Necessary for the formation of a functional phosphodiesterase holoenzyme (By similarity). Involved in retinal circadian rhythm photoentrainment via modulation of UVA and orange light-induced phase-shift of the retina clock (By similarity). May participate in processes of transmission and amplification of the visual signal (By similarity). Rod-specific cGMP phosphodiesterase that catalyzes the hydrolysis of 3',5'-cyclic GMP (By similarity). Necessary for the formation of a functional phosphodiesterase holoenzyme (By similarity). Involved in retinal circadian rhythm photoentrainment via modulation of UVA and orange light-induced phase-shift of the retina clock (By similarity). May participate in processes of transmission and amplification of the visual signal (By similarity). 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. Belongs to the cyclic nucleotide phosphodiesterase family.