Retinitis Pigmentosa

Definition

Retinitis pigmentosa (RP) is a group of eye diseases that often leads to severe vision problems. The retina is a layer of tissue that lines the back of the eye. It converts images that we see into nerve impulses that it sends to the brain. This disorder is named for the clumps of black pigment that are often found in the retina with this disease.

Normal Anatomy of the Eye.

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Causes

Many types of RP are caused by a change in a gene. Sometimes these changes are passed from parents to children. Sometimes the change happens on its own.

Vision loss occurs when cells in the retina slowly break down. There are 2 types of cells in the retina:

• Cones—These are found mostly in the center of the retina. Cones are needed for central vision and to see colors.
• Rods—Are mostly away from the center and respond to dim light. They provide night and side vision.

In most forms of retinitis pigmentosa, the rods die. This impairs vision at night. The ability to see things off to the side while looking ahead also decreases.

In some forms of RP, the cones are lost and central and color vision suffers. Vision loss often progresses over many years.

Risk Factors

RP is more common in males and in those with family members who have it.

Symptoms

Vision problems are often first noted in childhood or early adulthood. RP slowly gets worse. After many years, vision loss may become severe.

Symptoms vary depending on the type of cell that is affected. Both eyes often have similar vision loss.

In general, RP may cause:

• Night blindness—the most common symptom
• Decreased peripheral vision, or the visual field narrows—this is often called "tunnel vision"
• Eyes take longer to adjust to dim lighting or are slow adjust from bright sun to indoor lighting
• Trouble seeing in foggy or rainy weather
• Trouble seeing colors, especially blue
• Loss of vision that may by part or complete
• Clumsiness from lack of sight, especially in narrow spaces such as doorways

People may have blurry vision from cataracts as RP progresses.

Diagnosis

The doctor will ask about symptoms and health history. An eye exam will be done. A specialist who treats eyes may be needed.

Vision tests may include:

• Visual field testing—To check peripheral vision, which is how well a person sees off to the side without moving their eyes.
• Visual acuity—Checks how well a person can see objects that get smaller and smaller, such as a row of letters or numbers.
• Dark adaptometry—Tests how a person's vision adapts to darkness.
• Color testing—To check if a person can see different colors.
• Electroretinogram (ERG)—A test to measure electrical activity in the eye. This test checks the loss of cell function in the retina and is used to track progression of RP.
• Optical coherence tomography—Imaging to get highly detailed pictures of the retina

Treatment

People with RP may be referred to counseling to help them cope with vision loss.

Surgery may be needed for severe RP or to remove cataracts.

These can help a person who has vision loss and may include:

• Magnifying glasses
• Electronic magnifiers that project an enlarged image onto a screen
• Night vision scopes that can make objects in low light look easier to see
• Glasses or contact lenses for distant vision

Some community groups offer classes to help people with vision loss adjust and learn how to use vision aids. If you are considered legally blind, you are entitled to many low-vision services at no cost.

Prevention

RP cannot be prevented. People who have a family history of it may want to think about genetic counseling before starting a family.