Med. J. Cairo Univ., Vol. 81, No. 1, June: 513-517, 2013
www.medicaljournalofcairouniversity.net
Screening for Color Vision Defects among Male Saudi Secondary
School Children in Jizan City, Kingdom of Saudi Arabia
HESHAM M.A. DAHLAN, M.D.* and OSSAMA A. MOSTAFA, Ph.D.**
The Departments of Medicine, Jizan Military Hospital* and Family & Community Medicine, King Khalid College of Medicine**
Key Words: Color vision defects — X-linked disorder — Secondary school students — Consanguinity — Jizan
— Kingdom of saudi arabia.
Abstract
Aim of Study: To assess the prevalence of color visual
defects (CVD) among male Saudi secondary school children
in Jizan City, Kingdom of Saudi Arabia.
Introduction
HUMAN beings have the special ability to see in
Subjects and Methods: This study included 717 male
Saudi secondary school students in Jizan City. Study tools
included the Ishihara charts and a data collection questionnaire
designed by the researcher. Parents' consanguinity was classified into first degree, second degree or far relatives.
color, which distinguishes them from other species.
However, inherited color vision defects (CVD) is
relatively common 111. CVD occurs when there is
a problem with the color-sensing materials in the
cones of the retina. Missing just one pigment will
cause trouble telling the difference between red
and green colors. Some people may have trouble
seeing blue-yellow colors. They almost always
have problems in identifying red and green colors,
too. The most severe form of color blindness is
achromatopsia, i.e., inability to see any color [2,3].
Results: Almost one third of parents were first degree
relatives (30.4%) the rest of parents were either second degree
relatives (2%) or far relatives (19.7%). More than one third
of students did not know if they have normal vision or CVD
(39.6%). Prevalence of CVD among male Saudi secondary
school students amounted to 21.3%. More than one third of
students whose parents were 1st degree cousins were CVD
(35.8%), compared with about one fifth of students whose
parents were second degree cousins or far relatives (21.4%
and 21.3%, respectively). The prevalence of CVD was least
among students whose parents were not relatives (12.2%).
Differences were statistically significant (p<0.001). The
highest percentages of students with CVD expressed their
wish to study in medical or engineering colleges (28.7% and
32.1%, respectively). Differences were statistically significant
(p<0.001). Prevalence of CVD among students with positive
family history of CVD was highest (35.5%), compared with
those who did not have family history of CVD (20.5%) or
those who did not know if they have any family member(s)
with CVD (20.8%).
CVD is an X-linked disorder [4]. Testing for
CVD is commonly done during an eye examination,
using the "Ishihara Charts". It is a life-long condition. Symptoms of CVD vary from one person to
another, but may include trouble seeing colors and
the brightness of colors in the usual way and the
inability to tell the difference between shades of
the same or similar colors. Often, the symptoms
may be so mild that some persons do not even
know that they are CVD [2].
Recommendations: Reasons for the high rate of consanguinity in Jizan need to be investigated and the awareness of
people should be raised regarding the potential consequences
of consanguinity. School students with CVD should be guided
as regard the proper choice for their future studies. Premarital
examination should cover the common hereditary diseases,
including CVD. Pre-university screening of male students for
CVD should be applied to help students choose toward their
career.
Studies on prevalence rates of CVD among the
Arab population are very limited. In Jordan, AlAqtum and Dawasmeh [4] reported that the prevalence of CVD was 8.72% among males. However,
these studies in the Kingdom of Saudi Arabia
(KSA) are so scarce and even lacking.
The current rationale for school screening for
CVD is the potential preclusion from occupations.
Nevertheless, balancing the rights of an individual
to pursue his or her chosen career with the social
and economic costs of "mistakes" attributable to
Correspondence to: Dr. Ossama A. Mostafa,
The Department of Family & Community Medicine,
King Khalid College of Medicine
513
514
Screening for Color Vision Defects among Male Saudi
CVD is currently being debated. Young people
need to know their precise color vision status before
making occupational choices [5].
impact of consanguinity on this condition, how to
live normally with it and how to minimize the
probability of future transmitting this character to
their offspring. Furthermore, they were referred to
a professor of ophthalmology at Jizan College of
Medicine to receive the necessary specialized
clinical examination and to exclude any other
associated visual problems.
