Photoreceptor that binds cis-retinaldehydes (By similarity). Contributes to pupillar reflex, photoentrainment and other non-image forming responses to light (By similarity). May be involved in the optokinetic visual tracking response (By similarity). May be involved in the regulation of retinal hyaloid vessel growth and regression (By similarity). Eye; expressed in a photosensitive subset of retinal ganglion cells (at protein level). Belongs to the G-protein coupled receptor 1 family. Opsin subfamily.