G-protein coupled receptor which selectively activates G(i) type G proteins via ultraviolet A (UVA) light-mediated activation in the retina (PubMed:22043319). Preferentially binds the chromophore 11-cis retinal and is a bistable protein that displays emission peaks at 380 nm (UVA light) and 470 nm (blue light) (PubMed:22043319, PubMed:31607531). Required for the light-response in the inner plexiform layer, and contributes to the regulation of the light-response in the nerve fiber layer, via phosphorylated DAT/SLC6A3 dopamine uptake (PubMed:30936473). Involved in local corneal and retinal circadian rhythm photoentrainment via modulation of the UVA light-induced phase-shift of the retina clock (PubMed:26392540, PubMed:30240620). Acts as a circadian photoreceptor in the outer ear and vibrissal pads, via modulation of circadian clock-gene expression in response to violet light during the light-to-dark transition phase and night phase of the circadian cycle (PubMed:31607531). Required in the retina to negatively regulate hyaloid vessel regression during postnatal development via light-dependent OPN5-SLC32A1-DRD2-VEGFR2 signaling (PubMed:30936473). Involved in the light-dependent regulation of retina and vitreous compartment dopamine levels (PubMed:30936473). Expressed in the brain (at protein level) (PubMed:14623103, PubMed:22043319). Weakly expressed in the skin and liver (at protein level) (PubMed:22043319). Abundantly expressed in striated muscle cells (PubMed:22043319). Expressed in Math7/Atok7-dependent retinal ganglion cells in the ganglion cell layer (at protein level) (PubMed:14623103, PubMed:22043319, PubMed:26392540, PubMed:30240620, PubMed:31607531). Additionally expressed in horizontal and amacrine cells in the inner nuclear layer of the retina (at protein level) (PubMed:22043319). Expressed around the base of hair follicles and in epidermal and sebaceous gland cells of the outer ear (at protein level) (PubMed:22043319, PubMed:31607531). Abundantly expressed in vibrissae hair follicles and weakly expressed in the vibrissae skin pad, dorsal back skin, and tail (PubMed:31607531). Expressed weakly in the inner retina at postnatal day 5 (P5), with expression becoming abundant in retinal ganglion cells at P8 (PubMed:30936473). Expressed throughout the retinal sublaminae layers, with abundant expression in the ganglion cell layer and nerve fiber layer at P12 (PubMed:30936473). Expressed in ganglion cells in the optic tracts, superior colliculus and lateral geniculate nucleus of the brain at P28 (PubMed:30936473). Expressed around the base of hair follicles in the dorsal ear skin, in the vibrissal nose pad, and weakly expressed below the epidermis in the vibrissal nose pad at P8 (PubMed:31607531). It is uncertain whether Cys-315 or Cys-316 is palmitoylated. Ultrastructure of the retina is normal (PubMed:30936473, PubMed:30240620, PubMed:26392540). Newborn mice show normal hyaloid vessel numbers and normal vessel cellularity (PubMed:30936473). Retinas show normal expression patterns of rod and cone opsins including Opn4 (PubMed:26392540, PubMed:30240620). Decreased activated Vegfr2 in the hyaloid vessels and increased activated Akt1 at P5 (PubMed:30936473). Reduced levels of dopamine in the retina, however increased levels in the vitreous at P6 (PubMed:30936473). Reduced number of hyaloid blood vessels due to precocious regression, however no change in abundance of Vegfa or Flt1 at P8 (PubMed:30936473). Expression of tyrosine hydroxylase Th in retinal cell processes at P8, with increased expression in developed dopaminergic amacrine cells at P15 (PubMed:30936473). Loss of retinal and corneal circadian rhythm photoentrainment (PubMed:26392540, PubMed:30240620). Reduced UVA-induced phase-shift response and Fos expression in the suprachiasmatic nuclei (SCN) in the brain (PubMed:30240620). Abolishes retinaldehyde-dependent photoentrainment in the dermal tissues of the outer ear and vibrissal pad (PubMed:31607531). Loss of phase shifting activity in response to violet light and expression of circadian clock-genes in the skin of the outer ear during light-to-dark cycle, including Per1, Per2, Cry2, Dbp and Nr1d2 (PubMed:31607531). Pde6b and Opn5 double knockout mice also show loss of retinal ultrastructures and a more severe reduction in the rate of circadian photoentrainment, light-induced phase-shift response and Fos expression in the SCN (PubMed:30240620). Belongs to the G-protein coupled receptor 1 family. Opsin subfamily.