Corneal ulcer in dogs

Recognise the signs

• Squinting or keeping the eye partially or fully closed (blepharospasm)
• Excessive tearing or watery discharge from one eye
• Mucopurulent (yellow-green) discharge if secondary infection is present
• Pawing at the eye or rubbing the face on furniture or carpet
• Cloudiness or haziness of the cornea (the clear front of the eye)
• Redness of the white of the eye (conjunctival hyperaemia)
• Reluctance to go into bright light (photophobia)
• A visible scratch, dent, or whitish spot on the corneal surface
• Swelling of the eyelids
• In severe cases: a dark or reddish spot on the cornea (possible perforation or iris prolapse — emergency)

First aid steps

1. 1. Fit a buster (Elizabethan) collar immediately to prevent the dog from rubbing or pawing at the eye, which worsens the ulcer and risks perforation.
2. 2. Do not touch or attempt to examine the eye yourself beyond gentle observation.
3. 3. If you can see an obvious foreign body on the surface — such as a grass seed or grit — do not try to remove it yourself; you risk embedding it deeper.
4. 4. Phone your vet and arrange a same-day appointment.
5. 5. If the dog is in obvious pain, the eye is bulging, or there is a dark/brown spot on the cornea, treat as an emergency and contact an emergency vet.
6. 6. Do not apply any eye drops, creams, or ointments — especially do not use any product containing corticosteroids (steroids), which can dramatically worsen a corneal ulcer.
7. 7. Keep the dog out of wind and direct sunlight, both of which cause discomfort.
8. 8. Prevent the dog from swimming or getting water in the eye.

While transporting to the vet

• Keep the buster collar on throughout transport.
• Keep the dog calm and prevent head shaking.
• Avoid drafts — close windows near the dog's head.
• Do not let the dog hang its head out of the window.
• Phone ahead so the vet knows to prepare ophthalmology equipment including fluorescein stain.

When it can usually wait

• There are no signs of a possible corneal ulcer that can safely wait — all cases require same-day assessment. However, if signs are extremely mild (very slight squinting, no cloudiness, no discharge) and only appeared in the last hour, a phone consultation first thing in the morning may be acceptable — but err on the side of being seen today.

Common causes

• Trauma — the most common cause; scratch from a cat claw, grass seed, thorn, or rough play
• Grass seeds (grass awns) — penetrate the eye surface and can migrate; common in summer
• Dry eye (keratoconjunctivitis sicca, KCS) — reduced tear production damages the corneal surface
• Brachycephalic anatomy — dogs with protruding eyes have reduced blink reflex, reduced corneal sensation, and greater exposure to trauma
• Entropion — inward-rolling eyelids that cause lashes to rub the corneal surface
• Distichiasis — abnormal eyelash growth from the eyelid margin
• Foreign body under the eyelid — sand, grit, plant material
• Bacterial or viral infection (e.g., canine herpesvirus)
• Spontaneous chronic corneal epithelial defect (SCCED, or Boxer ulcer) — a specific indolent ulcer type common in Boxers

What the vet will need to know

• When did the signs start and did they appear suddenly?
• Any known trauma — a cat scratch, walk through long grass, rough play?
• Has the dog been diagnosed with dry eye (KCS) previously?
• Any existing eye conditions or previous eye surgery?
• What eye drops or medications is the dog currently using?
• Is only one eye affected?
• Is the dog vaccinated? (relevant to rule out canine herpesvirus in puppies)
• Breed of dog — important context for brachycephalic breeds

Aftercare

• The vet will confirm the ulcer using fluorescein stain (an orange dye that highlights damaged corneal tissue under blue light) and assess depth.
• Treatment typically involves antibiotic eye drops or ointment, artificial tear supplementation, and atropine drops to reduce pain from ciliary spasm.
• Keep the buster collar on for the entire treatment period — this is critical.
• Administer eye drops exactly as prescribed — missed doses slow healing.
• Attend all follow-up appointments — the vet will repeat the fluorescein test to confirm healing.
• Deep or complicated ulcers may require surgical intervention (e.g., conjunctival graft, corneoconjunctival transposition).
• For SCCED (Boxer ulcers) — a debridement procedure under local anaesthetic may be needed to remove the non-adherent epithelium.
• If KCS is the underlying cause, lifelong ciclosporin or tacrolimus eye drops will be prescribed to stimulate tear production.

Prevention

• Check the dog's eyes after every walk through long grass, woodland, or rough terrain — particularly in summer.
• Keep grass in the garden well mown and avoid areas with ripe grass seed heads.
• Protect brachycephalic dogs' eyes from trauma — avoid rough play with dogs with claws, and be cautious near branches.
• Treat underlying conditions such as dry eye or entropion as recommended by your vet.
• Apply artificial tear gel before walks in dusty or windy conditions for dogs with KCS.
• Regular veterinary eye checks for brachycephalic breeds and breeds prone to KCS.

Breed-specific notes

• Pugs, French Bulldogs, English Bulldogs, Shih Tzus, Lhasa Apsos, Cavalier King Charles Spaniels, Pekingese — exophthalmic (protruding) eyes with reduced blink reflex; corneal ulcers deteriorate rapidly and are prone to melting ulcers requiring emergency referral.
• Boxers — prone to SCCED (spontaneous chronic corneal epithelial defects, also called Boxer ulcers); these are indolent, slow-healing ulcers that often require debridement.
• West Highland White Terriers, Cocker Spaniels — higher incidence of dry eye (KCS).
• Shar-Peis — prone to entropion causing chronic corneal irritation.

Frequently asked questions

Related topics

• Dog with an eye injury
• Grass seed in dog's paw, ear, eye, or nose