The function of GUCY2D (guanylate cyclase 2D, retinal, ENSG00000132518) is as follows. Catalyzes the synthesis of cyclic GMP (cGMP) in rods and cones of photoreceptors. Plays an essential role in phototransduction, by mediating cGMP replenishment (PubMed:15123990, PubMed:21928830, PubMed:26100624, PubMed:30319355, PubMed:9600905). May also participate in the trafficking of membrane-associated proteins to the photoreceptor outer segment membrane (By similarity). {ECO:0000250|UniProtKB:P52785, ECO:0000269|PubMed:15123990, ECO:0000269|PubMed:21928830, ECO:0000269|PubMed:26100624, ECO:0000269|PubMed:30319355, ECO:0000269|PubMed:9600905}.