Retinitis pigmentosa is a type of genetic disorder. It is a group of eye disorders that are related, which can result in progressive vision loss. The disorders that make up this condition all affect the retina of the eye.
Children inherit the disorder from their parents. (Read More)
The symptoms generally begin in childhood. If a child is at risk for developing this condition, parents should be aware of the symptoms so they can recognize it if it occurs. (Read More)
What Causes Retinitis Pigmentosa?
While the condition itself is rare compared to other inherited retina diseases, it is among the most common. In Europe and the U.S., retinitis pigmentosa affects 1 person in every 3,500 to 4,000 people.
There is an autosomal dominant and autosomal recessive form of this condition. The dominant type is most often caused by the RHO gene. The recessive type has 35 genes associated with it; however, mutations of the USH2A gene appear to cause the most cases.
There is also an X-linked form of this condition. Experts believe that there are at least six genes that could contribute to it. Most X-linked cases are attributed to the RP2 and RPGR genes.
All of the genes associated with this condition affect the function and structure of the retina’s photoreceptors. Cones and rods are the two photoreceptors in the retina. Cones are responsible for color vision and bright-light vision. Rods are responsible for low-light vision.
When the gene mutations associated with this condition occur, there is a gradual loss of the retina’s cones and rods. This is what causes the symptoms associated with the disorder.
Children inherit this disorder from their parents. There have to be two copies of the gene that is mutated for autosomal recessive inheritance. When two people who carry the gene have a child, there is a one in four chance that they will develop the condition.
Only one copy of the gene that is mutated is necessary for autosomal dominance inheritance. If one parent has the gene, the chances of their child developing the condition is one in two.
For the X-linked form of this condition, the mom carries the abnormal gene. Her daughter cannot develop the disorder, but she has a one-in-two chance of becoming a carrier. Her son can develop the disorder, and he has a one-in-two chance of developing it.
Various types of vision loss occur when someone has this condition. People may start to lose their night vision first. This can make it hard for people to see anything in the dark. By day, their vision may be completely normal.
People can lose their peripheral vision gradually. This symptom is also referred to as tunnel vision. It prevents people from being able to easily see the objects around and below them. People may bump into things when they are moving around.
The central vision may be the next to go. This is the vision that is straight ahead. Losing central vision can make it hard to do a variety of daily tasks, such as threading a needle to sew a button or reading a book.
This condition can also cause people to lose their color vision. This can make colors look differently than they actually are. For some people, they may have difficulty seeing certain colors.
It is important to get an accurate diagnosis so the doctor can prescribe the proper treatments. There are four primary tests a doctor might perform.
- Genetic testing: This is a genetic disorder, so the doctor who suspects the disorder will usually order genetic testing. This type of testing identifies changes that occur in genes, proteins, or chromosomes. Since gene mutations are the primary concern with this condition, the doctor might perform molecular genetic testing. This examines short lengths of DNA or single genes to look for mutations or variations that could indicate the genetic disorder. This testing involves getting a tissue or blood sample for analysis. In addition to diagnosing this condition, this testing may also help to determine the possible severity or course of the condition.
- Visual field testing: This testing is performed to evaluate peripheral vision. This can be done during diagnosis and to determine if the person’s disorder is progressing. It evaluates for blind spots in a person’s vision.
- Electroretinography: This test explores the retina to determine its electrical activity. This is performed to see how well the retina is able to respond to light. The test is similar to the electrocardiogram that is used to evaluate the heart’s electrical activity.
- Optical coherence tomography: This is a type of imaging test, but the images that it obtains are special. The doctor is able to get highly detailed photos of the retina, which are used to diagnose the condition. It is also used to see how much this condition is affecting the retina.
Treating Retinitis Pigmentosa
This condition cannot be cured, but there are some treatments available that may help people to better cope with their vision loss.
One study looked into how certain vitamins may benefit people who have the condition. It showed that supplementation with vitamin A palmitate may be beneficial for some.
If a doctor recommends this vitamin, it is imperative that the person uses a high-quality brand. It is best to go with the one the doctor recommends.
If retinal swelling occurs, the doctor might prescribe an eye drop to reduce it. It is also possible for people with this condition to have cataracts at some point in life. Cataracts are characterized by clouding on the lens of the eye.
Scientists are looking into experimental treatments and technologies that might benefit people. For example, if someone has severe vision loss, the ARGUS II implant might be something their doctor discusses with them. This is a type of artificial retina that may help people to achieve clearer vision.
In many cases, doctors will discuss several options with people, and together, they’ll choose the best solution for the specific case.
The research is ongoing, so there will likely be better and more effective treatments for this condition in the future.
Retinitis Pigmentosa. Genetics Home Reference.
Retinitis Pigmentosa Symptoms. American Academy of Ophthalmology.
What Is Genetic Testing? Genetics Home Reference.
Facts About Retinitis Pigmentosa. National Eye Institute.
Treatment for Retinitis Pigmentosa Reported. National Eye Institute.