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Purpose: Despite the importance of information on the prevalence of strabismus, which can be effective in planning preventive and curative services, no study has addressed its prevalence comprehensively. In this study, a systematic search was done to estimate the regional and global prevalence of strabismus in different age and sex groups and factors affecting prevalence heterogeneity. Methods: A comprehensive and systematic search was done in different international databases, including Web of Science, Scopus, PubMed, Embase, etc. to find published articles on the total prevalence of strabismus and the prevalence of exotropia and esotropia. A binomial distribution was used to calculate the prevalence and 95% confidence interval (CI). The Cochran’s Q-test and I² were applied to evaluate heterogeneity and a random-effects model was used to assess the pooled prevalence. The Begg’s test was administered to investigate publication bias and finally, a meta-regression method was applied to determine the factors affecting the heterogeneity among studies. Results: Of 7980 articles, 56 articles with a total sample size of 229,396 were analyzed. Many of these articles (n = 14) were from the Regional Office for the Americas. The estimated of pooled prevalence (95% CI) of any strabismus, exotropia, and esotropia was 1.93% (1.64–2.21), 1.23% (1.00–1.46), and 0.77% (0.59–0.95), respectively. The heterogeneity in prevalence of strabismus and its subtypes according to I² was above 95% (p value <.001 for all). Age had a direct effect on heterogeneity in the prevalence of exotropia (b: 3.491; p: 0.002). Moreover, WHO region had a significant direct effect on heterogeneity in the prevalence of strabismus (b: 0.482; p < .001) and esotropia (b: 0.168; p: 0.027), and publication year had a significant direct effect on heterogeneity in the prevalence of exotropia (b: 0.059; p: 0.045). Sample size and publication year did not have any association with strabismus nor with other variables. There was no publication bias according to the Begg’s test. Conclusion: The prevalence of strabismus varies widely in the world. As for factors affecting heterogeneity in the prevalence of strabismus, the results showed that age affected heterogeneity in the prevalence of exotropia, WHO region affected heterogeneity in the prevalence of strabismus and esotropia, and publication year affected heterogeneity in the prevalence of exotropia. Information about the global prevalence of strabismus can help health care planners design interventions and prioritize resource allocation.
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Strabismus
ISSN: 0927-3972 (Print) 1744-5132 (Online) Journal homepage: https://www.tandfonline.com/loi/istr20
Global and regional prevalence of strabismus:
a comprehensive systematic review and meta-
analysis
Hassan Hashemi, Reza Pakzad, Samira Heydarian, Abbasali Yekta,
Mohamadreza Aghamirsalim, Fereshteh Shokrollahzadeh, Fahimeh
Khoshhal, Mojgan Pakbin, Shahroukh Ramin & Mehdi Khabazkhoob
To cite this article: Hassan Hashemi, Reza Pakzad, Samira Heydarian, Abbasali Yekta,
Mohamadreza Aghamirsalim, Fereshteh Shokrollahzadeh, Fahimeh Khoshhal, Mojgan
Pakbin, Shahroukh Ramin & Mehdi Khabazkhoob (2019): Global and regional prevalence
of strabismus: a comprehensive systematic review and meta-analysis, Strabismus, DOI:
10.1080/09273972.2019.1604773
To link to this article: https://doi.org/10.1080/09273972.2019.1604773
Published online: 23 Apr 2019.
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Global and regional prevalence of strabismus: a comprehensive systematic
review and meta-analysis
Hassan Hashemi
a
, Reza Pakzad
b
, Samira Heydarian
c
, Abbasali Yekta
d
, Mohamadreza Aghamirsalim
e
,
Fereshteh Shokrollahzadeh
a
, Fahimeh Khoshhal
f
, Mojgan Pakbin
a
, Shahroukh Ramin
g
, and Mehdi Khabazkhoob
h
a
Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran;
b
Department of Epidemiology, Faculty of Health, Ilam
University of Medical Sciences, Ilam;
c
Department of rehabilitation science, School of Allied Medical Sciences, Mazandaran University of
Medical Sciences, Sari;
d
Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad;
e
Eye Research Center, Tehran
University of Medical Sciences, Tehran;
f
Department of Pediatrics, Dezful University of Medical Sciences, Dezful;
g
Department of Optometry,
Shahid Beheshti University of Medical Sciences, Tehran;
h
Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid
Beheshti University of Medical Sciences, Tehran
ABSTRACT
Purpose: Despite the importance of information on the prevalence of strabismus, which can be
effective in planning preventive and curative services, no study has addressed its prevalence
comprehensively. In this study, a systematic search was done to estimate the regional and global
prevalence of strabismus in different age and sex groups and factors affecting prevalence
heterogeneity.
Methods: A comprehensive and systematic search was done in different international databases,
including Web of Science, Scopus, PubMed, Embase, etc. to find published articles on the total
prevalence of strabismus and the prevalence of exotropia and esotropia. A binomial distribution
was used to calculate the prevalence and 95% confidence interval (CI). The Cochrans Q-test and I
2
were applied to evaluate heterogeneity and a random-effects model was used to assess the
pooled prevalence. The Beggs test was administered to investigate publication bias and finally,
a meta-regression method was applied to determine the factors affecting the heterogeneity
among studies.
Results: Of 7980 articles, 56 articles with a total sample size of 229,396 were analyzed. Many of
these articles (n = 14) were from the Regional Office for the Americas. The estimated of pooled
prevalence (95% CI) of any strabismus, exotropia, and esotropia was 1.93% (1.642.21), 1.23%
(1.001.46), and 0.77% (0.590.95), respectively. The heterogeneity in prevalence of strabismus
and its subtypes according to I
2
was above 95% (p value <.001 for all). Age had a direct effect on
heterogeneity in the prevalence of exotropia (b: 3.491; p: 0.002). Moreover, WHO region had
a significant direct effect on heterogeneity in the prevalence of strabismus (b: 0.482; p < .001) and
esotropia (b: 0.168; p: 0.027), and publication year had a significant direct effect on heterogeneity
in the prevalence of exotropia (b: 0.059; p: 0.045). Sample size and publication year did not have
any association with strabismus nor with other variables. There was no publication bias according
to the Beggs test.
Conclusion: The prevalence of strabismus varies widely in the world. As for factors affecting
heterogeneity in the prevalence of strabismus, the results showed that age affected heterogeneity
in the prevalence of exotropia, WHO region affected heterogeneity in the prevalence of strabis-
mus and esotropia, and publication year affected heterogeneity in the prevalence of exotropia.
Information about the global prevalence of strabismus can help health care planners design
interventions and prioritize resource allocation.
KEYWORDS
Prevalence; strabismus;
exotropia; esotropia;
meta-analysis
Introduction
Strabismus is defined as any deviation of the binocular
alignment that can be the cause or the effect of poor
binocularity.
1
If strabismus is not treated in a timely
manner in children, in addition to cosmetic conse-
quences, it may have a dramatic impact on their
learning and educational ability and impair their phy-
siological and psychological performance,
2,3
eventually
affecting their development and maturity.
4
For this
reason, investigation of the prevalence of strabismus,
in addition to clinical significance, is important from
the perspective of public health.
CONTACT Mehdi Khabazkhoob khabazkhoob@yahoo.com Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid
Beheshti University of Medical Sciences, Tehran, Iran
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/istr.
STRABISMUS
https://doi.org/10.1080/09273972.2019.1604773
© 2019 Taylor & Francis Group, LLC
Epidemiological data of the prevalence of strabis-
mus, especially from population-based studies, help to
determine the extent and burden of the disease and
plan appropriate preventive and curative services to
prepare health and screening infrastructures.
4,5
A number of large studies have reported the prevalence
of strabismus across the world, including the Multi-
Ethnic Pediatric Eye Disease Study (MEPEDS),
6,7
Baltimore Pediatric Eye Disease Study (BPEDS),
8
and
Strabismus, Amblyopia, and Refractive Error in
Singaporean Children Study (STARS) in Singapore,
2
as well as other studies in India
7,912
and Iran.
1315
These studies have improved our knowledge of strabis-
mus in the world and provide policymakers with more
comprehensive local information.
16,17
Despite several studies across the world, our extensive
search showed no comprehensive study of the pooled
prevalence of strabismus and its epidemiological charac-
teristics and risk factors in children and adults.
Considering the medical, social, and psychological
impacts of this disease, there is an urgent need for relevant
information to designs plans for screening, early diagno-
sis, and timely intervention. The aim of the present study
was to present a systematic assessment of the sources to
provide an estimate of the global prevalence of strabismus
in different age and sex groups and determine the factors
affecting its variability.
Materials and methods
Search strategy and study selection
The results of this meta-analysis are presented accord-
ing to the Preferred Reporting Items for Systematic
Reviews and Meta-Analyses (PRISMA) guideline.
18
The protocol of the study was registered in the
International Prospective Register of Systematic
Reviews with CRD42019119961 code. Four interna-
tional electronic databases (Web of Science, PubMed,
Scopus, and Embase) were searched extensively and
systematically from inception to 29 September 2018 to
retrieve articles related to the prevalence of any stra-
bismus using its MeSH terms (Table 1). The PICO of
the study was as follows:
Population: child and adult
Intervention: none
Comparison: none
Outcome: prevalence of any strabismus, Exotropia
(XT), and Esotropia (ET))
The details of the search strategy, which was first
developed for Medline and then used for other data-
bases, are presented in Table 1. Google Scholar was
used to access the grey literature.
19
An expert was
consulted to access feature articles in the field of
strabismus.
The articles retrieved from each database were entered
into EndNote X6. After removing duplicates, screening
was done in three stages. First, the titles of the articles
were evaluated. Then, if the title was relevant, the abstract
was evaluated. If the abstract was deemed relevant, the
article was read in full. If the raw data of an article were
required, an email was sent to the corresponding author.
The above three steps were carried out by two raters (M.
KH. and R.P.) independently and any disagreement
between them was resolved by a third rater (H.H.).
Blinding and task separation were applied to the study
selection procedure. The kappa value for inter-rater
agreement was 87%.
Exclusion criteria
The inclusion criteria of this study were studies with
across-sectional design (population based and) and
surveys. Studies originating from the phase one of
large cohort studies with a cross-sectional design were
also included.
Since the aim of the study was to assess the preva-
lence of any strabismus in the general population, stu-
dies performed in certain groups like inpatients and
patients suffering from ocular or certain systemic dis-
eases (Down syndrome, etc.) were excluded from ana-
lysis. Moreover, cohort, follow-up and longitudinal,
retrospective, and hospital and clinic based studies,
conference reports, letters, editorials, commentaries,
reviews and case series also excluded.
