RESEARCH ARTICLE
Number of People Blind or Visually Impaired
by Glaucoma Worldwide and in World
Regions 1990 – 2010: A Meta-Analysis
Rupert R. A. Bourne
1
*, Hugh R. Taylor
2
, Seth R. Flaxman
3
, Jill Keeffe
4
, Janet Leasher
5
,
Kovin Naidoo
6
, Konrad Pesudovs
7
, Richard A. White
8
, Tien Y. Wong
9
, Serge Resnikoff
10
,
Jost B. Jonas
11
, Vision Loss Expert Group of the Global Burden of Disease Study
¶
1 Vision & Eye Research Unit, Postgraduate Medical Institute, Anglia Ruskin University, Cambridge, United
Kingdom, 2 Melbourne School of Population Health, University of Melbourne, Australia, 3 School of
Computer Science & Heinz College, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of
America, 4 L V Prasad Eye Institute, Hyderabad, India, 5 Nova Southeastern University, Fort Lauderdale,
Florida, United States of America, 6 African Vision Research Institute, University of Kwazulu-Natal, South
Africa & Brien Holden Vision Institute, Sydney, Australia, 7 NHMRC Centre for Clinical Eye Research,
Flinders University, Adelaide, Australia, 8 Department of Genes and Environment, Division of Epidemiology,
Norwegian Institute of Public Health, Oslo, Norway, 9 Singapore Eye Research Institute, Singapore,
Singapore, 10 Brien Holden Vision Institute, Sydney, Australia, 11 Department of Ophthalmology, Medical
Faculty Mannheim, Heidelberg University, Mannheim, Germany
¶ A list of the Vision Loss Expert Group members can be found in the Acknowledgments section and by
accessing this site:
http://www.anglia.ac.uk/ruskin/en/home/microsites/veru/other_research_areas/global_
burden_of_diseases.html
* rb@rupertbourne.co.uk
Abstract
Objective
To assess the number of individuals visually impaired or blind due to glaucoma and to
examine regional differences and temporal changes in this parameter for the period from
1990 to 2012.
Methods
As part of the Global Burden of Diseases (GBD) Study 2010, we performed a systematic lit-
erature review for the period from 1980 to 2012. We primarily identified 14,908 relevant
manuscripts, out of which 243 high-quality, population- based studies remained after review
by an expert panel that involved application of selection criteria that dwelt on population
representativeness and clarity of visual acuity methods used. Sixty-six specified the propor-
tion attributable to glaucoma. The software tool DisMod-MR (Disease Modeling–Metare-
gression) of the GBD was used to calculate fraction of vision impairment due to glaucoma.
Results
In 2010, 2.1 million (95% Uncertainty Interval (UI):1.9,2.6) people were blind, and 4.2 (95%
UI:3.7,5.8) million were visually impaired due to glaucoma. Glaucoma caused worldwide
6.6% (95% UI:5.9,7.9) of all blindness in 2010 and 2.2% (95% UI:2.0,2.8) of all moderate
and severe visual impairment (MSVI). These figures were lower in regions with younger
PLOS ONE | DOI:10.1371/journal.pone.0162229 October 20, 2016 1 / 16
a11111
OPEN ACCESS
Citation: Bourne RRA, Taylor HR, Flaxman SR,
Keeffe J, Leasher J, Naidoo K, et al. (2016) Number
of People Blind or Visually Impaired by Glaucoma
Worldwide and in World Regions 1990 – 2010: A
Meta-Analysis. PLoS ONE 11(10): e0162229.
doi:10.1371/journal.pone.0162229
Editor: Yuk Fai Leung, Purdue University, UNITED
STATES
Received: April 8, 2016
Accepted: August 20, 2016
Published: October 20, 2016
Copyright: © 2016 Bourne et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: Table B in
S3
Appendix
of the Supplementary Material gives a
reference for each of the data sources available in
the published literature. Data sources that cannot
be found publicly are also listed with information
on whether microdata was supplied, whether the
study involved rapid assessment methodology and
other notes that may assist the reader. Other data
are available from the Global Vision Database
(
http://www.globalvisiondata.org/). Some principal
investigators of studies that are included in this
database supplied detailed data on condition that
populations (<5% in South Asia) than in high-income regions with relatively old populations
(>10%). From 1990 to 2010, the number of blind or visually impaired due to glaucoma
increased by 0.8 million (95%UI:0.7, 1.1) or 62% and by 2.3 million (95%UI:2.1,3.5) or
83%, respectively. Percentage of global blindness caused by glaucoma increased between
1990 and 2010 from 4.4% (4.0,5.1) to 6.6%. Age-standardized prevalence of glaucoma
related blindness and MSVI did not differ markedly between world regions nor between
women.
