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Bulletin of the World Health Organization | January 2008, 86 (1)
Abstract Estimates of the prevalence of visual impairment caused by uncorrected refractive errors in 2004 have been determined at
regional and global levels for people aged 5 years and over from recent published and unpublished surveys. The estimates were based
on the prevalence of visual acuity of less than 6/18 in the better eye with the currently available refractive correction that could be
improved to equal to or better than 6/18 by refraction or pinhole.
A total of 153 million people (range of uncertainty: 123 million to 184 million) are estimated to be visually impaired from
uncorrected refractive errors, of whom eight million are blind. This cause of visual impairment has been overlooked in previous
estimates that were based on best-corrected vision. Combined with the 161 million people visually impaired estimated in 2002
according to best-corrected vision, 314 million people are visually impaired from all causes: uncorrected refractive errors become the
main cause of low vision and the second cause of blindness.
Uncorrected refractive errors can hamper performance at school, reduce employability and productivity, and generally impair quality
of life. Yet the correction of refractive errors with appropriate spectacles is among the most cost-effective interventions in eye health care.
The results presented in this paper help to unearth a formerly hidden problem of public health dimensions and promote policy
development and implementation, programmatic decision-making and corrective interventions, as well as stimulate research.
Bulletin of the World Health Organization 2008;86:63–70.
Une traduction en français de ce résumé figure à la fin de l’article. Al final del artículo se facilita una traducción al español.
Global magnitude of visual impairment caused by uncorrected
refractive errors in 2004
Serge Resnikoff,a Donatella Pascolini,a Silvio P Mariotti a & Gopal P Pokharela
a Chronic Disease Prevention and Management, WHO, 20 avenue Appia, 1211 Geneva 27, Switzerland.
Correspondence to Serge Resnikoff (e-mail: resnikoffs@who.int).
doi:10.2471/BLT.07.041210
(Submitted: 11 February 2007 – Revised version received: 28 May 2007 – Accepted: 11 June 2007 – Published online: 16 November 2007 )
Introduction
Refractive errors (myopia, hyperopia
and astigmatism; presbyopia is not in-
cluded in this study given the present
paucity of data, but it is recognized that
uncorrected, it could lead to an impaired
quality of life) affect a large proportion
of the population worldwide, irrespec-
tive of age, sex and ethnic group. Such
refractive errors can be easily diagnosed,
measured and corrected with spectacles
or other refractive corrections to attain
normal vision. If, however, they are
not corrected or the correction is inad-
equate, refractive errors become a major
cause of low vision and even blindness
(for a selection of studies, see http://ftp.
who.int/nmh/references/RE-estimates-
references.pdf).
Visual impairment from uncor-
rected refractive errors can have imme-
diate and long-term consequences in
children and adults, such as lost educa-
tional and employment opportunities,
lost economic gain for individuals, fami-
lies and societies, and impaired quality
of life. Various factors are responsible for
refractive errors remaining uncorrected:
lack of awareness and recognition of the
problem at personal and family level, as
well as at community and public health
level; non-availability of and/or inability
to afford refractive services for testing;
insufficient provision of affordable cor-
rective lenses; and cultural disincentives
to compliance.
e definition of visual impairment
in the International statistical classifica-
tion of diseases, injuries and causes of
death, 10th revision (ICD-10), H54,
is based on “best-corrected” vision, i.e.
visual acuity obtained with the best pos-
sible refractive correction.1 However, to
assess the extent of visual impairment
caused by uncorrected refractive errors,
estimates need to be based on “present-
ing” vision, i.e. visual acuity obtained
with currently available refractive cor-
rection, if any. us, presenting vision,
as opposed to best-corrected vision,
provides the prevalence of visual impair-
ment that could be improved simply by
appropriate corrective refraction. Basing
the definition of visual impairment on
presenting vision extends the current
definition to one that characterizes visual
impairment faced by people in day-to-
day activities.
