Review Article

Prevalence of Color Blindness in Iranian Students: A
Meta-analysis

Leila Rezaei1, MD; Ehsan Hawasi1, Medical Student; Nader Salari2, PhD; Masoud Mohammadi3, MS

1Department of Ophthalmology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
2Department of Biostatistics, School of Health, Kermanshah University of Medical Sciences, Kermanshah, Iran

3Cellular and Molecular Research Center, Gerash University of Medical Sciences, Iran

ORCID:
Leila Rezaei: https://orcid.org/0000-0001-6285-2629

Masoud Mohammadi: https://orcid.org/0000-0002-5722-8300

Abstract

Color blindness (color vision deficiency) is a disorder that impairs the true
perception of colors. Using the information in this study, appropriate policy can
be made to identify high-risk groups, as well as educational policies for families
to perform more effective genetic diagnosis methods.
This study aims to examine the prevalence of color blindness in Iranian
students through a meta-analysis. Articles related to color blindness published
between January 1990 and December 2020 were searched in Scopus, Cochrane
Library, Web of Science (WoS), Science Direct, Embase, SID, MagIran, IranDoc,
Medline, and Google Scholar databases. The keywords used were based on
medical subject topics (MeSH Terms) and, after careful review, articles were
selected according to varied sections of Participants, Exposure, Comparison,
and Outcomes (PECO). Participants: students; Exposure: students with color
blindness were examined; Comparison: Students from multiple provinces and
regions of Iran were surveyed for color blindness; Outcomes: the pooled
prevalence of color blindness in Iranian students reported from different
provinces. The prevalence of color blindness in Iranian students was 3.8% (95%
CI: 2.7–5.4%). The pooled prevalence of color blindness in Iranian male and
female students was 4.7% (95% CI: 3.5–6.4%) and 0.7% (95% CI: 0.3–1.3%),
respectively. The pooled prevalence of red–green color blindness (Tritan) was
41.7% (95% CI: 18.9–68.8%). The pooled prevalence of red color blindness (Protan)
was 13.9% (95% CI: 7.8–23.8%), and the pooled prevalence of green color
blindness (Deutan) based on meta-analysis was 45.3% (95% CI: 29–62.7%). Due
to the high prevalence of color blindness in students, especially male students,
it is necessary to be screened for through genetic tests in couples before having
children.

Keywords: Color Blindness; Color Vision Deficiency; Iran; Meta-analysis; Prevalence;
Students

J Ophthalmic Vis Res 2022; 17 (3): 413–423

© 2022 Rezaei et al . THIS IS AN OPEN ACCESS ARTICLE DISTRIBUTED UNDER THE CREATIVE COMMONS ATTRIBUTION LICENSE | PUBLISHED BY KNOWLEDGE E 413

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Color Blindness in Iranian Students; Rezaei et al

INTRODUCTION

Visual impairment is one of the most common
disorders affecting the students’ academic
performance that can directly affect their academic
future.[1] Some studies have addressed the
psychological and social issues resulting from
visual impairment problems in students.[2, 3]

Light receptors in the human retina called
photoreceptors transmit messages to the
brain and enable a person to perceive various
colors.[10–12] Color perception is a response to
the physical motion of a narrow handle of an
electromagnetic spectrum with a wavelength of
400–700 nm, absorbed by the photoreceptors
of visual pigments.[13, 14] This visible spectrum is
only a part of the electromagnetic waves, which
includes a wide range of waves with different
wavelengths.[12–15]

Color blindness or impaired color vision is the
inability to perceive the differences between some
colors.[12–15] It occurs when light-sensitive cells
either do not perceive color signals or do not
transmit them to the brain.[14, 15] In other words,
color blindness is a condition in which the ability
to distinguish some colors is considered to be less
than normal.[15]

Many patients are unaware of the existence
of their color blindness, and only during their
studies or employment, based on their needs and
tests, they discover that they have the color this
disorder.[13–15]

