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In a Cat's Eyes

Part 2: Why Cats See Better at Night

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Diagram of a Cat's Eye

Diagram of a Cat's Eye

Franny Syufy
Cats' nocturnal vision is far superior to that of humans, however they can't see in total darkness. They can see clearly with only one-sixth of the illumination we need to see, so when you're trying to read that newspaper at twilight, ask your cat for help! In the feline, the muscles of the iris surrounding the pupils are constructed in a fashion that allows the eye to narrow to a vertical slit in bright light and to open fully in very dim light, to allow a maximum of illumination.

In addition, a reflective layer behind the cat's retina called the tapetum lucidum reflects incoming light and bounces it back off the cones, making more use of the existing light. The tapetum is probably responsible for the fact that when a small amount of light hits a cat's eyes at night, you see shiny green orbs.

These special feline features have probably developed for survival purposes, as wild cats are nocturnal and do much of their hunting at night.

Testing Cats' Eyes to Help Humans

In 2000, a team of scientists at the University of California in Berkeley used cats to learn more about human vision. During the controversial experiment, the team, led by Yang Dan, assistant professor of molecular and cell biology, anesthetized the cats then implanted electrodes into their brains and showed them images. They were able to record the cats responses to light and dark, and, using a mathematical equation, convert the signals into images.

Since cats' eyes are so similar to humans' the team hoped to answer a number of questions about how the eye and the brain work together to capture, encode, and reassemble images. I have been unable to locate any published results of these tests available to lay persons.

Other Bits of Cats Eye Trivia

  • Cats cannot see directly beneath their noses. You can test this by offering your kitty a treat, such as Pounce. He can smell it, but if you drop it directly beneath his nose, he'll have to root around a bit before finding it.
  • Rumors aside, cats are not colorblind. Their ability to see color is not as enhanced as ours, but they can see some colors.
  • If normal human vision is 20/20, then that of the cat is 20/100. He has keen vision for objects far away, but things up close may appear fuzzy or blurred. Perhaps this is why cats do the sniff test when greeting friends.
  • Most white blue-eyed cats are deaf. A white cat with odd-eyes (one blue and one green or gold) will most often be deaf on the side with the blue eye.
  • Cats "Kiss" with their Eyes. Have you ever noticed your cat gazing at you for a long moment and then slowly blinking his eyes? That's the kitty equivalent of a kiss, and you should feel very flattered. Of course, a nip on the nose is also their way of giving a kiss. If you want to show your cat you love him, give him a kitty kiss right back. No, not on the nose. Just give him that long stare and slow blink and see what happens.

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