Eye issues in pets
Team Walmart Pets
June 9, 2021
When it comes to vital organs, the eyes are right up there with the heart, lungs and brain for our pets. Much of a dog’s or cat’s sensory information comes through their vision. Depth perception through stereoscopic sight in both eyes is critical for a cat’s predatory success or a dog’s herding ability.
Because the eyes are essential for an animal’s survival, they have many built-in protective defenses and reflexes. What happens when your pet has an object thrown toward them? They duck and blink. What if they hear a loud sound, feel a puff of air or become frightened? They squeeze their eyes shut.
Dogs and cats also produce additional reflex tears during threats to the eyes to flush away dirt and debris and fight potential infection. In fact, protecting the eyes is so important that dogs and cats have a third eyelid called the nictitating membrane that lies inside the upper and lower eyelids.
All of these protective measures don’t mean the eyes are immune to injury and disease. One of the key reasons the eyes must be protected is because when things go wrong with them, they tend to go very wrong without proper care. Part of this is because the eyes have a unique immune response that affects their ability and rate of healing. Complicating matters, the cells required to repair even minor eye injuries impair vision, increasing the animal’s risk of falling prey. Better to blink and duck.
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10 common eye problems in pets
The most common eye injuries in pets are abrasions to the cornea, the crystal-clear outer covering of the eye. It is made up of unique skin cells that allow light to pass through the lens and onto the back of the eye, the retina, where vision begins. The most common corneal injuries in dogs and cats are lacerations and abrasions, which can result from scratches, irritation from blades of grass or furniture as well as blown debris.
A tell-tale sign your pet may have a corneal injury is uncontrollable squinting and blinking of the eye. Rarely will you see blood, and if you manage to pry the lids apart, the eye may appear normal. Don’t bet on it. If your pet is holding its eye closed for any reason, have it examined by your veterinarian immediately. Because the eyes don’t heal the same as a cut on the skin, an infection can set in quickly and result in serious complications if not treated immediately.
Your veterinarian will perform a series of diagnostic tests and corneal stains to determine the extent of the abrasion, and treatments vary from topical pain relief medication and antibiotics to surgery.
Pink eye (conjunctivitis)
Another common eye infection in dogs and cats is conjunctivitis (aka pink eye) which appears as goopy, crusty eyes. Conjunctivitis in dogs can present as thick, greenish goo that reappears every few hours. Conjunctivitis in cats signals it’s arrival with caked-on crud and watery eyes.
Many pets will squint and blink but don’t walk around with their eyes screwed shut, as with a corneal injury. The tissues around the conjunctivitis-infected eyes often look swollen and red.
This is most likely a case of conjunctivitis, or inflammation of the skin around the eye, which can be caused by viruses, especially in cats, bacterial infections, allergies and irritating pollutants. Conjunctivitis in cats can even be triggered by a pet parent’s perfume! Once the cause is determined, appropriate treatment can begin. Don’t delay treatment on pink eye in pets; conjunctivitis can worsen quickly and cause potential damage to the cornea or other eye tissues.
Dry eyes (keratoconjunctivitis sicca)
Speaking of yucky eyes, let’s talk about “dry eyes” in pets. Don’t trust the name; the most common sign of dry eyes or keratoconjunctivitis sicca (KCS) is thick, crusty ocular discharge. The “dry” refers to the cornea — and that’s a very bad thing.
Part of the reason why the cornea remains clear is due to its high water content. Take away the water, and you take away the vision. Dry eyes cause many dogs and cats to become blind or nearly blind due to the corneal scars and pigmentation that result as the body tries to heal the dry and cracking cornea.
There are several causes of dry eyes in dogs and cats, with the most common being an immune-mediated disorder that affects the tear-producing part of the eye. To diagnose dry eye, your veterinarian will perform a simple tear-production test. If it’s too low, your pet will need to be treated with a drug to counter the disease and increase tear production. Artificial tear solutions and topical antibiotics are also used in many cases.
The great news is that most cases of dry eye can be successfully managed. The key is to diagnose the condition early because once scars or pigment deposits have formed, there is little that can be done to reverse them. They can cause a dog’s vision to be similar to driving with a windshield painted black in some spots. In some areas, you see just fine, but in others, you can only make out daylight. If you see thick mucus discharge from your pet’s eyes, have them checked immediately.
Uveitis is probably an eye disorder you’re not familiar with. Be thankful. The uvea is the inner part of the eye, from the iris (the butterfly wing-thick colored tissue that creates the pupil) back. Inflammation here is dangerous. In dogs and cats, uveitis can appear from anything as innocent as watery eyes to as serious as sudden blindness. Many cases of uveitis are the result of a systemic viral infection or are immune-mediated.
Pigmentary uveitis is a unique form of uveitis that creates iris cysts and increased pigment formation in Golden Retrievers. Another breed-specific form of uveitis is seen in Arctic Circle breeds (Japanese Akita, Samoyed, and Alaskan and Siberian Husky), as well as Golden Retrievers, Australian Shepherds, German Shepherds, Shetland Sheepdogs, Old English Sheepdogs, Chow Chows and St. Bernards.
Your veterinarian will perform a thorough eye exam and an ocular pressure test, known as tonometry, to determine if uveitis is present. Inflammation of the uvea results in decreased inner-eye fluid production, resulting in low intraocular pressure. Uveitis is a serious condition and many times the exact cause is undetermined. Treatment is primarily aimed at reducing inflammation and preserving vision and may be required for extended periods.
At the opposite end of the eye pressure spectrum is glaucoma, an increase in intraocular pressure. Think of the eye as a water-filled balloon. Too little pressure and the balloon sags: that’s uveitis. Too much pressure and it bulges and could burst: that’s glaucoma. But it’s a little more complicated than popping balloons.
