Prevalence and allele frequency of Congenital Colour Vision Deficiency (CCVD) among students at Hawassa University, Ethiopia

Abstract

Background: The prevalence of congenital colour vision deficiency (CCVD) varies from race to race and differs in different geographic regions. Colour vision deficiency or colour blindness, is the inability or decreased ability of discriminating certain colour combinations and colour differences under normal lighting conditions. This study aimed to determine the prevalence of congenital colour vision deficiency among students at Hawassa University. Methods: A cross-sectional survey was employed involving 4004 students (females = 1171 and males = 2833) from four campuses, namely, Institutes of Technology, College of Health Science and Medicine, College of Agriculture and Main Campus. The Ishihara pseudo-isochromatic 24 plate edition was used to test the colour vision of students under natural day light condition. Results: The prevalence of CCVD in the present study was 2.85%. A hundred and six (3.75%) males and eight (0.68%) females were affected with congenital colour vision deficiency. The frequencies of achromacy, deutan and protan in male subjects were 4 (0.14%), 82 (2.89%), and 24 (0.85%), respectively. Deutan was highest among students of Amhara ethnic origin (38, 2.51%), but the frequency of protan was highest amongst Oromo students (10, 0.8%). Conclusion and recommendations:The overall prevalence of CCVD found in the present study was lower compared to the previous studies done in Ethiopia. There was clear variation in the prevalence of colour vision deficiency among students of various ethnic groups. Proper screening, education and counseling are needed to minimize impacts of CCVD in the country, and can also be beneficial for the affected subject in tackling difficulties in everyday work and for proper choice of future profession.

Prevalence and Allele Frequency of Red-Green Color Vision Defects among School Children in Repi Primary School in Addis Ababa, Ethiopia

“…A comparable frequency of deutan and protan are reported in done in Gish-Abay town by Wale et al [19]. The slight difference in the prevalence could be due to genetic, geographic, population movements and cultural/religious factors [2,12,18]. Deutan cases occur in higher percentage than protan for both male and female subjects.…”

“…Females who had a recessive allele for deutan on one X chromosome, but a recessive allele for protan on the second X chromosome are called compound heterozygote [17]. The expected frequency of the compound heterozygote female in the present study is lower compared to the frequency in the general population [17]; and among university students [2]. Similarly, the expected frequency CCVD among the females lower relative to that of the general public (0.39%) [17].…”

“…Data on prevalence of CCVD are useful for identifying needs for treatment and rehabilitation services, planning, career choices, and focusing research priorities [2,5,12,24,25]. Undiagnosed color vision defect could pose a handicap to the performance of affected students.…”

“…However, genomic mutations encoding blue retinal cone pigment located on the autosomal chromosome 7 are responsible for tirtan defects [1,2]. None congenital colour vision defects could be due to neurological disease, metabolic disorders, drug toxicity, drug overdose etc [2,5].…”

“…Managing and organizing data on the prevalence and causes colour vision defects population wise are crucial for vision defect prevention and control; career choice, and prioritization of research activities depending on the severity of problems in the various groups. It is recommended that school children should undergo early diagnosis of colour vision defects to adjust better to tasks at school and to make career choice [2,5]. To date the number of studies done in Ethiopia, to assess the prevalence of congenital colour vision de ciency are hardly few.…”