Using best-corrected vision, visual
impairment was estimated to affect 161
million people globally in 2002, of
whom 37 million were blind.2 e main
cause of blindness and low vision was
cataract; however, it was recognized
that unless uncorrected refractive errors
were included among the causes, visual
impairment at global level was signifi-
cantly underestimated.
is paper presents the estimate
of the prevalence of visual impairment
from uncorrected refractive errors for all
ages over 5 years at regional and global
levels, based on recent published and
unpublished surveys. Some results from
this paper were reported in a WHO
press release on 11 October 2006 to
mark World Sight Day.3
Methods
Definitions
Presenting vision is defined by the visual
acuity in the better eye using currently
available refractive correction, if any.
Policy and practice
Global visual impairment caused by uncorrected refractive errors
64
Serge Resnikoff et al.
Bulletin of the World Health Organization | January 2008, 86 (1)
Best-corrected vision is the visual acuity
in the better eye achieved by subjects
tested with pinhole or refraction.
Visual impairment caused by un-
corrected or inadequately corrected re-
fractive errors is defined as visual acuity
of less than 6/18 in the better eye that
could be improved to equal to or better
than 6/18 by refraction or pinhole, thus
spanning the low vision and blindness
categories as currently defined in the
ICD-10.
It should be noted that in the
revision of the ICD-10 categories of
visual impairment proposed in 2003 by
a WHO consultation on the develop-
ment of standards for characterization
of vision loss, low vision is replaced by
two categories: moderate visual impair-
ment (presenting visual acuity less than
6/18 but equal to or better than 6/60)
and severe visual impairment (presenting
visual acuity less than 6/60 but equal to
or better than 3/60).4
Population estimates and WHO
subregions
Estimates of population size and struc-
ture were based on the latest estimates
of world population (for 2004) in the
World population prospects: the 2004
revision; estimates of demographics were
based on the World urbanization pros-
pects 2003 – both sources from the
United Nations Population Division.5,6
For the classification of WHO
Member States into 17 epidemiological
subregions, see Murray & Lopez, 1996.7
General inclusion criteria
e following criteria were used to select
studies.
e prevalence of best-corrected and •
presenting visual acuity of less than
6/18 had to be reported or, alterna-
tively, the distribution of causes of
presenting visual impairment.
In children, refractive diagnostics •
had to be determined by objective
refraction under cycloplegia plus sub-
jective refraction.8
e studies had to be population-•
based, representative of the area
sampled, with definitions of visual
impairment clearly stated. Studies
with inadequate sample sizes and re-
sponse rate were not included.
Data reported only for eyes or for •
the worse eye could not be included
in the estimates calculated for people
and the better eye.
For further discussion of selection cri-
teria, see Resnikoff et al.,2 and Pascolini
et al., 2004.9
Sources of epidemiological data
Literature sources were searched sys-
tematically in Medline up to April
2006. Most surveys meeting the selec-
tion criteria were conducted within the
past five years; the earliest surveys date
from 1995. Unpublished data were
provided by academic institutions and
national programmes for the prevention
of blindness.
Table 1 shows the 31 countries for
which surveys that met the selection
criteria were available, the bibliography
can be found at http://ftp.who.int/nmh/
references/RE-estimates-references.pdf
and in the WHO Prevention of Blind-
ness and Deafness Programme’s global
data on visual impairment.10
For the age group 5–15 years, 16
surveys were found to fit the selection
criteria. Of these, 10 were conducted
in different countries using a specially
designed protocol to estimate the preva-
lence of visual impairment from uncor-
rected refractive errors (the refractive
error study in children (RESC; see
Négrel et al., 2000, for the details of the
protocol).11 e RESC studies provided
extensive information on visual acuity,
refractive errors and use of spectacles.
