A Complete Guide to Canine Glaucoma Symptoms and Treatment

Eye HealthQ&AMeongsiljang Veterinary Advisory Board

Glaucoma in dogs is an emergency eye condition where increased intraocular pressure damages the optic nerve. Here’s a clear overview of symptoms, emergency criteria, and treatment options.

What Is Glaucoma in Dogs?

Illustration of the structural causes of increased intraocular pressure in canine glaucoma

Glaucoma in dogs is an emergency eye condition in which abnormally high intraocular pressure damages the optic nerve and retina, potentially leading to blindness. Time is of the essence. In acute glaucoma, where intraocular pressure rises rapidly, vision can be lost within just a few hours. If one eye suddenly becomes red and cloudy, seek veterinary care immediately. Never wait until the next day.

Why Does Intraocular Pressure Rise? Causes of Glaucoma

The inner part of the eye maintains a steady pressure through the continuous production and drainage of a clear fluid called aqueous humor. When the drainage pathway becomes blocked, this fluid accumulates, causing intraocular pressure to rise. Canine glaucoma is broadly categorized into two types. Primary glaucoma occurs in breeds with genetically narrow drainage structures, while secondary glaucoma develops as a result of uveitis, lens luxation, tumors, or complications from cataracts.

Comparison of Glaucoma by Breed and Type

First, check whether your pet belongs to a breed at high risk for glaucoma. Primary glaucoma occurs much more frequently in certain breeds, and if one eye is affected, the other eye can develop the condition sequentially, so both eyes require ongoing, careful monitoring.

Characteristics of Each Glaucoma Type

Item	Primary glaucoma	Secondary glaucoma
Cause	Genetic drainage angle abnormality	Uveitis · lens luxation · tumor
High-risk breeds	Cocker Spaniel, Basset Hound, Boston Terrier, Shar-Pei	Regardless of breed
Onset pattern	Both eyes may develop sequentially	Only the eye with the underlying condition
Progression speed	Often acute onset	Varies by cause
Prognosis	Preventive treatment of the other eye needed	Treating the underlying condition is key

This is the general classification per veterinary ophthalmology textbooks.

Suspect Glaucoma If You See These Symptoms

Glaucoma is easy to miss because its early symptoms resemble those of other eye conditions. Use the checklist below to assess your pet’s eyes.

Severe redness: The whites of the eyes appear red, and the blood vessels look enlarged.

Corneal cloudiness: The black part of the eye becomes hazy or cloudy.

Pupil dilation: One pupil is larger than the other and reacts slowly to light.

Bulging eye: The eyeball itself appears enlarged or protruding.

Signs of pain: Frequent eye rubbing, light avoidance, and decreased appetite.

Vision loss: Bumping into furniture or failing to track a moving hand.

A puppy's eye with redness and corneal clouding

Go to the Vet Immediately If You See These Signs

If any of the following signs are present, it’s an emergency. In glaucoma, vision can be determined within just a few hours. • One eye suddenly becomes red and appears enlarged. • The pupil is dilated and does not respond to light. • The pet rubs its eyes and presses its face against the floor. • The pet appears dazed or refuses to eat. In acute glaucoma, intraocular pressure can spike within hours, causing permanent damage to the optic nerve. Even on weekends or at night, please visit a 24-hour veterinary clinic immediately.

How Glaucoma Is Diagnosed at the Vet

Diagnosing glaucoma centers on measuring intraocular pressure. Your veterinarian will use a tonometer to measure the pressure inside the eye, with the treatment goal being to lower and maintain that pressure within the normal range for your pet’s species. If intraocular pressure remains elevated beyond the normal range, it can damage the optic nerve and retina and cause pain. During acute attacks, the pressure can rise even higher. In addition to pressure measurement, your vet will perform tests to check for remaining vision, such as the direct pupillary light reflex and menace response, as well as gonioscopy to examine the drainage angle of the aqueous humor and fundic examination to assess the extent of retinal and optic nerve damage. Distinguishing between primary and secondary glaucoma is the first step in determining the appropriate treatment plan.

