Retinitis pigmentosa (RP) refers to a group of inherited diseases causing retinal degeneration.
The cell-rich retina lines the back inside wall of the eye. The cells within the retina capture and process images which are then transmitted through the optic nerve to the brain. People with RP experience a gradual decline in their vision because retinal photoreceptor cells (rods and cones) die. Forms of RP and related diseases include Usher syndrome, Leber’s congenital amaurosis (LCA), rod-cone disease, Bardet-Biedl syndrome, and choroidermia, among others.
RP is typically diagnosed in adolescents and young adults. It is a progressive disorder. The rate of progression and degree of visual loss varies from person to person. Most people with RP experience loss of their peripheral vision but maintain their central vision until late in the disease.
What are the symptoms?
Symptoms depend on whether rods or cones are initially involved. In most forms of RP, rods are affected first. Because rods are concentrated in the outer portions of the retina and are triggered by dim light, their degeneration affects peripheral and night vision. When the more centrally located cones – responsible for color and sharp central vision – become involved, the loss is in color perception and central vision.
Night blindness is one of the earliest and most frequent symptoms of RP. People with mainly cone degeneration, however, first experience decreased central vision and ability to discriminate color.
RP is typically diagnosed in adolescents and young adults. It is a progressive disorder. The rate of progression and degree of visual loss varies from person to person. Most people with RP are legally blind by age 40, with a central visual field of less than 20 degrees in diameter. It is a genetic disorder and, therefore, is almost always inherited.