Middle East African Journal of Ophthalmology

: 2019  |  Volume : 26  |  Issue : 3  |  Page : 133--137

Prevalence and determinants of color vision defects among preparatory university students at Makkah, Saudi Arabia

Osama Abdulqadir Khairoalsindi1, Bayan Mutlaq Almasoudi1, Ashjan Yousef Bamahfouz2, Abdullah Atiah Alghamdi3, Muhammad Irfanullah Siddiqui4,  
1 College of Medicine, Umm Al-Qura University, Makkah, Saudi Arabia
2 Department of Ophthalmology, Faculty of Medicine, Umm Al-Qura University; Department of Ophthalmology, King Abdullah Medical City, Makkah, Saudi Arabia
3 Department of Ophthalmology, Faculty of Medicine, Umm Al-Qura University, Makkah; Department of Ophthalmology, King Faisal Specialist Hospital and Research Center, Jeddah, Saudi Arabia
4 Department of Community Medicine, Faculty of Medicine, Umm Al-Qura University, Makkah, Saudi Arabia

Correspondence Address:
Dr. Osama Abdulqadir Khairoalsindi
College of Medicine, Umm Al-Qura University, P.O. Box: 715, Makkah
Saudi Arabia


PURPOSE: To estimate the magnitude and determinants of color vision defects (CVD) among preparatory health science students. METHODS: A cross-sectional survey was conducted in 2017. Participants were assessed using 24-plate Ishihara's Test of Color Vision chart. If ≤9 plates were read correctly, the color vision was regarded as deficient. The CVD prevalence and its 95% confidence interval (CI) were calculated. CVD was associated with gender, family history of CVD, and other vision problems. RESULTS: We evaluated 1126 students (552, 49% males; mean age: 18.7 ± 0.7 years). The prevalence of CVD was 1.77% (95% CI: 1.0, 2.6). Among male students, it was 3.5% (95% CI: 1.9, 5.0). Only one female student had CVD. The Duran CVD was found in 18 (1.6%) students. However, only two students had Tritan CVD. Three among twenty CVD students knew that they suffer from CVD. CVD was positively associated to a family history of CVD (odds ratio [OR] = 3.8; 95% CI: 1.4, 10.1;P = 0.02) and male gender (OR = 20.4 [95% CI: 2.7, 153]). CVD was not significantly associated to other vision problems (OR = 0.8 [95% CI: 0.3, 2.0]). CONCLUSION: Eighteen in thousand health sciences students suffered from CVD. Ten percent of them had Tritan CVD. Duran CVD seems to be a male sex-related and/or a familial condition. Most of the CVD students seem to have adopted to this defect and were not aware of suffering from it. Screening for CVD is therefore debatable.

How to cite this article:
Khairoalsindi OA, Almasoudi BM, Bamahfouz AY, Alghamdi AA, Siddiqui MI. Prevalence and determinants of color vision defects among preparatory university students at Makkah, Saudi Arabia.Middle East Afr J Ophthalmol 2019;26:133-137

How to cite this URL:
Khairoalsindi OA, Almasoudi BM, Bamahfouz AY, Alghamdi AA, Siddiqui MI. Prevalence and determinants of color vision defects among preparatory university students at Makkah, Saudi Arabia. Middle East Afr J Ophthalmol [serial online] 2019 [cited 2020 Aug 13 ];26:133-137
Available from: http://www.meajo.org/text.asp?2019/26/3/133/268247

Full Text


Color vision perception is one of the visual functions of healthy human being. Three types of cones are responsible for trichromacy in color perception. Defects in these retinal cells result in congenital color vision defect (CVD).[1] Abnormal color vision is nonprogressive and untreatable and therefore does not meet criteria for health screening.[2] In the UK, screening for CVD is an established practice with argument that those identified can be counseled without stigmatizing them and offer career guidance when they are to leave the schools and when they start driving.[3]

Population in Saudi Arabia with a consanguinity rate reaching to 56% in some areas has higher rates of congenital disabilities and congenital anomalies.[4] Congenital color vision defect is genetic and transmitted in recessive trait, resulting in male offspring suffering from CVD more than females. Prevalence of CVD is reported to range from 2.3% in Nigeria to 2.75% in Pakistan.[5],[6] Persons with congenital CVD adapt, compensate, and cope in their daily living without significant negative impact of CVD. However, persons involved in skilled work like driving and medical and dental professions could suffer and be stressed; therefore, persons making such career choices should be screened for CVD and counseled about options for career accordingly.[6],[7],[8] The evaluation of CVD among prospective medical professionals among Saudi health students in areas with high rate of consanguinity and its impact on their daily activities will be of interest.

