Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4. Four other opsins in the mammalian retina are both involved in the formation of visual images: Rhodopsin and three photopsins in the rod and cone photoreceptor cells, respectively.

Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4. Four other opsins in the mammalian retina are both involved in the formation of visual images: Rhodopsin and three photopsins in the rod and cone photoreceptor cells, respectively.