Cole [6] stressed that schoolchildren should
know if they have CVD so they can be helped
more quickly to find adaptive strategies and be
able to take it into account when planning their
career. He added that screening could help choice
of medical career.
This study aimed to assess the prevalence of
CVD among male Saudi secondary school children
in Jizan City, KSA and to explore the association
between students' CVD and consanguinity among
their parents.
Subjects and Methods
Following a cross-section study design, this
study was conducted in Jizan City during December
2012. Jizan lies at the southwestern part of the
KSA. Its population is about 100,000. The target
population included male secondary school students
studying and living in Jizan, present at school on
the day of data collection.
Using the WHO Manual [7] for sample size
determination in health studies, with an anticipated
population proportion of 8%, and with an absolute
precision of 2% at 95% confidence interval, the
minimal sample size required for this study was
calculated to be 707. Following a simple random
sample and a sampling fraction of 50%, a total of
717 students were interviewed and tested for CVD.
The study tools comprised the Ishihara charts
and a data collection questionnaire, which was
designed by the researcher to include age, consanguinity between parents, family history of CVD
and their intentions for future college study or
occupation. Consanguinity was classified according
to Rohde et al. [81.
Prior to data collection, the objectives and
nature of the study were explained to all participant
students. They were assured that all collected data
are strictly confidential and will be used only for
research purposes and their participation is absolutely optional. The duration of data collection
from a student took about 10 minutes. After receiving the filled questionnaire sheets, the researcher
used the Ishihara charts to test the color vision of
each student, one by one.
Students who proved to have deficient color
vision received the necessary counseling and guidance as regard their condition, its prognosis, its
implication on their future career, the negative
The Statistical Package for Social Sciences
(SPSS ver. 17) was used to calculate the descriptive
statistics (e.g., frequency and percentage) and apply
tests of significance (i.e., x 2 -test). p-values ❑ 0.05
were considered as "statistically significant".
Results
Table (1) shows that about half of participants
aged 17-18 years (51.7%). Consanguinity was high
between parents of students. More than half of
students' parents were relatives (52%). Almost one
third of parents were first degree relatives (30.4%)
the rest of parents were either second degree relatives (2%) or far relatives (19.7%). Almost one
fourth of secondary school students stated that they
prefer to choose medical sciences university studies
(22.9%). Almost equal percentages of students
expressed their choice to study military sciences
or engineering (26.9% and 20.9%, respectively).
However, 208 students were still undecided as
regard their future university studies (29%).
Table (2) shows that 2.9% of students stated
that they have CVD, while more than one third of
students do not know if they have normal vision
(39.6%). More than half of students did not know
if there are family members who are with CVD
(55%), while only 4.3% of students mentioned that
they have a positive family history of CVD. Prevalence of CVD among Saudi male secondary school
students amounted to 21.3%.
Table (3) shows that prevalence rates for CVD
among Saudi male secondary school students were
almost equal according to students' age group. The
highest percentages of students with CVD expressed their wish to study in medical sciences
colleges or engineering colleges (28.7% and 32.1%,
respectively). Differences were statistically significant (p<0.001). More than one third of students
whose parents were Pt degree cousins were CVD
(35.8%), compared with about one fifth of students
whose parents were second degree cousins or far
relatives (21.4% and 21.3%, respectively). The
prevalence of CVD was least among students whose
parents were not relatives (12.2%). Differences
were statistically significant (p<0.001).
515
Hesham M.A. DahIan & Ossama A. Mostafa
Table (4) shows that 17.2% of students who
were not aware of having CVD, compared with
23.9% of students who did not know whether they
are with CVD. Differences were statistically significant (p<0.001). On the other hand, prevalence
of CVD among students with positive family history
of CVD was highest (35.5%), compared with those
who did not have family history of CVD (20.5%)
or those who did not know if they have any family
member(s) with CVD (20.8%). Differences between
prevalence rates of color visual defects according
to family history of CVD were not statistically
significant.
Table (1): Personal characteristics of study sample.
Variables
No.
