Corneal Sequestrum in Cats: The Dark Spot on Your Cat's Eye Explained

Oct 16 • 10 min read

You're giving your cat a gentle head scratch and you notice it a dark brown or black spot sitting right on the clear part of the eye. It wasn't there a few weeks ago. Your cat is also squinting a little more than usual on that side. Something is happening to the surface of the eye, and it's not just a smudge of dirt.

A corneal sequestrum is an area of dead corneal tissue that turns dark brown or black, and it is a condition seen almost exclusively in cats. It often develops after chronic irritation, injury, or feline herpesvirus infection, and it needs prompt veterinary attention because it can be painful and, in some cases, threaten the health of the eye.

Key Takeaways

A corneal sequestrum is a patch of dead corneal tissue that turns brown to black, usually in the center of the eye.
This condition is essentially unique to cats, and Persian, Himalayan, and Siamese cats are considered higher risk.
It is often linked to chronic irritation from prior corneal ulcers, feline herpesvirus, eyelid abnormalities, or poor tear film quality.
Signs include a dark spot on the eye, squinting, tearing, discharge, and light sensitivity.
Treatment ranges from close monitoring and pain control for small, stable lesions to surgical removal, sometimes with a graft, for deeper or more painful cases.
See your vet immediately if your cat has a new dark spot on the eye along with squinting, tearing, or obvious discomfort.

What Is Corneal Sequestrum in Cats?

Diagram showing where a corneal sequestrum forms within a cat's cornea

A corneal sequestrum is a painful eye condition in which part of the cornea, the clear front surface of the eye, dies and turns brown to black. It is considered a feline-specific problem, meaning it shows up almost exclusively in cats rather than dogs. The lesion often appears in the center or just off-center of the cornea and may start as a small dark spot before becoming denser, rougher, or more raised over time.

Many affected cats show signs of discomfort such as squinting, tearing, blinking more than usual, or keeping the eye partly closed. Some also develop discharge, redness, or visible blood vessels growing across the cornea. In mild cases, the lesion can stay stable for a while, but it can also worsen suddenly, which is why ongoing monitoring matters even when a cat doesn't seem to be in obvious pain.

Signs of Corneal Sequestrum in Cats

Illustration comparing early and advanced stages of corneal sequestrum in a cat's eye

Watch for the following changes, especially in the clear surface of the eye:

A dark brown, amber, or black spot on the cornea
Squinting or keeping one eye closed
Excess tearing or a persistently watery eye
Clear to mucus-like eye discharge
Redness around the eye
Pawing or rubbing at the eye
A cloudy appearance to the cornea
Visible blood vessels growing across the eye's surface
Sensitivity to bright light
Reduced activity or hiding because of eye discomfort

The most recognizable sign is that dark spot on the clear surface of the eye. Early lesions may look translucent brown or bronze, while more advanced lesions can appear opaque black. Not every cat shows the same level of discomfort. A superficial lesion may look dramatic but cause only moderate pain, while a deeper lesion can become far more serious. Any sudden worsening, bulging, marked cloudiness, or an eye your cat suddenly cannot open should be treated as an emergency.

What Causes Corneal Sequestrum in Cats?

The exact cause is not fully settled, but it is widely described as a response to chronic corneal irritation or injury. Repeated surface damage can interfere with the cornea's normal healing process, eventually leading to necrosis, or tissue death, in that patch of the corneal stroma. In plain terms, part of the cornea becomes so unhealthy that it dies and turns dark.

Common contributing factors include:

Prior corneal ulcers. Chronic or repeated ulceration can set the stage for sequestrum formation.
Feline herpesvirus-1 (FHV-1). This very common feline virus is frequently linked to recurrent corneal disease and delayed healing.
Eyelid abnormalities. Conditions like entropion, where the eyelid rolls inward, cause ongoing friction against the cornea.
Poor tear film quality. Reduced or unstable tears leave the corneal surface more vulnerable to damage.
Facial shape. Flat-faced (brachycephalic) breeds often have more corneal exposure and less complete blinking, both of which increase chronic irritation.

Breed matters here. Persian and Himalayan cats are frequently mentioned as higher-risk breeds, and Siamese cats are also noted in some sources. This is not something caused by anything a pet parent did wrong; it develops from an underlying combination of anatomy, prior injury, and sometimes viral disease.

How Is Corneal Sequestrum Diagnosed?

Diagnosis starts with a thorough eye exam. Your vet will look closely at the cornea, often using magnification and special lighting, to assess the size, depth, and appearance of the lesion. A fluorescein stain test may be used to check for an accompanying ulcer, though a true sequestrum may stain only faintly or in an atypical pattern compared to a straightforward ulcer.

Your vet will also look for underlying problems that may have contributed to the lesion, including feline herpesvirus-associated eye disease, chronic ulceration, dry eye, entropion, or abnormal eyelashes. If these root causes are missed, the eye may stay irritated or the lesion may return even after treatment. In more complex cases, referral to a veterinary ophthalmologist can help determine how deep the lesion extends and whether the eye is at risk of rupture, since depth is one of the biggest factors in deciding between medical management and surgery.