For the age group 50 years and
older, 38 surveys met the inclusion cri-
teria. Of these, 30 were surveys for the
Table 1. Surveys used to estimate global visual impairment from uncorrected
refractive errors by WHO subregion, 2004
WHO subregiona,b Number of
surveys
Countries
Afr-D 2 Mali, Mauritania
Afr-E 1 South Africa
Amr-A 3 United States of America
Amr-B 5 Argentina, Brazil, Chile, Paraguay, Venezuela
(Bolivarian Republic of)
Amr-D 2 Guatemala, Peru
Emr-B 5 Iran (Islamic Republic of), Lebanon, Oman, Qatar
Eur-A 2 Ireland, Italy
Eur-B2 2 Armenia, Turkmenistan
Sear-B 6 Malaysia, Philippines, Singapore
Sear-D 13 Bangladesh, India, Nepal, Pakistan
Wpr-A 4 Australia
Wpr-B1 7 China
Wpr-B2 16 Cambodia, Myanmar, Viet Nam
a Afr, WHO African Region; Amr, WHO Region of the Americas; Emr, WHO Eastern Mediterranean Region;
Eur, WHO European Region; Sear, WHO South-East Asia Region; Wpr, WHO Western Pacific Region.
b In subregions Emr-D, Eur-B1, Eur-C and Wpr-B3, no population-based surveys met the selection criteria.
rapid assessment of cataract surgical
services (RACSS), which also provide
prevalence of presenting and best-
corrected visual acuity.12
An additional 14 surveys reported
age-specific prevalence of presenting vi-
sual impairment and its causes in other
age groups.
Estimation of prevalence of visual
impairment from uncorrected
refractive errors
For the age group from 5 to 15 years,
the prevalence is estimated by the dif-
ference between the prevalence of pre-
senting and best-corrected visual acuity
of less than 6/18 with refraction under
cycloplegia: this difference corresponds
to the prevalence of presenting visual
acuity that could be improved to equal
to or better than 6/18 by appropriate
correction. In the case of studies report-
ing only the prevalence of presenting
visual acuity, the prevalence of visual
impairment due to refractive error was
determined from the distribution of
causes determined in the surveys.
e prevalence for people aged
16–39 years was estimated to be the
same as that for those aged 5–15 years,
on the assumption that from the ages of
16 years to 39 years, the refractive status
generally does not undergo changes that
require further correction.13
e prevalence for people aged
40–49 years was either estimated from
Policy and practice
Global visual impairment caused by uncorrected refractive errors
65
Serge Resnikoff et al.
Bulletin of the World Health Organization | January 2008, 86 (1)
the results of surveys that reported
age-specific data for this age group or
calculated by a linear fit between the
prevalence at age 39 and 55 years.
For the population aged 50 years
and older, the prevalence was estimated
from the difference between visual acu-
ity of less than 6/18 with the available
correction and visual acuity of less than
6/18 with best correction determined
using refraction or pinhole, assuming
that pinhole approximates complete
refraction.
Estimation of prevalence of
blindness from uncorrected
refractive errors
Uncorrected refractive errors in adults
aged 50 years and older have been
shown to lead to blindness in some
regions: the corresponding prevalence
of blindness was determined from the
difference between prevalence of pre-
senting and best-corrected visual acuity
of less than 3/60.
Blindness from uncorrected refrac-
tive errors was also reported in some
surveys for the age group 40–49 years.
Since there were insufficient data world-
wide, it was assumed that the global
number of people blind from this cause
in this age group was 5.13 times lower
than the corresponding number in
people aged 50 years and over, based on
the ratio of the total number of people
visually impaired 50 years and over and
those aged 40–49 years.
Estimation of refractive services
coverage
e RESC studies also report the preva-
lence of uncorrected visual acuity in the
age group 5–15 years: the prevalence
of uncorrected, presenting and best-
corrected visual acuity (VA < 6/18)
provides an estimate of the percentage
coverage of refractive services using the
formula:
100 – [ × 100]
(presenting VA –
best corrected VA)
(uncorrected VA –
best corrected VA)
Since percentage coverage is based on
presenting visual acuity, it is an esti-
mate of both the provision of refractive
services and the compliance to prescrip-
tion.