Data extraction and quality assessment
All articles on the prevalence of strabismus in all age
groups published that reached the final stage were scruti-
nized and data such as the authorsname,
publication year, country, study design, participants
characteristics including age, and sample size were
recorded. Finally, the prevalence and number of subjects
Table 1. Search strategy for MEDLINE (MeSH, Medical Subject
Headings).
1. Strabismus [text word] OR Strabismus [MeSH term]
2. Esotropia [text word] OR Esotropia [MeSH term]
3. Exotropia [text word] OR Exotropia [MeSH term]
4. 1 OR 2 OR 3
5. Prevalence [text word] OR Prevalence [MeSH term]
6. Frequency [text word] OR Frequency [MeSH term]
7: 5 OR 6
8: Cross sectional studies [text word] OR Cross sectional studies [MeSH term]
9: observational studies [text word] OR observational studies [MeSH term]
10: 8 OR 9
11: 4 AND 7 AND 10
2H. HASHEMI ET AL.
with any strabismus, XT, and ET and the criteria applied
to investigate strabismus were extracted and entered into
an Excel sheet. It should be noted that the term any
strabismusin this study was used to define any type of
strabismus, including vertical, horizontal, exotropia, eso-
tropia, etc. reported in the selected studies . Moreover,
phoria was not considered for prevalence of any
strabismus.
The STROBE checklist was used for quality assess-
ment. This checklist contains 22 questions to assess the
methodological aspects of descriptive and cross-sectional
studies.
20
To categorize the studies, each question was
assigned a score of 0 or 1 (the total score of each article
ranged from 0 to 22). Accordingly, the articles were
divided to 5 categories: very low quality (less than 20%
of the maximum score), low quality (2040% of the max-
imum score), moderate quality (4060% of the maximum
score), high quality (6080% of the maximum score), and
very high quality (more than 80% of the maximum score).
Definition of variables
Different definitions of strabismus were used in the
selected studies but all of them are part of following
definitions which were ordered form high to low sensi-
tive definition.
1 = Manifest far or near with or without glasses
2 = Any Tropia far or near- with or without glasses
3 = Constant or Intermittent 10 prism diopters
As for age categorization, according to the experts
opinion, the studies were divided to two categories:
studies conducted in children and adolescents (below
20 years) and studies performed in adults (above 20
years). The latest WHO regional grouping, including
six regions of African Regional Office (AFRO),
American Regional Office (AMRO), Eastern
Mediterranean Regional Office (EMRO), European
Regional Office (EURO), South-East Asia Regional
Office (SERO), and Western Pacific Regional Office
(WPRO), was also used to categorize countries.
Statistical analysis
The Stata version 14 (College Station, Texas) was used
for statistical analysis. The prevalence of strabismus was
extracted from the studies. For studies that did not
report these data, if the sample size and number of
subjects with strabismus were available, the prevalence
and 95% CI were calculated using a binomial distribu-
tion. It should be mentioned that since strabismus had
a low prevalence, the metaprop command was used to
merge the results.
21
The Cochrans Q-test was applied
to assess between-study heterogeneity and I
2
was used
to quantify it. According to the Higgins classification,
an I
2
> 0.7 indicated high heterogeneity. To estimate
the pooled prevalence of strabismus, a fixed-effects
model was applied if I
2
< 0.7 and a random-effects
model was used if I
2
> 0.7. Finally, a meta-regression
analysis was employed to examine the effect of age,
sample size, publication date, strabismus criteria, and
geographical region on heterogeneity between studies.
22
Also the Metabias command was used to detect pub-
lication bias.
23
The level of significance was set at 0.05
for all tests.
Results
In total, 7957 articles were retrieved from databases and
23 were retrieved from other sources. After removing
duplicates, 6039 articles were independently screened
by two raters. Assessment of titles and abstracts
resulted in exclusion of 4861 and 891 articles, respec-
tively. Then, the remaining 287 articles were read in
full, and 231 articles were excluded in this stage. The
corresponding authors of three articles were contacted
to obtain the required data but no response was
received; therefore, these articles were also excluded
from analysis.
Finally, final analysis was performed in 56
studies
1,2,415,2465
with a total sample size of 229,396
participants. Figure 1 shows the flow diagram of study
selection and Table 2 presents the characteristics of the
selected articles.
The highest and lowest number of articles was
related to AMRO (n = 14) and AFRO (n = 3), respec-
tively. The oldest study included was published in
the year 1986
52
and the most recent articles were pub-
lished in. 2018
26,45
The minimum and maximum age
range of the studies was 672 months and 2093 years,
respectively. Four articles of moderate quality, 23 were
of high quality, and 29 were of very high quality. Since
heterogeneity for strabismus, XT and ET according to
I
2
was above 95%, a random-effects model was used to
estimate the pooled prevalence.
Estimate of pooled prevalence of Strabismus, XT
and ET in overall and in World Health Organization
regions
Figure 2 shows the estimated pooled prevalence of
strabismus, XT, and ET in total and also according to
the gender, and age group. The estimated pooled pre-
valence and 95% CI of strabismus, XT, and ET was
1.93% (1.642.21), 1.23% (1.001.46), and 0.77%
(0.590.95), respectively. According to the WHO
region, the highest and lowest pooled prevalence (95%
STRABISMUS 3
CI) of strabismus was seen in AMRO (2.86%,
2.073.65) and AFRO (0.42%, 0.290.55), respectively.
Moreover, the highest and lowest pooled prevalence of
XT was seen in WPRO (1.54%, 0.582.51) and AFRO
(0.14%, 0.060.23) and the highest and lowest pooled
prevalence of ET was seen in EURO (2.17%, 1.133.21)
and AFRO (0.13%, 0.050.21), respectively (Figure 3).
Estimate of pooled prevalence of strabismus, XT
and ET based on sex and age group
Figure 2 also presents the pooled prevalence according
to age (above and below 20 years) and sex (male and
female). Since some studies have reported the total
prevalence of strabismus and its subtypes, it was not
possible to retrieve the data for age and sex.
1,64,66
Therefore, a smaller number of studies were included
to estimate the pooled prevalence according to age and
sex. According to the findings of this study, the esti-
mated pooled prevalence (95% CI) of strabismus, XT,
and ET was 1.78% (1.562.01), 1.07% (0.861.29), and
0.73% (0.560.91) in subjects below 20 years and 3.29%
(0.226.80), 4.60% (3.755.59), and 0.50% (0.210.80)
in subjects above 20 years, respectively. The estimated
pooled prevalence of strabismus, XT, and ET was 1.83%
(1.312.35), 1.54% (0.572.51), and 0.30% (0.090.51)
in women and 1.84% (1.282.39), 1.52% (0.112.93),
and 0.46% (0.070.85) in men, respectively.
Heterogeneity and meta-regression
The CochransQ-test of heterogeneity showed
a significant between-study heterogeneity (p value
<.001 for all). The value of heterogeneity for strabis-
mus, XT, and ET according to the I
2
index was
98.2%, 97.5%, and 96.4% respectively, indicating
high levels of heterogeneity. Table 3 presents the
results of univariate meta-regression analysis.
According to the results, age had a significant direct
relationship only with XT (b: 3.491; p: 0.002); in
other words, the prevalence of XT in subjects above
20 years was 3.49% higher compared to subjects
below 20 years on average. Moreover, there was
a significant difference in the prevalence of strabis-
mus and ET between the 6 WHO regions. On aver-
age, there was a 0.48% difference in the prevalence of
strabismus (p < .001) and a 0.16% difference in the
prevalence of ET (p: 0.027) among WHO regions. In
other words, the prevalence of strabismus in SERO
and EURO was 0.48% higher than its prevalence in
AFRO and EMRO, respectively. Moreover,
publication year had a significant positive
Figure 1. Flowchart of study and inclusion in studies with systematic review and meta-analysis.
4H. HASHEMI ET AL.
Table 2. characteristics of the studies included in this meta-analysis.
Author Design Year Country WHO region Age/Sex Group SS
Number of event (prevalence %)
QOS Definitionstrabismus XT ET
MEPEDS
6
CSS 2008 USA AMRO 672 months 6014 149 (2.47) 85 (1.41) 29 (0.48) VH 2
Ajaiyeoba et al.
24
CSS 2006 Nigeria AFRO 424 yrs. old 1144 3 (0.26) 2 (0.17) 1 (0.9) VH NA
Al Fara et al.
25
CSS 1992 KSA EMRO 620 yrs. old 3590 17 (0.47) NA NA VH NA
Alsaqr et al.
26
CSS 2018 KSA EMRO 1220 yrs. old 998 19 (1.90) NA NA VH 2
Azonobi et al.
27
CSS 2009 Nigeria AFRO 216 yrs. old 7288 32 (0.44) 10 (0.14) 10 (0.14) VH NA
Bigyabati et al.
4
CSS 2016 India SERO 515 yrs. old 1700 2 (0.11) NA NA VH NA
Chen et al.
5
CSS 2016 China WPRO 672 months 5667 320 (5.65) 259 (4.57) 43 (0.76) VH 2
Female 2648 149 (5.63) 119 (4.49) 18 (0.68)
Male 3019 171 (5.66) 138 (4.57) 25 (0.83)
Chia et al.
2
CSS 2010 Singapore WPRO 672 months 3009 24 (0.80) 20 (0.66) 3 (0.10) VH 2
Female 1431 10 (0.70) 8 (0.56) 2 (0.140)
Male 1561 14 (0.90) 12 (0.77) 1 (0.06)
Garcia et al.
1
CSS 2004 Brazil AMRO 620 yrs. old 1015 29 (2.85) 20 (2.16) 6 (0.59) VH 2
Dey et al.
28
CSS 2017 India SERO 615 yrs. old 208 2 (0.96) NA NA VH NA
Diniz et al.
29
CSS 2007 Brazil AMRO 012 yrs. old 525 45 (8.57) NA NA M NA
Ertekin et al.
30
CSS 2016 Turkey EURO 513 yrs. old 1938 43 (2.22) NA NA H 2
Faghihi et al.
13
CSS 2012 Iran EMRO 1418 yrs. old 1133 17 (1.50) 10 (0.88) 5 (0.44) H NA
Fischbach et al.
31
CSS 1993 USA AMRO 67 yrs. old 854 11 (1.29) NA NA H NA
Female 434 5 (1.38) NA NA
Male 420 6 (1.43) NA NA
Friedman et al.
