 396 (290 to 533) 185·6% (177·6 to 193·6) 2·97 (2·17 to 4·01) –0·9% (–3·1 to 1·4)
North Africa and Middle East 399 (288 to 540) 115·9% (106·3 to 125·6) 4·14 (3·00 to 5·53) –19·6% (–23·2