Ocular albinism

With ocular albinism, the color of the iris of the eye may vary from blue to green or even brown, and sometimes darkens with age. Despite its colour, light shines through the iris since very little pigment is present. However, the main problem with the eye in ocular albinism is in the fovea, which is the area of the retina which receives the sharpest light images inside the eye. With ocular albinism, the fovea does not develop completely, presumably because melanin pigment is needed for the growth processes that normally occur before birth. Therefore the eye cannot process sharp light images. Because the fovea does not develop well, it is difficult to correct vision completely with glasses.

Another defect in ocular albinism is that nerves from the back of the eye to the brain do not follow the usually pattern of routing. From the normal eye, nerve fibers go to both sides of the brain, that is, the same side as the eye and the side opposite from the eye. From the eye with ocular albinism, more of the nerve fibers cross from the eye to the opposite side of the brain.

The two most common types of ocular albinism are X-linked and autosomal recessive. These terms refer to the way in which the condition is inherited. X-linked ocular albinism occurs almost exclusively in males. It is passed from mothers who carry the gene to their sons. Each time a mother who carries the gene for ocular albinism gives birth to a son, there is a 1 in 2 chance that the son will have ocular albinism. Mothers who carry the gene may have mottled pigmentation in the back of their eyes, but do not have the full syndrome of ocular albinism. An ophthalmologist may be able to identify this mottling. X-linked ocular albinism is also called Nettleship-Falls ocular albinism.

Autosomal recessive is another pattern of inheritance of a genetic trait. Both parents of a child with autosomal recessive ocular albinism carry the gene for it. Boys and girls are equally affected. If both mother and father carry the gene, then at each birth there is a one in four chance that the child will have ocular albinism. Since there are these two different patterns of inheritance of ocular albinism, parents who have a child with ocular albinism and who plan to have more children may wish to consult a genetic counselor to answer questions about likelihood of having another child with ocular albinism.