8
CSS 2010 USA AMRO 671 months 2298 60 (2.61) 31 (1.35) 28 (1.22) H 2
Fu et al.
32
CSS 2014 China WPRO 1016 yrs. Old 2151 108 (5.02) NA NA H 2
Garvey et al.
33
CSS 2010 USA AMRO 4.879.42 yrs. Old 594 9 (1.51) 1 (0.17) 2 (0.34) H 2
Female 454 8 (1.76) NA NA
Male 455 4 (0.88) NA NA
Gronlund et al.
34
CSS 2006 Sweden EURO 415 yrs. old 143 5 (3.50) 1 (0.70) 4 (2.80) M 2
Gupta et al.
9
CSS 2009 India SERO 616 yrs. Old 1561 39 (2.50) NA NA H NA
Female 748 24 (2.21) NA NA
Male 813 16 (1.97) NA NA
Gupta et al.
10
CSS 2013 India SERO 616 yrs. old 9067 76 (0.84) NA NA VH NA
Female 3282 33 (1.01) NA NA
Male 3338 43 (1.29) NA NA
Hashemi et al.
15
CSS 2017 Iran EMRO 020 yrs. old 879 19 (2.16) 12 (1.37) 7 (0.80) H 2
2093 yrs. old 2369 121 (5.10) 109 (4.60) 12 (0.51)
Female 1830 77 (4.21) 4 (0.22) 8 (0.44)
Male 1418 63 (4.44) 4 (0.28) 6 (0.42)
Hashemi et al.
35
CSS 2015 Iran EMRO 7 yrs. old 3675 92 (2.50) 47 (1.28) 16 (0.44) H 2
Female 1757 22 (1.25) NA NA
Male 1918 42 (2.19) NA NA
Lanca et al.
36
CSS 2014 Portugal EURO 611 yrs. old 672 27 (4.02) 12 (1.79) 14 (2.08) VH 2
Lithander et al.
37
CSS 1998 Oman EMRO 612 yrs. old 6292 55 (0.87) 15 (0.24) 26 (0.41) VH 2
Lu et al.
38
CSS 2008 China WPRO 614 yrs. old 1084 27 (2.49) 23 (2.12) 4 (0.40) VH 2
Female 439 14 (3.19) 14 (3.19) 0 (0)
Male 645 13 (2.01) 9 (1.40) 4 (0.62)
McKean-Cowdin et al.
7
CSS 2013 USA AMRO 672 m 3036 103 (3.39) 43 (1.42) 56 (1.84) VH 2
Nepal et al.
39
CSS 2003 Nepal SERO 516 yrs. old 1100 18 (1.64) NA NA H NA
Female 595 10 (2.01) NA NA
Male 505 8 (1.58) NA NA
Ohlsson et al.
40
CSS 2003 Mexico AMRO 1213 yrs. old 1035 24 (2.32) NA NA H NA
Rajavi et al.
41
CSS 2015 Iran EMRO 712 yrs. old 2417 55 (2.28) 31 (1.28) 24 (0.99) VH 3
Reddy et al.
42
CSS 2006 Malaysia WPRO 712 yrs. old 1214 30 (2.47) NA NA VH NA
Schaal et al.
43
CSS 2016 Brazil AMRO 112 months 1852 30 (1.62) 6 (0.32) 21 (1.13) VH 2
Male 821 12 (1.46) NA NA
Female 1031 18 (1.76) NA NA
Schimiti et al.
44
CSS 2001 Brazil AMRO 612 yrs. old 13471 114 (0.85) 35 (0.30) 73 (0.54) M NA
Sandfeld et al.
45
CSS 2018 Denmark EURO 4.57 yrs. old 445 7 (1.57) NA NA H 2
Sharma-1 et al.
12
CSS 2017 India SERO 516 yrs. old 5918 24 (0.41) NA NA M 2
Female 2456 12 (0.49) NA NA
Male 3462 12 (0.35) NA NA
Sharma-2 et al.
12
CSS 2017 India SERO 615 yrs. old 1265 10 (0.79) NA NA H NA
Female 755 5 (0.66) NA NA
Male 510 5 (0.98) NA NA
Sherpa et al.
46
CSS 2011 Nepal SERO 015 yrs. old 466 2 (0.43) NA NA H 2
Singh et al.
47
CSS 2017 India SERO 515 yrs. old 4838 13 (0.27) NA NA H 2
Uddin et al.
48
CSS 2017 Bangladesh SERO 46 yrs. old 900 7 (0.78) NA NA H 2
Turacli et al.
49
CSS 1995 Turkey EURO 612 yrs. old 23810 60 (0.25) NA NA H NA
Wedner et al.
50
CSS 2000 Tanzania AFRO 719 yrs. old 1386 7 (0.51) NA NA H 2
Williams et al.
51
CSS 2008 UK EURO 7 yrs. old 7538 173 (2.30) NA NA H 2
Woodruff et al.
52
CSS 1986 Canada AMRO 6 yrs. old 6080 242 (3.98) 78 (1.28) 164 (2.70) VH 2
Yekta et al.
53
CSS 2010 Iran EMRO 717 yrs. old 2683 49 (1.83) 31 (1.16) 15 (0.60) VH 2
Yekta et al.
54
CSS 2017 Iran EMRO 615 yrs. old 1130 21 (1.86) NA NA VH 2
Female 520 7 (1.35) NA NA
Male 610 15 (2.46) NA NA
(Continued)
STRABISMUS 5
Table 2. (Continued).
Author Design Year Country WHO region Age/Sex Group SS
Number of event (prevalence %)
QOS Definitionstrabismus XT ET
Yekta et al.
55
CSS 2016 Iran EMRO 46 yrs. old 3628 44 (1.21) 44 (0.17) 25 (0.22) VH 2
Female 1758 12 (0.68) 1 (0.06) 4 (0.23)
Male 1870 32 (1.71) 5 (0.21) 4 (0.21)
Hashemi et al.
56
CSS 2012 Iran EMRO 617 yrs. old 1551 31 (1.99) NA NA VH 2
Ying et al.
57
CSS 2014 USA AMRO 35 yrs. old 3837 153 (3.98) NA NA VH 2
Yoon et al.
58
CSS 2011 ROK WPRO 2070 yrs. old 11048 168 (1.84) NA NA VH 1
320 yrs. Old 3416 63 (1.52) NA NA
Female 7947 119 (1.50) NA NA
Male 6517 98 (1.50) NA NA
Drover et al.
59
CSS 2008 Canada AMRO 1.611.6 yrs. old 946 41 (4.33) NA NA VH 2
Cotter et al.
60
CSS 2011 USA AMRO 672 months 5121 NA 61 (1.19) 48 (0.94) VH 2
Faghihi et al.
14
CSS 2011 Iran EMRO Female 942 39 (4.14) NA NA H 2
Male 1208 25 (2.07) NA NA
621 yrs. old 2150 67 (3.12) 45 (2.09) 19 (0.88)
Fan et al.
61
CSS 2011 China WPRO 36 yrs. old 1424 28 (1.97) 23 (1.62) 5 (0.35)
Nirmalan et al.
11
CSS 2003 India SERO 1 months 15 yrs. old 1065 4 (0.38) NA NA VH NA
Robaei D et al.
62
CSS 2006 Australia WPRO 12 yrs. old 2353 64 (2.72) 27 (1.15) 21 (0.89) VH 2
Robaei D et al.
63
CSS 2006 Australia WPRO 6 yrs. old 1739 48 (2.76) 14 (0.81) 26 (1.50) H 2
Sitompul et al.
64
CSS 2017 Indonesia SERO 170 yrs. old 667 1 (0.1) NA NA H NA
Matsuo et al.
65
CSS 2007 Japan WPRO 1.53 yrs. old 33929 22 (0.06) 11 (0.03) 7 (0.02) H NA
CSS = cross-sectional study; KSA = Kingdom of Saudi Arabia; UK = united kingdom; ROK = republic of Korea; USA; united states of America; NA = not
available; QOS = Quality of study; VH = very high; H = high; M; moderate.
Coding for definition: 1 = Manifest or latent far or near with or without glasses; 2 = Any Tropia far or near- with or without glasses; 3 = Constant or
Intermittent 10 prism diopters
MEPEDS: Multi-Ethnic Pediatric Eye Disease Study
Figure 2. Pooled prevalence and 95% CI of strabismus, exotropia, and esotropia in total and according to age, and sex subgroup.
The diamond marks illustrate the estimate of pooled prevalence.
6H. HASHEMI ET AL.
relationship with heterogeneity in the prevalence of
XT but its significance level was borderline (b: 0.059,
p: 0.045) (Figure 4). Sample size and publication year
did not have any correlation with strabismus nor
with other variables. Table 3 shows the status of
other variables.
Figure 3. Pooled prevalence and 95% CI of strabismus, exotropia, and esotropia according to WHO region. There were no data for
pooled estimation of esotropia and exotropia in SERO.
STRABISMUS 7
Publication bias
The results of the Beggstest showed no publication
bias for strabismus (z score: 0.85; p: 0.396), XT (z score:
0.60; p: 0.548), and ET (z score: 0.85; p: 0.396).
Discussion
It is very important to diagnose and treat strabismus in
early stages to achieve the maximum best binocular
vision.
1
Prevalence studies are of clinical and public
health significance since knowledge of the extent of
a disease is essential for providing treatment
infrastructures. There is a great variation in the preva-
lence of strabismus according to age, sex, etc. However,
regardless of these groupings, the pooled prevalence of
strabismus, XT, and ET was 1.93%, 1.23%, and 0.77%,
respectively. In other words, 106221, 100146, and
59123 in 10,000 population had strabismus, XT, and
ET, respectively. Although the pooled prevalence of this
disease may seem low, it should be noted that strabis-
mus develops in early years of life and, if untreated,
may result in different sensorial adaptation disorders,
including retinic correspondence anomaly and amblyo-
pia, which have lifelong effects on the quality of life of
the patients.
1
Although some studies have investigated the preva-
lence of strabismus and its subtypes in different ethnic
groups,
68,60
but none of them havent estimated the
pooled prevalence in the worldwide. Therefore, it is not
possible to compare our results with other studies.
However, the results of this study showed that the pre-
valence of strabismus varied in different countries and
WHO regions; for example, the highest prevalence of
strabismus was seen in AMRO and EURO and this dif-
ference was not due to the diagnostic criteria. Table 2
presents the prevalence of strabismus in different ethni-
cities and geographical regions. The prevalence of strabis-
mus was higher in western countries and white people
compared to Asian ethnicities like Chinese and Indian
peoples. Caution should be practiced when comparing the
prevalence of strabismus according to the geographical
region because variations in the results of the studies may
might simply reflect differences in the methodology and
age range of the study populations. Regardless of the
Table 3. Results of the univarate metaregresion analysis on the hertogenisity of the determinants.