Significance
By 2010, one out of 15 blind people was blind due to glaucoma, and one of 45 visually
impaired people was visually impaired, highlighting the increasing global burden of
glaucoma.
Introduction
Previous population-based investigations have shown that glaucoma is one of the most com-
mon, and thus most important, causes for vision loss worldwide [1–34]. Previous estimations
of global burden of glaucoma were based on meta-analyses which did not include studies, as
far as available, from all regions of the world, which did not include all available population-
based studies, which did not assess a change during the last 2 decades, or which mostly
reported on the prevalence of the disease [
1–3]. Many of the population-based glaucoma stud-
ies did not report on the number of people blind or visually impaired due glaucoma. For public
health purposes, however, the number of patients functionally affected is more important than
the number of patients with any stage of the disease. For the individual patient and thus for the
society, the burden of a disease is more important than just the presence of a disease including
its early stages. We therefore conducted this meta-analysis of all available population-based
studies performed worldwide within the last two decades to estimate the number of people
affected by blindness (defined as presenting visual acuity <3/60) and moderately to severe
visual impairment (MSVI; presenting visual acuity <6/18, 3/60) due to glaucoma, to assess
changes in that figures during the period from 1990 to 2010, to examine regional differences in
the prevalence of glaucoma related blindness and MSVI, and finally to compare the number of
blind and visually impaired people with glaucoma with the number of people blind and visually
impaired due to other diseases.
Methods
In a systemic literature research we used the systems of Medline, Embase and the WHO
(World Health Organization) library information system to search for articles on vision loss
and published in the period between 1980 and 2012. The methodology for this systematic
review is described in
Fig 1 as a PRISMA (Preferred Reporting Items for Systematic Reviews
and Meta-Analyses) flowchart with a PRISMA checklist in
S1 Appendix. The search strategy is
presented in S2 Appendix. Out of primarily identified 14,908 relevant manuscripts, we selected
243 high-quality, population-based studies after review by an expert panel. The latter involved
application of selection criteria that were based on population representativeness and clarity of
visual acuity methods used. As described in detail recently, search terms included concepts to
describe “blindness”, “visual impairment”, “population”, “eye”, “survey”, and a list of ocular
disorders [
35–37]. Additional unpublished data sources were found by personal
Vision Loss Due to Glaucoma
PLOS ONE | DOI:10.1371/journal.pone.0162229 October 20, 2016 2 / 16
only summary data would be publicly accessible
hence the restriction on complete access to the
completely disaggregated dataset. These data are
owned by the principal investigators and cannot be
made publicly available without permission of the
Global Vision Database Data Access Committee.
The Global Vision Database data files are stored
securely at Anglia Ruskin University, Cambridge,
UK, according to the university’s information
security guidelines. Qualified researchers who wish
to request access to the third party data may
contact the Global Vision Database through the
website (
http://www.globalvisiondata.org/c ontact.
html
) or using the following contact information:
Professor Shahina Pardhan. Email: shahina.
pardhan@anglia.ac.uk
. Address: Vision & Eye
Research Unit, Postgraduate Medical Institute,
Anglia Ruskin University, East Road, Cambridge,
UK.
Funding: This study was partially funded by the Bill
& Melinda Gates Foundation, Fight for Sight, Fred
Hollows Foundation and the Brien Holden Vision
Institute. The results in this paper are prepared
independently of the final estimates of the Global
Burden of Diseases, Injuries, and Risk Factors
study. The funders had no role in study design,
data collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
communication with researchers identified in the literature search. Population-based studies
that reported prevalence of visual impairment and blindness disaggregated by cause (128 stud-
ies) provided the basic data to calculate the proportion of blindness and MSVI that were due to
glaucoma, besides other causes such as cataract, macular degeneration, diabetic retinopathy,
trachoma, or undercorrection of refractive error. A full list of data sources used for each cause
has been presented recently (Table B in
S3 Appendix) [37]. Two studies per region were avail-
able for 18 of the 21 GBD (Global Burden of Disease) Study regions, while only one study was
identified for Central Europe. Eastern Europe and Central Africa did not have any study with
cause-specific data. No study was identified for 126 of 191 countries. Data were extracted from
published and unpublished reports into an electronic database (Microsoft Excel) by two inves-
tigators working independently with consistency checks in order to minimize data inputting
errors. Extracted data included prevalence of predefined severities of vision loss by age, gender,
country, region, and cause.
