Retinitis pigmentosa is a disorder in which the rods and cones of the retina (the light receptors ofthe eye) slowly degenerate. People with retinitis pigmentosa experience progressive loss of night vision, peripheral vision and visual sharpness in both eyes. Over time, the disorder leads to tunnel vision, in which the outer edges of vision are dark leaving a shrinking circle of vision in the center. Eventually, total blindness can result, but most people with retinitis pigmentosa retain some vision even in old age.
Approximately 100,000 people in the United States have retinitis pigmentosa, making it one of the leading causes of blindness. In people who have the disease, the first signs usually can be detected by about age 10, and the first symptoms usually show up in adolescence. The total amount of vision loss and how quickly the disease progresses vary from person to person.
No one knows exactly what causes retinitis pigmentosa. It is believed to be an inherited disorder, and research suggests that several different types of gene mutations (changes in genes) can cause this disease. In most cases, the disorder is linked to a recessive gene, a gene that must be inherited from both parents in order to cause the disease. But dominant genes and genes on the X chromosome also have been linked to retinitis pigmentosa. In these cases, only one parent has passed the disease gene. In some cases, a new mutation causes the disease to occur in a person who does not have a family history of the disease. The disorder also can show up as part of other syndromes, such as Bassen-Kornzweig disease or Kearns-Sayre syndrome.