Corneal Ulcers in Cats: Squinting, Pain and Why It Is Urgent

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

A cat that holds one eye shut is a cat in pain. The cause is often a corneal ulcer, a sore on the clear dome at the front of the eye. Eye problems escalate fast. A shallow scratch can become a deep, infected ulcer within a day or two, so quick care really matters.

The cornea

The cornea is a clear, thin layer that protects the eye and focuses light. It has several layers and a dense network of nerves, which is why damage hurts so much. When the surface layer is lost, a superficial ulcer forms. If the damage goes deeper, into the stroma, the ulcer is more serious, and the cornea may even rupture.

Causes

• Trauma, from scratches by claws, thorns, plants or foreign material.
• Feline herpesvirus. A leading cause, and recurrent ulcers are common, often with a branching pattern. See feline calicivirus and herpesvirus.
• Eyelid and lash problems, such as entropion, where the lid rolls in, or extra lashes.
• Dry eye, with low tear production.
• Chemical burns, from cleaning products or sprays. See cat-safe cleaning products.
• Bacterial infection, after an injury.
• Facial shape, in flat-faced breeds with prominent eyes, such as Persians. See persian cat breed profile.
• Nerve damage, or exposure from poor blinking.

Signs

• Squinting or keeping the eye shut.
• Watery or pus-like discharge.
• Redness and swelling.
• Pawing or rubbing the eye.
• Cloudiness or a bluish haze, or a visible pit or white spot.
• The third eyelid covering part of the eye.
• Light sensitivity.
• Behavior changes, such as hiding.

Why it is urgent

Corneal ulcers can deepen quickly, and bacterial infection can melt the cornea within hours. A ruptured cornea can lead to loss of the eye. See cat eye problems and conjunctivitis in cats.

Diagnosis

The vet examines the eye, applies fluorescein stain, which sticks to damaged corneal tissue and glows green under a blue light, and may measure tear production and eye pressure. Swabs for herpesvirus, or cultures for bacteria, may be taken.

Treatment

• Antibiotic drops or ointment, to prevent or treat infection.
• Pain relief, such as atropine drops, in some cases, or oral medication.
• Antivirals, for herpes-related ulcers.
• Lubricants, for dry eye.
• A cone, to stop rubbing.
• Surgery, for deep or non-healing ulcers, such as a conjunctival graft, or removing damaged tissue.
• Treating the cause, such as eyelid correction.

Never use leftover or human eye drops. Steroid drops can make ulcers worse, and even cause rupture. See how to give cat eye drops.

Home care

• Give drops exactly as prescribed, usually several times a day.
• Keep the cone on.
• Keep the cat indoors.
• Clean discharge gently.
• Recheck on schedule, since ulcers can change quickly.
• Watch for worsening redness, cloudiness or pain.

Recurrent ulcers

Cats with herpesvirus may have repeat ulcers. Reduce stress, keep vaccinations current and ask your vet about long-term management. See signs of stress in cats.

Prevention

Keep cats indoors, trim nails, remove plant hazards and avoid sprays near cats. Check eyes regularly.

How eye drops fit into daily life

Eye medication is a big part of treatment, and many owners worry about it. Wash your hands, gently hold your cat on your lap or wrapped in a towel, tilt the head back slightly and place a drop on the surface of the eye without touching it. Hold for a few seconds. If two medicines are prescribed, wait a few minutes between them, as your vet instructs. Ointment goes in last. Give a treat afterwards. See how to give cat eye drops.

Warning signs of a deep ulcer

A deep ulcer may look like a pit, or have a white or yellow center, a cloudy surrounding area or a gel-like appearance. Pain may be severe, and the eye may leak. Seek care at once. Some deep ulcers need surgery within hours. Do not wait for the next day, particularly if the cornea looks like it is bulging or you see a dark spot.

Why a cone is essential

Scratching or rubbing at an ulcer can turn a minor injury into a major one. Keep the cone on at all times, including at night, until your vet says it can come off. Soft cones and inflatable collars are options, but check with your vet.

After healing

Once healed, a small scar may remain as a faint cloudy patch, and may or may not affect vision. Your vet will recheck the eye, and may continue treatment for herpesvirus or dry eye to prevent recurrence. Keep an eye out for squinting, and report it early.

When to see a vet

See a vet the same day if your cat is squinting or has a cloudy eye. Use the US vet directory to find a clinic.

This article is general educational information, not veterinary advice. Every cat is different. If your cat is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.