Real Dictionary

retinitis pigmentosa in American English
an inherited, incurable eye disease that gradually destroys the retina and optic nerve, slowly reducing the field of vision until total blindness occurs
noun: degeneration of the retina manifested by night blindness and gradual loss of peripheral vision, eventually resulting in tunnel vision or total blindness

retinitis pigmentosa in British English
hereditary eye disease
noun: a degenerative hereditary disease of the human eye, characterized by pigmentary changes in the retina, night blindness, and eventual loss of vision