Rod-specific cGMP phosphodiesterase that catalyzes the hydrolysis of 3',5'-cyclic GMP (PubMed:20940301). This protein participates in processes of transmission and amplification of the visual signal. 3',5'-cyclic GMP + H2O = GMP + H(+) Binds 2 divalent metal cations per subunit. Site 1 may preferentially bind zinc ions, while site 2 has a preference for magnesium and/or manganese ions. Oligomer composed of two catalytic chains (alpha and beta), an inhibitory chain (gamma) and the delta chain. The disease is caused by variants affecting the gene represented in this entry. Belongs to the cyclic nucleotide phosphodiesterase family. Retina International's Scientific Newsletter