What is Ocular Albinism?
Ocular albinism is an inherited condition that affects a person’s eyes. People with ocular albinism lack melanin, which gives eyes their blue, green, brown, or hazel color. Melanin also acts like sunscreen to protect the eyes from the sun’s harmful UV rays. It can cause vision problems, such as nearsightedness, farsightedness, and astigmatism.
Ocular albinism affects the retina, which is the light-sensitive tissue lining the inside of the eye, and the optic nerve that sends signals about what the person sees to the brain. The condition prevents the retina from developing properly, which causes things to look blurry.
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.
Unlike other types of albinism, ocular albinism does not noticeably affect a person’s complexion or hair. They may have slightly lighter skin than do other members of their family, but the differences in complexion are usually minor.
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.
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 may have trouble driving.
- Vision impairment, such as extreme nearsightedness or farsightedness
- Rapid, back-and-forth eye movements, known as nystagmus
- Head movements, such as tilting or bobbing the head, usually as an effort to reduce nystagmus and to see better
- Inability of the eyes to move in unison or stay directed on the same point
- Poor depth perception
- Legal blindness
As well, 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.
It may also cause 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.
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.
Optic Nerve Fibers
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 learn about the condition, feel less isolated, and learn healthy coping skills from others.
Assistive Technology for Ocular Albinism
eSight’s users commonly live with ocular albinism.
eSight is a low vision eyewear device that stimulates synaptic activity from the remaining photoreceptor function of its users’ eyes. Many successful eSight users live with ocular albinism, such as the Collins siblings, who experienced significantly enhanced vision after receiving their eSight.
eSight has a cutting edge camera, smart algorithms and high resolution screens. It is clinically validated to result in enhanced vision of up to 7 lines on a doctor’s eye chart, while simultaneously boasting superior mobility for its users.
As well, for those with ocular albinism who experience photophobia, eSight lets users adjust both the brightness and contrast of the screens, which means it is well-suited for people with light sensitivity.
How is ocular albinism different from other types of albinism?
Unlike other types of albinism that affects a person’s skin and hair color as well as the eyes, ocular albinism affects only the eyes.
How common is ocular albinism?
The most common form of ocular albinism, ocular albinism type 1, affects at least 1 in 60,000 males.
Are people with ocular albinism completely blind?
No – their vision can vary from 20/40 to 20/400. Some people with ocular albinism are legally blind, which means they have visual acuity of 20/200 or worse with corrective lenses.
How does someone get ocular albinism?
Albinism is a genetic condition, passed down through the generations. It is the result of a malfunctioning gene, which is responsible for making melanin. Doctors refer to it as “typically autosomal recessive,” which means each parent has to contribute one malfunctioning gene for a child to develop ocular albinism.
If two people with albinism have a baby together, will the child have ocular albinism?
Not necessarily – there are several types of albinism, and each affects a different gene. Ocular albinism is the result of malfunctions in the GPR143 gene. In order for a child to have ocular albinism, both parents must contribute a malfunctioning GPR143 gene. If a baby inherits one normal GPR143 gene and one albinism gene, the normal gene will take over and the baby’s eyes will produce enough melanin.
How do doctors diagnose ocular albinism?
Doctors can diagnose ocular albinism by looking at the patient’s eyes and by finding out if the patient’s female relatives have retinal pigment abnormalities. Genetic testing may be helpful.
Is there a cure for ocular albinism?
There is currently no cure for ocular albinism – medical scientists have not yet found a treatment that can help the body produce enough melanin to lessen the symptoms of ocular albinism. Glasses, contact lenses and low vision aids, such as eSight, can help.