CONDITION

Glaucoma

Why this matters now

Glaucoma involves elevated pressure within the eye and is one of the most painful eye conditions in dogs. Certain breeds have a genetic predisposition, including Cocker Spaniels, Basset Hounds, Beagles, and Arctic breeds like Siberian Huskies. Glaucoma can be primary (inherited) or secondary to other eye conditions. The condition may be present from middle age onwards in predisposed breeds.

Acute glaucoma develops rapidly, causing sudden severe pain and vision loss. Pressure elevation damages the retina and optic nerve, with irreversible damage occurring within hours to days if untreated. Chronic glaucoma may develop more insidiously, with gradual vision loss. Once one eye is affected by primary glaucoma, the other eye carries significant risk of developing the condition as well.

Signals & patterns

Early signals

Red, painful eye

The white of the eye appears intensely red, and the animal shows signs of discomfort.

Squinting or holding the eye closed

Pain causes reluctance to keep the affected eye open.

Cloudiness of the cornea

Elevated pressure causes fluid accumulation in the cornea, creating a hazy blue appearance.

Dilated, non-responsive pupil

The pupil appears enlarged and may not constrict normally in bright light.

Later signals

Enlargement of the eyeball

Prolonged pressure elevation stretches the eye, making it appear larger than normal (buphthalmos).

Visible lens displacement

The lens may shift from its normal position as supporting structures stretch.

Apparent vision loss

Bumping into objects or hesitancy in unfamiliar environments indicates visual impairment.

Lethargy or behaviour change

Chronic pain affects overall demeanour and activity levels.

Click to read about the biological mechanisms

How this is usually investigated

Diagnosis relies on measuring intraocular pressure and assessing the eye for underlying causes. Evaluation of the other eye helps assess bilateral risk.

Tonometry

Purpose: To measure intraocular pressure and confirm elevation
Considerations: Various devices measure pressure by touching the cornea briefly. Normal dog pressures are typically below 25 mmHg. Glaucomatous eyes often have pressures of 30-50 mmHg or higher.

Gonioscopy

Purpose: To examine the drainage angle and assess its structure
Considerations: A special lens allows visualisation of the iridocorneal angle. Narrow or closed angles indicate primary glaucoma risk.

Ophthalmoscopy

Purpose: To examine the retina and optic nerve for damage
Considerations: Changes to the optic nerve head indicate pressure damage. Retinal changes help assess visual potential.

Ultrasound of the eye

Purpose: To assess internal structures when the cornea is too cloudy for direct examination
Considerations: Identifies lens luxation, tumours, or other abnormalities contributing to pressure elevation.

Assessment of the unaffected eye

Purpose: To evaluate risk of glaucoma developing in the other eye
Considerations: Dogs with primary glaucoma in one eye have approximately 50% chance of developing it in the other eye within two years.

Options & trade-offs

Treatment aims to reduce intraocular pressure, preserve vision where possible, and ensure comfort. Approach depends on whether the eye retains visual potential.

Emergency pressure reduction

Intravenous or topical medications to rapidly lower intraocular pressure.

Trade-offs: Necessary for acute glaucoma. Time is critical for preserving vision. Hospitalisation may be required for aggressive treatment.

Topical medications

Eye drops to reduce fluid production or improve drainage.

Trade-offs: Ongoing treatment for maintaining pressure control. Multiple medications may be needed. Requires consistent daily application.

Laser or surgical procedures

Techniques to improve drainage or reduce fluid production.

Trade-offs: Various procedures available at specialist centres. May provide longer-term control than medications alone.

Prophylactic treatment of the unaffected eye

Preventive medication to delay or prevent glaucoma in the at-risk eye.

Trade-offs: May extend the time before the second eye develops glaucoma. Benefit varies between individuals.

Enucleation or intrascleral prosthesis

Removal of a blind, painful eye or placement of an implant for cosmetic appearance.

Trade-offs: Appropriate for eyes that have lost vision and remain painful. Provides permanent pain relief. Dogs adapt well to life with one eye.

Common misconceptions

Misconception:

"A red eye is not serious"

Reality:

Redness can indicate glaucoma, which causes severe pain and rapid vision loss. Differentiating glaucoma from other causes of red eye is important for appropriate management.

Misconception:

"Vision loss from glaucoma can be reversed"

Reality:

Damage to the retina and optic nerve from pressure elevation is typically permanent. Treatment aims to preserve remaining vision and prevent further damage.

Misconception:

"Removing a blind eye is cruel"

Reality:

Chronically elevated pressure is extremely painful. Removing a blind, painful eye significantly improves quality of life and is a kindness rather than cruelty.

Being aware of breed predispositions helps with early recognition of signs. Noting any changes in eye appearance, including redness, cloudiness, or apparent size difference between eyes, aids early detection. Understanding that eye pain may cause subtle behaviour changes rather than obvious distress helps with recognition. Baseline eye examinations may be valuable in predisposed breeds.

Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS