|Retinitis pigmentosa affects the rods and the cones and may lead to poor night vision, loss of peripheral vision, distortion of color vision or total blindness.
Retinitis pigmentosa (reh-tin-EYE-tis pig-men-TOE-sah), or RP, is a group of inherited conditions in which the
rods in the
retina slowly degenerate and change the way light is seen. The cones may also be affected, distorting color vision. Affecting at least 100,000 people in the U.S., it causes a progressive loss of night vision, peripheral vision and general visual sharpness. As the disease progresses, tunnel vision may occur; some people may experience total blindness although most with RP may retain some vision.
Although its exact cause is unknown, RP is believed to be caused by mutations in any of at least 10 different genes. In most cases, the disorder is linked to a recessive gene, one that is inherited from both parents in order to cause the disease. But mutations in dominant genes and genes on the X-chromosome have also been linked to some cases, especially in those with no family history of the disease. RP can also show up as part of other syndromes, such as Bassen-Kornzweig disease or Kearns-Sayre syndrome, and may be associated in those with
nearsightedness, cataracts, degenerative
vitreous conditions and inherited hearing loss.
The first symptom of retinitis pigmentosa is usually diminished night vision – a difficulty to see in dimly lit or dark places – which can begin in early childhood. Vision may further deteriorate in adolescence or early adulthood. Besides poor night vision, other symptoms include:
- Loss of visual acuity
- Loss of peripheral vision
- Tunnel vision
- Inability to differentiate colors
Because RP is believed to be a genetic disorder, it cannot be prevented.
Early diagnosis is essential for successful treatment and for planning its expected progression. Medical consultation and monitoring is required for all forms of the disease and methods of treatment. Most commonly, an ophthalmologist will diagnosis RP with an instrument called an ophthalmoscope that looks at the inside of the eye through the pupil. In a normal eye, the
fundus will be orange; in those with RP, there will be brown or black blotches.
To confirm diagnosis, an electroretinogram (ERG) is used to measure electrical activity in the retina (those with RP have lower activity levels). During this test, lights of various colors and intensities are flashed inside the eye as you look into a reflective globe. A contact lens that contains an electrode is placed on your eye, and through a wire it transmits a record of your eye's retina activity.
There are no medical or surgical procedures for RP at this time, and no known cure. Experimental treatments may slow the disease's progression. Preliminary trials have been promising in the use of dilatiazem, a commonly prescribed heart medication, and in large doses of vitamins A and E; however, excess amount of these nutrients can cause side effects and must be done under a doctor’s supervision. Protecting the eyes from sunlight and eye patching may also be recommended.
Low-vision aids such as magnifying and telescopic lenses can help compensate for diminished eyesight. Psychological counseling can also help deal with the emotional affects of RP, while genetic can detect the likelihood that children will inherit the genetic defect from their parents.