What is Color Vision Deficiency (CVD)?
Defective color vision is usually congenital. In Caucasians, approximately 8% of males and less than 0.5% of females have inherited color defective vision. Of the males, approximately 2% are dichromats with severe deficiency. The largest group is actually trichromatic — color weak rather than color deficient. Dichromatics are protanopes if they have a red-green deficiency related to red-insensitivity, deuteranopes if they are red-green deficient related to green-insensitivity, and tritanopes if they have blue-yellow deficiency related to blue-insensitivity. At night, dichromats may be further reduced to monochromaticity when the physiological phenomenon of small field tritanopia is added. Color vision can be affected after optic neuritis or in macular degeneration, central serous retinopathy, multiple sclerosis or as a sequela to heavy metal poisoning.
