Retinitis pigmentosa is a disease of the eye that causes the retina to slowly degenerate. The retina is the layer of tissue at the back of the eye that sends light images and signals to the brain.
Photoreceptor cells are rod cells and cone cells that are affected by retinitis pigmentosa. These are the cells that control peripheral and night vision in the retina, and will degenerate when a person has the disease.
How fast the degeneration occurs depends on the genetic disorder the person has. Symptoms of retinitis pigmentosa can be found in young children and can lead to blindness for life, or it can affect elderly people. It is a rare hereditary degenerative disease that can be devastating no matter what the age of the person affected. Genetic testing can determine whether children will be at risk for the condition.
Symptoms of Retinitis Pigmentosa
Symptoms can include a loss of central and peripheral vision and a loss of vision in low light or at night. The progression of the disease is slow so the symptoms might not be noticed early. The loss of a small amount of central vision can last a long time, and night blindness may not be noticed for years. Complete blindness is not usually associated with symptoms of this condition.
Retinitis Pigmentosa Causes
Approximately 75,000 people in the United States are affected with this condition.
The symptoms involve both eyes; even if they start it one eye, it will eventually exhibit the same condition in the other eye in a few years. The condition is inherited through dominant, recessive or sex-related genes. However, the condition can be found in people who have no familial history.
Many people can have the gene for this disease at birth but will not exhibit any symptoms until teenage or later years. When the symptoms occur later in life they are usually mild cases that do not progress quickly.
Factors that can contribute to this condition are a breakdown of the rods and cones called photoreceptors in the retina. These receptors are where the inherited disorders cause abnormalities leading to progressive loss of vision.
Histopathologic changes associated with gene mutations also have been documented in retinitis pigmentosa. The thin layer of tissue called the retina is housed in the back of the eye where light is captured enabling a person to see.
The cells deteriorate with the condition leading to progressive vision loss. First a person develops night blindness and years later may develop tunnel vision.
This disease can be caused by other disorders such as macular degeneration. It can be a combination of a number of other disorders that cause the condition of retina degeneration, so it is difficult to pinpoint any one cause.
Complications of retinitis pigmentosa include the loss of central and peripheral vision and the development of cataracts early in life. These cataracts can be treated with surgery. There are other conditions that are similar to retinitis pigmentosa such as muscular or myotonic dystrophy, Usher syndrome which includes hearing loss, Friedreich’s ataxia and Laurence-Moon syndrome.
Retinitis Pigmentosa Screening
There are a few things a person with this condition will begin to notice.
- Loss of peripheral vision
- Decreased night or low light vision
- Loss of central vision
The only way this condition can be diagnosed is with a vision screening which consists
of two tests.
- Visual Field Test
This test will uncover any defects or problems with peripheral vision loss. The person with the condition will develop tunnel vision which means that their visual field is greatly reduced to central or straight-ahead vision only. - Electrophysiological Testing
A diagnostic test where electrodes are placed on the eye surface and responses to flashes of light are measured. Though it sounds complicated this test is painless. - Gene testing is also done to determine any hereditary traits.
Other tests that evaluate the retina can include intraocular pressure tests, pupil reflex responses, refraction tests, visual acuity tests, fluorescein angiography, color vision tests, retinal photography and slit lamp examination.
At this point there is no cure for this disease. Researchers are working to uncover the complexities of the disease and perhaps will determine how to stabilize or prevent the disease. Though there is no cure, vitamin A therapy is recommended by many doctors as an effective way to slow down the progression of the disease.
Wearing sunglasses to protect the eyes from ultraviolet rays can also help to protect the vision.
Early trials using microchip implants inside the retina that resemble a video camera are being used to help with the treatment of blindness.
Studies have also shown that eating a diet that is rich in omega-3 can slow the progression of the disease. This diet would consist of oily fish including salmon, tuna, herring, sardines and mackerel. Some researchers estimate that eating an omega-3 rich diet and taking vitamin A could provide a person with 20 years of good vision if they start this regimen before age 30.