Albinism and Low Vision
What Is Albinism?
Albinism represents a group of conditions characterized by a defect in the production of the pigment melanin, normally found in skin, eyes, and hair.
Any one of a number of genes responsible for the production of melanin can lead to albinism. There are two major types of albinism:
- Is inherited in an autosomal recessive fashion. This means that both copies of the gene must be abnormal (one inherited from each parent) in order to manifest the disease.
- Having only one abnormal gene results in "gene carrier" status, which means that the individual does not manifest the disease.
- In oculocutaneous albinism, there is little to no pigmentation/coloring of the skin, hair, and eyes.
- Is inherited in an "X-linked" fashion.
- Females carry two X chromosomes, while males carry one X chromosome and one Y chromosome.
- Therefore, this disease affects primarily men, who need only one X chromosome with the albinism gene to manifest the disease.
- Unlike oculocutaneous albinism, which affects the skin, hair, and eyes, ocular albinism affects primarily the eyes. The skin and hair may be only slightly less pigmented than unaffected siblings.
How Does Albinism Affect the Eyes?
Albinism can affect the eyes in multiple ways, and individuals with albinism can vary significantly in how much their eyes and vision are affected:
- People who have albinism have little to no pigmentation of the iris. They also lack pigment in the "retinal pigment epithelial" cells that lie between the retina and the choroid. This gives a unique appearance to the retina and makes the underlying blood vessels of the choroid more visible.
- Since pigment in the eye absorbs light and helps us tolerate most kinds of bright light, the lack of pigment in these structures makes individuals with albinism very sensitive to light, called photosensitivity.
- People with albinism also have an underdeveloped fovea. The fovea is the part of the retina responsible for much of visual acuity.
- In addition, people with albinism may have misrouting of the visual pathways connecting the eye to the part of the brain responsible for vision. "Misrouting" means that the nerve signals traveling from the retina to the brain do not follow the usual eye-to-brain pathway.
- These abnormalities result in decreased best-corrected visual acuity, ranging from 20/40 to 20/200. Albinism is non-progressive and visual acuity may improve somewhat until mid-teens, after which it remains fairly stable, unless additional eye conditions develop.
- Infants with albinism also frequently exhibit abnormal, involuntary, rapid side-to-side or up-and-down movements of the eyes called nystagmus, as well as abnormalities in the alignment of the eyes called strabismus.
- Both nystagmus and strabismus can impede vision. In addition, nystagmus and strabismus can cause the individual with albinism to hold or tilt his or her head in an unusual way in order to see objects or surroundings as clearly as possible.
- Infants with albinism will often have a refractive error, which causes near-sightedness, far-sightedness, and/or astigmatism.
- Female carriers for the ocular albinism gene (i.e. females in whom only one of their two X chromosomes carry the disease-causing gene) may exhibit abnormal retinal pigmentation and mildly decreased iris pigmentation. Rarely, female carriers can be affected more severely and exhibit some of the findings described previously.
Is Albinism Associated with Other Medical Donditions?
There are two forms of oculocutaneous (autosomal recessive) albinism associated with systemic medical disease:
- In addition to albinism, individuals with this syndrome exhibit abnormalities in white blood cells of the immune system and are predisposed to infections. They may also have peripheral neuropathy, an abnormality in the peripheral nerves that may cause decreased sensation, or abnormal sensations such as burning or tingling. Peripheral nerves transmit signals from the spinal cord to the rest of the body.
- In addition to albinism, individuals with this syndrome have an abnormality in platelets (the components of blood that help create blood clots and stop bleeding), which predisposes them to bleeding. These individuals also accumulate a substance within various cells of the body, called a ceroid, which can lead to abnormalities in the lungs, intestines, and other organs.
How Is Albinism Treated?
There is no cure for albinism, but a variety of measures can be taken to address some effects of the disease:
- Refractive errors should be diagnosed and treated promptly to maximize visual acuity and minimize amblyopia.
- A comprehensive low vision examination, along with optical and non-optical low vision devices and vision rehabilitation services and training, can be helpful for some individuals with albinism.
- Absorptive sunlenses/sunglasses can reduce light sensitivity/photosensitivity.
- Glasses with prisms can decrease nystagmus and help the eyes align better; i.e., help both eyes point or look in the same direction. Prisms are special glasses that bend light and can help redirect the direction of light entering a misaligned eye.
- Surgery may also be considered to reduce nystagmus or to align the eyes, especially if either is causing a significant abnormality in head position.
- Genetic counseling can help parents and adult patients with albinism.
- Because of the decreased skin pigmentation that accompanies albinism, individuals should use hats and sunscreens and avoid excessive sun exposure to protect the skin from sunburns and skin cancer.