Extrapolations
Since data were not available for every
country, extrapolations were made to
estimate the global prevalence of visual
Table 2. Number of people visually impaired from uncorrected refractive errors and corresponding prevalence, by age group and
WHO subregion or country, 2004
WHO subregiona
or country
Age 5–15 years Age 16–39 years Age 40–49 years Age >50 years Total (5 to >50 years)
No. in millions
(prevalence %)
No. in millions
(prevalence %)
No. in millions
(prevalence %)
No. in millions
(prevalence %)
Population
in millions
No. in millions
(prevalence %)
Afr-D, Afr-E 0.534 (0.24) 0.683 (0.24) 0.647 (1.13) 4.529 (5.94) 640.4 6.393 (1.00)
Amr-A 0.501 (1.00) 1.098 (1.00) 0.810 (1.60) 3.417 (3.60) 305.4 5.826 (1.91)
Amr-B 0.709 (0.70) 1.331 (0.70) 0.998 (1.81) 3.204 (4.07) 432.4 6.242 (1.44)
Amr-D 0.137 (0.70) 0.209 (0.70) 0.127 (1.81) 0.486 (4.86) 66.4 0.959 (1.44)
Emr-B, Emr-D 0.405 (0.55) 0.688 (0.55) 0.356 (1.20) 1.708 (4.76) 264.3 3.157 (1.19)
Eur-A 0.516 (1.00) 1.379 (1.00) 0.991 (1.60) 5.289 (3.60) 398.3 8.175 (2.05)
Eur-B1, Eur-B2, Eur-C 0.721 (1.00) 1.740 (1.00) 1.065 (1.60) 3.335 (2.80) 431.7 6.861 (1.59)
Sear-B, Wpr-B1,
Wpr-B2, Wpr-B3
(China excluded)
1.098 (0.79) 1.806 (0.74) 1.244 (1.70) 4.511 (4.67) 554.0 8.659 (1.56)
Sear-D
(India excluded)
0.606 (0.63) 0.986 (0.73) 0.909 (2.39) 9.295 (19.45) 317.5 11.796 (3.71)
Wpr-A 0.034 (0.20) 0.097 (0.20) 0.039 (0.20) 1.177 (1.99) 144.4 1.347 (0.93)
China 5.940 (2.66) 14.414 (2.66) 7.209 (3.95) 26.903 (9.61) 1229.0 54.466 (4.43)
India 1.610 (0.63) 2.695 (0.63) 4.042 (3.39) 30.970 (18.70) 966.9 39.317 (4.07)
World 12.811 (0.97) 27.126 (1.11) 18.437 (2.43) 94.824 (7.83) 5750.7 153.198 (2.67)
a See Table 1, footnote a.
impairment from uncorrected refractive
errors. e rationale for the extrapola-
tions was the similarity of the epidemi-
ology of refractive errors, the availability
and/or affordability of refractive services
and compliance. Various kinds of ex-
trapolations were made, based on the
data selected:
the prevalence in urban and rural •
areas within a country was extrapo-
lated to all urban and rural areas, re-
spectively, of the country; the coun-
try prevalence was determined by
weighting the prevalence by the ru-
ral–urban distribution of the popu-
lation;
in subregions with data from several •
countries, an average prevalence was
determined and applied to all other
countries in the subregion. e av-
erage was calculated by weighting
the prevalence from the countries by
their share of the population in the
subregion and taking into account
the urban and rural distribution of
the population;
in the case of whole subregions lack-•
ing data, the prevalence was extrapo-
lated from other subregions with
similar epidemiology of refractive
errors and with similar WHO epide-
miological classification.6
Policy and practice
Global visual impairment caused by uncorrected refractive errors
66
Serge Resnikoff et al.
Bulletin of the World Health Organization | January 2008, 86 (1)
For China and India, estimates were
made separately because of the popula-
tion size. Some subregions estimated to
have similar prevalence of visual impair-
ment from uncorrected refractive errors
and provision of refractive services were
combined.