We present the magnitude, determinants of CVD, and its perceived impact on daily living among preparatory university students of Mecca region in Saudi Arabia.


Ethical approval was obtained from the Faculty of Medicine, Umm Al-Qura University (UQU). A web-based questionnaire was sent to all students. The questionnaire form was anonymous and without any reference of the participating students. The students were informed that their participation is optional and voluntary.

The study was conducted at UQU of Makkah city, Saudi Arabia. The study population was the preparatory students who subsequently join colleges of medicine, dentistry, applied medical sciences, nursing, and clinical pharmacy. The field part of the study was between December 2017 and April 2018.

This was a questionnaire-based, observational, cross-sectional study. We assumed that the rate of CVD in our target population of 2000 students will be 2.75%.[6] To achieve 95% confidence interval (CI), 0.75% acceptable error margin, and 1.2 study design effect in our study, we need to interview and assess 1146 students. We used Open Epi software Centre for Disease Control (CDC, Atlanta, USA) to calculate this sample size.[9] For attaining the maximal representativeness, all the population of the study were accounted and were invited to participate. Students were contacted through text-messages and e-mail invitations.

An online uploaded Google form was filled by each participant [Appendix 1]. The first part of the form contained demographics (age, gender), previous history of ocular abnormalities, visual acuity disorders, color vision deficiency, and family history of color blindness. Each participant was assessed for color vision using 24-plate Ishihara's Test of Color Vision using smartphone which was validated earlier by Sorkin et al.[10] The participants were instructed not to elapse >5 s on each plate. They kept a distance of 75 cm from the color vision testing plates. They also kept the plates at right angle to the line of vision. If the number in English language was correctly identified in 13 or more of the total 15 plates, the participant was considered to have normal color vision. If a participant identified 10–13 plates correctly, they were retested and were considered as equivocal and confused. They were retested using 15 plates of Ishihara chart with adequate illumination of 70 lux in the presence of investigators. If only 9 or <9 plates are read correctly, the color vision was regarded as red-green deficient.

We piloted the 15-plate Ishihara chart on 20 persons who were not part of the present study. Five of them were known red-green color deficient. All five red-green color-deficient persons were correctly identified, while the other 15 were correctly identified as normal. Thus, color vision 15-plate Ishihara plate sensitivity and specificity were 100%.

The data were collected in Microsoft Excel spreadsheet. After checking for quality of the data, it was transferred into spreadsheet of Statistical Package for the Social Studies (IBM, Chicago, USA) for univariate analysis using parametric method. The qualitative variables were presented as frequency percentage proportion with their 95% CI. The quantitative variables were plotted to study their normal distribution. If distributed normally, we presented their mean and standard deviation. For associating the outcome variable CVD to other variables, we estimated odds ratio (OR), its 95% CI, and two-sided P value. A P < 0.05 was considered statistically significant.


We invited all 1410 preparatory students. Of them, 1126 participated. The response rate was 80%. The mean age of examined sample was 18.7 ± 0.7 years. Male constituted 552 (49%) of the participants.

There were 20 participants among 1126 with CVD. The prevalence of CVD was 1.77% (95% CI: 1.0, 2.6). Of the 20 participants with CVD, 19 were males with a prevalence of 3.5% (95% CI: 1.9, 5.0). The prevalence of CVD among female participants was 0.2%. Of the 20 participants with CVD, 18 had Duran type of CVD while two had Titran type of CVD.

The CVD was associated to gender, family history of CVD, and other eye problems [Table 1]. Male gender (P < 0.001) and positive family history of CVD (P = 0.02) were significantly associated with CVD in students.{Table 1}

Of the twenty students with CVD, two students with Tritan and one with deuteron were aware of their defect. The other 17 (85%) students with CVD were detected for the first time during this screening.

The difficulty in daily living among twenty CVD students was compared with those without CVD. Two children with Tritan expressed difficulty in daily living and 18 children with deuteron responded that they did not face difficulties in daily living. In contrast, only 11 (1%) students without CVD faced difficulties in daily living and 1095 students did not face any difficulties. There was significantly more difficulty in daily living among those with CVD compared to those without CVD (OR = 10.9 {95% CI: 2.2, 52.7}, P= 0.02).

With the knowledge of their CVD status, only one of the twenty students expressed his/her desire to change the career from health studies. Other seven students with CVD suggested that their CVD is not affecting the work so will continue their career and 12 students with CVD could not decide what to do with their career.

