Information Bulletin - Ocular Albinism
Ocular albinism in an inherited condition in which the eyes lack melanin pigment, while the skin and hair show normal or near-normal coloration.
The lack of pigment in the eyes causes various vision problems:
•Reduced visual acuity from 20/60 to 20/400 and sometimes as good as 20/25 in African-Americans,
•Nystagmus - involuntary back-and-forth movement of the eyes,
•Strabismus - crossed eyes or "lazy" eye, and
•Sensitivity to bright light and glare.
The reduced visual acuity may result in difficulty in school, such as inability to read what is written on a chalkboard except when very close, and difficulty with ball sports. It may also result in inability to drive.
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. However, when an eye doctor examines the eye by shining a light from the side of the eye, the light shines back through the iris since very little pigment is present. There may be areas of the iris which have very little pigment.
The main problem with the eye in ocular albinism is in the fovea, small area of the retina which affords acute vision. 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. A test called a visually evoked potential, which is performed like an EEG or brain wave test, can show this difference. These eye problems are very similar to those of oculocutaneous albinism (albinism which involves the skin and hair as well as the eye).
In most cases ocular albinism is X-linked, which means the gene for it is on the X chromosome. 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 in about 80% of cases. X-linked ocular albinism is also called Nettleship-Falls ocular albinism.
A less common type of ocular albinism shows a different pattern of inheritance, autosomal recessive. With this type of inheritance, 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. Newer research suggests that autosomal recessive ocular albinism is a variant of oculocutaneous albinism. The skin and hair color may be somewhat lighter than that of other family members. Autosomal recessive ocular albinism may be a variant of either tyrosinase-related (type 1) or P gene (type 2) oculocutaneous albinism (see Information Bulletin, What is Albinism?).
Testing for the Ocular Albinism Gene
Researchers have identified some, but not all of the DNA defects in ocular albinism. Therefore blood tests to identify genes for various types of albinism are not conclusive enough to be used for genetic counseling. Most of the time an ophthalmologist can identify a carrier of the X-linked albinism gene by seeing mottling of pigment in her retinas. If this mottling is not apparent, research labs can examine a hair bulb or skin biopsy from a child. This will show unusually large granules of pigment in X-linked ocular albinism, but not in autosomal recessive ocular albinism.
Those with questions about their own situation and inheritance of ocular albinism should seek a genetic counselor. Many parents of children with ocular albinism decide to have more children. These parents find their children can function well despite their visual disabilities if they are provided with appropriate support and services.
Treatment of ocular albinism includes using visual aids and environmental changes to expand the limits of vision. Surgery for strabismus is sometimes helpful, but usually does not result in fine coordination of the eyes. Surgery can improve the field of vision if the eyes are crossed, and may improve appearance and the child's self image.
The choice of optical aids for a child or adult is an individual one. Some children may do well with ordinary glasses. For older children and adults, glasses with small telescopes mounted on the lenses may help with both close and distant vision. Contact lenses sometimes provide additional correction that glasses cannot.
Also important in the treatment of ocular albinism is attention to emotional and social adjustment. Often parents and people with ocular albinism feel anger and shame about the condition and try to deny it or pretend it does not exist. This denial can result in the person with albinism experiencing low self esteem, difficulties in relationships with others, and low functioning in school and work.
It is important for parents of a child with ocular albinism to learn as much as possible about the condition. and about low vision. Parents must be open and honest with the child, family members, friends, and others about the child's low vision and the reason for it. (See also the NOAH Information Bulletin "Social and Emotional Aspects of Albinism.")
Participation in support groups such as NOAH and NAPVI (National Association of Parents of Visually Impaired) can help in gathering information as well as in dealing with feelings about the condition.
Children and adults with ocular albinism can benefit from participation in peer support groups such as NOAH and Council of Citizens with Low Vision International. These groups can help the individual to feel less isolated, to learn positive attitudes and coping skills from others with low vision, and to gather valuable resource information.
NOAH can provide other information bulletins on visual aids, assisting students with albinism in the classroom, and resources for social and emotional support. More technical information for health professionals on ocular albinism can be found in:
Lewen RM: Ocular albinism. Arch Ophthalmol 1988, 106:121-122. This is a photo essay about X-linked ocular albinism.
King RA, Hearing VJ, Creel DJ, Oetting WS: Albinism, 4353-4393, in Scrivner, Charles R. et al, The Metabolic and Molecular Bases of Inherited Disease, 7th ed., McGraw Hill Inc. Health Professions Division, New York 1995. This textbook is available in most medical libraries.
Funds for publication of this bulletin were provided by the Innovating Worth Projects Foundation of Somers Point, NJ.