Results
Prevalence of visual impairment
from uncorrected refractive errors
by age and subregion
It is estimated that globally 153 million
people over 5 years of age are visually
impaired as a result of uncorrected re-
fractive errors, of whom 8 million are
blind. Table 2 shows the number of
people in the WHO subregions with vi-
sual impairment from this cause and the
corresponding prevalence by age. ere
is no evidence of visual impairment
caused by uncorrected refractive errors
in children aged less than 5 years.
From the data reported in surveys it
was not possible to distinguish conclu-
sively between the prevalence of male
and female cases of uncorrected refrac-
tive errors for any of the age groups.
Some 12.8 million in the age group
5–15 years are visually impaired from un-
corrected or inadequately corrected refrac-
tive errors, a global prevalence of 0.96%,
with the highest prevalence reported in
urban and highly developed urban areas
in south-east Asia and in China.
e number of people aged 16–39
years visually impaired from uncorrected
refractive errors is 27 million, a prevalence
of 1.1% globally. is could, however, be
an underestimate, being derived directly
from the prevalence in the age group 5–15
years, although the prevalence of refrac-
tive errors, especially myopia, is higher
between the ages of 13 and 18 years.
e prevalence in people aged
40–49 years globally is 2.45%; it is high
in subregions or countries where the
prevalence for people aged 50 years and
older is also high. Almost 95 million
people aged 50 years and older are visu-
ally impaired from uncorrected refrac-
tive errors: the prevalence is between
2% and 5% in most regions of the
world, but is almost 10% in China and
almost 20% in India and in Sear-D
(WHO subregions defined in Murray
& Lopez, 1996).7
Of the 95 million people aged
50 years and older visually impaired
from uncorrected refractive errors, 6.9
million are blind (Table 3). Based on
this, it is estimated that 1.3 million
people in the age group 40–49 years are
blind from uncorrected refractive errors.
ere was no evidence in any surveys of
significant blindness in the age groups
5–15 years and 16–39 years.
e average coverage of refractive
corrections calculated from the RESC
studies for visual acuity cut-off point of
less than 6/18 is shown in Table 4.
Discussion
Limitations: uncertainties of the
data and extrapolations
e sampling and examination methods
in the RESC studies were designed to
produce results that could be directly
compared between countries: for pre-
senting visual acuity of less than 6/18,
the uncertainties given were between
20% and 25%. ese uncertainties in
turn affect the estimates for the age
group 16–39 years, which are based
on the results for the age group 5–15
years. e uncertainties reported in the
RACSS studies are between 15% and
25% for the prevalence of visual acuity
of less than 6/18; other studies reported
Table 3. Blindness from uncorrected refractive errors in adults aged 50 years and
older, by WHO subregion or country, 2004
WHO subregiona
or country
Population
type
Millions of adults >50 years blind from
uncorrected refractive errorsb
Afr-D, Afr-E – 1.250 (1.64)
Amr-A – NRB
Amr-B – 0.233 (0.3)
Amr-D – 0.075 (0.75)
Emr-B, Emr-D Rural 0.142 (0.95)
Urban 0.084 (0.4)
Eur-A – NRB
Eur-B1, Eur-B2, Eur-C – NRB
Sear-B, Wpr-B2, Wpr-B3 – 0.319 (0.26)
Sear-D and Myanmar
(India excluded)
– 0.834 (1.74)
Wpr-A – NRB
Wpr-B1
(China excluded)
– 0.032 (0.2)
China Rural 0.528 (0.33)
Urban 0.240 (0.2)
India – 3.147 (1.9)
World – 6.884 (0.57)
NRB, no reported blindness.
a See Table 1, footnote a.
b Figures in parentheses are prevalence percentages.
uncertainties from 15% to more than
20%. In all the studies, the uncertain-
ties become higher for the prevalence of
visual impairment of less than 3/60.
