Princeton's WordNet(0.00 / 0 votes)Rate this definition: 1  shimmer, play(verb) a weak and tremulous light. 2  shimmer(verb) shine with a weak or fitful light. 3  shimmer(verb) give off a shimmering reflection, as of silk.
Cats, like humans, have both rods and cones in the retina. Rods are the receptors that the eye uses for night time viewing and sudden movement. Cones are used during the daytime, and process color information. Cats have more rods than cones, as compared with humans, making cat night vision superior to humans.
Vision and color perception. 1  Human eyes have a light-sensitive layer--the retina--which carries two types of light-sensitive cells: rods and cones. Rods are sensitive to dim light (scotopic vision) but do not provide color information. 2  For greatest acuity look straight; for greatest sensitivity, look to the side.