What is glaucoma in dogs?

Glaucoma is elevated intraocular pressure (IOP) above normal values (12-25 mmHg in dogs). High pressure damages the optic nerve and retina, causing intense pain and — without urgent treatment — permanent blindness within hours or days.

What are the symptoms of canine glaucoma?

Very red eye (scleral/conjunctival hyperaemia), obvious pain (rubbing the eye, head held low), dilated pupil that does not respond to light, cloudy or bluish cornea, and enlarged globe (buphthalmos) in chronic cases.

Is glaucoma in dogs always permanent?

If treated within the first few hours, vision can be preserved. More than 24-48 hours with very high IOP causes irreversible retinal and optic nerve damage. This is why it is a veterinary ophthalmic emergency.

Which dog breeds are most at risk of glaucoma?

Chow Chow, Basset Hound, Cocker Spaniel, Shiba Inu, Shar Pei, Samoyed and Beagle. Also Flat-Coated Retriever and Dalmatian. Primary glaucoma has a strong hereditary component in these breeds.

Dog Glaucoma: Symptoms, Treatment and Preventing Blindness

What Is Canine Glaucoma?

The eye constantly produces aqueous humour that drains through the iridocorneal angle. When drainage fails, intraocular pressure (IOP) rises — that's glaucoma. Elevated pressure crushes the retinal ganglion cells and optic nerve fibres, producing intense pain and vision loss that can become permanent within hours.

Types

Primary: malformation of the drainage angle — hereditary cause. Usually bilateral (the other eye develops glaucoma within months to years).
Secondary: consequence of another eye disease (uveitis, lens luxation, tumour, trauma). May be unilateral.

Symptoms — Recognising the Emergency

Very red eye (scleral/conjunctival hyperaemia) — the most striking sign.
Cloudy or bluish cornea (corneal oedema from pressure).
Dilated pupil that does not constrict with light.
Obvious pain: the dog rubs the eye, keeps their head low, refuses to be touched near the eye.
Lacrimation or discharge.
Buphthalmos (enlarged globe): sign of chronic established glaucoma.

⚠️ If your dog has a very red eye with signs of pain, go to the vet within hours — do not wait until the next morning.

Diagnosis

Tonometry (IOP measurement) with a rebound or applanation tonometer. IOP >30 mmHg with clinical signs = glaucoma. The ophthalmologist will also perform gonioscopy (evaluate the drainage angle) and fundoscopy (assess the optic nerve).

Treatment

Acute emergency:

IV mannitol: hyperosmotic agent, reduces IOP within 30-60 minutes.
Eye drops: dorzolamide + timolol (reduce aqueous production), latanoprost (miotic, increases drainage).

Maintenance (if vision is preserved):

Combined hypotensive eye drops (dorzolamide-timolol, latanoprost) lifelong.
Surgery: drainage tube implant (Ahmed valve), laser cyclophotocoagulation.

Blind, painful eye: enucleation (removal of the eye) or intrascleral gentamicin injection. Enucleation eliminates pain and dogs adapt perfectly to monocular vision.

Protecting the Other Eye

In predisposed breeds, the fellow eye is at high risk. Many ophthalmologists recommend starting preventive treatment (latanoprost once daily) in the healthy eye from the time of the first eye's diagnosis.