The Eyes
The eyes of a cat can be round, almond-shaped, or anywhere in between. Cat's eyes are the largest of any mammal in relation to their body size. Although they can't see in total darkness, as alluded to in folklore, they can see in darkness that would leave a human blind and bumping into things. Their pupils can contract to as little as a bare split or expand to such an extent that only a tiny rim of color is showing. When open to their fullest, the eye allows all possible light to enter. Any night hunter will have larger eyes than other carnivores.
As sharp as their eyesight appears to be, cats are farsighted. They see better between seven and twenty feet than up close, such as within a few inches.
The cat has a third eyelid called the haw or nictitating membrane. This thin, whitish lid is situated at the inner corner of the eye. It is automatically activated to protect the eye from damage and to lubricate the corneal surface by evenly distributing tears.
The eyes of a cat are very large in relation to the rest of the head, and they glow with an exotic light at night. This night shine is different in cats according to the color of their eyes. Cats with gold to copper colored eyes will reflect a yellow-green or blue-green shine, while those with blue eyes will reflect red. The paranoid witch hunters and their church supporters believed that this night shine was a reflection of the fires in hell. Other tales say that this night shine is really luminous jewels inside the cat's head.
This night shine or eye shine is caused by light reflecting off the guanin on the back of the cat's eyes. Guanin are the masses of tiny metallic-like particles coated on the lining at the back of the eye. When struck by light, the guanin particles amplify and brighten any picture focused on the retina. After a certain amount of time, these particles retreat into their cells and the eye shine ceases.
©1999
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