ABSTRACT
Colour blindness is a frequent entity, mostly occurred among males. It is mainly genetically in origin, however, acquired cases have been described. The present study was designed to determine the prevalence of colour vision deficiency among male guidance school students. This descriptive study was performed on 500 randomly selected male guidance school students from different districts of Tehran. They were tested for congenital colour blindness using [Ishihara] pseudoisochromatic color plates. Totally, 26 students were found to have color deficiency [5.2%] among whom 18 had relative colour deficiency whereas 8 had complete deficiency. Twelve [2.4%] students showed deuteranomaly, 6 [1.2%] had protanomaly, 5 [1%] had protanopia and 3 [0.6%] had deuteranopia. Colour blindness is more frequent in males. Most of the cases are hereditary, meanwhile, they usually have problem in differentiating red and green colours