Understanding RP

Retinitis pigmentosa, commonly called RP, is a group of inherited eye conditions that affect the retina. The retina is the light-sensitive tissue at the back of the eye that turns light into signals the brain recognizes as sight.

RP causes some of the retina's light-sensing cells, called photoreceptors, to gradually deteriorate. This leads to vision loss that usually develops over many years.

RP affects everyone differently. The symptoms, age of onset, and rate of progression can vary greatly, even among members of the same family.

For many people, the first noticeable sign of RP is difficulty seeing at night or in dimly lit places. It may take longer for their eyes to adjust when entering a dark room, or they may have trouble moving around safely at night.

Peripheral vision often begins to narrow later. A person may not notice objects, steps, or people approaching from the side. As more peripheral vision is lost, this can create what is often described as “tunnel vision.”

RP can eventually affect central vision, which is used for reading, recognizing faces, driving, and seeing fine details. Some people also experience sensitivity to bright light or changes in color vision.

These changes do not follow the same timeline for everyone. Some forms of RP progress slowly over decades, while others cause significant vision loss much earlier.

RP is caused by changes in genes that the retina needs to develop, function, and remain healthy. These genetic changes are often called variants or mutations.

Depending on the gene involved, RP may be inherited in different ways:

• Autosomal dominant: A person inherits one altered copy of a gene from one parent.
• Autosomal recessive: A person inherits an altered copy of a gene from each parent. The parents are usually unaffected carriers.
• X-linked: The altered gene is located on the X chromosome. These forms often affect males more severely, although some female carriers also develop vision loss.

A person can have RP even when no one else in the family is known to have it. Parents may carry a recessive variant without having symptoms, the condition may not have been recognized in earlier generations, or a genetic change may have occurred for the first time in that person.

RP sometimes occurs as part of a condition that affects more than the eyes. Usher syndrome (definition: A genetic condition that causes both retinitis pigmentosa and hearing loss, sometimes with balance problems.), for example, causes both RP and hearing loss.

RP is not one disease with one cause. Disease-causing variants in more than 130 genes are known to cause it, and researchers continue to learn more about how those genes affect the retina.

Some of the more common RP genes include RHO, USH2A, and RPGR, but many others are involved. Each gene plays a different role in the retina, and changes in different genes can produce different patterns of vision loss.

The gene involved may influence:

• When symptoms are likely to begin
• Which parts of vision are affected first
• How the condition is inherited
• Whether hearing or other parts of the body may also be affected
• Which research studies or clinical trials may be relevant

Even people with changes in the same gene can have different experiences. A genetic result can provide useful information, but it cannot predict exactly how one person's vision will change.

RP is usually diagnosed by an ophthalmologist, often one who specializes in the retina or inherited retinal diseases.

The evaluation may include:

• A dilated eye exam to look closely at the retina
• Visual field testing to measure peripheral vision
• An electroretinogram, or ERG (definition: A test (often abbreviated ERG) that measures the retina's electrical response to light, used to check how well photoreceptors are working.), to measure how the retina responds to light
• Optical coherence tomography, or OCT (definition: An imaging test (often abbreviated OCT) that creates a detailed, layer-by-layer picture of the retina without touching the eye.), to create detailed images of the retina
• Fundus autofluorescence imaging to show patterns of change in the retina
• Genetic testing to look for the underlying genetic cause

No single test tells the whole story. Doctors consider the results alongside a person's symptoms, medical history, and family history.

Genetic testing can identify the cause of RP for many people, but it does not provide a clear answer in every case. An inconclusive result does not mean that a person does not have RP. The result may become more useful later as testing improves and researchers learn more about previously uncertain variants.

Genetic testing usually uses a blood or saliva sample. It may be ordered by an ophthalmologist, inherited retinal disease specialist, or genetic counselor.

Knowing your gene can help you:

• Better understand how your RP may have been inherited
• Learn whether family members could also be affected or carry the variant
• Find research focused on your genetic form of RP
• Identify clinical trials that may be relevant
• Learn whether a gene-specific treatment is available or being studied

Genetic results can be complicated. A genetic counselor or qualified eye specialist can explain what the result means, what it does not mean, and whether testing other family members may be useful.

There is currently no cure for most forms of RP, but care and support can help people adapt as their vision changes.

Low-vision rehabilitation, orientation and mobility training, accessible technology, and other tools can help people continue working, studying, traveling, and managing daily life. Regular eye care is also important because people with RP may develop additional conditions, such as cataracts or swelling in the retina, that can sometimes be treated.

An FDA-approved gene therapy (definition: A treatment that delivers a working copy of a gene into cells to take over for a copy that isn't functioning properly.) called LUXTURNA is available for certain people with an inherited retinal disease caused by disease-causing variants in both copies of the RPE65 gene. It does not treat RP caused by other genes.

Researchers are studying many other approaches, including gene therapies, medicines, cell therapies, optogenetics (definition: An experimental approach that adds a light-sensitive protein to retinal cells that don't normally respond to light, giving them a new way to detect it.), and technologies designed to restore useful vision.