retinitis pig·men·to·sa 
(pĭg′mĕn-tōsə, -mən-)
(pĭg′mĕn-tōsə, -mən-)n.
A hereditary degenerative disease of the retina, characterized by night blindness, pigmentary changes within the retina, and eventual loss of vision.
[New Latin pigmentōsa, feminine of pigmentōsus, pigmented.]