Are yams and sweet potatoes the same?
retinitis pigmentosa retinitis pig·men·to·sa (pĭg'mən-tō'sə, -měn-)
A hereditary degenerative disease of the retina, producing conditions such as night blindness, pigmentation changes in the retina, narrowing of the visual field, and the eventual loss of vision. Also called pigmentary retinopathy, tapetoretinal retinopathy.
group of hereditary eye diseases in which progressive degeneration of the retina leads to severe impairment of vision. In the usual course of disease, the light-sensitive structures called rods-which are the visual receptors used in dim light-are destroyed early on, causing night blindness in youth. Over time, further atrophy of the retina and changes in the layer of supporting cells known as the pigment epithelium occur. Commonly the field of vision becomes constricted until the affected person sees objects as if looking through a tunnel.