Color vision defects may be inherited or acquired. This is a rare disorder of red-green color confusion associated with extreme nearsightedness and physical changes in the eye. The name is derived from the name of a Danish island where the first cases were found.
Individuals are presumably born with high myopia (nearsightedness) and difficulty discerning red and green colors. It is a non-progressive disorder in which the vision remains good throughout life. The appearance of the retina is light in color suggesting that the usual pigmentation is absent and perhaps the optic nerve is abnormally small. The electrophysiologic test called an ERG shows that the cones (the cells of the retina that mediate color vision) are not functioning normally.
The gene responsible for this disorder is located on the X chromosome but so far has not been identified further. Only males are affected and their mothers who carry the mutation on one of their two X chromosomes do not have evidence of disease (X-linked recessive). However they can expect on average that half of their sons will be affected. Males with this disorder do not transmit it to their children but all their daughters will receive the mutated X chromosome.
This is a stationary disorder with no evidence of progression of the myopia or colorblindness. There are no other health issues and longevity is normal. Ophthalmologists and vision scientists usually diagnose this disorder.