Those Amazing Cat Eyes

One of the most amazing things I have ever seen my cat "Bunny" do is catch a fly in mid-air with his two paws. Bunny is in the picture to the right. His fly catching feat is impressive enough for any cat, but Bunny is also cross-eyed and has chronically inflamed third eyelids.

I have often wondered what Bunny sees because he certainly sees double as I notice him looking at me from side to side, wondering which of me is the real one. Another impressive cat feat I saw was one of our hospital cats getting a look in his eye about something he wanted outside the hospital. His focus was unwavering and as soon as a client opened the door, Marbles shot out and caught a baby squirrel fifteen feet up in a tree. We were able to get the squirrel away from him and nurse it back to health luckily.

Cats have large eyes for their body size and are known for their night vision and nocturnal hunting. Large eyes gather more light, but also come with the defect of being more difficult to focus. Cats and Owls can see prey perfectly far away, but they almost can't find it when it is right at their feet.

The cat's pupil is vertical and slit shaped and can open very broadly to let in a maximum amount of light that allows them to see clearly in eight times dimmer light than we can see in. The cat's eye lens is also bigger, and can focus more light onto their retinas, but the bigger lens makes closeup focusing more difficult. The cat's retinas are larger too and have light sensitive cones everywhere on the retinas, with no cone-only areas like we have that give us fine color vision. A person can distinguish over two million color variations.

Consequently, cats have great night vision, but they would qualify as color blind in the same way that color-blind people have difficulty differentiating certain colors from one another. Greens and blues and reds and yellows blend into similar color perceptions for the cat like they do in color blind people.

The tapetum lucidum is a reflective surface behind the retina that bounces light back to the retina for another exposure to the rods and cones. This effectively doubles the amount of light exposure to the retinas and gives cats that glowing eyes in the dark appearance when a light is flashed on them.

If a cat went in for eye glasses testing, their vision would be an average 20/100, on our scale of 20/20 as they are very far-sighted, and again have poor close-up vision. Other interesting facts about cat eyes are that they have a 200 degree field of vision, because of the binocular integration of their eyes, and they have a protective third eyelid, the nictitating membrane, that covers the whole eye on the inside when they are fighting and attacking prey or acting defensively. Bunny's third eyelids are always half way up as you can see in the photo. The third eyelids being up can also be an indication of illness in your cat, so see your veterinarian immediately if your cat's third eyelids are up.

White cats with blue eyes are genetically deaf seven percent of the time. The old wives tale is that all white cats with blue eyes are deaf, but it only occurs with the double recessive gene phenotype, which is one in sixteen of the bunch. Lastly, when a cat blinks at you, it is sending you a kiss. Their blink says they like you, so look for those sleepy eyed cat blinks to know if your kitty truly loves and appreciates you.

Dr. Doug Ikeler http://www.ikelerbooks.com/