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| | Albinism |
 | | Albinism affects approximately 1 in 20,000 individuals, producing pigmentary deficiency, abnormal crossings of the temporal fibers in the optic chiasm, nystagmus, photophobia, variable visual acuity and, frequently, strabismus. |
 | | The main subdivisions of albinism include oculocutaneous, ocular, and albinoidism (absence of pigment in localized areas; the pigment in the skin, hair and eyes is less than normal but does not affect the individual as severely as the oculocutaneous or ocular types). |
 | | In tyrosinase-negative oculocutaneous albinism, the congenital inactivity of the enzyme tyrosinase prevents the cells use of tyrosine in the formation of the pigment melanin. |
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