Variables
Strabismus XT ET
Coefficient p-value Coefficient p-value Coefficient p-value
Age 1.376
(0.546 to 3.299)
0.157 3.491
(1.456 to 5.525)
0.002* 0.259
(1.562 to 1.044)
0.686
WHO region 0.482
(0.275 to 0.688)
<0.001* 0.060
(0.200 to 0.322)
0.637 0.168
(0.020 to 0.315)
0.027*
Sample size 0.001
(0.001 to 0.001)
0.301 0.001
(0.001 to 0.001)
0.173 0.001
(0.001 to 0.001)
0.210
Publication years 0.001
(0.057 to 0.055)
0.974 0.059
(0.001 to 0.117)
0.045* 0.026
(0.064 to 0.011)
0.167
Sex (Female = 0) 0.034
(0.994 to 0.926)
0.943 0.158
(2.890 to 2.573)
0.897 0.085
(0.411 to 0.583)
0.696
Definition criteria 0.397
(1.515 to 2.309)
0.676 0.237
(2.410 to 1.935)
0.823 0.076
(1.270 to 1.424)
0.907
QOS 0.031
(0.641 to 0.704)
0.926 0.323
(0.334 to 0.982)
0.322 0.086
(0.307 to 0.481)
0.654
XT: Exotropia; ET: Esotropia.
*: Significance
Coding of Age: 1 = lower than 20 years old; 2 = upper than 20 years old
Coding of WHO region: 1 = AFRO; 2 = SERO; 3 = EMRO; 4 = EURO; 5 = WPRO; 6 = AMRO
Coding of QOS (Quality of study): 1 = very low; 2 = low; 3 = moderate; 4 = high; 5 = very high
Coding for definition: 1 = Manifest or latent far or near with or without glasses; 2 = Any Tropia far or near- with or without glasses; 3 = Constant or
Intermittent 10 prism diopters
Figure 4. The relationship between the prevalence of exotropia
with publication year study by means of meta-regression. Size
of circles indicates the precision of each study. There is sig-
nificant relationship with respect to Prevalence of exotropia and
publication year study. Prevalence of exotropia has been
approximated increased during years of study in this survey.
8H. HASHEMI ET AL.
above factors, many studies have reported the role of
environmental factors and ethnic-racial differences,
screening programs,
13
and even the dominant refractive
error in strabismus prevalence differences; for example, it
has been suggested that the high prevalence of strabismus
in white people could be due to the high prevalence of
hyperopia,
2
The high prevalence of strabismus in AMRO
in this study and the high prevalence of hyperopia in
western countries in other studies
16
could support this
hypothesis.
Similar to other studies
1,5,6
, our study also showed that
XT was the most common subtype of strabismus as the
prevalence of XT and ET was 1.23% and 0.77%, respec-
tively. Our study also showed a difference in the prevalence
of the dominant strabismus subtype between WHO
regions; for example, ET had a higher prevalence in
AMRO and EURO while XT was the dominant subtype
in Asia, especially WPRO, confirming the results of several
previous studies.
1,7,15,36,40,51,63,67
Studies have shown
a higher prevalence of esotropia in western countries, espe-
cially in white people and Caucasians,
1,7,15,36,40,51,63,67
while
exotropiahasahigherprevalenceinblackpeopleand
Asians, including the Chinese, Indian, and Iranian
populations.
7,15
It should be noted that variation in the
prevalence of strabismus subtypes in different parts of the
world could be due to different reasonssuchasethnicity,
genetics, environmental factors, and even other unknown
factors. Some review studies showed that the prevalence of
exotropia was sometimes higher in African and lower in
Europe, and attributed the reason to the distance from the
Equator.
68,69
However, one of the most important reasons
for the difference in the prevalence of strabismus subtypes
may be the dominant refractive error
13
such that the higher
prevalence of XT than ET in Asians can be due to the
higher prevalence of myopia in this population.
2
On the
other hand, ET has a stronger correlation with hyperopia
70
because subjects suffering from ET need more accommo-
dation to compensate hyperopia.
35
Studies in Japan
65
and
Korea have shown an increase in the ratio of XT to ET over
the past decade
71
duetoanincreaseintheprevalenceof
myopia in the world
16
and a decrease in the prevalence of
ET due to early diagnosis of intermittent ET with provision
of hypermetropic glasses,
8
indicating the important role of
refractive errors.
Despite several studies about strabismus, there is still
inconsistency about the strabismus trend change with age.
Studies in children aged 672 months,
6
3672 months,
5
and 3072 months
7
have shown a higher prevalence of
strabismus in older children. Kvarnström et al.
67
studied
children aged 112 years and reported that age was an
important determinant of the difference in the prevalence
of strabismus between different age groups. In this study,
the highest prevalence of strabismus was seen in children
4 years of age followed by a decreasing trend thereafter,
which was attributed to decreased prevalence of hypero-
pia with age
67
and early detection of the disease at lower
ages.
13
However, the results of other studies do not sup-
port this finding
15,30,36
; for example, Hashemi et al.
15
studied subjects aged 3 to 93 years and rejected any
difference in the prevalence of strabismus with age. The
results of this study and several other studies indicate that
age does not affect the prevalence of strabismus and
variations in different populations may be due to other
factors like genetic and environmental differences.
7
There are different reports of an inter-gender differ-
ence in the prevalence of strabismus and its subtypes.
Some studies have shown a higher prevalence of stra-
bismus in girls and have attributed the reason to the
higher prevalence of hyperopia in this gender.
14
However, several other studies have rejected any inter-
gender difference.
5,6,15,35
Our study pooled the data of
56 studies and showed no inter-gender difference in the
prevalence strabismus, XT, and ET. In other words,
inter-gender differences observed in other studies may
be due to other factors such as the age distribution of
the study population, ethnicity, and genetic and envir-
onmental factors. Lack of difference in the prevalence
of strabismus in multi ethnic studies confirms this
finding.
68
According to Vision 2020, many countries have
embarked on different programs for early detection
and treatment of some ocular disorders, including
strabismus.
72
In this regard, although we expected
a decrease in its prevalence in the recent three decades,
the results of meta-regression showed no change except
for a borderline significant increase in the prevalence of
XT. In other words, it seems that efforts to control the
disease are not yet at a scale to make a difference and
there is a need for more systematic screening programs,
especially in developing countries where screening pro-
grams are less efficient.
13
There were concerns over publication bias due to the
large number of exclusion criteria; therefore, we inves-
tigated publication bias in the reported prevalence of
strabismus, XT, and ET but the results showed no bias.
Hence, the results were robust to publication bias.
This study suffered some limitations. First, we were
willing to include all studies investigating the prevalence
of strabismus, XT, and ET but we had to exclude many of
them due to differences in their design and population
that impeded merging their results. Second, few studies
were published from some continents and therefore it
was not possible to provide a more robust estimate
according to the WHO region. However, our study had
some strong points. For example, this study presented an
estimate of the prevalence of strabismus, XT, and ET in
STRABISMUS 9
the global population and in WHO regions for the first
time. Our extensive search resulted in the retrieval of
a large number of articles of which 56 articles with
a total sample size of 229,396 subjects entered the final
analysis, which provided a sufficient statistical power.
Moreover, for the first time in the past three decades,
we also calculated the prevalence of strabismus, XT, and
ET in the age group above 20 years as a neglected age
group in most ophthalmologic studies.
Conclusion
The findings of this systematic review showed a higher
prevalence of strabismus in some countries and ethni-
cities, especially western countries and white people.
This study revealed that 1 in every 50 people had
strabismus, which severely affects their quality of life.
The results showed no significant difference in the
prevalence of strabismus between different age and
sex groups. Information about the global prevalence
of strabismus can help health care planners design
proper interventions and prioritize resource allocation.
Conflict of Interest
No conflicting relationship exists for any author.
Funding
This project was supported by Noor Research Center for
Ophthalmic Epidemiology.
References
1. Garcia C, de Sousa A, Mendonça M, de Anderade L,
Oréfice F. Prevalence of strabismus among students in
Natal/RN-Brazil. Arq Bras Oftalmol.2004;67
(5):791794. doi:10.1590/S0004-27492004000500018.
2. Chia A, Dirani M, Chan Y, et al. Prevalence of amblyo-
pia and strabismus in young Singaporean Chinese
children. Invest Ophthalmol Vis Sci.2010;51
(7):34113417. doi:10.1167/iovs.09-4461.
3. Jackson S, Harrad R, Morris M, Rumsey N. The psy-
chosocial benefits of corrective surgery for adults with
strabismus. Br J Ophthalmol.2006;90(7):883888.
doi:10.1136/bjo.2005.089516.
4. Bigyabati R, Victor R, Rajkumari B. A study of pre-
valence of ocular morbidities in school going children
in a rural District of Manipur. J Evol Med Dent Sci.
2016;5(53):35403543. doi:10.14260/jemds/2016/816.
5. Chen X, Fu Z, Yu J, et al. Prevalence of amblyopia and
strabismus in Eastern China: results from screening of
preschool children aged 3672 months. Br J Ophthalmol.
2016;100(4):515519. doi:10.1136/bjophthalmol-2015-
306999.
6. Group M-ePEDS. Prevalence of amblyopia and strabis-
mus in African American and Hispanic children ages 6 to
72 months: the Multi-ethnic Pediatric Eye Disease Study.
Ophthalmology.2008;115(7):12291236. doi:10.1016/j.
ophtha.2007.08.001.
7. McKean-Cowdin R, Cotter SA, Tarczy-Hornoch K,
et al. Prevalence of amblyopia or strabismus in Asian
and non-Hispanic white preschool children:
Multi-ethnic Pediatric Eye Disease Study.
Ophthalmology.2013;120(10):21172124. doi:10.1016/
j.ophtha.2013.03.001.
8. FriedmanD,RepkaM,KatzJ,etal.Prevalenceofamblyo-
pia and strabismus in white and African American chil-
dren aged 6 through 71 months: the Baltimore Pediatric
Eye Disease Study. Ophthalmology.2009;116
(11):21282134. doi:10.1016/j.ophtha.2009.04.034.
