Photoreceptor required for image-forming vision at low light intensity. Can use both retinal and 3-dehydroretinal as visual pigment. Light-induced isomerization of 11-cis to all-trans retinal triggers a conformational change that activates signaling via G-proteins. Signaling via GNAQ probably mediates the activation of phospholipase C. Homodimer. Interacts with GNAQ. Detected on the rhabdomere membrane in the photoreceptor outer segment. Contains one covalently linked retinal chromophore. Belongs to the G-protein coupled receptor 1 family. Opsin subfamily.