Stratifying by age, sex, and geographical region, we estimated trends in causes of vision
impairment and included an analysis of uncertainties. For geographical stratification, we used
the 21 regions defined in the GBD Study [
38]. As part of the statistical analysis, we first identi-
fied and accessed the data and then estimated fractions for each cause. We stratified the results
by the severity of vision impairment, sex, age, and region. We finally applied the cause fractions
to the prevalence of all-cause presenting vision impairment [
37]. The method has been
described in detail previously [
37].
For the statistical analysis, the Disease Modeling–Metaregression (DisMod-MR) model
from the GBD Study was used to determine the fraction of vision impairment caused by glau-
coma or due to other causes mentioned above (more detailed information is available in
S3
Appendix
with an explanation of country and regional groupings, Table A, and a full list of
citations of the studies, Table B) [
37]. Briefly, the DisMod-MR model is a negative binomial
regression model which included the following elements: covariates that predicted the variation
in the true proportion of vision impairment from each disease; fixed effects that adjusted for
definitional differences (e.g. whether the causes of presenting vs. best-corrected vision
impairment were reported); a hierarchical model structure which fitted random intercepts in
individual countries derived from the data observed in the country, in its region, and in other
regions based on the availability and consistency of country- and region-specific data; age-spe-
cific fixed-effects which allowed for a non-linear age pattern; and a fixed effect for data on
males. For the assessment of the fractions of blindness and visual impairment which were
caused by glaucoma, we fitted one DisMod-MR model and used three covariates: an indicator
variable which described whether the data were for blindness or for MSVI, an indicator vari-
able describing whether the data were based on presenting visual acuity or best-corrected visual
acuity measurements, and a country-level covariate which reflected the health systems access.
We made two sets of the prediction for glaucoma, one for best-corrected blindness and one for
best-corrected MSVI. Using the WHO reference population, we age-standardized the preva-
lences [
39]. We also calculated the numbers of people with vision impairment and blindness
caused by glaucoma. It reflected each region’s population size and age structure.
Results
Blindness caused by glaucoma was found to be present in 2.1 million (95% uncertainty interval
(UI): 1.9, 2.6) people, and MSVI caused by glaucoma was detected for 4.2 million (95%UI: 3.7–
5.8) million individuals (
Table 1). Taking into account that overall 32.4 million people were
blind and 191 million people were vision impaired in 2010, glaucoma caused worldwide 6.6%
(95%UI: 5.9, 7.9) of all causes for blindness in 2010 and 2.2% (95%UI: 2.0, 2.8) of all causes for
Vision Loss Due to Glaucoma
PLOS ONE | DOI:10.1371/journal.pone.0162229 October 20, 2016 4 / 16
Table 1. Number of people (mean, 95% uncertainty interval) blind (presenting visual acuity <3/60) or visually impaired (MSVI) (presenting visual
acuity <6/18, 3/60) due to glaucoma and the age-standardized prevalences (mean, 95% uncertainty interval) in different world regions in 2010.