None of the students with CVD had fatal, serious accident or head injury. In 1106 students without CVD, there were 30 (2.7%) students who had head injury and/or accident (relative risk = 36 (95% CI: 26, 52.5). Thus, the risk of road traffic accident (RTA) and head injury among students with CVD seems to be significantly less compared to other students of same age.

We also studied the predictor value of risk factors, gender and family history for detecting CVD. Female gender (adjusted OR = 0.05 [95% CI: 0.007, 0.4], P= 0.003) and negative history of CVD in family (adjusted OR = 0.3 [95% CI: 0.1, 0.7], P= 0.01) were independent protective factors for CVD in students.


In this study, 18 per thousand students related to health profession were found to have color vision defect. Ten percent of them had Tritan type while rest 90% had deuteron type of CVD. The ailment was mainly in male students and having family member with CVD was a predictor of CVD in other family member. The students with CVD faced significantly more difficulties in daily living. However, they were not very keen to change the career. CVD was not linked with other vision-related eye problems. CVD seems to be protecting students from accidents.

This is perhaps first study in an Arab country to evaluate the magnitude of CVD, its type, risk factors, and its impact on daily living and career selection rethinking among prospective health-related students. In view of its asymptomatic nature and minimum influence on daily living, justification of universal screening for CVD is debatable. However, a case of Tritan type of CVD may be counseled to select profession carefully and adopt new devices to address the CVD.

The prevalence of CVD in our study was similar to that noted in secondary students of Nigeria.[5] In Pakistan, the rate of CVD in medical and dental students was 2.75%.[6] In Nepal with small sample size of medical students, Pramanik et al. found CVD prevalence of 5.6%.[8]

The prevalence of CVD in males was 3.5% compared to 0.5% in females in our study. This confirms earlier findings suggestive of X-linked recessive manner inheritance of the condition.[11] The prevalence of CVD among male secondary students of Jizan city of Saudi Arabia also shows this gender-specific visual function disability.[12] This suggests perhaps male gender-specific screening for CVD in high-risk population. In contrast to these findings, a study in Pakistan did not find association of male gender to CVD.[13] Small male sample compared to female dental students in this study could be the reason for this unusual finding.

Positive family history of CVD was strong predictor of CVD in students in our study. Positive family history seems to be a proxy indicator for high consanguinity in the population carrying the genes responsible for the CVD in family. In another study of Saudi students, CVD was associated with parents consanguineous behavior.[12] In Saudi population, high consanguinity rate and resultant high rates of congenital disabilities and genetic disorders have been documented and prompted to undertake genetic screening and premarital genetic counseling.[14]

Only 15% of CVD cases were aware of their defect while 85% were detected for the first time through screening. This implies that there are only mild negative effects of CVD especially those with Duran type. Since, to the best of our current knowledge, there is no cure and possibility of labeling a person with such defect as blind, screening is not justified for early detection of CVD.[2]

In our study, CVD was not significantly associated with other ocular or vision problems. This is commonly observed in deuterons.[1] A rare disease called Bornholm syndrome is documented to have congenital myopia with dichromacy.[15] In the absence of refractive status assessment, we could not find if any of students with CVD had high myopia. Further assessment is therefore recommended of these identified students with CVD to rule out such comorbidity.

The CVD is documented to be risk factor for driving and accidents.[2] In our study, there was negative association of CVD to RTA and head injuries. Perhaps, these students are subconsciously extravigilant and more cautious in driving and thus could avoid risk of accidents. It could also be possible that overall students of this age are more careless, and therefore, those without CVD also had higher rate of accident, resulting in nonassociation of CVD to such injuries and RTA.[16]

There were few limitations to our study. This being web-based survey, color vision testing in first stage was done using web-based Ishihara plates. Those with doubtful outcomes were reassessed in person. Thus, web-based testing tool for color vision could be less reliable than a number of more precise tools for color vision testing. Therefore, it could be argued that a marginal underestimation of CVD prevalence is possible. Color vision is interpreted at cortical level and other visual cues such as contrast help in this process.[17] The testing of contrast was not part of our study and thus could have variation among students using web-based Ishihara plates.


It seems that most of the students planning to undertake health studies were adopted to daily living even with CVD and were not very keen to think about change in career. In such circumstances, universal screening for students is still debatable, and our study could not support either CVD screening as it is done in the UK nor think about not warning the potential health professionals who could face difficulties compared to their fellow students without CVD. However, high-risk predictors noted in the present study such as male sex and those with family history of CVD could be assessed if choosing professions needing precise color cues for their tasks.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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