9. Gupta M, Gupta B, Chauhan A, Bhardwaj A. Ocular
morbidity prevalence among school children in Shimla,
Himachal, North India. Indian J Ophthalmol.
2009;57:133138.
10. Gupta N, Arya S, Walia D, Mallik A, Sood S. Ocular
morbidity among school-going children in the Union
Territory of Chandigarh. Int Ophthalmol.2014;34
(2):251257. doi:10.1007/s10792-013-9825-4.
11. Nirmalan PK, Vijayalakshmi P, Sheeladevi S,
Kothari MB, Sundaresan K, Rahmathullah L. The
Kariapatti Pediatric Eye Evaluation Project: baseline
ophthalmic data of children aged 15 years or younger in
Southern India. Am J Ophthalmol.2003;136:703709.
12. Sharma A, Maitreya A, Semwal J, Bahadur H. Ocular
morbidity among school children in Uttarakhand: hima-
layan state of India. Ann Trop Med Public Health.2017;10
(1):149153. doi:10.4103/1755-6783.196823.
13. Faghihi M. The prevalence of refractive errors, strabis-
mus and amblyopia in schoolboys of Varamin, Iran, in
2010. Iran J Ophthalmol.2012;24:3339.
14. Faghihi M, Ostadimoghaddam H, Yekta A. Amblyopia
and strabismus in Iranian schoolchildren, Mashhad.
Strabismus.2011;19(4):147152. doi:10.3109/09273972.
2011.622341.
15. Hashemi H, Nabovati P, Yekta A, Ostadimoghaddam H,
Behnia B, Khabazkhoob M. The prevalence of strabismus,
heterophorias, and their associated factors in underserved
rural areas of Iran. Strabismus.2017;25(2):6066.
doi:10.1080/09273972.2017.1317820.
16. Hashemi H, Fotouhi A, Yekta A, Pakzad R,
Ostadimoghaddam H, Khabazkhoob M. Global and
regional estimates of prevalence of refractive errors: sys-
tematic review and meta-analysis. JCurrOphthalmol.
2018;30(1):322. doi:10.1016/j.joco.2017.08.009.
17. Hashemi H, Pakzad R, Yekta A, et al. Global and regional
estimates of prevalence of amblyopia: A systematic review
and meta-analysis. Strabismus.2018;26(4):168183.
doi:10.1080/09273972.2018.1500618.
18. Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred
reporting items for systematic reviews and meta-analyses:
the PRISMA Statement. PLOS Med.2009;6(7):e1000097.
doi:10.1371/journal.pmed.1000097.
19. Haddaway NR, Collins AM, Coughlin D, Kirk S. The role
of Google Scholar in evidence reviews and its applicability
to grey literature searching. PloS one.2015;10(9):
e0138237. doi:10.1371/journal.pone.0138237.
10 H. HASHEMI ET AL.
20. Von Elm E, Altman DG, Egger M, et al. The
Strengthening the Reporting of Observational Studies
in Epidemiology (STROBE) statement: guidelines for
reporting observational studies. PLOS Med.2007;4
(10):16231627. doi:10.1371/journal.pmed.0040296.
21. Nyaga VN, Arbyn M, Aerts M. Metaprop: a Stata com-
mand to perform meta-analysis of binomial data. Arch
Public Health.2014;72(1):210. doi:10.1186/2049-3258-
72-2.
22. Harbord R, Higgins J, 2004.METAREG: stata module
to perform meta-analysis regression,Statistical
Software Components S446201, Boston College
Department of Economics, revised 05 Jan 2009.
23. Harbord RM, Harris RJ, Sterne JAC, Steichen T, 2000.
METABIAS: stata module to test for small-study
effects in meta-analysis,Statistical Software
Components S404901, Boston College Department of
Economics, revised 08 Jan 2009.
24. Ajaiyeoba A, Isawumi M, Adeoye A, Oluleye T.
Prevalence and causes of eye diseases amongst students
in south-western Nigeria. Ann Afr Med.2006;5:197203.
25. Al M. Prevalence of ocular disorders among schoolboys in
five villages in Al-Baha region. Ann Saudi Med.
1992;12:37.
26. Alsaqr A, Sharha A, Fagehi R, et al. The visual status of
adolescents in Riyadh, Saudi Arabia: a population study.
Clin Ophthalmol.2018;12:965972. doi:10.2147/OPTH.
S162319.
27. Azonobi I, Olatunji F, Addo J. Prevalence and pattern of
strabismus in Ilorin. West Afr J Med.2009;28:253256.
28. Dey A, Nath A. Prevalence of ocular morbidities
among school children in a rural block of Cachar,
Assam. J Evol Med Dent Sci.2017;6(55):41244127.
doi:10.14260/Jemds/2017/893.
29. Diniz B, Pachá PM. Ocular profile of the pediatric popula-
tion seen at the ophthalmology Service of Petropolis
Medical School-RJ. Rev. Bras. Oftalmol.2007;66:4548.
30. Ertekin Y, Tekin M, Uludag A, Arikan S, Sahin E.
Vision screening in children: is 7-9 years of age
a threshold for visual impairment? Pak J Med Sci.
2016;32(5):11941198. doi:10.12669/pjms.325.10367.
31. Fischbach L, Lee D, Englehardt R, Wheeler N. The
prevalence of ocular disorders among Hispanic and
Caucasian children screened by the UCLA Mobile
Eye Clinic. J Community Health.1993;18:201211.
32. Fu J, Li S, Liu L, et al. Prevalence of amblyopia and
strabismus in a population of 7th-grade junior high
school students in Central China: the Anyang
Childhood Eye Study (ACES). Ophthalmic Epidemiol.
2014;21(3):197203. doi:10.3109/09286586.2014.904371.
33. Garvey K, Dobson V, Messer D, Miller J, Harvey E.
Prevalence of strabismus among preschool, kindergarten,
and first-grade Tohono Oodham children. Optometry.
2010;81(4):194199. doi:10.1016/j.optm.2009.10.010.
34. Grönlund M, Andersson S, Aring E, Hård A, Hellström A.
Ophthalmological findings in a sample of Swedish children
aged 415 years. Acta Ophthalmol Scand.2006;84
(2):169176. doi:10.1111/j.1600-0420.2005.00615.x.
35. Hashemi H, Yekta A, Jafarzadehpur E, et al. The pre-
valence of strabismus in 7-year-old schoolchildren in
Iran. Strabismus.2015;23(1):17. doi:10.3109/
09273972.2014.999795.
36. Lança C, Serra H, Prista J. Strabismus, visual acuity,
and uncorrected refractive error in Portuguese children
aged 6 to 11 years. Strabismus.2014;22(3):115119.
doi:10.3109/09273972.2014.932395.
37. LithanderJ.Prevalenceofamblyopiawithanisometropia
or strabismus among schoolchildrenintheSultanateof
Oman. Acta Ophthalmol Scand.1998;76:658662.
38. Lu P, Chen X, Zhang W, Chen S, Shu L. Prevalence of
ocular disease in Tibetan primary school children. Can
J Ophthalmol.2008;43(1):9599. doi:10.3129/i07-194.
39. Nepal B, Koirala S, Adhikary S, Sharma A. Ocular
morbidity in schoolchildren in Kathmandu. Br
J Ophthalmol.2003;87:531534.
40. Ohlsson J, Villarreal G, Sjöström A, Cavazos H,
Abrahamsson M, Sjöstrand J. Visual acuity, amblyopia,
and ocular pathology in 12-to 13-year-old children in
Northern Mexico. J AAPOS.2003;7(1):4753.
doi:10.1067/mpa.2003.S1091853102420113.
41. Rajavi Z, Sabbaghi H, Baghini AS, et al. Prevalence of
amblyopia and refractive errors among primary school
children. J Ophthalmic Vis Res.2015;10(4):408.
doi:10.4103/2008-322X.176909.
42. Reddy S, Hassan M. Refractive errors and other eye
diseases in primary school children in Petaling Jaya,
Malaysia. Asian J Ophthalmol.2006;8:195198.
43. Schaal LF, Schellini SA, Pesci LT, Galindo A,
Padovani CR, Corrente JE. The prevalence of strabis-
mus and associated risk factors in a southeastern
region of Brazil. Semin Ophthalmol.2018;33
(3):357360. doi:10.1080/08820538.2016.1247176.
44. Schimiti RB, Costa VP, Gregui MJF, Kara-José N,
Temporini ER. Prevalence of refractive errors and ocular
disordersin preschool and school children of Ibiporã-PR,
Brazil (1989 to 1996). Arq Bras Oftalmol.2001;64
(5):379384. doi:10.1590/S0004-27492001000500002.
45. Sandfeld L, Weihrauch H, Tubæk G, Mortzos P.
Ophthalmological data on 4.5-to 7-year-old Danish
children. Acta Ophthalmol.2018;96(4):379383.
doi:10.1111/aos.13650.
46. Sherpa D, Pant C, Joshi N. Ocular morbidity among
primary school children of Dhulikhel, Nepal. Nepal
J Ophthalmol.2011;3(2):172176. doi:http://dx.doi.
org/10.3126/nepjoph.v3i2.5272.
47. Singh V, Malik K, Malik V, Jain K. Prevalence of ocular
morbidity in school going children in West Uttar
Pradesh. Indian J Ophthalmol.2017;65(6):500508.
doi:10.4103/ijo.IJO_676_15.
48. Uddin M, Omar R, Feizal V, Alam K. Ocular morbidity
among preschool children in urban area of Chittagong
in Bangladesh. Int Eye Sci.2017;17:1620.
49. Turacli M, Aktan S, Dürük K. Ophthalmic screening of
school children in Ankara. Eur J Ophthalmol.
1995;5:181186.
50. Wedner SH, Ross DA, Balira R, Kaji L, Foster A.
Prevalence of eye diseases in primary school children
in a rural area of Tanzania. Br J Ophthalmol.
2000;84:12911297.
51. Williams C, Northstone K, Howard M, Harvey I,
Harrad R, Sparrow J. Prevalence and risk factors for
common vision problems in children: data from the
ALSPAC study. Br J Ophthalmol.2008;92:869.
doi:10.1136/bjo.2007.134700.
STRABISMUS 11
52. Woodruff M. Vision and refractive status among grade
1 children of the Province of New Brunswick. Am
J Optom Physiol Opt.1986;63:545552.
53. Yekta A, Fotouhi A, Hashemi H, et al. The prevalence
of anisometropia, amblyopia and strabismus in school-
children of Shiraz, Iran. Strabismus.2010;18
(3):104110. doi:10.3109/09273972.2010.502957.
