Corneal Ulcers in Cats: Signs, Treatment, and When Surgery Is Needed

Oct 17 • 10 min read

Your cat won't open one eye all the way. There's watery discharge running down that side of the face, and every time you get close, they squint harder and pull away. This isn't just a bit of irritation. The clear surface of the eye may have an open sore on it, and it needs attention today, not next week.

A corneal ulcer in cats is a break in the clear front surface of the eye, and it is genuinely painful. In cats, the most common causes are feline herpesvirus-1 and trauma from scratches, foreign material, or self-injury from rubbing. Most superficial ulcers heal within about a week with prompt treatment, but deeper, infected, or herpes-related ulcers can take longer and sometimes need surgery.

Key Takeaways

A corneal ulcer is an open sore on the clear front surface of the eye, and even a small one can be very painful.
Feline herpesvirus-1 (FHV-1) and trauma are the two leading causes of corneal ulcers in cats.
Signs include squinting, tearing, redness, cloudiness, and pawing at the eye.
Diagnosis relies on a fluorescein stain test, which highlights damaged corneal tissue under the vet's exam light.
Most superficial ulcers heal in 3 to 7 days with prompt treatment, but deep, melting, or infected ulcers can need urgent surgery.
Never use leftover eye medication on your cat, especially steroid-containing drops, since these can make some ulcers dramatically worse.

What Is a Corneal Ulcer in Cats?

A corneal ulcer is an erosion, or open sore, on the cornea, which is the clear outer layer at the front of your cat's eye. Vets sometimes call this ulcerative keratitis. Because the cornea is packed with nerve endings, even a small ulcer can be intensely painful. Cats with a corneal ulcer often squint hard, tear excessively, and try to avoid bright light.

Some ulcers affect only the surface layer of the cornea and heal quickly with medical treatment. Others extend deeper, where they carry a much higher risk of becoming infected, softening or "melting," or in the worst cases, rupturing. This range in severity is exactly why a painful eye should never be treated as a wait-and-see problem at home.

In cats specifically, corneal ulcers matter for a particular reason: feline herpesvirus-1 (FHV-1) is a very common trigger, and it behaves differently from a simple scratch. Trauma is also common, including scratches from another cat, plant material in the eye, or self-inflicted damage from a cat rubbing at an already irritated eye.

Signs of a Corneal Ulcer in Cats

Illustrated checklist of common corneal ulcer signs in cats including squinting and discharge

Watch for the following signs, particularly if they appear suddenly or affect just one eye:

Squinting or keeping one eye tightly shut, often a sign of significant pain
Excessive tearing or watery discharge, sometimes with mucus mixed in
Redness of the white of the eye or swelling of the tissue around it
Pawing at the eye or rubbing the face against furniture or carpet
A cloudy, blue, or hazy appearance on the surface of the eye
Light sensitivity and a tendency to hide in darker areas
A visible pit, dent, or dark spot on the eye surface, which can suggest a deeper ulcer
Yellow-green discharge, worsening pain, or a sudden change in the eye's shape, which can point to infection or a risk of rupture

Corneal ulcers are painful and can turn into emergencies quickly. See your vet the same day if your cat is squinting, has a cloudy eye, or keeps rubbing at the face. Treat it as urgent if the eye looks sunken, bulging, very cloudy, has thick discharge, or your cat suddenly cannot open it at all.

What Causes Corneal Ulcers in Cats?

Feline herpesvirus-1 (FHV-1) is one of the most common causes of corneal ulceration in cats. After a cat's first infection, the virus can remain dormant in the body and flare up again during periods of stress or illness. These flare-ups can cause recurrent eye pain, conjunctivitis, and ulcers that heal more slowly and behave differently than a straightforward scratch.

Trauma is the other major cause. Cats can injure the cornea during play or fights with other cats, from plant material or dust getting into the eye, from grooming mishaps, or simply from rubbing an eye that's already irritated. A foreign body trapped under the eyelid can keep scraping the cornea with every blink, turning a small injury into a persistent problem.

Other possible contributors include bacterial infection, dry eye, eyelid or eyelash abnormalities, exposure to irritating chemicals, and chronic corneal disease. In some cats, a nonhealing ulcer is actually a sign that an underlying problem, not just the visible sore, still needs to be addressed.

How Are Corneal Ulcers Diagnosed?

The single most important diagnostic test is a fluorescein stain. Your vet places a small amount of a special dye onto the surface of the eye, and any damaged corneal tissue absorbs the stain, making the ulcer's presence, size, and pattern clearly visible under the exam light. This test is quick, painless, and a routine part of evaluating any painful eye.

Your vet will also examine the eyelids, tear film, and the rest of the eye structure to look for an underlying cause, such as a scratch, trapped foreign material, herpes-related disease, or an eyelid abnormality. If the ulcer looks deep, chronic, infected, or isn't healing as expected, additional testing such as tear testing, cytology, culture, or referral to a veterinary ophthalmologist may be recommended.

Illustration of a veterinarian performing a fluorescein stain test on a cat's eye

Depth is the key factor in deciding next steps. A superficial ulcer is often manageable with medical treatment from your primary vet, while a deep or melting ulcer may need urgent specialty care to protect the eye from rupturing.

Treatment Options for Corneal Ulcers in Cats

Infographic comparing conservative, standard, and advanced treatment tiers for corneal ulcers in cats

Vets generally offer a spectrum of care, meaning there are treatment paths at different price points depending on how deep and complicated your cat's ulcer is.

