Pakistan J. Zool., vol. 48(4), pp. 1045-1049, 2016. Incidence of Protanopia and Deuteranopia, Defects of Colour Vision in Quetta, Pakistan Hamida, 1 Tehmina Sajid, 1 Amna Bibi, 1 Nabeela Tariq, 1 Naheed Sajjad, 2 Kashif Umer, 3 Muhammad Ali 4 and Rehana Iqbal 3* 1 Zoology Department, Sardar Bahadur Khan Women’s University, Quetta, Pakistan 2 Biotechnology Department, Sardar Bahadur Khan Women’s University, Quetta, Pakistan 3 Institute of Pure and Applied Biology, Bahauddin Zakariya University, Multan.60800 4 Government College University, Faisalabad. A B S T R A C T Colour vision deficiency (CVD), an X-linked recessive disorder, is predominantly present in males. Congenital disorders usually occur due to abnormality in any one or all three cone photoreceptors. Protanopia and deuteranopia result when long wavelength (L) photopigments (red) and middle wavelength (M) photopigments (green) are missing, respectively. The study aimed to screen the inherited colour vision defects among random populations of different ethnicity in Quetta. The study subjects (n=1450; males=452; females=998; mean age=23.17±9.38) were randomly selected and examined for CVD using the Standard Ishihara Chart. Results revealed that 5.75% (26) males and 1% (10) females were colour vision deficient. The distribution of protanopia and deuteranopia among males were 2% (9) and 3.8% (17), respectively. Females showed 0.6% (6) and 0.4% (4) protanopia and deuteranopia, respectively. No significant difference (P>0.05) was observed in the prevalence of CVD among different age groups. Familial cases were far more prevalent than the sporadic cases. Among ethnic groups the highest proportions of CVD in males and females were observed in Pathan (7.39% and 1.16%, respectively). No significant difference (P>0.05) in the proportion of disorder was found among different ethnic groups. Overall 2.48% of the populations of Quetta had this abnormality with deuteranopia being more prevalent. The proper screening of CVD at early age can help individuals avoid certain occupational hazards and such studies can also be helpful in decreasing the proportion of disorder by discouraging consanguinity. INTRODUCTION Colour vision deficiency (CVD) is the inability to perceive differences among certain colours of spectrum. Normal colour vision is actually trichromatic that is the combination of red, green, and blue lights (Curcio et al., 1990). It requires three types of cone photopigments that differ in their relative spectral sensitivities, and are generally termed as red (long wavelength), green (middle wavelength), and blue (short wavelength) cone pigments (Cruz et al., 2010). There are three types of inherited CVD: monochromacy, dichromacy and anomalous trichromacy. Monochromacy, being so rare, is the total absence of colour vision and occurs when two or all three of the cone pigments are missing. Dichromacy occurs when only one of the cone pigments is missing and is categorized into protanopia (characterized by the complete absence of red cone), deuteranopia (characterized by the absence of green cone) and tritanopia (complete absence of blue cone). Anomalous trichromacy involves reduced sensitivity to one of the __________________________________ * Corresponding author: rehanaiqbal82@gmail.com 0030-9923/2016/0004-1045 $ 8.00/0 Copyright 2016 Zoological Society of Pakistan three cone pigments and includes protanomaly, deuteranomaly and tritanomaly in which the spectral sensitivity of the red, green and blue cone receptors is altered. Achromatopsia is the most severe kind of colour vision defect (Adams et al., 2009). Red and green CVD (protanopia and deuteranopia, respectively) have the highest frequency in the general populations (Oriowo and Alotaibi, 2008). The genes causing red-green defects are localized on the long arm of the X-chromosome at Xq28 (Filosa et al., 1993; Norn, 1997; Deeb and Kohl, 2003), whereas the blue pigment gene is located on an autosome, chromosome 7 at 7q32 (Nathans et al., 1986; Motulsky, 1988; Deeb and Kohl, 2003). The tritanopia type, a rare autosomal dominant disorder, occurs in 0.002-0.007% in the population (McIntyre, 2002). Achromatopsia, a rare autosomal recessive disorder, occurs when the functions of all three cone receptors are lost and is the complete inability to distinguish between different colours. It has a prevalence of about 0.003% of the population (Deeb, 2004; Alexander et al., 2007). Colour vision defect may be congenital or acquired. Acquired CVD may be caused due to factors such as damage to the optic nerves, metabolic disorders (e.g. diabetes), eye diseases (e.g. glaucoma, macular degeneration), chronic illness (e.g. Article Information Received 18 June 2015 Revised 26 November 2015 Accepted 10 January 2016 Available online 1 June 2016 Authors’ Contribution MA designed and supervised the study. H, TS and AB collected the data. NT and NS performed experimental work. KU statistically analyzed the data. RI wrote the article. Key words X-linked recessive, photoreceptor, Ishihara chart, consanguinity.