Genetic, epidemiologic and social features of colour blindness.

Red-green colour blindness is an inherited defect which shows interesting epidemiologic and social features. Its mean frequency within the indigenous population of Calabria (Southern Italy) was found to be 5.25%, one of the highest in continental Italy, showing a decreasing trend from the province of Cosenza (Northern Calabria, 6.23%), to the province of Catanzaro (Central Calabria, 4.65%) and the province of Reggio Calabria (Southern Calabria, 3.43%). A similar trend has not been previously recognized, according to the recent literature, because no other region has been fully screened. The mean frequency (7.40%) of red-green colour blindness in the Albanian ethnic minority in Calabria is significantly different from that of the indigenous population, and this minority does not have the protanomalous phenotype. Screening showed that 96% of the colour-blind students attending middle school and 65% of the colour-blind university students are not aware of their anomalous vision status. Thus, screening during the school years would greatly help affected students to choose their future professional orientation.