Glaucoma in Cats and Dogs: Causes and Treatment

Name: Glaucoma in Cats and Dogs: Causes and Treatment
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Glaucoma in cats and dogs is a serious eye disease caused by a buildup of fluid inside the eye that raises pressure and damages the optic nerve. Dogs get it far more often than cats, and the two species tend to show it differently. Treatment can control pressure and ease pain, but vision lost to glaucoma cannot be restored.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Glaucoma means the fluid inside the eye cannot drain normally, so pressure rises and damages the retina and optic nerve [1][2].
In dogs, glaucoma affects about 1.7% of the population in North America, and certain breeds are hit hardest [2].
In cats, glaucoma is less common and usually follows inflammation inside the eye or a tumor, though Siamese and Burmese cats can inherit a primary form [1][3].
Early signs include a dilated pupil that reacts slowly, red whites of the eyes, a cloudy or swollen cornea, and a firm eyeball [1].
Glaucoma is not reversible. By the time you notice signs, meaningful vision loss has often already happened, so same-day veterinary care matters [3].

What Is Glaucoma in Cats and Dogs?

The eye keeps its shape with a clear fluid called aqueous humor. This fluid is produced behind the lens and drains out through a network of tiny channels near the front of the eye. When production and drainage fall out of balance, fluid builds up and pressure inside the eye climbs to unhealthy levels [1][2].

That pressure presses on the retina and the optic disk, the spot where the optic nerve leaves the eye. The nerve tissue does not tolerate this well. Pressure kills nerve fibers, and the damage is permanent [1][2].

Veterinarians divide glaucoma into two broad types.

Primary glaucoma starts on its own, usually because of an inherited drainage problem. It is relatively rare in cats and often breed related [3]. In dogs, primary glaucoma is common in certain purebreds, and the frequency of breed-predisposed glaucoma in both eyes is the highest of any animal species except humans [2].

Secondary glaucoma happens because something else damaged the drainage system. This is the more common form in cats, where it usually follows inflammation of the anterior uvea or a tumor [1]. In dogs, secondary glaucoma can follow lens problems, inflammation, or trauma.

There is also a difference in how fast pressure rises. Open-angle glaucoma is a painless, gradual loss of vision over a long period [2]. Closed-angle glaucoma is a sudden spike in pressure with severe pain, redness, and rapid vision loss [2]. The sudden form is the emergency.

Glaucoma Symptoms in Pets: What Owners Notice

Owners often miss the early stage because pets adapt well and because the first eye to fail may not be obvious. Watch for these changes.

Signs you can see at home

A pupil that stays wide and moves slowly or not at all [1]
Redness in the whites of the eyes [1]
A cloudy, bluish, or discolored cornea, sometimes with swelling [1]
An eyeball that feels firm or hard when you gently touch the closed lid [1]
Bumping into furniture, hesitating on stairs, or startling easily
Squinting, pawing at the face, or avoiding bright light

How dogs and cats differ

Dogs with the sudden closed-angle form often show obvious pain. They may whine, refuse food, hold the eye shut, or become restless. The eye can look red and cloudy within hours [2].

Cats hide pain well. In cats, pain usually shows up as behavioral changes and occasional soreness around the eye instead of repeated winking [1]. A cat may simply seem quieter, eat less, or avoid being handled near the head. That quiet change is easy to dismiss, which is one reason feline glaucoma is often advanced at diagnosis.

If pressure stays high for a long time, the eyeball itself can stretch and enlarge, a condition called buphthalmos. The lens can shift out of place, and the cornea can develop breaks in its surface layer [1]. These are late changes and signal chronic, uncontrolled disease.

If your cat has red or bloodshot eyes, our guide to Why Is My Cat having bloodshot eyes? Uveitis Glaucoma and Trauma Guide walks through the common causes. Sudden blindness in a cat is a separate emergency, covered in Why Is My Cat suddenly going blind? Hypertensive Retinal Detachment and Uveitis.

Causes and Risk Factors

In dogs

Primary glaucoma in dogs is largely inherited. It is far more common in some purebred lines than in mixed-breed dogs, and it frequently affects both eyes over time [2]. Secondary glaucoma in dogs can follow cataracts, lens luxation, uveitis, or injury to the eye.

In cats

Most feline glaucoma is secondary. Inflammation of the anterior uvea and tumors are the leading triggers [1]. Primary open-angle glaucoma does occur on its own in cats, particularly in the Siamese breed [1]. Burmese and Siamese cats are among the predisposed breeds, and a cat with primary glaucoma will inevitably be affected in both eyes [3].

Lens instability is another route to glaucoma in cats. In one review of 34 cats with presumed primary lens instability, pressure was elevated above 25 mmHg in 38% of eyes overall, and 73% of subluxated lenses progressed to full luxation within a median of 15 days [4]. That is a fast timeline, which is why lens changes in cats deserve prompt attention.