54. Yekta A, Hashemi H, Norouzirad R, et al. The preva-
lence of amblyopia, strabismus, and ptosis in school-
children of Dezful. Eur J Ophthalmol.2017;27
(1):109112. doi:10.5301/ejo.5000795.
55. Yekta A, Hashemi H, Ostadimoghaddam H, et al.
Strabismus and near point of convergence and amblyo-
pia in 46 year-old children. Strabismus.2016;24
(3):113119. doi:10.1080/09273972.2016.1205103.
56. Hashemi H, Rezvan F, Derakhshan A. The prevalence
of amblyopia and strabismus among schoolchildren in
Northeastern Iran, 2011. Iran J Ophthalmol.
2012;24:310.
57. Ying GS, Maguire MG, Cyert LA, et al. Prevalence of
vision disorders by racial and ethnic group among
children participating in head start. Ophthalmology.
2014;121(3):630636. doi:10.1016/j.ophtha.2013.09.036.
58. Yoon KC, Mun G-H, Kim S-D, et al. Prevalence of eye
diseases in South Korea: data from the Korea national
health and nutrition examination survey 2008-2009.
Korean J Ophthalmol.2011;25(6):421433. doi:10.3341/
kjo.2011.25.6.421.
59. Drover J, Kean P, Courage M, Adams R. Prevalence of
amblyopia and other vision disorders in young
Newfoundland and Labrador children. Can
J Ophthalmol.2008;43(1):8994. doi:10.3129/i07-187.
60. Cotter S, Varma R, Tarczy Hornoch K, et al. Risk
factors associated with childhood strabismus: the
multi-ethnic pediatric eye disease and Baltimore pedia-
tric eye disease studies. Ophthalmology.2011;118
(11):22512261. doi:10.1016/j.ophtha.2011.06.032.
61. Fan D, Lai C, Lau H, Cheung E, Lam D. Change in
vision disorders among Hong Kong preschoolers in 10
years. Clin Exp Ophthalmol.2011;39(5):398403.
doi:10.1111/j.1442-9071.2010.02470.x.
62. Robaei D, Rose KA, Kifley A, Cosstick M, Ip JM,
Mitchell P. Factors associated with childhood strabismus:
findings from a population-based study. Ophthalmology.
2006;113(7):11461153. doi:10.1016/j.ophtha.2006.02.019.
63. Robaei D, Kifley A, Mitchell P. Factors associated with
a previous diagnosis of strabismus in a
population-based sample of 12-year-old Australian
children. Am J Ophthalmol.2006;142(6):10851087.
doi:10.1016/j.ajo.2006.06.053.
64. Sitompul R, Lestari YD, Siregar S, et al. The burden of
ocular diseases in an underdeveloped village in Southwest
Sumba, Eastern Indonesia, 2016. Med J Indones.2018;26
(4):277285. doi:10.13181/mji.v26i4.1808.
65. Matsuo T, Matsuo C, Matsuoka H, Kio K. Detection of
strabismus and amblyopia in 1.5-and 3-year-old chil-
dren by a preschool vision-screening program in Japan.
Acta Med Okayama.2007;61(1):916. doi:10.18926/
AMO/32910.
66. Germano R, Kawai R, Souza B, Germano F,
Germano C, Germano J. Frequency of ocular condi-
tions in native Brazilians from Avaí City, São Paulo
State. Rev Bras Oftalmol.2017;76(5):227231.
doi:10.5935/0034-7280.20170047.
67. Kvarnström G, Jakobsson P, Lennerstrand G. Visual
screening of Swedish children: an ophthalmological
evaluation. Acta Ophthalmol Scand.2001;79:240244.
68. Bhola R, Intermittent exotropia: a major review.
Eyerounds.org, Jan 2006.
69. Jenkins RH. Demographics: geographic variations in the
prevalence and management of exotropia. Am Orthopt J.
1992;42(1):8287. doi:10.1080/0065955X.1992.11981899.
70. Ekdawi N, Nusz K, Diehl N, Mohney B. The develop-
ment of myopia among children with intermittent
exotropia. Am J Ophthalmol.2010;149(3):503507.
doi:10.1016/j.ajo.2009.10.009.
71. Yu C, Fan D, Wong V, Wong C, Lam D. Changing
patterns of strabismus: a decade of experience in Hong
Kong. Br J Ophthalmol.2002;86:854856.
72. Yang Y, Dcole M. Visual acuity testing in schools: what
needs to be done. BMJ.1996;313(7064):1053.
doi:10.1136/bmj.313.7064.1053.
12 H. HASHEMI ET AL.
... Strabismus impacts on visionrelated quality of life (Hultman, 2019;Yoon, 2011), and had negative sensory and social effects, as amblyopia, impaired depth perception, reduced academic or work performance etc. Early screening programs, diagnosis and appropriate treatment of strabismus should be medical goals while it will improve vision-related quality of life and will achieve better academic and work performance (Hashemi et al., 2019). There is a need for more systemic screening programs, especially in developing countries such as Macedonia (Faghihi, 2012). ...
... The prevalence of strabismus varies in different countries and WHO regions. The prevalence of strabismus is higher in western countries and Caucasians compared to Asian ethnicities such as Chinese and Indian people (Hashemi et al., 2019). One in every 50 people had strabismus, which severely affects their quality of life. ...
... One in every 50 people had strabismus, which severely affects their quality of life. Information about prevalence of strabismus can help health care planners design proper interventions and screening programs (Hashemi et al., 2019). It is very important to diagnose and treat strabismus in early stages to achieve maximum best binocular vision (Garcia et al., 2004). ...
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Aim: To investigate the prevalence of strabismus by age groups in Caucasian Macedonian population. Methods: A study population of 1900 patients (aged 0-86 years) from the capital city, Skopje, Macedonia, were analysed in a secondary health institution in the central urban area. Ophthalmological examination included: visual acuity, slit-lamp biomicroscopy, autorefraction, and ocular motility examination. Results: In our retrospective cohort (1900), 60 patients did have strabismus (3.2%). The highest prevalence of strabismus was in primary school children (10-14 years-20.2 %; 0-4 years-16.2 %; 15-19 years-11.8% and 5-9 years-8.6%). Our adult population showed results similar to Caucasian Danish population with prevalence of strabismus of 0.7% (age group 50-54 years) and 0.8 % (age group 55-59). The most frequently identified subtype was esotropia (73.3%), followed by exotropia (23.4%) and cyclovertical strabismus (3.3 %). Conclusion: The overall prevalence of strabismus on Macedonian cohort was 3.2%. Our results on primary school children are much higher than other studies on Caucasian and Asian population, but similar to prevalence in the population in Saudi Arabia. The most prevalent type of strabismus was esotropia (73.3%). Regarding gender distribution , both esotropia and exotropia were more frequent in males.
... A meta-analysis of various studies across the world on strabismus showed an estimated pooled prevalence of 1.93%. [1] In this meta-analysis, the prevalence of exotropia (1.23%) was higher than esotropia (0.77%). This analysis revealed that the distribution and pattern of strabismus are heterogeneous in different parts of the world and within the same region of the world. ...
... [5][6][7] The worldwide pooled prevalence of strabismus by a meta-analysis was estimated to be 1.93%. [1] A similar meta-analysis on African studies found the prevalence to be 0.8%. [8] Studies from China found the prevalence of strabismus to vary from 1.98% to 5%. ...
... [16][17][18] The frequency of IDS was greater in the age group of 0-19 years (8), followed by 20-39 years (5) and 40-59 (1) years of age. [1] This supports the natural history of progression of IDS, which becomes constant with time. The IDS being the most common subtype of exotropia in the literature could be attributed to the fact that it becomes constant over time and most of the strabismus studies have been conducted in the pediatric population. ...
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A BSTRACT Purpose To determine the clinical pattern and burden of strabismus in a teaching institute of Northeast (NE) India. Methods In this hospital-based, cross-sectional study, detailed clinical evaluation of patients with manifest strabismus was carried out for a period of one and half years. Results Out of the 7222 new outpatient department attendances, a total of 110 new patients with manifest strabismus were found, with a hospital-based burden of 1.52% [95% confidence interval: 1.3–1.8]. Comitant strabismus was seen in 84.55%, and incomitant in 15.45%. Exotropia comprised 70%, esotropia 26.36%, hypertropia 10%, and hypotropia 2.72%. The angle of deviation was large in most of the participants (69.09%) with a mean of 34.90 ± 17.08 PD for horizontal and 13.29 ± 8.97 PD for vertical deviations. A cause of strabismus could be identified in 30.91%. Paralytic strabismus was seen in 15.45%, sensory in 11.82%, infantile in 1.82%, and accommodative in 1.82%. Amblyopia was found in 5.45%. In our study, 25.45% patients underwent strabismus surgery, while 74.55% patients either needed conservative management or were being worked up for surgery till the end of this study. Conclusion This study determined the pattern and burden of strabismus in a teaching institute of NE India. Since the institute caters to patients from different states of NE India, this study gives an indirect picture of the burden of strabismus of the whole of NE India. It is hoped that these data will aid in determining the overall burden of strabismus in the country. They will also help the family medicine and primary care physicians to have an idea about the burden and pattern of strabismus in the community, thus enabling them to create awareness about strabismus, remove the undue apprehensions of patients, and do timely referrals for treatment and prevent irreversible visual loss.
... Strabismus is defined as any deviation of the binocular alignment that can be the cause or the effect of poor binocularity. 1 The prevalence of strabismus in the general population has been reported to range from 2% to 5%. 2,3 Strabismus includes manifest strabismus and latent strabismus. ...
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Purpose The prevalence of depression symptoms in patients with strabismus is high. This study aimed to examine the relationship between social support, resilience, and depression symptoms in patients with strabismus and how the relationship between social support and depression symptoms is mediated by resilience. Patients and Methods A cross-sectional study was conducted among adult patients undergoing strabismus surgery at an ophthalmic centre in Guangzhou, China, between March 2021 and May 2023. Patients completed the Self-Rating Depression Scale (SDS), Social Support Rating Scale, and Connor-Davidson Resilience Scale. Multiple linear regression and structural equation modeling explored the relationship between social support, resilience, and depression symptoms. Results Of the 200 patients, 28.5% had depression symptoms (21.5% mild, 6.0% moderate, and 1.0% severe). The mean SDS score (45.50 ± 11.60) was significantly higher than in the healthy reference group (p < 0.001). Social support (β=−0.407, P<0.001) and resilience (β=−0.367, P<0.001) were predictors of depression symptoms, which explained 44.2% of all variations. Resilience partially mediated between social support and depression symptoms, accounting for 22.22% of the total effect (−1.543/-6.944). Conclusion Resilience mediates the relationship between social support and depression symptoms in patients with strabismus. The findings of the present study highlight the importance of social support and psychological resilience in improving depressive symptoms in patients with strabismus.