World Region Blindness / Moderate to
Severe Visual
Impairment (MSVI) by
Glaucoma
Total
Population
2010
Number of People Affected in
2010
Age-Standardized
Prevalence in People
Aged 50+ Years in 2010
Percent of Blindness /
Visual Impairment by
Glaucoma in 2010
Mean
Value
Lower
Value
Upper
Value
Mean
Value
Lower
Value
Upper
Value
World BLIND 6,890,000,000 2,129,010 1,867,190 2,631,980 0.1% 0.1% 0.2% 6.6 (5.9, 7.9)
Asia Pacific,
High Income
BLIND 169,000,000 41,236 21,680 92,060 0.0% 0.0% 0.1% 11.7 (7.1, 18.8)
Asia, Central BLIND 68,800,000 16,146 10,742 26,920 0.1% 0.1% 0.2% 12.0 (8.7, 17.2)
Asia, East BLIND 1,190,000,000 280,664 179,792 445,252 0.1% 0.1% 0.1% 5.4 (3.5, 8.5)
Asia, South BLIND 1,120,000,000 493,126 328,286 787,091 0.2% 0.2% 0.4% 4.7 (3.3, 7.5)
Asia,
Southeast
BLIND 460,000,000 195,036 128,088 280,470 0.2% 0.1% 0.3% 5.6 (4.3, 8.2)
Australasia BLIND 20,500,000 4,359 2,279 12,153 0.0% 0.0% 0.1% 11.3 (6.8, 18.8)
Caribbean BLIND 34,300,000 21,996 13,683 33,690 0.2% 0.1% 0.3% 11.2 (8.0, 15.1)
Europe,
Central
BLIND 122,000,000 40,894 28,224 93,954 0.1% 0.1% 0.2% 12.5 (9.1, 17.0)
Europe,
Eastern
BLIND 222,000,000 79,285 39,916 154,466 0.1% 0.0% 0.2% 13.5 (8.6, 20.6)
Europe,
Western
BLIND 381,000,000 101,391 65,985 159,726 0.0% 0.0% 0.1% 10.6 (8.2, 14.0)
Latin America,
Andean
BLIND 38,600,000 22,996 13,920 35,935 0.3% 0.2% 0.4% 11.7 (7.9, 17.1)
Latin America,
Central
BLIND 166,000,000 118,569 80,675 177,954 0.3% 0.2% 0.4% 13.0 (9.6, 18.2)
Latin America,
Southern
BLIND 48,900,000 28,401 18,116 50,815 0.2% 0.1% 0.3% 12.6 (7.9, 19.3)
Latin America,
Tropical
BLIND 154,000,000 123,409 65,267 262,580 0.3% 0.2% 0.6% 15.5 (9.6, 21.9)
North Africa/
Middle East
BLIND 301,000,000 300,578 216,888 434,025 0.5% 0.4% 0.7% 9.6 (7.5, 13.2)
North
America, High
Income
BLIND 281,000,000 50,464 28,478 90,572 0.0% 0.0% 0.1% 10.7 (7.0, 15.7)
Oceania BLIND 5,814,186 1,375 704 2,694 0.2% 0.1% 0.4% 4.2 (2.5, 7.2)
Sub-Saharan
Africa, Central
BLIND 53,400,000 14,663 7,574 34,857 0.2% 0.1% 0.5% 5.2 (3.4, 8.8)
Sub-Saharan
Africa, East
BLIND 208,000,000 83,252 57,759 121,613 0.3% 0.2% 0.4% 4.0 (3.1, 5.4)
Sub-Saharan
Africa, South
BLIND 52,600,000 21,870 10,551 34,971 0.3% 0.1% 0.4% 7.3 (5.2, 10.4)
Sub-Saharan
Africa, West
BLIND 201,000,000 91,532 64,503 129,601 0.3% 0.2% 0.5% 4.4 (3.4, 5.9)
World MSVI 6,890,000,000 4,209,790 3,693,040 5,808,270 0.3% 0.2% 0.4% 2.2 (2.0, 2.8)
Asia Pacific,
High Income
MSVI 169,000,000 72,451 41,009 284,553 0.1% 0.0% 0.3% 3.7 (2.3, 6.9)
Asia, Central MSVI 68,800,000 42,894 26,157 91,467 0.3% 0.2% 0.6% 3.6 (2.6, 5.4)
Asia, East MSVI 1,190,000,000 519,648 296,002 911,581 0.2% 0.1% 0.3% 1.6 (0.94, 2.5)
Asia, South MSVI 1,120,000,000 1,111,183 707,164 1939,554 0.5% 0.3% 0.8% 1.6 (1.0, 2.6)
Asia,
Southeast
MSVI 460,000,000 330,064 227,354 687,535 0.3% 0.2% 0.7% 1.8 (1.3, 3.0)
Australasia MSVI 20,500,000 14,724 6,098 41,810 0.1% 0.1% 0.4% 3.2 (1.9, 5.9)
(Continued)
Vision Loss Due to Glaucoma
PLOS ONE | DOI:10.1371/journal.pone.0162229 October 20, 2016 5 / 16