Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: Titanscape on 11/09/2006 14:09:10

Title: Albinism And Blindness
Post by: Titanscape on 11/09/2006 14:09:10
Is it true that albinos tend to be blind and that then pigment is neccesary for vision.

Title: Re: Albinism And Blindness
Post by: iko on 14/09/2006 14:12:54
It seems to be as you wrote:
Albinism refers to a group of inherited conditions. People with albinism have absent or reduced pigment in their eyes, skin or hair. They have inherited genes that do not make the usual amounts of a pigment called melanin which is essential for the full development of the retina. Lack of melanin in development of the retina is the primary cause of visual impairment in albinism. In the USA it is estimated that one person in 17,000 has some type of albinism.

There are two major categories of albinism (overlap of these categories often occurs):

Ocular Albinism (OA) is divided into two types according to the inheritance pattern:
autosomal recessive OA occurring equally in males and females, and X-linked OA with symptoms occurring primarily in males. In the X-linked cases, mothers carry the gene and pass it to their sons. Although the mothers usually have normal vision, they have subtle eye changes that can be identified by an ophthalmologist. If a woman does carry the gene, with each pregnancy there is a one in two chance of having a son with X-linked ocular albinism. For specific information, families should seek the advice of a qualified genetic counselor.

Oculocutaneous Albinism (OCA, involves the lack of pigment in the hair, skin and eyes. Each parent must carry the gene for this form which follows an autosomal recessive inheritance pattern, meaning there is a one in four chance at each pregnancy that the baby will be born with albinism. Within OCA there are two primary types of albinism.
Type 1 (formerly known as Tyrosinase Negative) involves the complete lack of pigment. These children have white skin and hair and moderate to severe visual impairment. Children with
Type 2 (formerly known as Tyrosinase Positive) have various amounts of pigmentation, yellow or blonde hair and usually less severe visual impairment.

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