... S trabismus is a common eye problem during childhood, with an estimated global pooled prevalence of 1.93% [95% confidence interval (CI) 1.64%-2.21%]. Ethnicity appears to have effect on heterogeneity in the prevalence of strabismus [1] . Abnormal ocular alignment may be manifest or intermittent presentation; however, it has a direct effect on binocular vision function, leading to strabismic amblyopia, reduced visual function and psychological disabilities. ...
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AIM: To evaluate the characteristics of exotropia (XT) and motor-sensory outcomes after surgical correction and to determine the factors associated with sensory outcomes of XT surgery. • METHODS: The medical records of all patients that were diagnosed with XT and underwent strabismus surgery in 13 major government hospitals in Thailand; from January 2012 to December 2019, were retrospectively reviewed. Univariable and multivariable logistic regression were performed to identify factors related to binocular vision. • RESULTS: Data of five hundred and thirty-seven patients were analyzed. Two hundred and twenty-six patients were men (42.1%). The median age of onset was 3 years old [Interquartile range (IQR): 1, 8]. The median age at diagnosis was 9.21 years old (IQR; 4.64, 21.06). intermittent exotropia [X(T)] was the most common type (52.1%); 19.5% of the patients had amblyopia. For refractive error, spherical equivalent refraction on right eye (RE) and left eye (LE) were-0.53±2.45 diopters (D) (range-14.88 to +10 D) and-0.48±2.37 D (range-19.50 to +7.75 D), respectively. The mean angle of deviation at distance and near before surgery were 42.06±14.91 prism diopters (PD) and 40.81±16.09 PD, respectively. Follow-up time after first operation was 2.48±2.27y. Four hundred sixty-two patients (86%) needed only one operation and 299 (55.6%) patients had bilateral lateral rectus recession. At final visit, the mean angles of deviation at distance and near decreased to 5.76±8.96 PD and 5.01±8.73 PD, respectively. After surgery, two hundred seventy-three patients (50.8%) were evaluated for binocular function, but the others did not have result. From multivariable logistic regression in 273 patients, the factors related to better binocular function were type of XT which was X(T) [adjusted odds ratio (aOR) 10.35; 95%CI: 4.73, 22.66] compared to constant XT, without amblyopia (aOR 3.97; 95%CI: 1.84, 8.53), underwent only single operation compared with more than 1 operation (aOR 3.80, 95%CI: 1.58, 9.16), the angle of deviation at near in last visit less than 10 PD better than 10-30 PD with aOR 0.42 (95%CI: 0.18, 0.96) and type of refraction revealed isometropia better than anisometropia with aOR 4.13 (95%CI: 1.19, 14.32). • CONCLUSION: The surgical outcomes of XT within one operation in Thailand is 86%. The factors related to achieve binocular function includes type of XT as X(T), without amblyopia, angle of deviation at final visit less than 10 PD, isometropia type of refraction and underwent only one surgical correction. • KEYWORDS: exotropia; intermittent exotropia; sensory outcome
... In United States population ranging between 5-15 million individuals suffer from strabismus and several studies of clinical populations have reported that 1 in every 50 people suffer from strabismus which has a significant impact on their quality of life. 4 Strabismus is a multifactorial influenced trait and shows variations according to genetic and environmental variables. Study results from India, Japan and China show exotropia frequency to be higher. ...
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Objective: To find the frequency of esotropia, its sub types and subsequent management carried out in pediatric age group presenting to a tertiary care hospital in Quetta.Study Design: Cross-sectional study.Place and Duration of Study: Ophthalmology Department, Tertiary Care Hospital, Quetta Pakistan, from Jul to Dec 2020.Methodology: Two hundred and forty patients were enrolled in the study with age 6 months to 13 years presenting with manifest or latent squint. Data was collected through consecutive sampling technique. A designed form for refraction and orthoptic assessment was used with complete ophthalmological examination on each visit. Diagnosis was made based on international definitions of strabismus and treatment was planned accordingly. Follow up was carried out to observe and analyze the effects of treatment in strabismus.Results: Among 240 patients with strabismus, 152 patients had esotropia. More common in males (n=88) and most common refractive error was hypermetropia (n=94). Out of these 32 had anisometropia and 47 had amblyopia. According toclassification of esotropia, 34.2% of patients had fully accommodative esotropia and 13.2% patients had essential infantile esotropia. Combination of treatment modalities was used. 21 patients were prescribed executive bifocals. Patching for 2 hours daily during activity under observation was advised to patients with amblyopia. 36 patients had surgery and 14 patients were kept under observation.Conclusion: Our study concluded that esotropia was the most prevalent type of strabismus in pediatric age group at tertiary care hospital in Quetta with accommodative type being the most common which can successfully be......
... trabismus is a binocular vision disorder where one eye deviates from the normal fixation point. The prevalence of strabismus ranges from 0.5 to 5% [1]. Strabismus is more than a cosmetic defect associated with impaired binocular vision and stereopsis. ...
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Introduction: Vertical strabismus, commonly caused by the overaction of the inferior oblique (IO) muscle, is a frequent oculomotor disorder. It affects one-third of all patients with strabismus, with 70% of these cases coexisting with esotropia. Currently, there is no universally accepted method for quantifying the magnitude of IO overaction (IOOA), as existing classifications are subjective and may not be entirely appropriate. Standardization of IOOA classification is crucial to better understand its severity, develop effective treatment strategies, and predict surgical outcomes. The mechanism of action of the IO muscle is complex and varies with the globe's position during contraction. Beyond horizontal and vertical movements, the IO muscle also contributes to torsional eye movements, impacting the diagnosis and treatment of vertical strabismus and cyclotropia. Materials and Methods: The biomechanical properties of the IO muscle and its triple-action characteristics (horizontal, vertical and torsional movements) were analyzed. A review of current diagnostic practices was conducted, emphasizing the need for comprehensive clinical examinations to identify the signs and symptoms of IOOA and determine its severity. Results: Disorders of the IO muscle often result in vertical strabismus and cyclotropia, complicating strabismus treatment. The variability of the IO muscle's mechanism of action highlights the inadequacy of subjective classification systems. Incorporating the triple-action characteristics of the IO muscle into diagnostic evaluations enables a more accurate understanding of IOOA and its clinical manifestations. Conclusion: Standardizing the classification of IOOA is essential for accurately assessing its severity, guiding treatment strategies, and predicting surgical outcomes. Comprehensive diagnostic examinations that consider the triple-action nature of the IO muscle are necessary to improve the management and treatment of patients with IOOA.
... A report from Repka et al. (2018) stated that the incidence of reoperation in strabismus patients in the United States reached 6.72%. [1][2][3][4] Scar tissue forms during the chronic phase of wound healing. This process begins in the acute phase, where blood cells infiltrate, which produce cytokines that trigger the fibrosis process, resulting in scar tissue. ...
Article
Current clinical measurements of strabismus angles (SAs) are manual and require a skilled examiner and active cooperation by patients. This results in high interexaminer variability, and clinical use is limited by the availability of trained examiners. An objective and automated procedure, independent of the examiner, would be useful. This single-center, prospective, diagnostic feasibility study compared the vertical and horizontal SA of patients, as measured with a commercially available virtual reality headset (VRH) and custom software with the gold standard measurements performed manually with the Harms tangent screen (HW) and the alternate prism cover test (ACT). We implemented the ACT by showing the patient a fixation target on each eye alternatively with the VRH while recording the eye position of the patient. We then processed the data with custom written software to calculate the SA of the patients. These measurements were then compared to the SA measured with HW and the clinical ACT. Thirty-three patients took part in our study. We found good correlation between the VRH method and the HW as well as the clinical ACT. Best correlation was found for horizontal SA in the primary position, with the vertical SA in the primary position also correlating well. Peripheral gaze resulted in a slightly lower correlation due to the overestimation of horizontal SA and underestimation of vertical SA; cyclorotation was not measured with the VRH. Overall, VRH, HW, and clinical ACT correlated similarly well as the published interexaminer correlation for ACT. The automated measurement of strabismus with a VRH is feasible, easily applicable, fast, accurate, and can be run on consumer hardware that is affordable and increasingly available.
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Purpose. We sought to determine the prevalence of strabismus and the esotropia/exotropia ratio in Down syndrome. Wide ranges of an increased strabismus prevalence have been reported and it is unclear by how much esotropia exceeds exotropia in people with Down syndrome. Methods. We compiled in a systematic review and meta-analysis the results of over 100 studies that report the strabismus prevalence and ratio of esotropia/exotropia in cohorts of Down syndrome. We calculated the pooled global prevalence and established the geographical distribution of the strabismus prevalence and the esotropia/exotropia ratio. Results. The ethnically-adjusted global prevalence of strabismus in Down syndrome is 30.2%. In subjects 15 years and older, the global prevalence is 53.2%, and the lifetime prevalence is 51.0%. In populations which normally have more esotropia than exotropia (e.g., Caucasians), Down syndrome subjects have a further increased bias towards esotropia. In populations which normally have more exotropia (e.g., West Africans, Asians and Hispanics), Down syndrome subjects have a significantly lower esotropia/exotropia ratio (3.21) than reported in Caucasians with Down syndrome (9.98). Conclusion. Worldwide, about 1.81 million people with Down syndrome have strabismus: 1.42 million of them have esotropia, and 0.37 million have exotropia. Differences in the esotropia/exotropia ratio between ethnicities point to the orbital anatomy as a major contributing factor to the etiology of strabismus in Down syndrome. The narrow-set eyes (reduced orbital width) in Down syndrome favor esotropia over exotropia, especially in Caucasians, thus explaining why Down syndrome patients from different ethnicities have different prevalences of esotropia and exotropia.
