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Corneal ulcer in cats
The cornea is the transparent window located at the front of the eye. An ulcer is a loss of its surface layer, like a scratch on a windshield. It is a very painful injury because the cornea is one of the most richly innervated tissues in th...
What is it?
The cornea is the transparent window located at the front of the eye. An ulcer is a loss of its surface layer, like a scratch on a windshield.
It is a very painful injury because the cornea is one of the most richly innervated tissues in the body.
An ulcer can remain superficial and heal in a few days, or deepen and threaten the eye in a few hours. It is this possible development that makes it an emergency.
Key point
A painful, red or closed eye is an ophthalmological emergency. An ulcer can deepen within a few hours and cause loss of vision in that eye.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Eye held closed or incessant blinking.
Profuse tearing, first clear then sometimes thick.
Marked redness of the white of the eye.
Clear pain: the cat avoids contact with the head, hides, eats less.
Cloudy, grayish or bluish area on the surface of the eye; sometimes a hollow visible in raking light.
Discomfort to light, cat who seeks darkness.
In deep forms, the surface of the eye may appear distorted and vision on that side diminish.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Direct trauma: claw scratch during a fight, bramble, piece of litter, toy, friction against a rough surface.
Foreign body stuck under an eyelid or behind the third eyelid.
Infection with feline herpesvirus, which can directly attack the cornea and cause characteristically shaped ulcers, which often recur.
Failure to produce tears or eyelids that close poorly, leaving the cornea to dry out.
Eyelashes or hairs constantly rubbing against the eye, especially in flat-faced breeds.
Irritant product projected into the eye.
Bacterial superinfection of an initially benign lesion, which can deepen the ulcer very quickly.
Cats going outside and exposed to fights.
Breeds with flattened faces such as the Persian and the exotic shorthair: protruding eyes, blinking less effectively, tears poorly evacuated.
Cats carrying feline herpesvirus.
Older or weakened cats, whose healing is slower.
Use of eye drops containing a corticosteroid without prior examination.
Households with several cats, where scratching is more frequent.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian assesses the pain, examines the eyelids and looks for a foreign body.
The fluorescein test is the key test: the dye attaches to the area lacking its surface layer and makes the ulcer visible, even when it is tiny.
The depth of the lesion is assessed, because it determines the treatment and urgency.
A sample for bacteriological analysis is taken when the ulcer is deep, dirty or does not heal.
Tear production is measured if dry eye is suspected.
Close checks are scheduled: an ulcer must be reassessed, it cannot be treated blindly.
Treatment
The principle is to protect the cornea, fight against infection and calm pain during healing.
A local antibiotic is prescribed to avoid or treat secondary infection, often with frequent applications.
Analgesics are given systemically: the pain from an ulcer is intense and should not be neglected.
An antiviral is added when herpesvirus is the cause.
A collar is essential to prevent the cat from aggravating the lesion by rubbing.
Deep, perforated, or non-healing ulcers may require surgery to strengthen the cornea.
No eye drops containing a corticosteroid should be applied to an ulcer: it slows down healing and can lead to perforation of the eye. This is why eye drops prescribed for another condition, or for another animal, should never be reused on your own initiative.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Have any red, closed or watery eyes examined quickly before the lesion deepens.
Limit fights: sterilization, supervised outings, separation of cats who don't get along.
Monitor the eyes of flat-faced breeds closely and report any changes.
Never use eye drops without a prescription for the current episode.
Follow the entire treatment and follow-up visits, even if the eye seems to be doing better.
Choose low-dust litter for cats prone to irritation.
Possible complications
Deepening of the ulcer to the internal layers, with risk of perforation of the eye.
Infection deep in the eye, very difficult to control.
Opaque scar leaving a permanent stain on the cornea and hindering vision.
Evolution towards a corneal sequestrum, brown lesion specific to cats.
Loss of the eye in the most serious cases, with the need for surgical removal.
When to see a veterinarian
Your cat keeps one eye closed or blinks constantly: consult the same day.
The eye is so painful that the cat hides or refuses to be touched.
A cloudy, bluish or sunken area appears on the surface of the eye.
The appearance of the eye changes within a few hours.
The cat was scratched in the face during a fight.
The signs reappear after stopping treatment.
Liquid is leaking from an area of the cornea where the eye appears deformed: immediate emergency.
Prognosis
A superficial ulcer treated quickly most often heals within a few days, without significant after-effects.
Deep, infected or herpesvirus-related ulcers require longer treatment and sometimes leave a scar.
The factor that weighs the most on the prognosis is the delay: each day of waiting increases the risk of complications and loss of vision.
Frequently asked questions
How do I know if my cat has an ulcer and not simple conjunctivitis?
You can't reliably tell with the naked eye, and that's the problem. Only the fluorescein test, carried out in consultation, makes the difference, and this difference changes the entire treatment.
Can I use the eye drops the vet gave me last year?
No, never. If it contains a corticosteroid, it can transform a benign ulcer into a perforation of the eye. Eye drops are prescribed after examination, for the current episode.
Is the collar really necessary?
Yes. A cat that rubs just once can ruin several days of healing. The collar stays on until the green light from the veterinarian.
Will my cat still see out of this eye after healing?
In most cases yes, especially if the lesion was superficial and treated early. A central and extensive scar, on the other hand, can leave lasting discomfort.
References
AAFP — American Association of Feline Practitioners
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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