e assumption that in adults the
measurement of visual acuity with pin-
hole approximates the results obtainable
with full refraction brings some addi-
tional bias to the estimates.14
Significant limitations are intro-
duced by the need to extrapolate the
prevalence and provision of services data
from one rural or urban area to all rural
and urban areas in a country or sub-
region, as well as from one country to
other countries, or from one country to
whole subregions. Some extrapolations
could be particularly prone to error, as
in the case of countries such as China
or India, for which extrapolations are
made for very large populations, or in
the case of subregions with scarce data,
such as Eur-B1, Eur-B2 and Eur-C
(WHO subregions defined in Murray
& Lopez, 1996).7
To check the consistency of the
extrapolations, the estimates were veri-
fied using studies that did not fit the
inclusion criteria due to the visual acu-
ity ranges or the testing and reporting
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Global visual impairment caused by uncorrected refractive errors
67
Serge Resnikoff et al.
Bulletin of the World Health Organization | January 2008, 86 (1)
Table 4. Estimated average coverage of refractive services for age group 5–15 years,
by WHO subregion or country, 2004
WHO subregiona
or country
Population type Coverage of refractive services
for age group 5–15 years (%)
Visual acuity <6/18
Afr-D, Afr-E Rural and urban 30
Amr-A – –
Amr-B, Amr-D Rural 30
Urban 45
Emr-B, Emr-D Rural 45
Urban 80
Eur-A – –
Eur-B1, Eur-B2, Eur-C – –
Sear-B, Sear-D, Wpr-B1,
Wpr-B2, Wpr-B3
(China and India excluded)
Rural 30
Urban 55
Most developed urban 80
Wpr-A – –
China Rural 45
Urban 85
Rural, 13–17 years 70
India Rural 30
Urban 55
a See Table 1, footnote a.
methods used. Studies on the epide-
miology of refractive errors have also
been taken into consideration in all
extrapolations.
e assumptions and extrapola-
tions were reviewed by a group of inde-
pendent experts convened by the WHO
Prevention of Blindness Programme.15
Extent of visual impairment from
uncorrected refractive errors
worldwide
Uncorrected refractive errors are a major
cause of blindness and low vision: it
is estimated that 8 million people are
blind and 145 million have low vision
because of lack of adequate refractive
correction (Table 5). e uncertain-
ties associated with the data and the
extrapolations can lead to overestimates
as well as underestimates of these figures:
if the uncertainties are estimated at
20%, the total of 153 million could vary
from 123 million to 184 million.
e estimate of visual impairment
caused by uncorrected refractive errors
presented in this paper confirms that the
problem is of public health concern, as
emphasized previously.16,17 is finding
is significant considering that refractive
errors could be easily diagnosed and that
spectacle correction is among the most
cost-effective interventions in eye care.
Global causes of visual
impairment
If blindness and low vision from uncor-
rected refractive errors (this paper) and
from all other causes (2002 estimate)
are combined, 314 million people are
visually impaired globally (Table 5).
Uncorrected refractive errors are the
second cause of blindness after cataract
(Fig. 1) and the main cause of low vision:
overall, they are the cause of almost half
of all visual impairment.
Given the magnitude of the prob-
lem, uncorrected refractive errors need
Table 5. Global estimate of number of people visually impaired, 2004
Category of
impairment
Number of people visually impaired (in millions)
from uncorrected
refractive errors
from all other causes,
2002 estimatea
from all
causes
Blind 8.226 36.857 45.083
Low vision 144.972 124.264 269.236
Visual impairment 153.198 161.121 314.319
a These estimates were based on best-corrected visual acuity and the population in 2002: the global
population change from 2002 to 2004 is estimated to be around 3%.
to be assessed and reported as a cause of
visual impairment. It is expected that
the ICD-10 definition of visual impair-
ment will include, from the next revi-
sion in 2009, presenting vision along
with the currently used best-corrected
vision.
