Retinitis pigmentosa (RP) is a group of genetic eye conditions that leads to incurable blindness. In the progression of symptoms for RP, 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. Progression of RP is different in each case.
RP 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 loss of central vision. - Wikipedia