The color blindness disorder is divided into
congenital and acquired categories.[4] Congenital
color blindness is often red–green and gender-
dependent, with a prevalence of 8% in men and
about 0.4% in women and between 4% and 6.5%
in men of Chinese and Japanese ethnicities.[5] The
results of this study reported that the male-to-
female prevalence ratio is markedly different.[5]

Correspondence to:

Masoud Mohammadi MS. Cellular and Molecular
Research Center, Gerash University of Medical
Sciences, Imam Hossein Blvd, Daneshjoo Blvd, Gerash
74417-58666, Iran
E-mail: Masoud.mohammadi1989@yahoo.com
Received: 04-01-2022 Accepted: 16-04-2022

Access this article online

Website: https://knepublishing.com/index.php/JOVR

DOI: 10.18502/jovr.v17i3.11580

Monochrome or complete color blindness is a
rare type in which none of the cone cells are
able to receive color. As a result, the person
does not see any color,[4, 5] but if one of the
three cone cells is damaged, the person does
not see one of the colors. In fact, in one of the
colors, the color becomes blind and the nose
becomes dichromatic.[5] Trichromat is one of the
most common models of color blindness in which
all three types of cone cells are active, but their
irritability has changed.[5]

Dichromates usually have one of the defects of
Deuteranomaly, Protanomaly, or Tritanomaly.[6–9]

Deuteranomaly: In this disorder, due to the
proximity of the green and red spectra, the person
does not see the green color correctly.[9]

Protanomaly: In this disorder, the cells do
not process red color properly, because the
wavelengths of red and green are close, and so
these people see red as close to green.[6–9]

Tritanomaly: In this disorder, a person’s
sensitivity to the color blue decreases.[6–9]

Studies conducted in Iran on the prevalence of
color blindness in students have reported different
prevalence from various parts of the country. In
a study conducted on students located in the
city of Sari, the pooled prevalence was 2.41%,
which was reported as 2.4% in male students and
0.06% in female students.[16] However, a study
on students from the city of Qazvin reported a
pooled prevalence of 6.5%, which was 5.1% in
male students and 1.4% in female students.[17] In
another study conducted on students from the
city of Ahvaz, the pooled prevalence was 3.7%,
which was 5.4% in male students and 2.1% in
female students.[18] Our study aims to determine
the prevalence of color blindness in students
through a meta-analysis.

METHODS

According to the Preferred Reporting Items for
Systematic Reviews and Meta-Analyses (PRISMA)

This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

How to cite this article: Rezaei L, Hawasi E, Salari N, Mohammadi
M. Prevalence of Color Blindness in Iranian Students: A Meta-
analysis. J Ophthalmic Vis Res 2022;17:413–423.

414 JOURNAL OF OPHTHALMIC AND VISION RESEARCH Volume 17, Issue 3, July-September 2022

https://knepublishing.com/index.php/JOVR


Color Blindness in Iranian Students; Rezaei et al

criteria, systematic search of databases was
performed based on organizing documents
for review, selection of studies, extraction and
analysis.

Search Strategy

A systematic search for articles was performed
in three Iranian databases, IranDoc, MagIran,
and SID using Iranian keywords, and in the
international databases of PubMed, Cochrane
Library, Science Direct, Scopus, Web of Science
(WoS), and Embase using English keywords. The
Google Scholar search engine using English
keywords was also examined. The keywords
used were based on medical subject topics
(MeSH Terms) and, after careful review, were
selected according to the varied sections of
PECO.

PECO: Participants: students; Exposure:
students with color blindness were examined;
Comparison: students from multiple provinces
and regions of Iran were surveyed for color
blindness; Outcomes: the pooled prevalence
of color blindness in Iranian students reported
from various provinces. The search process:
“color blindness”, “visual disturbances”, “students”,
“visual impairment”, “color vision impairment”,
“visual impairment”, and their Persian equivalent
words and possible combinations. (AND)
and (OR) operators were used for more
comprehensive access to all articles. The search
was conducted between January 1990 and
December 2020.

(AND) and (OR) operators: (Color blindness OR
Color Vision Defects OR Tritan Defect OR Retinal
Diseases OR Deutan Defect OR Achromatopsia
OR Protan Defect), (Visual Disturbances OR Vision
Disability OR Visual Impairment), (Color Vision
OR Color Perception). The word AND between
keywords (Color blindness AND color vision AND
students AND Iran) was used in the MeSH
browser.

