Retinitis pigmentosa

Any one of a large group of inherited disorders in which abnormalities of the photoreceptors (the rods and cones) in the retina lead to progressive visual loss.

People with retinitis pigmentosa (RP) first experience defective dark adaptation ('night blindness'), then constriction of the visual field ('tunnel vision') and eventually loss of central vision.

RP may be inherited in a number of different ways: as an autosomal dominant, autosomal recessive, or X-linked recessive trait or as a mitochondrial disorder.

More than 30 different genes are known to cause RP.

RP can occur alone or be part of a syndrome involving abnormalities outside the retina.

For example, Usher syndrome (of RP and deafness) is a relatively common form of syndromic RP.