Breed and age patterns

Breed predisposition is the single biggest risk factor in dogs [2]. In cats, breed matters mainly for the primary form, while any cat with chronic uveitis or an eye tumor is at risk for the secondary form [1]. Age varies widely. The cats in the lens instability review ranged from 1 to 13 years old, with a median of 3 years, and 82% were male [4].

How Glaucoma Is Diagnosed

Your veterinarian starts with the history and a hands-on eye exam. They will check how the pupil responds to light, look at the cornea and the inside of the eye, and compare the firmness of both eyes by touch.

The key measurement is intraocular pressure, or IOP. A small instrument called a tonometer touches the surface of the eye and gives a number. Normal pressure differs between dogs and cats, and your veterinarian interprets the reading alongside the exam findings. Pressure is measured in both eyes every time, because the second eye is often quietly affected.

Other tests your veterinarian may use:

Gonioscopy, which examines the drainage angle to see whether it is open or closed
Ophthalmoscopy, to look at the retina and optic disk for damage
Ultrasound, when the cornea is too cloudy to see through
Blood work and blood pressure, to look for underlying disease

Because glaucoma in cats is so often secondary, the search for a cause matters as much as the pressure reading. Uveitis, tumors, and lens problems all change the treatment plan. For a deeper look at feline eye conditions in general, see Feline Ocular Diseases: Common Conditions and Treatment.

Treatment Options for Glaucoma in Dogs and Cats

Treatment has two goals. The first is to lower pressure and protect whatever vision remains. The second is to control pain. Once the optic nerve is damaged, no treatment brings vision back [3].

Medical treatment

Medications lower pressure in two ways. Some reduce how much fluid the eye makes, and others help fluid drain out. Your veterinarian calculates the dose from your pet's weight and health, and many of these drugs are human eye drops used off label in pets.

Response differs by species. In a study of cats with congenital glaucoma, both latanoprost and latanoprostene bunod produced only transient pressure reduction, and neither drug significantly lowered pressure in normal cats [5]. A separate pilot study found that topical omidenepag isopropyl lowered pressure in both normal and glaucomatous cats, with a maximal drop of 16.7 mmHg in the glaucoma group, and it caused no significant pupil change or eye irritation [6]. These findings are why feline glaucoma is often harder to manage with drops alone than canine glaucoma.

Surgical treatment

When drops fail, surgery can help.

Laser procedures target the tissue that produces fluid. In a review of 22 eyes from 15 cats treated with diode endoscopic cyclophotocoagulation, successful pressure control at or below 30 mmHg was achieved in 86% of cases at three months and 94% at one year. Vision was present in 77% of cases at three months and 71% at one year [7]. Those numbers show that surgery can work in cats, though vision can still be lost over time.

Drainage implants route fluid away from the eye. In dogs with primary angle-closure glaucoma, researchers measured higher levels of transforming growth factor beta 2 and total protein in the aqueous humor of glaucomatous eyes compared with normal eyes, both before and after Ahmed valve surgery [8]. This kind of work helps veterinarians understand why implants sometimes scar over and stop working.

Removing the eye is the definitive option for a blind, painful eye that no longer responds to treatment [9]. It sounds drastic, but pets feel immediate relief once the source of chronic pain is gone. A recent case series described 11 dogs with chronic refractory glaucoma that had the eye removed and replaced with a custom 3D printed implant made of a biocompatible plastic. The implant matched the volume and weight of the natural eye, which helps the socket and eyelids keep a normal appearance [9].

A note on pain control

Glaucoma hurts. Even when vision cannot be saved, controlling pain is a valid and important goal. In one report of a Siberian tiger with advanced primary open-angle glaucoma and irreversible vision loss, the treatment goal shifted away from saving vision and toward comfort and quality of life [10]. The same principle applies to your dog or cat.

Feature	Dogs	Cats
How common	About 1.7% in North America [2]	Less common than in dogs [1]
Usual cause	Inherited primary glaucoma in predisposed breeds [2]	Often secondary to uveitis or tumor [1]
Pain signs	Obvious squinting, whining, restlessness in the sudden form [2]	Subtle behavior changes, occasional soreness [1]
Breed risk	Many purebred lines [2]	Siamese and Burmese [1][3]
Drop response	Often useful	Variable, sometimes only short lived [5][6]

Recovery, Outlook, and Long-Term Management

Glaucoma is a lifelong condition, not a one-time problem. Expect regular pressure checks, often every few weeks at first and then every few months once stable. Your veterinarian will recheck both eyes at every visit, because the second eye is at real risk, especially in dogs with the inherited form [2].

Realistic expectations matter. Glaucoma cannot be reversed, and by the time clinical signs appear, substantial vision loss has usually already occurred [3]. Treatment aims to preserve what is left and keep your pet comfortable. Some pets keep useful vision for years. Others lose vision despite good care.