Reasons why refractive errors
remain uncorrected
In the age group 5–15 years, non-
correction of refractive errors is due to
several factors: the lack of screening,
and the availability and affordability of
refractive corrections are the most im-
portant. However, cultural disincentives
also play a role, as shown in surveys
from countries where routine screen-
ing and provision of corrections are
free of charge or easily accessible, but
compliance remains low (S Wedner,
unpublished observations, 2006).18,19
Perhaps one of the most remarkable
findings in this study is that even in
economically advantaged societies,
refractive errors can go undetected or
uncorrected in children.20
e estimated number of people
aged 50 years and older visually im-
paired from uncorrected refractive
errors is over 94 million, a figure that
could be an underestimate, being based
in part on studies that used only pinhole
in place of full refraction.14 In coun-
tries where the prevalence is very high,
important underlying causes are index
myopia caused by cataract, uncorrected
aphakia and insufficient intra-ocular
lens correction.21,22 is is particularly
true in rural areas.
For the age group 5–15 years, the
prevalence of visual impairment from
uncorrected refractive errors in some
regions appears to be higher in urban
areas than in rural areas, despite the
reported better access to services. is
may be due to a high incidence of myo-
pia in these populations: it is suggested
that there may be a direct cause–effect
relation between increased access to
Policy and practice
Global visual impairment caused by uncorrected refractive errors
68
Serge Resnikoff et al.
Bulletin of the World Health Organization | January 2008, 86 (1)
Résumé
Prévalence mondiale des déficiences visuelles dues à des défauts de réfraction non corrigés en 2004
Des estimations mondiales et régionales pour l’année 2004 de
la prévalence des déficiences visuelles dues à des défauts de
réfraction non corrigés chez les plus de 5 ans ont été établies à
partir d’enquêtes récentes publiées et non publiées. Ces estimations
ont été obtenues d’après la prévalence d’une acuité visuelle
inférieure à 6/18 pour le meilleur des deux yeux avec la correction
réfractive actuellement disponible, susceptible d’être ramenée à
une valeur supérieure ou égale à 6/18 par une correction réfractive
ou un trou sténopéique.
On estime à 153 millions (plage d’incertitude : 123 à 184
millions) le nombre total de personnes souffrant d’une déficience
visuelle due à un défaut de réfraction non corrigé, dont huit millions
d’aveugles. La cause de la déficience visuelle a été laissée de côté
dans les estimations antérieures reposant sur la meilleure vision
corrigée. Si l’on combine ce chiffre à l’estimation de 2002 du
nombre d’individus déficients visuels établie d’après la meilleure
vision corrigée, 314 millions de personne présentent une déficience
visuelle toutes causes confondues, les défauts de réfraction non
corrigés devenant la principale cause de mauvaise vision et la
seconde cause de cécité.
Les défauts de réfraction non corrigés peuvent nuire aux
résultats scolaires, réduire la capacité à occuper un emploi et
la productivité et, de manière générale, détériorer la qualité de
vie. La correction des défauts de réfraction par des lunettes
adaptées reste l’intervention la plus rentable en termes de soins
ophtalmologiques.
Les résultats présentés dans cet article contribuent à faire
ressortir un ample problème de santé publique formellement
masqué, à favoriser le développement et la mise en œuvre de
politiques, ainsi que la prise de décisions programmatiques et de
mesures correctives, et à stimuler la recherche.
Fig. 1. Global causes of blindness as a percentage of total blindness, 2004
Cataract
Uncorrected
refractive error
Glaucoma
Age-related
macular degeneration
Corneal opacities
Diabetic retinopathy
Childhood blindness
Trachoma
Onchocerciasis
Other
39.1
18.2
10.1
7.1
4.2
3.9
3.2
2.9
0.7
10.6
education and myopia, but other secular
changes could be contributing factors.
