Retinitis pigmentosa (RP) is an eye disease that leads to incurable blindness, which is caused by a progressive degeneration of the retina which affects night vision and peripheral vision. Retinitis pigmentosa is a genetic disorder which can be caused by a number of genetic defects. In this disease, retinal cone cells are damaged the most. Nevertheless, retinal rods which control night vision, are affected too.
Symptoms of retinitis pigmentosa include: decreased vision at night or in low light; loss of side vision, that causes tunnel vision; loss of central vision. Retinistis pigmentosa is a type of progressive retinal dystrophy, a group of inherited disorders in which abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) of the retina lead to progressive visual loss. Affected individuals first experience defective dark adaptation or nyctalopia (night blindness), followed by reduction of the peripheral visual field (known as tunnel vision) and, sometimes, loss of central vision late in the course of the disease.
In the progression of symptoms for retinitis pigmentosa, night blindness generally precedes tunnel vision by years or even decades. Many people with RP do not become legally blind until their 40s or 50s and retain some sight all their lives. Others go completely blind from RP, in some cases as early as childhood.