Absence of the pigment melanin in the eyes, skin, hair, scales, or feathers. It arises from a genetic defect and occurs in humans and other vertebrates. Because they lack the pigments that normally provide protective coloration and screen against the sun's ultraviolet rays, albino animals rarely survive in the wild. Humans have long intentionally bred certain albino animals (e.g., rabbits) for their appearance. In humans with generalized, or total, albinism, the affected person has milk-white skin and hair; the iris of the eye appears pink, the pupil red. Vision abnormalities such as astigmatism, nystagmus (rapid involuntary oscillation of the eye), and photophobia (extreme sensitivity to light) are common. Generalized albinism occurs throughout the world in about one in 20,000 persons.