Moderate severity

Corneal Ulcer

An erosion or open sore on the clear front surface of the eye (the cornea). Painful and potentially sight-threatening, but usually treatable if caught early.

⚠️ Common symptoms

Squinting or holding the eye shutExcessive tearing or watery dischargeRedness around the eyeA cloudy or hazy spot on the surfacePawing or rubbing at the eyeSensitivity to light

The cornea is the transparent, dome-shaped window at the front of the eye. It has no blood vessels — which keeps it clear — but it is packed with nerve endings, which is why any damage to it is intensely painful. A corneal ulcer is a defect where the protective outer layer (the epithelium) is lost and the deeper tissue is exposed.

In cats, one of the single most important causes is feline herpesvirus. The same virus responsible for cat 'flu can attack the cornea directly, producing characteristic branching (dendritic) ulcers that may recur throughout a carrier cat's life during periods of stress. Trauma is the other big cause — a swipe from a housemate, a bramble in the garden, or self-inflicted damage from rubbing an already-irritated eye.

Diagnosis is quick and painless: the vet applies a fluorescein stain that glows bright green wherever the surface is damaged, revealing the size and depth of the ulcer. Depth matters enormously. A shallow ulcer usually heals within a week on antibiotic drops. A deep ulcer that reaches the inner layers risks rupturing the eye and needs urgent, sometimes surgical, intervention.

The two golden rules for owners are speed and caution. Speed, because ulcers can worsen literally overnight. Caution, because the wrong medication can be catastrophic — steroid-containing eye drops (often prescribed for other conditions) suppress healing and can let an ulcer melt through the cornea. Always have a sore eye examined rather than reaching for something in the cupboard.

🔍 Causes

Ulcers form when the corneal surface is breached. Common causes in cats include trauma (a scratch from another cat or a claw), foreign material under the eyelid, dry eye, and — very commonly in cats — infection with feline herpesvirus (FHV-1). Flat-faced brachycephalic breeds such as Persians are more prone because their prominent eyes and shallow sockets leave the cornea exposed.

🛡 Prevention

You cannot prevent every scratch, but you can reduce risk: keep vaccinations up to date to limit herpesvirus flare-ups, remove sharp hazards, treat eye infections promptly, and monitor flat-faced breeds closely. Never let an eye problem "wait and see" — a minor irritation can deepen into a serious ulcer within a day or two.

💊 Treatment

Superficial ulcers are treated with topical antibiotic drops or ointment to prevent infection, often with atropine drops to relieve painful spasm, and an Elizabethan collar to stop self-trauma. Any underlying cause — such as feline herpesvirus — is treated alongside. Deep or non-healing ulcers may need a debridement procedure or surgery (a conjunctival graft) to save the eye, so prompt veterinary care is essential.

When to see a vet: A painful, weepy, or squinting eye is always an emergency — see a vet the same day. Corneal ulcers can deepen rapidly, and a delay of even 24–48 hours can be the difference between simple eye drops and losing the eye. Never use leftover or human eye medications, as some steroid drops make ulcers dramatically worse.

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⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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