Despite a clear causal association between some eye diseases and mutations in specific genes (CORD2 for cone-rod distrophy type 2, PRPH2 for CACD, as reinforced in this research; rhodopsin (RHO) for retinitis pigmentosa), mutations in the same gene could lead to different degrees of disease severity and mutations in different genes may lead to similar phenotypes. This evidence concerns the gene RHO and retinitis pigmentosa.