Incidence of protanopia and deuteranopia, defects of colour vision in Quetta, Pakistan

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.