Retinitis pigmentosa, or RP, is the name given to a group of inherited eye diseases that affect the retina. The retina is located in the back of the eye and acts much like the film in a camera. The retina contains special cells that respond to light, called photoreceptors. Photoreceptor cells capture and process light, helping us to see.
There are two types of photoreceptor cells: rods and cones. The rod cells help us to see in dark and dimly lit environments. They also help us to see images that come into our peripheral or side vision. The cone cells allow us to see fine detail in the center of our vision, and allow us to perceive color. Together, rods and cones convert light into electrical impulses that are transmitted to the brain where “seeing” actually occurs. As these cells degenerate and die, as in retinitis pigmentosa, patients experience progressive vision loss.
Symptoms:The symptoms of RP are usually noticed in children, adolescents and young adults, with progression of the disease continuing throughout life. Symptoms usually become worse over a period of years.
- Vision decreased at night or in reduced light
- Loss of peripheral vision
- Loss of central vision (in advanced cases)
Causes:RP 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 pigmented spots in the retina.
Risk factors:The main risk factor is a family history of RP. The condition is uncommon, affecting about 1 in 4,000 people in the United States. The disease may be X-linked (passed from a mother to her son), autosomal recessive (genes required from both parents) or autosomal dominant (gene required from one parent) trait.
Detection and diagnosis:RP is often discovered when a patient complains of difficultly seeing at night. An eye doctor will examine the retina with an ophthalmoscope. The classic sign of RP is clumps of pigment in the retina called "bone-spicules." A test called electroretinography (ERG) may also be ordered to study how the eye responds to light. This test reveals information about the functioning ability of the rods and cones in the retina.
Treatment:There is currently no effective treatment for RP. However, intensive research is under way to discover the cause, prevention, and treatment of RP. While not a cure, vitamin A has been found to slightly slow the progression of retinitis pigmentosa in some patients. Also, using sunglasses to protect the retina from ultraviolet light rays may help preserve vision. A low vision specialist can also be very helpful in coping with the condition. Although the disorder will continue to progress slowly, complete blindness is uncommon.
Things you should know:Many of the same symptoms are found in other forms of retinitis. They sometimes occur with cloudiness of the vitreous humor (the liquid that fills the cavity behind the lens of the eyeball). An eye doctor can detect this by examining the eye with a special lighted instrument called an ophthalmoscope.
Because of the genetic nature of RP, genetic counseling may determine the risk of this disease occurring in a person's children.
Call your eye doctor if it becomes difficult to see at night or if other symptoms of this disorder develop.
Source: Schartman, Jerome and Ingrid Scott. "How to Manage Vision Loss in Retinitis Pigmentosa." EyeNet Magazine 05 June 2007.
Schartman, Jerome and Ingrid Scott. "How to Manage Vision Loss in Retinitis Pigmentosa." EyeNet Magazine 05 June 2007.