(Original extract taken from wikipedia.org)
Retinitis pigmentosa, or RP, is a group of genetic eye conditions.
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 life. Others go completely
blind from RP, in some cases as early as childhood. Progression
of RP is different in each case.
RP is 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 constriction of the peripheral visual field and, eventually,
loss of central vision late in the course of the disease.