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Background: Amblyopia is one of the most important causes of vision impairment in the world, especially in children. Although its prevalence varies in different parts of the world, no study has evaluated its prevalence in different geographical regions comprehensively. The aim of the present study was to provide global and regional estimates of the prevalence of amblyopia in different age groups via a systematic search. Methods: In this study, international databases, including Embase, Scopus, PubMed, Web of Science, and other relevant databases, were searched systematically to find articles on the prevalence of amblyopia in different age groups published in English. The prevalence and 95% CI were calculated using binomial distribution. The Cochran’s Q-test and I² statistic were applied to assess heterogeneity, a random-effects model was used to estimate the pooled prevalence, and a meta-regression method was utilized to investigate the factors affecting heterogeneity between studies. Results: Of 1252 studies, 73 studies were included in the analysis (sample volume: 530,252). Most of these studies (n = 25) were conducted in the WHO-Western Pacific Regional Office. The pooled prevalence estimate of amblyopia was 1.75% (95% CI: 1.62–1.88), with the highest estimate in European Regional Office (3.67%, 95% CI: 2.89–4.45) and the lowest in African Regional Office (0.51%, 95% CI: 0.24–0.78). The most common cause of amblyopia was anisometropia (61.64%). The I² heterogeneity was 98% (p < 0.001). According to the results of univariate meta-regression, the variables of WHO region (b: 0.566, p < 0.001), sample size (b: −0.284 × 10⁻⁴, p: 0.025), and criteria for definition of amblyopia (b: −0.292, p: 0.010) had a significant effect on heterogeneity between studies, while age group, publication date, and cause of amblyopia had no significant effect on heterogeneity. Conclusion: The prevalence of amblyopia varies in different parts of the world, with the highest prevalence in European countries. Geographical location and criteria for definition of amblyopia are among factors contributing to the difference across the world. The results of this study can help stakeholders to design health programs, especially health interventions and amblyopia screening programs.
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Purpose The visual status of adolescents in Saudi Arabia (SA) has not been well reported. To date, the prevalence and types of refractive errors (REs), amblyopia, strabismus, and correctable visual impairments have not been quantified. The aim of the study was to investigate the visual status in adolescents in Riyadh, SA. Methods This study was based on a population cross-sectional and random cluster design. After design and the sample calculations, 1,007 participants, 12–20 years of age, were screened during the study. Nine participants were excluded due to ocular disorders. The participants were assessed for REs, distance visual acuity logarithm of the minimum angle of resolution, contrast sensitivity, stereoacuity, pinhole test findings, and cover–uncover test findings. Results The results showed that 55.5% of the participants had some form of REs, while correctable visual impairment was found in one-fifth of the screened participants. Myopia was the dominant type (53.3%, ranged from −0.50 DS to −14.00 DS), whereas hyperopia was found in 2.2% (+2.00 DS to +5.50 DS) and astigmatism was present in 15% (−0.75 DC to −5.25 DC). Only 43% of the participants had corrected REs; however, the noncompliance for spectacle use was 20.25%. Conclusion This study was the first attempt to investigate the visual status in adolescents in SA. It provided estimations of the REs, amblyopia, and strabismus. The high prevalence of REs emphasizes the need to identify the best proactive strategies to detect and manage REs to reduce the incidence of visual impairment in SA. Increasing awareness about eye health and employing efficient screening programs could help to address the need for REs corrections.
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p> Background: Prevalence estimates of ocular diseases in a given district are important to plan the programs of eye care services. This study aimed to describe the burden of ocular diseases as an initial step in improving eye care services in underdeveloped areas in Indonesia. Methods: A cross-sectional study was performed among residents of Perobatang Village in Southwest Sumba district in July 2016. Eye examinations were conducted by ophthalmologists, and visual acuity was measured by optometrists. Participants were provided with appropriate treatment according to diagnosis. Surgical services were offered two months after the examination. Results: After eximining a total of 667 of 1,459 (46%) residents, the result showed that the most frequent ocular problems were presbyopia (30.8%), cataract (12.8%), refractive error (11.3%), and pterygium (10.7%). The proportion of myopia was 5.9%, hyperopia was 5.0%, and astigmatism was 2.2%. Moreover, the proportion of blindness was 10%. Cataract caused blindness in 44 participants. Other causes of blindness included age-related macular degeneration, retinopathy, optic atrophy, glaucoma, retinal detachment and trauma. Conclusion: The burden of ocular problems in Perobatang Village, Southwest Sumba, Eastern Indonesia was high. These findings showed the importance of public health action from local government and non-governmental organizations to improve eye care services in Southwest Sumba district.</p
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AIM: To determine the pattern of ocular morbidity among preschool children at urban area of Chittagong. METHODS: A random cross-sectional survey was conducted to determine the prevalence of ocular morbidity among preschool children in the urban area of Chittagong. Preschool children aged 4 to 6 years old in all 60 preschools were registered, interviewed and their eyes examined. All the data obtained was analyzed according to the sex, age, and causes of visual impairment and type of ocular diseases. RESULTS: A total of 900 preschool children from 60 preschools were examined where boys were (52.6%) more than girls (47.4%). The age range of students varied from 4 to 6 years. The mean and median ages were 5.47±0.64. About 16.89% ocular morbidity was found among preschool going children and of these abnormalities 7.66% of children have Refractive error followed by Conjunctivitis 3.66%, Blepharitis 2.77%, Nasolacrimal Duct Obstruction (NDO) 1.66%, Infective conjunctivitis was 0.88%, Stye 0.33%, Chalazion 0.44%. Amblyopia was present in 1.11%, Strabismus in 0.77%, Development Cataract 0.11%, and Corneal Opacity in 0.33% cases which was a matter of concern. CONCLUSION: Ocular morbidity among preschool children can be easily identified by ongoing eye screening programs and if treated timely to reduce the prevalence of ocular diereses and visual impairment. The present study shows uncorrected refractive errors as the main cause of visual disability in preschool children.
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Purpose: To perform an epidemiological study of eye diseases in the population of four indigenous communities in the City of Avai in the state of São Paulo - Brazil: Ekeruá, Kopenoti, Nimuendaju and Tereguá. Methods: This is a prospective, cross-sectional, population-based study performed by the Medical Residency Program of the Center of Excellence in Ophthalmology (CEO-Bauru), including all the inhabitants of four indigenous tribes, between the months of March and April 2016. All participants were submitted to a complete eye examination that included refraction test and best-corrected visual acuity, external ocular motility and strabismus, measurement of intraocular pressure (IOP), color vision test, slit lamp examination and a complete evaluation of the fundus. Results: From a total of 584 natives from four villages, 377 (64.55%) attended the project. 283 appointments were performed at CEO - Bauru and 94 evaluations in the health center of Kopenoti village using a mobile ophthalmology unit. 48.54% of the participants were male and 51.46% female. The mean age was 32.03 ± 21.45 years. Our study found prevalence of pterygium of 14.05%, cataract of 6.63%, glaucoma of 1.85% and diabetic retinopathy of 1.59%. These numbers are higher than found in other epidemiological studies. Regarding refractive errors, 36.99% presented astigmatism, 4.24% simple myopia and 8.35% simple hyperopia. Conclusion: These information are extremely important because they show higher rates of eye diseases in a needy and remote population of urban health centers, and in need of medical care. It is noteworthy that all patients from this study who presented refractive errors, received glasses with the corrected refractive lenses.
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Purpose The aim of the study was a systematic review of refractive errors across the world according to the WHO regions. Methods To extract articles on the prevalence of refractive errors for this meta-analysis, international databases were searched from 1990 to 2016. The results of the retrieved studies were merged using a random effect model and reported as estimated pool prevalence (EPP) with 95% confidence interval (CI). Results In children, the EPP of myopia, hyperopia, and astigmatism was 11.7% (95% CI: 10.5–13.0), 4.6% (95% CI: 3.9–5.2), and 14.9% (95% CI: 12.7–17.1), respectively. The EPP of myopia ranged from 4.9% (95% CI: 1.6–8.1) in South–East Asia to 18.2% (95% CI: 10.9–25.5) in the Western Pacific region, the EPP of hyperopia ranged from 2.2% (95% CI: 1.2–3.3) in South-East Asia to 14.3% (95% CI: 13.4–15.2) in the Americas, and the EPP of astigmatism ranged from 9.8% in South-East Asia to 27.2% in the Americas. In adults, the EPP of myopia, hyperopia, and astigmatism was 26.5% (95% CI: 23.4–29.6), 30.9% (95% CI: 26.2–35.6), and 40.4% (95% CI: 34.3–46.6), respectively. The EPP of myopia ranged from 16.2% (95% CI: 15.6–16.8) in the Americas to 32.9% (95% CI: 25.1–40.7) in South-East Asia, the EPP of hyperopia ranged from 23.1% (95% CI: 6.1%–40.2%) in Europe to 38.6% (95% CI: 22.4–54.8) in Africa and 37.2% (95% CI: 25.3–49) in the Americas, and the EPP of astigmatism ranged from 11.4% (95% CI: 2.1–20.7) in Africa to 45.6% (95% CI: 44.1–47.1) in the Americas and 44.8% (95% CI: 36.6–53.1) in South-East Asia. The results of meta-regression showed that the prevalence of myopia increased from 1993 (10.4%) to 2016 (34.2%) (P = 0.097). Conclusion This report showed that astigmatism was the most common refractive errors in children and adults followed by hyperopia and myopia. The highest prevalence of myopia and astigmatism was seen in South-East Asian adults. The highest prevalence of hyperopia in children and adults was seen in the Americas.
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BACKGROUND School-age children constitute a particularly vulnerable group, where ocular morbidity including uncorrected refractive error may have a dramatic impact on learning capability and educational potential. Present study was conducted with the objective of estimating the prevalence of ocular morbidity among school children in rural area. MATERIALS AND METHODS A cross-sectional study was conducted among school going children studying from 1st to 10th standard in the age group 6-15 years in rural area. The ocular examination of school children was done at the respective schools. All the data obtained was entered in excel workbook and analysed. Chi square test was used to observe the association of the ocular morbidities with respect to age, sex, education of father, occupation, class, and nutritional status. RESULTS Prevalence of ocular morbidities was found to be 20.19%. Refractive errors and allergic conjunctivitis were the most common ocular disorders. The prevalence of ocular morbidity showed significant association with education of father (χ2 = 9.497, p = 0.050), education of mother (χ2 = 13.063, p = 0.005), family type (χ2 = 4.270, p = 0.03), while no significant association was found between ocular morbidity and sex of the school children (χ2 = 0.352, p = 0.553), occupation of father (χ2 = 3.372, p = 0.498) and religion (χ2 = 0.168, p = 0.682) of the school children. Nutritional status of children was significantly associated with the occurrence of ocular morbidity (χ2 = 3.763, p = 0.052). CONCLUSION High prevalence of uncorrected refractive error among school children in rural area was observed. Periodic screening of school children and utilisation of corrective spectacles is very essential to improve the quality of eye-sight.
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