Ocular albinism

What is 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 characterized by severely impaired sharpness of vision (visual acuity) and problems with combining vision from both eyes to perceive depth (stereoscopic vision). Although the vision loss is permanent, it does not worsen over time. Other eye abnormalities associated with this condition include rapid, involuntary eye movements (nystagmus); eyes that do not look in the same direction (strabismus); and increased sensitivity to light (photophobia). Many affected individuals also have abnormalities involving the optic nerves, which carry visual information from the eye to the brain.

Unlike some other forms of albinism, ocular albinism does not significantly affect the color of the skin and hair. People with this condition may have a somewhat lighter complexion than other members of their family, but these differences are usually minor.

The most common form of ocular albinism is known as the Nettleship-Falls type or type 1. Other forms of ocular albinism are much rarer and may be associated with additional signs and symptoms, such as hearing loss.

How common is ocular albinism?

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.

What genes are related to ocular albinism?

Mutations in the GPR143 gene cause ocular albinism.

Ocular albinism type 1 results from mutations in the GPR143 gene. This gene provides instructions for making a protein that plays a role in pigmentation of the eyes and skin. It helps control the growth of melanosomes, which are cellular structures that produce and store a pigment called melanin. Melanin is the substance that gives skin, hair, and eyes their color. In the retina, this pigment also plays a role in normal vision.

Most mutations in the GPR143 gene alter the size or shape of the GPR143 protein. Many of these genetic changes prevent the protein from reaching melanosomes to control their growth. In other cases, the protein reaches melanosomes normally but mutations disrupt the protein's function. As a result of these changes, melanosomes in skin cells and the retina can grow abnormally large. Researchers are uncertain how these giant melanosomes are related to vision loss and other eye abnormalities in people with ocular albinism.

Rare cases of ocular albinism are not caused by mutations in the GPR143 gene. In these cases, the genetic cause of the condition is often unknown.

Read more about the GPR143 gene.

How do people inherit ocular albinism?

Ocular albinism type 1 is inherited in an X-linked pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the GPR143 gene in each cell is sufficient to cause the characteristic features of ocular albinism. Because females have two copies of the X chromosome, women with only one copy of a GPR143 mutation in each cell usually do not experience vision loss or other significant eye abnormalities. They may have mild changes in retinal pigmentation that can be detected during an eye examination.

Where can I find information about treatment for ocular albinism?

These resources address the management of ocular albinism and may include treatment providers.

• Gene Review: Ocular Albinism, X-Linked
• MedlinePlus Encyclopedia: Albinism

You might also find information on treatment of ocular albinism in Educational resources and Patient support.

Where can I find additional information about ocular albinism?

You may find the following resources about ocular albinism helpful. These materials are written for the general public.

• MedlinePlus - Health information (3 links)
• Educational resources - Information pages (5 links)
• Patient support - For patients and families (5 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Gene Tests - DNA tests ordered by healthcare professionals
• ClinicalTrials.gov - Linking patients to medical research
• PubMed - Recent literature
• Online Books - Medical and science texts
• Scriver's Online Metabolic and Molecular Bases of Inherited Disease (OMMBID): Albinism
• OMIM - Genetic disorder catalog (3 links)

What other names do people use for ocular albinism?

• Albinism, Ocular
• OA
• XLOA

See How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about ocular albinism?

• See How can I find a genetics professional in my area? in the Handbook.
• Ask the Genetic and Rare Diseases Information Center.
• Submit your question to Ask the Geneticist.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding ocular albinism?

albinism ; cell ; chromosome ; gene ; involuntary ; melanin ; melanosome ; mutation ; nystagmus ; optic nerve ; photophobia ; pigment ; pigmentation ; protein ; retina ; sensitivity ; sex chromosomes ; sign ; stereoscopic vision ; strabismus ; symptom ; tissue ; visual acuity

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.

References

These sources were used to develop the Genetics Home Reference condition summary on ocular albinism.

• Camand O, Boutboul S, Arbogast L, Roche O, Sternberg C, Sutherland J, Levin A, Heon E, Menasche M, Dufier J, Abitbol M. Mutational analysis of the OA1 gene in ocular albinism. Ophthalmic Genet. 2003 Sep;24(3):167-73. PubMed citation
• Cortese K, Giordano F, Surace EM, Venturi C, Ballabio A, Tacchetti C, Marigo V. The ocular albinism type 1 (OA1) gene controls melanosome maturation and size. Invest Ophthalmol Vis Sci. 2005 Dec;46(12):4358-64. PubMed citation
• Gene Review: Ocular Albinism, X-Linked
• Oetting WS. New insights into ocular albinism type 1 (OA1): Mutations and polymorphisms of the OA1 gene. Hum Mutat. 2002 Feb;19(2):85-92. Review. PubMed citation
• Tak WJ, Kim MN, Hong CK, Ro BI, Song KY, Seo SJ. Ocular albinism with sensorineural deafness. Int J Dermatol. 2004 Apr;43(4):290-2. No abstract available. PubMed citation