Retinitis pigmentosa commonly runs in families. The disorder can be caused by defects in a number of different genes which have recently been identified.

The cells controlling night vision, called rods, are most likely to be affected. However, in some cases, retinal cone cells are most damaged. The hallmark of the disease is the presence of dark pigmented spots in the retina.

As the disease progresses, peripheral vision is greadually lost. The condition may eventually lead to blindness, but this is usually not complete blindness. Signs and symptoms often first appear in childhood, but severe visual 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 one in 4,000 people in the U.S.

• Vision decreased at night or in reduced light
• Loss of peripheral vision
• Loss of central vision (in advanced cases)

Tests determine the integrity of the retina:

• Visual acuity
• Refraction test
• Color defectiveness determination
• Pupillary reflex response
• Slit lamp examination
• Intraocular pressure determination
• Retinal examination by ophthalmoscopy
• Ultrasound of the eye
• Retinal photography
• Fluorescein angiography
• Electroretinogram (a record of the action currents of the retina produced by visual stimuli)

There is no effective treatment for this condition. The use of sunglasses to protect the retina from ultraviolet light may have a vision-preserving effect.

Though controversial, recent studies have indicated that treatment with antioxidant agents (such as Vitamin A palmitate) may delay the progression of this disease.

Referral to a low vision specialist is very helpful in maintaining patient independence. Regular visits to your eye care specialist are important to monitor for the development of cataracts or retinal swelling -- both of which can be treated.

The disorder will continue to progress, though at a very slow pace. Complete blindness is uncommon.

Peripheral and central loss of vision will eventually occur.

Many other syndromes with features similar to retinitis pigmentosa have been described including:

• Friedreich's ataxia
• Mucopolysaccharidosis
• Muscular dystrophy (myotonic dystrophy)
• Laurence-Moon syndrome (also called Laurence-Moon-Bardet-Biedl syndrome, an inherited disorder causing mental deficiency, obesity, short stature, vision problems, and muscular weakness)

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

Genetic counseling may determine the risk of this disease occurring in a person's offspring.