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.
One type of cone perceives blue light, another perceives green and the third perceives red. When you look at an object, light enters your eye and stimulates the cone cells. Your brain then interprets the signals from the cones cells so that you can see the colour of the object. The red, green and blue cones all work together allowing you to see the whole spectrum of colours. For example, when the red and blue cones are simulated in a certain way you will see the colour purple. The exact physical causes of colour blindness are still being researched but it is believed that colour blindness is usually caused by faulty cones but sometimes by a fault in the pathway from the cone to the brain.