Processes for Checking the Entry and Exit of
Articles

Cross-sectional studies that reported the
prevalence of color blindness in students were
eligible for inclusion. Other observational studies
as well as interventional studies and clinical trials
were excluded from the study.

Selection of Finalized Studies

The research in the mentioned databases was
done independently and blindly by two researchers
(EH and LR) and then the obtained articles were
entered into Endnote software for secondary
review as well as removal of duplicate and
unrelated articles. The two researchers reviewed
the articles considering the inclusion criteria; if they
could not reach an agreement and decide on an
article, a third researcher (MM) reviewed the article
and provided the final opinion on the study.

Quality Assessment

The quality of the studies confirmed by the STROBE
checklist was assessed.[15] This checklist uses 32
items to examine different aspects of the articles
and rates the studies in the range of 0–32. In this
review, scores >23 to 32 were classified as high
quality and grades between 22 and 14 as moderate
quality.

Data Extraction

After the search was completed, all articles with
keywords such as “prevalence”, “color blindness”,
and “Iranian student” in their titles were included
in the initial list. Then a checklist including the
author’s name, title, year and month of the
publication, place of study, age, sample size, and
the pooled prevalence by sex was made. All stages
of data extraction were performed by two reviewers
independently.

Statistical Review

CMA software (version 2) and Begg and Mazumdar
tests and funnel plots were used to analyze the
information extracted in the studies to investigate
the publication bias. To evaluate and detect
the degree of heterogeneity in the studies, the
I2 heterogeneity test was used, and a meta-
regression test based on population size and study
time was used to investigate the effect of the
heterogeneity factors.

RESULTS

Literature Search

Based on the PRISMA flowchart, the process of
reviewing, extracting, and finalizing articles for

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Color Blindness in Iranian Students; Rezaei et al

entering into the meta-analysis was reported;
consequently, 11 studies were entered into the
meta-analysis. Fifteen studies were excluded from
the study due to lack of relevance, and three
studies due to the low quality [Figure 1; Table 1].

Investigation Bias in Studies

The result of the I2 test was 97.3%, and a random-
effects model was used to meta-analyze the results
of the studies. The results of publication bias
were measured using the Begg test and were not
statistically significant (P = 0.212).

The Pooled Prevalence of Color Blindness

In 26,660 people in the age range of 7–18 years,
the pooled prevalence of color blindness in Iranian
students was 3.8% (95% CI: 2.7–5.4%) [Figure 2].

The Prevalence in Male Students

The total number of samples included in the study
was 11,982 people. Based on the meta-analysis,
the pooled prevalence of color blindness in Iranian
male students was 4.7% (95% CI: 3.5–6.4%) with
the I2 test (92.4%). The highest prevalence of color
blindness was reported in the city of Yasuj with
9.5% (95% CI: 8.3–11%) in 2000,[20] and the lowest
prevalence of color blindness was reported in the
city of Sari with 2.4% (95% CI: 1.8–3.4%) in 2001[16]
[Figure 3].

The Prevalence in Female Students

The pooled prevalence of color blindness reported
was 0.7% (95% CI: 0.3–1.7%) with I2 test (95.04%).
The highest color blindness was reported in the city
of Yasuj with 6.2% (95% CI: 5–7.8%) in 2000,[20] and
the lowest rate of color blindness was in the city
of Sari with 0.06% (95% CI: 0.05–0.07%) in 2001[16]
[Figure 4].

Color Blindness by Its Types

The prevalence of red–green color blindness
(Tritan) in Iranian students was 41.7% (95% CI: 18.9–
68.8%) with the I2 test (93.8%) [Figure 5]. The
prevalence of red color blindness (Protan) in Iranian
students was 13.9% (95% CI: 7.8–23.8%) with the I2

test (88.01%) [Figure 6]. The prevalence of green
color blindness (Dutan) in Iranian students was
45.3% (95% CI: 29–62.7%) with the I2 test (95.01%)
[Figure 7].

