Retinitis pigmentosa is an eye disease in which there is damage to the retina. The damage gets worse (progresses) over time.

Retinitis pigmentosa commonly runs in families. The disorder can be caused by a number of genetic defects.

The cells controlling night vision (rods) are most likely to be affected. However, in some cases, retinal cone cells are damaged the most. The main sign of the disease is the presence of dark lines in the retina.

As the disease gets worse, side (peripheral) vision is gradually lost. The condition may eventually lead to blindness, but usually not complete blindness. Signs and symptoms often first appear in childhood, but severe vision problems do not usually develop until early adulthood.

The main risk factor is a family history of retinitis pigmentosa. It is an uncommon condition affecting about 1 in 4,000 people in the United States.

• Decreased vision at night or in low light
• Loss of side (peripheral) vision
• Loss of central vision (in advanced cases)

Tests to evaluate the retina:

• Color vision
• Examination of the retina by ophthalmoscopy after the pupils have been dilated
• Fluorescein angiography
• Intraocular pressure
• Measurement of the electrical activity in the retina (electroretinogram)
• Pupil reflex response
• Refraction test
• Retinal photography
• Side vision test (visual field test)
• Slit lamp examination
• Visual acuity

There is no effective treatment for this condition. Wearing sunglasses to protect the retina from ultraviolet light may help preserve vision.

Controversial studies have suggested that treatment with antioxidants (such as vitamin A palmitate) may slow the disease from getting worse.

Several clinical trials are in progress to investigate new treatments for retinitis pigmentosa.

Microchip implants that go inside the retina are in the early stages of development for treating blindness associated with this condition.

It can help to see a low-vision specialist. Make regular visits to an eye care specialist, who can screen for cataracts or retinal swelling -- both of which can be treated.

The disorder will continue to progress, although slowly. Complete blindness is uncommon.

Peripheral and central loss of vision will eventually occur.

Patients with retinitis pigmentosa often develop cataracts at an early age. Cataracts can be removed if they cause vision loss.

Many other conditions have similarities to retinitis pigmentosa, including:

• Friedreich's ataxia
• Laurence-Moon syndrome (also called Laurence-Moon-Bardet-Biedl syndrome)
• Mucopolysaccharidosis
• Muscular dystrophy (myotonic dystrophy)
• Usher syndrome (a combination of retinitis pigmentosa and hearing loss)

Call your health care provider if night vision becomes difficult or if you develop other symptoms of this disorder.

Genetic counseling may determine whether your children are at risk for this disease.

Sieving PA. Retinitis Pigmentosa and Related Disorders. In: Yanoff M, Duker JS, Augsburger JJ, Azar DT. Yanoff: Ophthalmology. 2nd ed. Philadelphia, PA; Mosby:chap 108.