Ocular albinism

Submitted by Anonymous (not verified) on Fri, 04/14/2017 - 14:34

Image of an individual with ocular albinism

Ocular albinism is a genetic condition that primarily affects the eyes. This condition reduces the coloring (pigmentation) of the iris, which is the colored part of the eye, and the retina, which is the light-sensitive tissue at the back of the eye. Pigmentation in the eye is essential for normal vision. Ocular Albinism is an X-linked recessive genetic condition caused by mutations in the G protein coupled receptor 143 (GPR143) gene.

X-linked recessive genetic disorders are conditions caused by an abnormal gene on the X chromosome. Females have 2 X-chromosomes, 1 of the X chromosome is “turned off” causing the genes on that chromosome to be inactivated. Women who have a diseased X-linked gene become a carrier for that gene, therefore they typically will not show phenotype. Males on the other hand only have a single X chromosome, so if they have a diseased X-linked gene they typically will show phenotype.

GPR143 gene controls the growth of melanosomes, which are cellular structures which produce the pigment melanin. Melanin is responsible for the coloration in hair, skin and eyes. In the retina this coloration plays an important role in normal vision. Mutations in the GPR143 gene alter the size or shaper of the protein. These changes prevent the protein from reaching melanosomes to control their growth. The protein can also reach the melanosomes but the mutations disrupts the protein's function. In rarer cases of ocular albinism the genetic causes are often unknown and do not result from a mutation of the GPR143 gene.

Ocular albinism is a condition in which the eyes lack melanin pigment, while the skin and hair show normal or near normal coloration. This lack of pigment in the eyes causes various vision problems, such as; reduced visual acuity from 20/60 to 20/400. Involuntary back-and-forth movement of the eyes (nystagmus), crossed eyes or "lazy" eye (strabismus), and sensitivity to bright light and glare (photophobia). 

The most common form of this disorder, ocular albinism type 1, affects at least 1 in 60,000 males. The classic signs and symptoms of this condition are much less common in females.

OA cannot be treated with corrective lenses because underdevelopment of the fovea does not allow the retina to take an accurate picture, and thus transmit an accurate picture to the brain. Both the transmission of images and the balance of wiring from each eye to each side of the brain are altered, the brain cannot interpret the impulses correctly causing an imperfect image. So using corrective lens, the film of the retina does not take a good enough image and the brain does not receive good transmission.