More than meets the cat's eye

IT'S NOT just the fur or the purr that cats use to hold us spellbound: It's those eyes. Whether they are blue, green, gold, copper or some variation of those shades, a cat's eyes are one of his most beautiful features. Here's how they come to be that way.

Eye color is genetically linked to coat color. Kittens are born with blue eyes, which may stay that way or change color as the kitten matures. For instance, all pointed cats have blue eyes. Cats who are solid white or mostly white may have blue, green, gold or copper eyes. The most common eye colors range from greenish-yellow to gold.

You may have heard that white cats are always deaf. Not necessarily. Some are, and some aren't. White cats with blue eyes are more likely to be deaf, however, than white cats with gold or green eyes.

Between 10 and 20 percent of white cats with eyes of other colors may be deaf. White cats with only one blue eye may be deaf only in the ear that's on the same side as the blue eye.

Eyes with the brilliant copper of a shiny new penny or the bright green of an emerald usually are the result of selective breeding, but genes don't discriminate. Those eye colors can appear in cats without a pedigree, as well.

Pedigreed cats noted for their distinctive eye color include the Burmese (large, round gold eyes), the tonkinese (sparkling aqua eyes) the Egyptian mau (gooseberry-green eyes) and the Russian blue (vivid green eyes).

Some cats have "odd eyes," meaning one eye is blue and one is green or gold. The scientific term for this is "heterochromia," from the Greek words "hetero," meaning "different," and "chromia," referring to color. The difference in color might not be noticeable in a kitten, but changes gradually as the kitten moves toward adulthood.

We usually see odd eyes in white cats or cats with the white spotting gene, such as bicolor and tuxedo cats. Breeds in which odd eyes are common include Turkish angoras and Turkish vans.

A description of angoras stated that the eyes should be "as green as the lake and as blue as the sky." Other breeds that may sport odd eyes are Persian, sphynx, Oriental shorthair and Japanese bobtail cats.

Odd eyes occur when a dominant white gene (meaning it masks other colors) or a white spotting gene blocks the concentration and distribution of natural pigments within the iris tissues during development.

An unusual and attractive look is the dichromatic, or dichroic, eye, usually seen in white cats. That's one with two colors in one iris. For instance, the eye might be half green and half blue or have a green iris encircled by yellow. One or both eyes can be dichromatic, sometimes with each eye mirroring the other.

Even more rarely, only a section of the eye may be a different color. Think of a pie-sliced shape of brown in what is otherwise a blue or green eye. Those eyes aren't just odd; they're downright weird, but undoubtedly beautiful.

Pet Connection is produced by a team of pet-care experts headed by "The Dr. Oz Show" veterinarian Dr. Marty Becker and award-winning journalist Kim Campbell Thornton. They are affiliated with Vetstreet.com and are the authors of many best-selling pet-care books. Joining them is dog trainer and behavior consultant Mikkel Becker.