visual cycle
the cyclic association of 11-cis retinal with an opsin followed by photon-induced conformational changes in the compound protein (rhodopsin or an iodopsin) and dissociation of opsin and an all-trans isomeric form of retinal; the cycle is completed by direct or indirect reconversion of retinal to the 11-cis isomer. The conformational changes create an electric potential and initiate the cascade generating a sensory nerve impulse in vision. See illustration.
Visual cycle of retinal rod cells; an analogous cycle occurs with iodopsins in the cones.
Medical dictionary.
2011.