What is Ocular Albinism?
Ocular albinism is a condition that decreases the amount of pigment the eye produces. Pigment gives eyes their color, but it is also important for vision. Lower pigment production associated with ocular albinism can cause vision problems. Fortunately, early diagnosis and treatment can help. Advances in medical technology can help people with ocular albinism see better.
Ocular albinism is a rare condition. It occurs in about one male in every 20,000 births, according to the National Organization for Rare Disorders. It is a genetic condition that tends to affect males more often but can also occur in females.
Pigment gives the iris of the eye its blue, brown, green or gray color, but it also helps the eye function better. The iris’s job is to limit the amount of light entering the eye, for example, and the pigment makes the iris opaque so that less light gets through.
Pigment is also present in other tissues of the eye, including the retina, which is the light-sensitive tissue lining the back of the eye. Light carries visual information about the world into the eye; the light strikes the retina, which converts the information into impulses. The optic nerve carries the impulses to the brain, which interprets the impulses into visual images.
Unlike other types of albinism, ocular albinism does not noticeably affect a person’s complexion or hair. Those with ocular albinism may have slightly lighter skin than do other members of their family, but the differences in complexion are usually minor.
Common Signs and Symptoms
Ocular albinism affects the sharpness of vision, known as visual acuity. Vision professionals measure visual acuity by the ability to discern letters and numbers at a fixed distance, with perfect vision measuring 20/20. Ocular albinism can reduce visual acuity to anywhere from 20/60 to 20/400, according to the National Organization for Albinism and Hypopigmentation (NOAH).
Reduced visual acuity can cause a variety of challenges, especially for children. Poor vision makes it hard to read the chalkboard from far away, for example, and interferes with a child’s ability to play sports. Adults with ocular albinism may have trouble driving.
Some people with ocular albinism experience other signs and symptoms, such as the involuntary back-and-forth eye movements known as nystagmus. Ocular albinism can cause strabismus, commonly known as crossed or “lazy” eyes. Many people with the condition experience hypersensitivity to bright light and glare, a condition known as photophobia.
Ocular albinism causes permanent vision loss but it is not a progressive condition, which means the symptoms do not worsen over time.
Mutations in the GPR143 gene cause ocular albinism. This gene provides the instructions for making a specific protein, known as the GPR143 protein, involved in the pigmentation made by the eyes and skin. The protein also controls melanosomes, which are cell structures that make and store the pigment, melanin. Melanin gives skin, hair and eyes their color. The pigment also plays an important role in normal vision. The GPR143 protein controls the growth of melanosomes to prevent the melanosomes from getting too large.
Most mutations in the GPR143 gene alter the size or shape of the GPR143 protein. Altering the size or shape of the protein can prevent it from ever reaching the melanosomes, which allows the melanosomes to grow too large. In other cases, the protein reaches the melanosomes, but the genetic mutations prevent the protein from doing its job of keeping the size of the melanosomes in check.
In short, changes in the gene can cause melanosomes to grow too large. Researchers are still working to discover exactly how these giant melanosomes cause vision loss and other eye problems in people with ocular albinism.
What researchers do know is that ocular albinism affects a specific area in the retina, known as the fovea, responsible for sharp vision. The fovea does not develop properly in people with ocular albinism, presumably because the fovea relies on pigments for the eye growth that occurs before birth. Because the fovea does not develop properly, the eye cannot process sharp images – even with the help of glasses or contacts.
Furthermore, the optic nerve fibers of people with ocular albinism follow a different path than do the nerve fibers of those without the condition. Nerve fibers normally go to both sides of the brain, with some of the nerve fibers going to the same side as the eye and some of the fibers going to the opposite side of the brain. In people with ocular albinism, however, more of the nerve fibers cross over to the opposite side of the brain than normal.
Options and Support
Options and support include vision correction, support groups, and low vision aids. Vision correction with glasses can sharpen vision somewhat. Sunglasses, transition lenses, or special filter glasses can relieve hypersensitivity to light, although they may reduce visual acuity when worn indoors.
Support groups, such as NOAH and the National Association of Parents of Visually Impaired (NAPVI) are great places for parents to learn valuable information about the condition and share tips for managing it in their children. Support groups associated with NOAH and Council of Citizens with Low Vision International help children and adults with ocular albinism learn about the condition, feel less isolated, and learn healthy coping skills from others.
Low vision aides, like eSight, help people with central vision loss to see and live independently. The most advanced systems use cameras, smart algorithms and high-resolution screens to create clear, real time images of objects directly in front of the user.
Using advanced technology, support groups and information, people living with this condition and their families can make the most out of life. While there is no cure for this vision problem, support and advanced technology can help keep the world in focus.
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