Congenital red–green color blindness is an inherited condition that is the root cause of the majority of cases of color blindness. It has no significant symptoms aside from its minor to moderate effect on color vision. It is caused by variation in the functionality of the red and/or green opsin proteins, which are the photosensitive pigment in the cone cells of the retina, which mediate color vision. Males are more likely to inherit red–green color blindness than females, because the genes for the relevant opsins are on the X chromosome. Screening for congenital red–green color blindness is typically performed with the Ishihara or similar color vision test. It is a lifelong condition, and has no known cure or treatment.
This form of color blindness is sometimes referred to historically as daltonism after John Dalton, who had congenital red–green color blindness and was the first to scientifically study it. In other languages, daltonism is still used to describe red–green color blindness, but may also refer colloquially to color blindness in general.