Glaucoma is typically caused by a decrease in the drainage of aqueous humor or inner eye fluid. It’s similar to a plugged drain causing a buildup of water when the shower’s on. As the pressure within the eye builds, it collapses the microscopic blood vessels that supply the business end of the eye, the retina.
Take away the retina’s blood supply, and the cells begin to die. If enough retinal cells die, blindness occurs. This is why glaucoma is a medical emergency; as soon as pressure begins to build, it can take only hours before a dog or cat becomes blind.
Glaucoma can be caused by many conditions, including a luxated lens that blocks the drainage area, uveitis that causes swelling and closure of the drains, blood clots that plug the drain (hyphema), tumors and trauma. Advanced cataracts can lead to glaucoma by blocking the drain or causing swelling.
The clinical signs of glaucoma depend on its severity and duration. Symptoms often begin with squinting and blinking the eyes, red or bloodshot eyes, rubbing the eyes, changes in behavior from withdrawal to
Left untreated, dogs with glaucoma can be in such pain they ram their heads against the wall, and cats roll over and over as if fleeing from an unseen predator. It’s truly a disturbing sight. Treatment is directed at opening the drainage angle and decreasing fluid production. Most patients can be successfully managed if diagnosed quickly.
Cataracts are one of the more common eye conditions in older dogs and cats. Most of us have seen an older dog, cat or person with milk-white eyes. Developing cataracts can be thought of in simple terms as hardening of the lens, one of the most intriguing pieces of anatomy in the body.
Think about it: there’s a specialized tiny tissue that is completely transparent, can focus light by slightly stretching or thickening at the flick of minuscule muscular bands attached to its edges, yet is tough enough to survive the demands of the fiercest fighting predators. Way cool.
As age, ultraviolet light exposure and diseases such as diabetes progress, the lens can become damaged, lose its resiliency and become cloudy, thus the term “hardening.” Veterinarians once accepted cataracts as something they couldn’t do much about, but the past 20 years have seen cataract treatments go from “rare” to “routine.” Today’s pets can have cataract surgery performed by specialized veterinary ophthalmologists, saving them from blindness and potential complications such as glaucoma.
Most pets can have the surgery performed in a single visit and are literally “better than before” just hours after surgery. Unless a pet is totally blind, it can be difficult to determine the extent of visual impairment. It’s only after the damaged lens is removed that the “puppy underneath” can re-emerge. If cataract surgery is a possibility for your pet, do it, especially since it’s usually covered by pet insurance.
While we’re on the subject of eye problems you can easily see, let’s not forget entropion. Entropion is a common eyelid condition in which the eyelid rolls inward toward the eyeball. (Outward rolling of the eyelid is called ectropion and is much rarer.)
Dogs with entropion will have a variety of symptoms including excessive eye watering, squinting, redness, rubbing and thick ocular discharges. The true danger of entropion is that the eyelids rub against the cornea, causing damage that leads to blindness.
Surgery to correct the inward rolling is the only treatment for entropion. There are a variety of surgical techniques used based on the location and severity of entropion present. Most pets will do well after one surgery, but others may require a second surgery later as the eyelid tissues begin to stretch and sag.
One of the easiest eye conditions to spot is the cherry eye. It looks just like it sounds: a small tissue protruding in the inner corner of the eye identical to an itsy-bitsy cherry. Only that’s no cherry; it’s an integral part of the eye that helps produce part of the tear film needed to protect the cornea.
Thirty years ago, vets simply “pruned the cherry” and snipped that sucker out. Fast-forward 10 years, and that puppy often develops, you guessed it, dry eye. That’s why it’s so important to save this “cherry.”
Cherry eye, or prolapse of the third eyelid gland, typically affects both eyes. If only one eye is prolapsed, chances are good the other gland will pop out before too long. Surgery is the only treatment, and every effort should be made to replace the third eyelid gland.
Progressive Retinal Atrophy
One of the most hated eye diseases is progressive retinal atrophy (PRA). This is actually a catch-all term for a variety of genetic eye conditions that result in the gradual loss of vision. It starts with a decrease in dim-light sight and advances to total blindness over months or years. In general, the younger an animal is affected, the faster the blindness develops.
Many pet parents don’t know that their pet is going blind. They just know their dog stops wanting to go outside at night, hesitates when going up or downstairs, or that their cat’s pupils seem larger or “glow” more when light is shined on them. Currently, more than 70 breeds of dogs have been documented to have progressive retinal atrophy, but mixed breed dogs may also be affected.
DNA testing for progressive retinal atrophy is available for an increasing number of breeds and can help distinguish between the affected, carrier and normal animals. If you’re going to breed or buy a breed known to inherit progressive retinal atrophy insist that the parents be tested first.
While there is no specific treatment, pet owners of affected dogs are often encouraged to use an antioxidant supplement such as Ocu-GLO rich in grapeseed extract, lutein and omega-3 fatty acids to potentially slow the disease. The good news is that blind pets adapt very well to a sightless life and learn to perfectly navigate their world on smell and sound alone.
Cancer can strike the eyes, especially in older pets. Cats and dogs can develop tumors on the eyelids (all three), within the eye, on the iris, almost anywhere. If you notice anything strange about your pet’s stare, have it checked out.
Caught early, many forms of ocular cancer can be cured. Diagnosed even a few days to weeks later, and the time to act may have passed.
If you live in a sunny climate or if your cat prefers to perch on a porch or windowsill catching rays, be aware that eyelid and facial melanomas are being diagnosed with alarming frequency. A little sunshine is great, just keep it healthy, especially in light-colored or thinly-furred pets. Don’t forget pet-specific sunscreens for your sun-worshipping pet.
Photo by Jamie Street on Unsplash