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Human ophthalmologists call glaucoma “the silent thief of sight,” because it sneaks up on patients who may not know they have it. The same thing can happen to pets, who can’t communicate even when they’re aware something’s wrong. That’s the nature of pet glaucoma.
Glaucoma affects the retina and optic nerve, causing painfully high pressure inside the eye. In dogs, glaucoma can develop extremely quickly and cause permanent vision loss if left untreated. It similarly strikes cats, though it may be more gradual.
Vets classify glaucoma as primary and secondary. Primary glaucoma, a genetic condition, can’t be prevented and is often breed-related. Burmese and Siamese cats are predisposed to it, while dozens of dog breeds are likelier to get it. Those include cocker spaniels, Boston terriers, huskies, Samoyeds, Chow Chows, Shiba Inus and beagles, among many others.
Secondary glaucoma has other causes inside the eye itself: inflammation, a blood disease, perhaps a tumor. This blog will focus on primary glaucoma, the more common version.
What Causes Glaucoma?
Think of the eye as a sink. Fluid (which doctors call aqueous humor) acts like a faucet, and the iridocorneal angle acts as the drain. In a healthy eye, ciliary bodies produce fluid, which drains at the same rate. When a pet has glaucoma, the drain clogs, but the faucet keeps producing fluid. That fluid builds up unnaturally, creating pressure inside the eye.
The excess fluid causes significant pain, similar to a migraine headache in humans. It may also produce vision loss by putting extra pressure on the optic nerve and damaging it. In extreme or advanced cases, the dog or cat may become completely blind.
The condition can’t be cured or reversed. (This is also true for people.) Because it develops so quickly and painfully, a pet owner should immediately consult an ophthalmologist after seeing abnormal eye-related behavior or appearance.
Pet owners should also ask primary care vets to examine a pet’s eyes at least once a year. When a breed is predisposed to glaucoma, that vet might also check eye pressure or refer you to a specialist.
Symptoms of Glaucoma
If you suspect your pet has an eye problem, look for clinical signs that might indicate glaucoma:
- Redness or cloudiness of the eye
- Squinting or excessive tearing
- Swelling of the eye
- General sense of not feeling well, marked by lethargy and lack of appetite
- Vision loss, often noticeable when the pet bumps into objects on the affected side or gets easily startled on that side
Diagnosing Glaucoma
Vets identify glaucoma by using an instrument that measures intraocular pressure, the level of pressure within the eye. A vet may also order a painless gonioscopy test, which looks at the drain in the eye to see if it is abnormal and at risk for glaucoma. If tests indicate abnormally high pressure, the vet will recommend treatment.
Medicated Drops for Glaucoma
Doctors initially treat most cases of primary glaucoma with medication. Commonly used drops decrease fluid production and increase drainage, and they’re effective in most cases.
Yet even when a patient responds well to medication — pressure goes down, vision stays steady — drops tend to be effective only for short periods, typically weeks to months. Glaucoma is a progressive disease; eventually, pressure will rise again and require more aggressive treatment.
Surgery for Glaucoma
Ophthalmologists with specialized training perform two kinds of surgeries at CARE, often combining them for optimal results. First, they use a laser procedure called endoscopic cyclophotocoagulation; they go inside the eye with a small probe that contains a light, a laser and a camera, zapping ciliary bodies that produce fluid — essentially, turning down the faucet. In the second surgery, an ophthalmologist places a gonioimplant valve/shunt, letting fluid drain via a different route.
The combination of these two surgeries has proven to help pets maintain good pressure in the eye for several years. If pressure rises again later, vets may be able to repeat the surgery to save your animal’s vision for a longer period of time.
Focusing on Your Pet’s Comfort
If glaucoma causes your pet to lose sight permanently, CARE doctors focus on comfort and quality of life. They evaluate three different options:
- Ciliary ablation, an injection inside the eye to “kill” the eye and control the pressure
- Complete removal of the eye
- A prosthetic eye. The pain’s gone, and for cosmetic reasons, the pet still appears to have two eyes.
Primary glaucoma is a genetic disease, so there’s no way to prevent it. But keeping an eye out for vision abnormalities may help keep secondary glaucoma and other ocular issues at bay.
Charlotte Animal Referral and Emergency is the animal equivalent of a human medical center. It’s open 24 hours a day, 365 days a year. CARE offers all types of treatment, from emergency attention to board-certified specialty work after you get a referral from your primary care veterinarian. Please take a visual tour of the practice at carecharlotte.com/tour.
