Glaucoma in dogs is a build-up of fluid pressure inside the eye that damages the retina and optic nerve. It is painful, it can cause permanent blindness, and a sudden red, cloudy or swollen-looking eye with a wide pupil should be treated as an emergency: call your vet or an emergency clinic the same day. Slow, "open-angle" forms are quieter and easier to miss, which is why knowing the early signs matters for Canadian dog owners from Vancouver to Halifax.
What is glaucoma in dogs?
The eye constantly makes a clear fluid (aqueous humour) and drains it out through a narrow angle at the edge of the iris. Glaucoma happens when production and drainage fall out of balance, so pressure climbs to a level that injures the retina and optic nerve. The Merck Veterinary Manual describes two broad patterns: a slow, often painless loss of vision (open-angle), and a sudden pressure spike with severe pain, red eyes and vision loss (closed-angle).
Glaucoma is also either primary (an inherited drainage problem, common in purebreds) or secondary (pressure raised by another problem such as uveitis, a displaced lens or a tumour). Secondary glaucoma is one reason a vet looks at the whole eye rather than only the pressure reading.
Signs of glaucoma in dogs
Early signs are subtle. Later signs are not. Watch for:
- Early: a slightly enlarged or sluggish pupil, faint redness or engorged veins on the white of the eye, mild eye enlargement, or "off" behaviour such as hiding or head-shyness on one side.
- Advanced: a bluish or cloudy cornea, a firm or bulging eyeball, a dilated pupil that barely reacts to light, obvious redness, and bumping into furniture.
- Pain: usually shows up as behaviour change (lethargy, appetite loss, pawing the face) rather than constant squinting.
Redness and cloudiness have many causes, so compare with our guides to why dogs' eyes are red and dog cloudy eye. If one eye looks different from the other, do not wait to see whether it passes.
Which dogs are most at risk?
A large North American hospital-database study (Gelatt and MacKay, 2004) found the prevalence of breed-related glaucoma rose from 0.29% in 1964–1973 to 0.89% in 1994–2002. In that last period, the highest rates were in the American Cocker Spaniel (5.52%), Basset Hound (5.44%), Chow Chow (4.70%) and Shar-Pei (4.40%), followed by the Boston Terrier, Wire Fox Terrier, Norwegian Elkhound, Siberian Husky, Cairn Terrier and Miniature Poodle. Most breeds were first diagnosed between 4 and 10 years of age.
Genetics plays a role: a variant in the ADAMTS10 gene is considered the likely cause of open-angle glaucoma in Beagles (Kuchtey et al., 2013). If you share your life with a high-risk breed, ask your vet whether routine eye-pressure checks (tonometry) make sense at annual exams.
Types of glaucoma at a glance
| Type | Onset | What owners notice | Urgency |
|---|---|---|---|
| Closed-angle (primary) | Sudden | Red, painful, cloudy eye; wide pupil; vision loss | Emergency: same day |
| Open-angle (primary) | Gradual | Subtle pupil change, slow vision loss, often little pain early on | Book a vet exam promptly |
| Secondary | Varies | Signs of the underlying problem (inflammation, lens change) plus pressure signs | Same-day to urgent |
How do vets diagnose and treat glaucoma?
Diagnosis centres on measuring intraocular pressure with a tonometer, plus an exam of the pupil, cornea and the drainage angle. Because the cause matters, many Canadian general practices refer to a board-certified veterinary ophthalmologist.
Treatment aims to lower pressure quickly and then keep it stable. According to Merck, that usually means medications that draw fluid out or reduce fluid production, often combined with surgery or long-term drops depending on the type. A blind, enlarged, painful eye may be removed for comfort. Our guide to dog cataract surgery cost explains how specialist eye-care fees tend to be structured, and uveitis in dogs covers one common cause of secondary glaucoma.
What about the other eye?
A 2025 multicentre study of 117 dogs with primary angle-closure glaucoma in one eye found that 70.9% developed glaucoma in the second eye within 5 years, with a median time of 2.15 years. No prophylactic drop regimen tested was clearly better than another. Practically, this means a healthy-looking second eye still needs regular monitoring, so keep those recheck appointments (Donohue et al., 2026).
What not to do at home
- Do not wait overnight "to see if it clears up" when the eye is red, cloudy or painful.
- Do not use human redness-relief drops; they do not address pressure and can mask worsening signs.
- Do not use leftover prescription drops from another pet or condition.
- Do not press or massage the eye.
A squinting dog is a different but equally urgent picture; see dog squinting one eye and dog eye ulcer for the differentials a vet will consider.
Daily eye hygiene alongside veterinary care
Once your vet has diagnosed and started treatment, gentle daily hygiene keeps the lids and surrounding fur clean while you manage medication. A sterile, pH-matched rinse is a sensible support step. Pure Majesty Pets Dog Eye Drops are ophthalmic-grade, sterile-filtered (10 micron), pH 7.0–7.2 to match natural tears, and made in Canada with sodium hyaluronate 0.05%, chamomile 2%, aloe vera 8% and sodium phytate 0.15%. Plain saline contains none of those. They are non-medicated hygiene drops: they do not lower eye pressure or treat glaucoma, and they never replace your vet's prescribed medication. Ask your vet before adding any new product to an eye being treated for glaucoma. Shipping is free worldwide.
For the full picture of infections, discharge and when to escalate, read our pillar guide on dog eye infection warning signs, or browse the full Pure Majesty Pets eye-care range.
Frequently asked questions
Is glaucoma in dogs painful?
Yes, especially when pressure rises quickly. Pain often appears as lethargy, hiding, reduced appetite or rubbing the face rather than obvious squinting.
Can a dog go blind from glaucoma?
Yes. High pressure damages the retina and optic nerve, and the damage can be permanent, which is why fast treatment matters.
Can glaucoma in dogs be cured?
Current care focuses on lowering pressure and keeping it controlled with medication and sometimes surgery, rather than a one-time cure. Your vet or ophthalmologist will set the plan.
Will my dog's other eye get glaucoma too?
It is common in primary angle-closure glaucoma: one 2025 study found 70.9% of dogs developed it in the second eye within 5 years. Regular pressure checks are recommended.
Are eye drops from the pet store safe for glaucoma?
Non-medicated rinses can support hygiene but do not treat glaucoma. Only prescription medication prescribed by your vet lowers eye pressure.
Scientific References
- Gelatt KN, MacKay EO. Prevalence of the breed-related glaucomas in pure-bred dogs in North America. Vet Ophthalmol. 2004;7(2):97-111. PMID 14982589.
- Kuchtey J, et al. Screening ADAMTS10 in dog populations supports Gly661Arg as the glaucoma-causing variant in beagles. Invest Ophthalmol Vis Sci. 2013;54(3):1881-6. PMID 23422823.
- Donohue LK, et al. Factors influencing the incidence and onset of primary angle-closure glaucoma in the unaffected eye of dogs. Vet Ophthalmol. 2026;29(1):e70038 (Epub 2025). PMID 40485308.
- Merck Veterinary Manual (pet owner version). Glaucoma in Dogs.
This article is for informational purposes and is not veterinary advice. A red, cloudy, painful or enlarged eye is an emergency: contact your veterinarian or nearest emergency clinic immediately. Talk to your veterinarian before starting any product, especially if your dog is pregnant, nursing, on medication, or has a diagnosed condition.