At home, give every medication exactly as prescribed and on schedule. Missing doses lets pressure climb. Watch for the return of redness, cloudiness, or behavior changes, and call your veterinarian instead of waiting for the next appointment.

If vision is gone in one eye, most pets adapt well. Keep furniture in familiar places, talk to your pet before you touch them, and use night lights. A blind pet can still have an excellent quality of life.

For dogs specifically, our article on Canine Glaucoma: Diagnosis and Management goes deeper into breed screening and monitoring.

Prevention

You cannot prevent every case, but you can lower the odds of a late diagnosis.

Know your breed risk. If you own a breed with a known predisposition, ask your veterinarian about screening exams and pressure checks [2].
Treat uveitis promptly. In cats, inflammation of the anterior uvea is a leading cause of secondary glaucoma, so eye inflammation deserves a same-week visit [1].
Screen the second eye. In dogs with primary glaucoma, the other eye is at high risk, and early detection there gives the best chance of saving vision [2].
Follow up on lens problems. In cats with lens instability, most subluxated lenses progressed to full luxation within a median of 15 days, so these eyes need close monitoring [4].
Keep routine eye exams as part of your pet's yearly checkup, especially after age 6.

Limitations and When to Contact a Veterinarian

No article can tell you what is happening in your pet's eye. Pressure readings, breed, the cause of the glaucoma, and how long it has been present all change the plan. Your veterinarian sets the treatment and the dose for your individual pet.

Call an emergency clinic now if:

Your pet's eye is suddenly red, cloudy, or swollen
Your pet is squinting hard, crying, or pawing at the face
Your pet bumped into walls or seems to have lost vision in minutes to hours
The eyeball looks larger than the other one

Call for a same-day appointment if:

You notice a dilated pupil that reacts slowly to light
One or both eyes look red without discharge
Your pet seems quieter, hides more, or flinches when the head is touched
Your pet has a known eye condition and the medications are running low

Bring it up at the next routine visit if:

Your pet is a breed with known glaucoma risk and has not had a pressure check
Your pet has had uveitis before and seems fine now
You have noticed mild cloudiness that comes and goes

Frequently Asked Questions

Can glaucoma in dogs and cats be cured?

No. The nerve damage caused by high pressure is permanent, and the condition is not reversible [3]. Treatment controls pressure, slows further damage, and manages pain, but it does not restore lost vision.

Will my pet go blind?

Not always, but the risk is real. By the time signs are noticed, substantial vision loss has often already occurred [3]. With early treatment, some pets keep useful vision for a long time, while others lose it despite care.

Is glaucoma painful for pets?

Yes, especially the sudden closed-angle form, which causes severe pain along with redness and vision loss [2]. Cats tend to hide eye pain and show it through behavior changes instead of obvious squinting [1].

Does my pet need the eye removed?

Only if the eye is blind, painful, and no longer responds to treatment. Removal is a definitive way to relieve pain in advanced glaucoma [9]. Some pets can have the eye replaced with an implant to keep a normal appearance [9].

Can the other eye be saved?

Often yes, if you act early. In dogs with inherited glaucoma, the second eye is at high risk, and regular pressure checks give the best chance of catching it before vision is lost [2]. In cats with primary glaucoma, both eyes are inevitably affected [3].

If your cat has a red or irritated eye, our guide to Cat Conjunctivitis Treatment Pets At Home covers the milder causes, but any eye that is firm, cloudy, or painful needs a veterinarian the same day.

References

Glaucoma in Cats - Cat Owners. Merck Veterinary Manual.
Glaucoma in Dogs - Dog Owners. Merck Veterinary Manual.
Feline Glaucoma. Cornell University College of Veterinary Medicine.
Clinical Features and Surgical Outcomes of Cats With Presumed Primary Lens Instability: A Retrospective Study of 34 Cases (2018-2022). Veterinary ophthalmology, 2026.
Effects of 0.024% latanoprostene bunod on intraocular pressure and pupil diameter in normal cats and cats with congenital glaucoma. Veterinary ophthalmology, 2026.
Topical Omidenepag Isopropyl Lowers Intraocular Pressure in Normal and Glaucomatous Cats: A Pilot Study. Veterinary ophthalmology, 2026.
Retrospective Evaluation of Surgical Outcomes in Cats With Glaucoma Following Diode Endoscopic Cyclophotocoagulation. Veterinary ophthalmology, 2026.
A Pilot Investigation of Transforming Growth Factor-β2 and Total Protein Concentrations in Aqueous Humor of Canine Glaucomatous Eyes With and Without Ahmed Glaucoma Valve Surgery. Veterinary ophthalmology, 2026.
3D printed eyeball implants in dogs with advanced glaucoma: a case series study. Frontiers in veterinary science, 2025.
Glaucoma in a Siberian Tiger (Panthera tigris altaica) Maintained Under Human Care: A Case Report. Animals : an open access journal from MDPI, 2026.