The secrets and the beauty behind feline eyesight
By Kim Campbell Thornton
Andrews McMeel Syndication
Sparkling sapphires, emeralds and topazes glow up from their furry setting. They aren’t gemstones or precious metals, though, but the eyes of our cats, in blue, green, gold and amber, orange, yellow and hazel -- to name just a few of the colors reflected in a cat’s eyes.
These gorgeous orbs have some unique features that contribute to the feline aura of mystery as well as to their mastery of darkness and the hunt.
In structure, a cat’s eye is similar to a human eye. They each have a cornea, the clear front part of the eye; a retina, the light-sensitive membrane containing photoreceptor cells; and a pupil, the opening at the center of the eye, which is surrounded by the iris, the colored or pigmented part of the eye.
But the cat’s pupil and iris work a little differently than in humans.
“What is unique about the domestic cat is the pupil,” says veterinary ophthalmologist Cindy Mar. “The cat pupil has a vertically oriented slit. This pupil shape is due to the orientation of the iris muscles, which create a scissorlike action during closure.”
This allows cats to control the amount of light reaching their eyes and make precise adjustments to accommodate different lighting, whether they are in bright sunlight or a darkened room. It’s one of the factors that makes them superb hunters. (Fascinating fact: Big cats such as lions and tigers have round pupils.)
Two other features that cats have but humans don’t is a third eyelid on the inner corner of the eye, which offers extra protection, and a shiny reflective layer, called the tapetum lucidum, in the back of the eyes.
“The tapetum increases the amount of light in the eye, allowing the cat to have better night vision,” Dr. Mar says. Interestingly, not every cat has a tapetum. Blue-eyed cats and some cats with dilute colors lack a tapetum.
How do you know if your cat has good eyesight? In fact, how does a veterinary ophthalmologist know? It’s not as if they can show a cat an eye chart and ask if they can read the letters M-O-U-S-E.
It’s a challenge, Dr. Mar says. And evaluating cat vision is even more challenging than evaluating dog vision. Dogs offer more clues because they are more likely to walk around the exam room and make their way around objects. Cats may simply want to hide unless they have been given time first to adjust to being in the exam room.
“A lot of time I depend on the history, or what the owner tells me the cat sees,” Dr. Mar says. “I can check to see if the cat sees light and dark -- the dazzle reflex -- or sees my hand when I wave in front of the eye -- the menace response.”
It’s a good idea to gaze into your cat’s eyes regularly not only to give “kitty kisses” -- a slow blink -- but also to check that they are shining with health.
Your cat’s regular veterinarian should give eyes a look-see at every annual exam. And your cat should be seen by the veterinarian if eyes are red, cloudy, squinting or have excessive discharge. A referral to an eye specialist may be in order if a cat’s eye condition doesn’t improve or if it worsens with conventional therapy.
A common eye problem in cats is conjunctivitis, which is often associated with herpesvirus infection. Brachycephalic cats -- the ones with smushed faces, like Persians or exotics -- may be more prone to develop corneal sequestrum, a peculiar cat eye condition associated with chronic, nonhealing corneal ulcers, Dr. Mar says. And brachycephalic cats may be more prone to eye injuries and poor blinking ability because the eyeball is more exposed. Fortunately, cats in general don’t have as many breed-related eye problems as dogs.
How often should
old pets see vet?
Q: Does my older pet really need wellness checks twice a year now, or is the vet just trying to make money off of me?
A: Regular preventive-care visits are absolutely important for aging dogs and cats (and other pets). The reason we veterinarians recommend bringing pets in twice a year once they get to be 7 or 8 years old is because pets age faster than humans. If we can check them over twice a year, we have a better chance of catching diseases early, when they are more treatable. It’s a good way to prolong your pet’s healthy life.
This is important to me because many times I’ve had to give people bad news about their pet’s prognosis, knowing that if I had seen the pet earlier, the problem could have been treated more effectively and at less cost.
A senior pet wellness visit is the time to talk to your veterinarian about whether a new diet is needed, and to mention any changes in activity level or behavior that you’ve noticed. In addition to a nose-to-tail exam, including eyes and teeth, your veterinarian may recommend diagnostics such as chest radiographs, which might identify an enlarged heart; a blood pressure check; and blood, urine and fecal tests.
The other thing to remember is that different animals age at different rates. Large dogs age more rapidly than small dogs and cats, for instance. So the age at which pets become seniors varies. We might want to start seeing large or giant-breed dogs when they are 6 years old and cats or small dogs at 8 years old. Your veterinarian can advise you based on your individual pet’s health history.
By keeping your pet’s care on the right track with wellness checkups, you can help to give him additional years of good health. -- Dr. Marty Becker
Do you have a pet question? Send it to firstname.lastname@example.org or visit Facebook.com/DrMartyBecker.
-- First it was hip replacements, then elbow joints. Now total ankle, or hock, replacement is available for dogs with severe arthritis that limits mobility. A 7-year-old Labrador named Leo underwent the surgery in January at the University of Florida College of Veterinary Medicine’s small animal hospital and is back on the hiking trail with his owner -- UF veterinary student Maggie Smallwood -- after a five-month recovery. The procedure involves replacing damaged surfaces of the joint with a prosthetic implant. “We now have a promising treatment for a condition that was previously difficult to manage,” said UF associate professor and veterinary surgeon Stanley Kim, who performed the procedure.
-- Have you ever wondered how dog DNA tests work? They compare genetic information from a dog’s DNA sample -- usually saliva, although your dog doesn’t have to spit into a test tube -- to a reference panel of different breeds and types of dogs. Matches help determine breeds in your dog’s background. Accuracy depends on such factors as number of genetic markers used, comprehensiveness of the reference panel (100 breeds, 400 breeds, different types of dogs from around the world?), and sophistication of the algorithms used to process the data.
-- If you’re considering a bird as a pet, take your allergies into account. Feathers and feather dust (produced by powder-down feathers) are allergens. All birds produce some feather dust, but certain birds are dustier than others. Species that distribute a lot of feather dust and dander include cockatoos, cockatiels, African greys and Amazon parrots. Why are birds dusty? Feather dust helps keep birds clean and waterproofs their feathers. To help keep dust down, use a HEPA filter in the room where your bird spends most of her time. A vacuum cleaner with a HEPA filter can also help to remove feather dust from the environment. -- Dr. Marty Becker, Kim Campbell Thornton and Mikkel Becker
ABOUT PET CONNECTION
Pet Connection is produced by a team of pet care experts headed by “The Dr. Oz Show” veterinarian Dr. Marty Becker, founder of the Fear Free organization and author of many best-selling pet care books, and award-winning journalist Kim Campbell Thornton. Joining them is behavior consultant and lead animal trainer for Fear Free Pets Mikkel Becker. Dr. Becker can be found at Facebook.com/DrMartyBecker or on Twitter at DrMartyBecker. Kim Campbell Thornton is at Facebook.com/KimCampbellThornton and on Twitter at kkcthornton. Mikkel Becker is at Facebook.com/MikkelBecker and on Twitter at MikkelBecker.