Seeing in the Light and Dark Font Size: [small] [medium] [large] Shine a light on a cat in a darkened room or look at a photograph of a cat taken with a flash and you'll observe the eerie green or yellow glow reflecting from its eyes. To take full advantage of available light, the back of the cat's retina contains a layer of mirror like cells, called the tapetum lucidum, that collects and reflects light back to re-stimulate the retina's rods — much like the effect seen when a car's headlights shine on a road marker at night. Present in nearly all carnivores and many other mammals, this layer of cells is particularly thick, up to as many as fifteen cells, in cats. Not visible in normal conditions, the tapetum lucidum appears only when light is aimed directly into the animal's eyes. A cat's vision is sharpest between 2 and 3 feet from its face, and its focus is on the center of what the cat observes rather than on the entire landscape. This is a helpful adaptation when it comes to zeroing in on small prey. Cats also can detect motion much better than humans can. Since the many rods in the cat's retina serve as motion detectors as well as light receptors, anything running across a cat's field of vision is more likely to be detected than something coming straight toward it. < back to original page