%
219
371
127
30.5
51.7
17.7
235
227
255
32.8
31.7
35.6
344
373
218
14
141
48.0
52.0
30.4
2.0
19.7
193
164
150
210
26.9
22.9
20.9
29.3
Age group:
<17 years
17-18 years
>18 years
Scholastic year:
1st
2nd
3rd
Consanguinity among students' parents:
No
Yes:
1st degree cousins
2nd degree cousins
Far relatives
Preferred future college studies:
Military
Medical sciences
Engineering
Undecided
Table (2): Color visual defects among students and their
families
Variables
No.
%
412
21
284
57.5
2.9
39.6
292
31
394
40.7
4.3
55.0
564
153
78.7
21.3
Is the student known to have any
color vision defect?
No
Yes
Not sure
Family history of color blindness:
-
No
Yes
Not sure
Results of testing for visual color defects:
Normal color vision
Visual color defects
Table (3): Prevalence of color vision defects according to
personal characteristics of study sample.
Color vision
defects
No
Yes
(n=564)
(n=153)
No. % No. %
Personal
Characteristics
Age group:
<17 years
17-18 years
>18 years
Preferred future
college studies:
Military colleges
Medical sciences colleges
Engineering colleges
Undecided
Consanguinity
among parents:
Not relatives
1st degree cousins
2nd degree cousins
Far relatives
P
value
171 78.1
292 78.7
101 79.5
48 21.9
79 21.3
26 20.5 0.951
144
107
131
182
87.8
71.3
67.9
86.7
20 12.2
43 28.7
62 32.1
28 13.3 <0.001
302
140
11
111
87.8
64.2
78.6
78.7
42 12.2
78 35.8
3 21.4
30 21.3 <0.001
Table (4): Prevalence of color blindness according to history
of color vision defects among students and their
families.
Color vision
defects
No
Yes
(n=564)
(n=153)
No. % No. %
Variables
The student knows he has
color visual defect:
No
Yes
Do not know
Family history of
color visual defect:
No
Yes
Do not know
P
value
341 82.8
7
33.3
216 76.1
71
14
68
17.2
66.7
23.9 <0.001
232 79.5
20 64.5
312 79.2
60
11
82
20.5
35.5
20.8 0.144
Discussion
This study revealed that prevalence of CVD
among Saudi male secondary school students in
Jizan is relatively high. More than one-fifth of the
students (21.3%) had CVD. Moreover, consanguinity between parents of students was extremely
high. More than half of students' parents were
relatives. Almost one third of parents were first
degree cousins. Moreover, this study indicated that
more than one third of students, whose parents
were 1st degree cousins, had CVD, compared with
about one fifth of students whose parents were
second degree cousins or far relatives. The prevalence of CVD was least among students whose
parents were not relatives.
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Screening for Color Vision Defects among Male Saudi
The prevalence of CVD among participants is
higher than that reported by several authors in
different countries, which may reflect the high
prevalence of consanguinity.
photography and industrial design, etc.). However,
within these broad occupation categories, the specific functional requirements may vary, and therefore specialist assessment of color vision is recommended in the specific context each job [16] .
Osuobeni [9] screened Arab males from Riyadh,
Saudi Arabia for the prevalence of congenital redgreen CVD using the Ishihara plates. He reported
that a prevalence of 2.93%. In Port Harcourt City,
Niger, Tabansi et al. [1 0] screened 1,300 primary
school students for congenital CVD. They reported
a prevalence rate of 2.6%. In New York, USA,
Swanson and Cohen [11] reported that congenital
color defects affect 8-10% of males. In Oregon,
USA, Rabin [12] stated that hereditary color deficiency affects up to 10% of males. In Sydney,
Australia, Simunovic [13 ] stated that congenital
CVD affects as many as 8% of males. Citirik et
al. [14] investigated a healthy population of men
from different regions of Turkey for the presence
of congenital red-green CVD using Ishihara plates.
The mean prevalence of red-green CVD was
7.33±0.98%. They stressed that percentages of
students with CVD were found in regions with
more consanguineous marriages.
This study showed that the highest percentages
of students with CVD expressed their wish to study
in either medical sciences colleges or engineering
colleges.
Cumberland et al. [1] stated that color vision is
integral to an individual's understanding of their
visual world, and those with CVD can experience
difficulties in everyday life. The rationale for
screening for CVD remains the population-level
impact of these conditions, particularly on occupational choice.