In this age group the prevalence of
myopia reported in studies that used
the same definitions and cut-off levels
ranges from 3% to 35%, hypermetropia
from 0.4% to 17%, astigmatism from
2.2% to 34% depending on the region
and on the urban/rural setting.
e coverage of refractive correc-
tions determined from the RESC stud-
ies is less than or around 50% in most
regions of the world; urban areas have,
as expected, better service coverage than
rural areas (Table 4).
Conclusions
ese findings warrant the urgent
implementation of the following fun-
damental policies.
Screening of children for refractive •
errors should be conducted at com-
munity level and integrated into
school health programmes, accom-
panied by education and awareness
campaigns to ensure that the cor-
rections are used and cultural barri-
ers to compliance are addressed and
removed.
As the cost of refractive corrections •
is still high compared with the per-
sonal and family resources in many
regions, corrections must be acces-
sible and affordable for people of all
ages.
Eye-care personnel should be trained •
in refraction techniques. Training
and information programmes should
also be designed for teachers and
school health-care workers.
Reliable and affordable equipment •
for refractive assessments should be
developed.
Refraction services need to be inte-•
grated with eye-care systems and in-
cluded as a part of cataract surgery
services.
Impairment from uncorrected re-•
fractive errors, provision of refrac-
tive services and outcomes of the
provisions should be monitored at
national level to identify communi-
ties in need and evaluate the most
cost-effective interventions.
Another aspect of visual functioning
that has not been discussed in this pa-
per is near vision: the unmet need of
correction of presbyopia is currently
unknown and should be assessed and
included in future estimates of visual
impairment. ■
Acknowledgements
e authors would like to acknowledge
the contribution of the WHO Refrac-
tive Errors Working Group. is study
was supported financially by a grant
from the World Optometry Founda-
tion of the World Council of Optom-
etry. Particular appreciation is due to
all experts from around the world who
have generously provided survey re-
ports, journal articles and unpublished
results.
Competing interests: None declared.
Policy and practice
Global visual impairment caused by uncorrected refractive errors
69
Serge Resnikoff et al.
Bulletin of the World Health Organization | January 2008, 86 (1)
Resumen
Magnitud mundial de las discapacidades visuales por defectos de refracción no corregidos en 2004
Se ha estimado la prevalencia de las discapacidades visuales
causadas por los defectos de refracción no corregidos en 2004 a
nivel regional y mundial en la población de 5 o más años a partir
de encuestas recientes publicadas o inéditas. Las estimaciones
se basaron en la prevalencia de una agudeza visual inferior a
6/18 en el mejor ojo con la corrección refractiva del momento,
pero mejorable hasta 6/18 o más con medidas de corrección de
la refracción o con un agujero estenopeico.
Se estima que un total de 153 millones de personas
(interva lo de inc ert idumbre: 123 - 184 mill ones) sufr en
discapacidad visual como consecuencia de defectos de refracción
no corregidos, incluidos ocho millones que padecen ceguera.
Esta causa de discapacidad visual no se ha tenido debidamente
en cuenta en estimaciones anteriores basadas en la mejor visión
corregida. Si se suman a ello los 161 millones de personas con
discapacidad visual estimados en 2002 de acuerdo con el criterio
de la mejor visión corregida, se obtiene un total de 314 millones
de personas con discapacidad visual por todas las causas: los
defectos de refracción no corregidos se convierten así en la
principal causa de disminución de la agudeza visual y la segunda
causa de ceguera.
Los defectos de refracción no corregidos pueden reducir el
rendimiento escolar, la empleabilidad y la productividad, y por lo
general merman la calidad de vida. Sin embargo, la corrección de esos
defectos con unas gafas apropiadas es una de las intervenciones
más costoeficaces de la atención oftalmológica.
Los resultados aquí presentados pueden contribuir a hacer
aflorar un problema hasta ahora oculto de gran trascendencia
en el campo de la salud pública, y promover la formulación y
ejecución de políticas, la toma de decisiones programáticas, las
intervenciones correctivas y la realización de investigaciones en
ese terreno.
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