Albinism is a genetic defect that prevents the body from producing melanin, the pigment that gives hair, skin, and the iris of the eye their color. About one in 17,000 people have albinism. The two major forms of albinism are called oculocutaneous albinism (OCA), which causes individuals to have white or pink hair and skin, a very light blue iris, and ocular albinism (OA), which generally affects only the eyes. Individuals with albinism have reduced vision due to an underdevelopment of the macula. They usually also have nystagmus a side-to-side or up-and-down rhythmic movement of the eyes. They may also have high amounts of astigmatism and often a turned eye (strabismus).