According to Figure 8, color blindness in
students decreases with an increasing sample
size (P < 0.05). Furthermore, according to Figure
9, overall color blindness in students increases
with the length of the research year but is not
statistically significant (P = 0.765).

The Begg test measured the results of the
publication bias in the studies and the Mazumdar
rank correlation test, according to the large sample
size entered in the studies. The publication bias
was not statistically significant (P = 0.275) [Figure
10].

DISCUSSION

Understanding the epidemiology of a disease can
help in addressing it on a macro level.[27] Although
color blindness is not a very common or dangerous
disease, such a complication in students can
have psychological effects on their educational
status and future careers. Therefore, this disorder
presents a significant challenge when addressing
the effects of medical disorders on the educational
success in students.

Based on our analysis, the prevalence of color
blindness in Iranian students was reported as
3.8%, and the color blindness in Iranian male and
female students was reported as 4.7% and 0.7%,
respectively. Studies show that color blindness
affects 1 in every 12 men and 1 in every 200
women.[28] One in six people carries the color
blindness gene, which is passed on to their son
causing color blindness.[28] Due to the genetic
nature of this disease, it was revealed that the
greater the number of consanguineous marriages
in the population, the higher the prevalence of
color blindness.[28]

The results of the prevalence of the current
study was higher than the color blindness reported
as 2.1% in Nepal,[29] 2.6% in Nigeria,[30] and 1%
in Bangladesh.[31] In studies conducted in Europe
and Spain, the prevalence was 4.02% in boys and
0.46% in girls.[6–9, 33, 34]

In a study by Khataminia et al, it was reported
that approximately 6% of men of European descent
have color vision problems, compared with 4.9%
of men and 0.64% of women in Asian countries.[18]

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Color Blindness in Iranian Students; Rezaei et al

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Records identified through database 

searching  

(n = 161) 

Duplicates removed  

(n = 132)

Records screened  

(n = 29) 

Articles assessed for 

eligibility  

(n =14) 

Studies included in quantitative 

synthesis (meta-analysis)  

(n = 11) 

Records 

excluded  

(n =15) 

 

Articles 

excluded, 

with reasons  

(n = 3) 

Figure 1. Flow chart of the review process and selection and separation of studies based on PRISMA.

This ratio is 3.1% in men and 0.7% in women
of African countries, Native American or Mexican
descent.[18, 28]

In a study reported in Africa and Ethiopia, the
prevalence was 4.2% in boys and 0.2% in girls.[35]
In a United States study, a prevalence of 2.6% was
reported in boys.[36] A study in Australia reported
that 8% of men and 0.4% of women have color
blindness.[17]

In the present study and in reviewing the meta-
regression results, it was reported that with an
increasing sample size, the prevalence of color
blindness in Iranian students decreases, and the
prevalence of color blindness in Iranian students
increases with increasing research years.

Methods used for determining the disorder and
tools needed to investigate the disorder are not
the same among different studies. Multiple tests
have been utilized to perform research including
the use of Ao-HR. R and Pseudoisochromatic
tests have been common[16, 37] since most studies
have used the Ishihara booklet.[16] However,
different studies have mentioned the number of
people surveyed and different age groups in
justifying the significant differences in various
studies.[16]

The pooled prevalence of red–green color
blindness (Tritan) in Iranian students was 41.7%,
the pooled prevalence of red color blindness
(Protan) was 13.9%, and the pooled prevalence of

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Color Blindness in Iranian Students; Rezaei et al

Table 1. Specifications of studies entered into the meta-analysis of the prevalence of color blindness in Iranian students

Quality
assessment

Prevalence
(Female)

Sample
size

(Female)

Prevalence
(Male)

Sample
size

(Male)

Pooled
prevalence

Sample
size

Participants’
age

Area Publication
year

Author Row

Moderate 0.06 1450 2.4 1650 2.41 3000 – Sari 2001 Farokhfar et
al[16]

1

High 1.4 900 5.1 900 6.5 1800 9.3 ± 1.5 Qazvin 2016 Mehrpour et
al[17]

