A B C D E F G H I K L M N O P R S T U V W X Choroideremia Definition: An X chromosome-linked abnormality characterized by atrophy of the choroid and degeneration of the retinal pigment epithelium causing night blindness. Broader term(s) Eye Diseases Eye Diseases, Hereditary Choroideremia MeSH © U.S. National Library of Medicine®.