Conservative care suits cats with a small, superficial ulcer and stable eye exam findings, provided you can reliably give medication and return for rechecks. This tier typically includes an office exam with fluorescein stain, a topical broad-spectrum antibiotic to reduce the risk of secondary bacterial infection, pain relief (often oral medication, sometimes with atropine if your vet feels it's appropriate), an e-collar to prevent rubbing, and a recheck about 3 to 5 days later. Outcomes are often very good when the ulcer is shallow and caught early, with many uncomplicated cases healing within several days.

Standard care is the most common path for most cats with painful ulcers, herpes-associated eye disease, ulcers not improving on basic care, or cases where the underlying cause isn't yet clear. This includes a comprehensive eye exam with repeat fluorescein staining at rechecks, tailored topical antibiotic therapy, pain control and an e-collar, antiviral treatment when herpesvirus is suspected (often oral famciclovir or compounded topical cidofovir), evaluation for underlying causes, and one or more recheck visits over one to two weeks. Outcomes are good in many cases, though healing time is more variable than with a simple scratch, and herpes-related ulcers may recur later even after the current one heals.

Advanced care applies to cats with deep ulcers, descemetoceles (an ulcer that has reached the last thin layer before perforation), melting ulcers, actual perforations, severe pain, or ulcers that haven't responded to medical treatment. This involves referral to a veterinary ophthalmologist, advanced diagnostics, intensive topical treatment sometimes given every few hours early on, procedures or surgery such as debridement, conjunctival grafting, corneal grafting, or repair of a perforation, sedation or anesthesia as needed, and close follow-up. The outlook here is guarded to fair for vision depending on depth and how quickly treatment starts, though timely specialty care can often save comfort and sometimes preserve useful vision.

"Deep, melting, or perforated ulcers may need urgent specialist surgery." — SpectrumCare, Corneal Ulcers in Cats

Why Steroid Eye Drops Can Be Dangerous Here

It's worth repeating clearly: never use leftover eye medication on your cat unless your vet specifically confirms it's safe for the current problem. Eye products containing corticosteroids can delay healing and, in some cases, make a corneal ulcer dramatically worse. This is exactly why an accurate diagnosis from a fluorescein stain test matters before any treatment starts, rather than reaching for whatever drops are left in the cabinet.

Can Corneal Ulcers Be Prevented?

Not every corneal ulcer can be prevented, especially in cats with recurrent herpesvirus disease. Still, there are practical ways to lower the risk. Keeping cats indoors reduces the chance of eye trauma from fights, plants, and debris. In multi-cat households, reducing conflict and overcrowding may also help lower stress-related herpes flare-ups, since stress is a well-known trigger for viral recurrence.

If your cat has a history of herpes-related eye disease, talk with your vet about early warning signs to watch for and whether an ongoing management plan, including lysine supplementation, makes sense. Evidence for lysine has been mixed in research, so it's best to discuss this with your vet rather than relying on it alone.

The single biggest preventive step is acting early. A red, watery, or squinting eye should be checked promptly rather than waiting to see if it clears up, since fast treatment can keep a small surface injury from becoming a deeper, far more painful problem.

Caring for Your Cat During Recovery

Whether your cat is on conservative medical care or recovering from surgery, a few habits make a real difference in how smoothly healing goes:

Give every dose of prescribed eye medication on schedule, even once the eye starts looking more comfortable
Keep the e-collar on for the full period your vet recommends, since rubbing is one of the most common reasons a healing ulcer gets worse again
Attend every recheck appointment, since your vet needs to repeat the fluorescein stain to confirm true healing, not just visual improvement
Call your vet promptly if the eye becomes more painful, cloudier, more swollen, or starts producing thicker discharge during recovery
If herpesvirus is part of your cat's history, ask your vet whether ongoing lysine support or stress reduction at home makes sense for reducing future flare-ups

FAQ Section

How long does it take for a cat's corneal ulcer to heal?
Most superficial ulcers heal within about 3 to 7 days with prompt treatment. Herpes-related or infected ulcers can take 1 to 3 weeks and may recur later, especially during times of stress. Deep or complicated ulcers can take considerably longer and may need surgery.

What is the most common cause of corneal ulcers in cats?
Feline herpesvirus-1 (FHV-1) is one of the leading causes, along with trauma from scratches, foreign material, or self-inflicted rubbing. FHV-1 is especially important to recognize because it can cause ulcers that heal more slowly and return later during stressful periods.

Can I treat my cat's eye ulcer at home?
No. Corneal ulcers need a proper veterinary diagnosis using a fluorescein stain test before any treatment starts. Using leftover eye drops, especially ones containing steroids, can actually make some ulcers significantly worse and delay healing.

When does a corneal ulcer in a cat need surgery?
Surgery is typically reserved for deep ulcers, descemetoceles, melting ulcers, perforations, or ulcers that haven't responded to medical treatment. These cases are usually referred to a veterinary ophthalmologist for procedures such as debridement or grafting.

How much does treating a corneal ulcer in a cat cost?
Costs vary depending on severity. An uncomplicated visit with medical treatment for a superficial ulcer sits at the lower end of the cost range, while advanced procedures or an ophthalmology referral for a deep or complex ulcer costs significantly more. Your vet can give you a specific estimate after examining your cat's eye.