A veterinarian measuring a dog’s intraocular pressure with a tonometer

How Is Glaucoma Treated?

The treatment goals are to rapidly lower intraocular pressure and to preserve vision as much as possible.

Emergency medical therapy: Intraocular pressure is urgently reduced using intravenous mannitol (an osmotic diuretic) and intraocular pressure-lowering eye drops.

Maintenance eye drops: Long-term management is achieved by reducing aqueous humor production with carbonic anhydrase inhibitor (CAI) eye drops, such as dorzolamide or brinzolamide.

Surgical treatment: If medication fails to control the condition, options such as endoscopic cyclophotocoagulation (ECP) or implantation of an aqueous drainage device may be considered.

Enucleation: If the eye has already lost vision and the patient is experiencing severe pain, enucleation or chemical cycloablation may be chosen to relieve pain.

The specific medications and dosages are determined by your veterinarian based on your pet’s individual condition and intraocular pressure.

Be Sure to Provide Preventive Treatment for the Other Eye

Primary glaucoma often affects the other eye after it develops in one, so we proactively prescribe preventive eye drops for the unaffected eye to help lower intraocular pressure. Please don’t hesitate to use them just because the eye looks healthy—follow your veterinarian’s instructions and apply the prescribed drops without missing a dose. Consistency is key, so try to administer the drops at the same time each day.

Be Sure to Follow These Points When Managing at Home

Stick to the eye drop schedule: If the eye drops are prescribed every 12 hours, administer them at exactly the same times each day, such as 8 AM and 8 PM.

Use a harness instead of a collar: Pulling on a collar can cause a sudden spike in intraocular pressure. Please use a harness when walking your pet.

Minimize excitement: Excessive barking or sudden, vigorous movements can also raise intraocular pressure.

Regular recheck appointments: Intraocular pressure should be rechecked at least once a month.

Monitor the other eye: Check daily for early warning signs such as redness or pupil dilation.

A dog wearing a harness and going for a walk

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can glaucoma in dogs be cured?

Unfortunately, primary glaucoma is difficult to cure and requires lifelong management. However, if detected early and treated consistently with eye drops, vision can be preserved for a longer period, and pain can be effectively controlled.

Can I use human glaucoma eye drops?

Absolutely not. Dog eye drops contain ingredients that are unsuitable for cats, and the dosage differs as well. You should only use eye drops prescribed by a veterinarian, and it’s important to follow the correct application method and sequence.

How should I care for an eye that has already lost its vision?

Even if the eye is blind, high intraocular pressure can cause severe pain. In such cases, pain-relieving eye drops may be used continuously, or if the pain is not well controlled, options such as enucleation (removal of the eye) or intravitreal injections to reduce aqueous humor production may be considered. Please consult with your veterinarian and make a decision that prioritizes your pet's quality of life.

Is it possible to prevent glaucoma?

Primary glaucoma has a strong genetic component, making complete prevention difficult. However, for high-risk breeds, the most effective preventive measure is to have regular ophthalmic exams once or twice a year and to ensure that secondary causes such as uveitis and cataracts are not left untreated.

How does a dog’s quality of life change if it becomes blind in both eyes?

Dogs have highly developed senses of smell and hearing, so they often adapt well even after losing their sight. By keeping furniture in the same place, using rugs to mark boundaries on the floor, and maintaining a consistent walking route, they can live comfortably with minimal inconvenience.

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References

[1] Gelatt KN, Veterinary Ophthalmology, 6th Edition, 2021

[2] Maggs DJ et al., Slatter's Fundamentals of Veterinary Ophthalmology, 6th Ed, 2018

[3] Notes on Canine Internal Medicine, 4th Edition, Chapter on Ocular Disorders