Cat Eyes by Frank Utchen, DVM

Cats are famous for their great eyesight and rightly so. They have fantastic night vision and are extremely sensitive to movement, thanks to their former hunting days.  This week's article will help you get a cat's eye view of this amazing feline organ.

Cats have many of the same parts found in human eyes, but they've got some special structures, too. Ever wonder why cats' eyes seem to glow in the dark? That's because they have a group of light reflecting cells in the back of each eye in an area called the tapetum lucidum. Cats also have a third eyelid, a light pink membrane that behind the eyelids which slides across the eye when cats blink. This gives them extra protection and contains a gland that secretes some of their tears.

Common Problems
Most cats never have any trouble with their vision. Others have problems at birth or develop them as they age.   It's not always easy to spot vision problems because cats have a tremendous ability to rely on other senses, like hearing and smelling. Here are some signs you'll want to be on the lookout for:

Watery eyes
A small amount of tearing is normal, especially in breeds with short noses like Persians and Himalayans. However, if your cat tears a lot and/or repeatedly squints or rubs an eye, if there is pus or other unusual material coming out of the eye, or if the pink tissue lining the eyelid (the conjunctiva) swells to the point that you see it, it's time to call your veterinarian. Watery eyes can be caused by infections, allergies, or injuries. Perhaps the most serious problem this time of year for cats and their eyes is the presence of "foxtails." These pointy grass seeds drop from the dry grass on the hills in our area, and for the unlucky cat stalking through the grass these seeds sometimes become stuck behind a cat's eyelid. The ensuing damage to the cornea (the clear layer that constitutes the front surface of the eyeball) can be severe and require prolonged used of eye medications before healing.

Cloudy eyes
Your cat's cornea can become inflamed (a condition called Keratitis). The most common cause for this is a viral infection spread among cats, which is not contagious to humans. This can make the eye cloudy and painful. It's important to get this problem treated early to drive the virus in remission. Left unchecked, this virus has the ability to cause such severe damage to the eye that blindness can result.

Eye color changes
Another type of eye inflammation is referred to as Uveitis. This involves swelling of the iris which can cause the color of the iris to appear to change and make your cat very sensitive to light. Without treatment, this too can lead to blindness.

Swelling around the eyes
Cats occasionally get in a fight with other cats and may be bitten or scratched around the eyes. If an abscess develops around the eyelids as a result of puncture wounds around the face there can be significant swelling involving the eyelids. Less frequently, cats will develop an abscessed root of one of the upper teeth. This can lead to swelling of the tissues in the upper jaw and behind the eyeball as well.

Constantly dilated pupils
Cats can become blind for different reasons, and when they do the pupils remain fully dilated, even in bright light. Sometimes—generally related to poor nutrition—the retina itself can degenerate. Feeding a high quality cat food will be adequate to avoid this problem. It should be noted, however, that dog food is deficient in the amino acid Taurine and this can lead to retinal degeneration. This condition is permanent. Of course, no self respecting cat would resort to eating dog food voluntarily, so this condition is rare. In addition to retinal degeneration as a result of Taurine deficiency, cats can become blind from hypertension (high blood pressure). Cats develop hypertension (high blood pressure) for several reasons, and this can lead to damage of the blood vessels that nourish the retina. The best way to be sure your cat's vision is fine is to have your cat examined yearly by your veterinarian.

Staying Healthy
Spot check your cat's eyes regularly—they should be bright and shiny, without a lot of tearing, and the pupils should be equal in size.

Also examine your pet's eyes for any unusual discharge, redness, swelling, or cloudiness.

Never use soaps or cleaners near the eye.

If your cat is squinting it is best to have him or her checked by your veterinarian as soon as possible.