Holroyd and Hall [1 5] stated that there are a
number of occupations from which individuals
with CVD should be excluded, on the basis of
potential hazard to safety and/or in the interest of
quality assurance in the workplace, even though
the functional impact of a given congenital CVD
is known to depend on both its nature and severity
as well as the specific visual tasks to be undertaken.
Cumberland et al. [1] added that the UK Health
and Safety Executive advised that certain occupations require normal color vision, for either reasons
of safety or quality of product (e.g., medicine,
pharmacy, health diagnosing and treatment; Armed
forces; Aircraft and ships officers; police, firefighting and protective services; electrical and
electronic engineering; laboratory and engineering
technology; painting and related coating; printing,
paper and photographic processing; art, sculpture,
Holroyd and Hall [15] stated that there is already
evidence of deficiencies in the implementation of
school screening for CVD, together with concerns
that despite being identified, affected children
remain ill-informed about the occupational significance of their condition.
Spalding [1 7] emphasized that pre-vocational
screening for the CVD and further testing for
severity should be practiced for a number of occupations where certain standards of color vision are
required. In Taiwan, applying students are screened
for CVD by all medical schools. Color is often
used as a sign in the practice of medicine. Many
descriptive and diagnostic terms in common use
indicate its value when used in this way. Jaundice,
cyanosis, pallor erythema, melena, are examples.
It is also used in histology, biochemistry, and
coding for many new technologies. Yet, there are
few enquiries into the effects of a CVD on doctors'
medical skills.
In some common medical procedures, individuals with CVD perform less well than those with
normal color vision. This has been shown for
patients using colorimetric tests for glucose in
urine and in blood, and it clearly is likely also to
be true for doctors with these conditions [1 8] .
Moreover, Tocantins and Jones [1 9] stated that
medical students studying in laboratories have
been shown to perform less well with certain colorimetric tests and in microscopy. Rather strong
evidence has shown that histopathologists perform
less well in examining slides using a wide range
of staining techniques [2 0] .
Rubin et al. [21] added that, given the prevalence
of CVD in the general population, it is likely that
this reliance upon color differentiation poses a
significant obstacle for several medical students.
For example, examination of histologic and histopathologic microscopic sections relies upon differential colors provided by staining techniques, such
as hematoxylin and eosin, to delineate normal
tissue components and to identify pathologic alterations in these components.
This study showed that 17.2% of students who
denied being with CVD, actually have CVD, while
almost one fourth of students who did not know
whether they have CVD were definitely with CVD.
This finding has been noted by Spalding [22] , who
Hesham M.A. DahIan & Ossama A. Mostafa
517
stated that the evidence for the need for screening
of all medical students for CVD, is derived from
many sources. The finding that doctors commonly
do not know their CVD is very significant. The
evidence also suggests that many of these doctors
will not know of its severity in their own case and
a few will not know that they have any deficiency
at all.
7- LWANGA S.K. and LEMESHOW S.: Sample size determination in health studies. World health organization,
Geneva 1990.
Cumberland et al. ill noted that there is now a
good case for existing screening programs, whose
primary purpose should be to advise affected children against certain careers, to be discontinued.
Other ways of informing young people about potential occupational difficulties and pathways for
referral for specialist assessment are likely to be
more useful.
10- TABANSI P.N., ANOCHIE I.C., NKANGINIEME K.E.
and PEDRO-EGBE C.N.: Screening for congenital color
vision deficiency in primary children in Port Harcourt
City; teachers' knowledge and performance. Niger. J.
Med., 17 (4): 428-32, 2008.
This study showed that prevalence of CVD
among students with positive family history was
highest, compared with those who did not have
family history of CVD or those who did not know
if they have any family member(s) with CVD.
These findings are in agreement with those of
Frederick and Asbury [23] , who noted that risk
factors for CVD include family history, ethnicity
and gender.
13- SIMUNOVIC M.P.: Colour vision deficiency. Eye (Lond),
2009.
Reasons for the high rate of consanguinity in
Jizan need to be investigated and the awareness of
people should be raised regarding the potential
consequences of consanguinity School students
with CVD should be guided as regard the proper
choice for their future studies. Premarital examination should cover the common hereditary diseases, including CVD. Pre-university screening of
male students for CVD should be applied to help
students choose toward their career.
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