The function of RGR (retinal G protein coupled receptor, Ensembl gene identifier ENSG00000148604) is as follows. Non-visual opsin that functions as a light-dependent facilitator of retinoid isomerization and trafficking in retinal pigment epithelium (RPE) and Mueller glia (PubMed:18474598). Participates in a photic visual cycle by complementing the classical enzymatic RPE65/RDH pathway for chromophore regeneration (By similarity). Binds all-trans-retinal via a conserved Schiff-base lysine and, upon illumination, promotes photoisomerization of all-trans- retinal to 11-cis-retinal required for regeneration of visual pigments (By similarity). Also mediates light-dependent mobilization of stored all-trans-retinyl esters from lipid droplets to endoplasmic reticulum membranes, facilitating their processing into 11-cis-retinoids (PubMed:18474598). May also modulate isomerohydrolase activity independent of light (By similarity). Although RGR is structurally a GPCR-family opsin, there is no consistent evidence that RGR activates G proteins or initiates a canonical second-messenger signaling cascade (Probable). {ECO:0000250|UniProtKB:Q9Z2B3, ECO:0000269|PubMed:18474598, ECO:0000305}.