2

Moderate 2.1 1250 5.4 1250 3.7 2500 13–18 Ahwaz 2006 Khataminia et
al[18]

3

High 0.4 1000 3.6 1000 2 2000 – Oromieh 2011 Sharifi et al[19] 4

Moderate 6.2 1166 9.5 1760 8.2 2926 11-14 Yasouj 2000 Nabavizadeh
et al[20]

5

Moderate – – – – 5.2 500 – Tehran 2006 Rezae et al[21] 6

High 0.4 1992 5.1 2408 3 4400 – Mashhad 2011 Ostadi et al[22] 7

Moderate 0.2 1414 3.3 1414 1.7 2828 – Kermanshah 2000 Omidian et
al[23]

8

Moderate 0.35 – 7 – 4.4 706 – Hamadan 1996 Ramezani et
al[24]

9

Moderate – – – – 8.7 3000 – Zanjan 2006 Hossaini et
al[25]

10

Moderate 0.33 1500 4.2 1500 2.3 3000 – Isfahan 2001 Azarian et
al[26]

11

Figure 2. The prevalence of color blindness in Iranian students.

green color blindness (Deutan) based on the meta-
analysis was 45.3%. This is based on the opinion
of the American Ophthalmological Society reports’
red–green vision deficiency in 8% of men and 0.5%
of women.[18]

A study conducted in Croatia reported that 8.4%
of the participants were color blinded, of which

1.2% were Protan and 4.2% were Deutan.[17,18] The
Deutan in Ethiopia was 3.4%,[35] in Turkey 2.2%,[38]
in Saudi Arabia 1.9,[39] and in a Spanish study
2.1%.[40]

Although color blindness is almost ineffective
in most job activities, due to its high prevalence,
especially among students, it can affect their

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Color Blindness in Iranian Students; Rezaei et al

Figure 3. The prevalence of color blindness in Iranian male students.

Figure 4. The prevalence of color blindness in Iranian female students.

academic performance and limit their academic
achievement, thus increasing public awareness
through the mass media. And social media is
essential to enhance genetic testing in couples
before their children are born. Parents of children
should also be informed about color vision
disorders in their child’s eyes so that with early
diagnosis, specific treatment measures can be
performed. Also, since there is no effective
treatment for color blindness, the psychological

damage of this disorder can be reduced by
reassuring individuals and students that color
blindness does not affect their future careers,
as well as providing their own education in
schools. Based on the information obtained,
it is recommended that periodic screening of
students for early detection of color blindness
along with parental training to identify children
who have color blindness symptoms should be
performed.

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Color Blindness in Iranian Students; Rezaei et al

Figure 5. The prevalence of red–green color blindness (Tritan) in Iranian students.

Figure 6. The prevalence of red color blindness (Protan) in Iranian students.

Strengths and Limitations

The most important strength of this research
is that it is the first Iranian meta-analysis and
provides accurate population-based information.
An important limitation of the study is the limited
number of studies conducted in Iran.

CONCLUSION

Due to the high prevalence of color blindness in
students, especially male students, it is necessary
to take appropriate measures through appropriate

screening for genetic tests in couples and parents
who have color-blind children, screening parents
with color blindness, as well as genetic counseling
for parents who have a color-blind child and
planning to conceive again. This study also
reports that the prevalence of different types of
color blindness in students is high and requires
continuous follow-up and screening.

Ethics Approval

The study protocol was approved by
the Vice Chancellor for Research and

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Color Blindness in Iranian Students; Rezaei et al

Figure 7. The prevalence of green color blindness (Dutan) in Iranian students.

 

Figure 8. Heterogeneity check diagram of the color blindness by sample size.

Technology of Kermanshah University of
Medical Sciences with the following code:
IR.KUMS.REC.1400.009.

Financial Support and Sponsorship

This study was funded by the Vice-Chancellor
for Research and Technology of Kermanshah
University of Medical Sciences. This fund had no
effect on the process of conducting the present
study.

Conflicts of interest

The authors declare that they have no conflict of
interest.

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