Treatment Options for Corneal Sequestrum

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

Conservative care suits very superficial, stable lesions, or cats needing short-term stabilization before a referral. This typically focuses on pain control, lubricating eye medication, topical antibiotic coverage if ulceration is present, and frequent rechecks. Some superficial sequestra may loosen and slough away on their own over time, but this process can be slow, and the eye needs close watching for worsening pain or deeper damage throughout.

Standard care is the most common path for painful, nonhealing, or progressive lesions where tissue support is still reasonably adequate. This usually means surgical removal of the sequestrum through a procedure called a superficial or lamellar keratectomy. Removing the dead tissue can relieve pain faster and stops it from extending deeper into the cornea. Cats typically go home afterward with topical medications, pain relief, and an e-collar, along with several rechecks scheduled during healing.

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

Advanced care applies to deep or complex lesions, eyes at real risk of perforation, recurrent cases, or significant corneal thinning. This tier often involves a corneal or conjunctival graft placed over the surgical site, additional imaging or specialty testing, and more intensive follow-up monitoring to support the cornea structurally while it heals.

"Standard care for many cats is surgical removal of the sequestrum with a superficial or lamellar keratectomy. This can relieve pain faster and remove devitalized tissue before it extends deeper." — SpectrumCare, Corneal Sequestrum in Cats

Can Corneal Sequestrum Be Prevented?

Not every case can be prevented, since some cats have breed-related anatomy or viral eye disease that makes them naturally more vulnerable. Still, prompt attention to eye irritation can lower the chance of chronic corneal damage building up over time. If your cat squints, tears excessively, develops discharge, or seems light sensitive, book an eye exam promptly rather than waiting to see if it clears up on its own.

Managing underlying problems matters most. Cats with recurrent herpesvirus eye disease, chronic ulcers, entropion, abnormal eyelashes, or tear film problems may need ongoing monitoring and a treatment plan from your vet, since addressing those root issues can reduce the repeated corneal irritation that sets the stage for a sequestrum.

At home, keep things gentle. Never use leftover eye drops, especially steroid-containing products, unless your vet specifically prescribed them for the current problem, since some medications can actually worsen corneal disease in cats. During regular grooming and handling, look for cloudiness, dark discoloration, tearing, crusting, or one eye that seems more closed than the other, since catching small changes early makes treatment simpler.

Will My Cat Lose Vision?

Not always. Many cats keep useful vision, especially when the sequestrum is treated before the cornea becomes severely damaged. Some degree of corneal scarring may remain afterward, particularly if the lesion was deep or centrally located, but this doesn't necessarily mean significant vision loss. The outlook is generally good when treatment happens before the cornea becomes dangerously thin.

Can Corneal Sequestrum Come Back?

Yes, recurrence is possible. Cats with low tear production, thick lesions, ongoing chronic irritation, or herpesvirus-related eye disease may be more likely to develop a new sequestrum, even in the same eye or the other eye, later on. This doesn't mean the original treatment failed; it simply means some cats need longer-term management and closer follow-up care from their vet.

Recovery After Corneal Sequestrum Surgery

Recovery depends on how deep the lesion was, whether surgery involved a graft, and whether an underlying cause like herpesvirus is still active. After a keratectomy, rechecks are commonly scheduled every 7 to 10 days at first, then spaced further apart as healing progresses. A few things help recovery go smoothly at home:

Keep the e-collar on for the full period your vet recommends, since rubbing is a major risk factor for reopening the surgical site
Give all prescribed eye medications on schedule, even once the eye starts looking more comfortable
Keep every recheck appointment so your vet can confirm the eye is healing as expected
Call your vet right away if the eye becomes more painful, cloudy, swollen, or starts producing heavier discharge during recovery
Keep your cat calm and indoors during the healing window to avoid dust, scratching, or accidental trauma to the eye

A soothing lubricating eye drop can help keep the surface comfortable during healing, and if feline herpesvirus is part of your cat's history, your vet may also recommend ongoing lysine supplementation to help manage future flare-ups.

FAQ Section

Is corneal sequestrum in cats an emergency?
It should be treated as urgent. See your vet immediately if your cat has a dark spot on the cornea along with squinting, tearing, or obvious eye pain. Some lesions stay stable for a time, but others can deepen or loosen suddenly and threaten the health of the eye.

Can a corneal sequestrum heal without surgery?
Sometimes a very superficial lesion can slough off on its own with close monitoring and supportive care, but this process can be slow and uncomfortable for the cat. Many cats ultimately need surgery because the lesion stays painful, deepens over time, or doesn't heal well on its own.

What does a corneal sequestrum look like?
It typically looks like a brown, bronze, or black spot on the clear front surface of the eye. The area may appear flat early on, then become denser, rougher, or slightly raised as the condition progresses.

Are some cat breeds more likely to get corneal sequestrum?
Yes. Persian and Himalayan cats are commonly listed as higher-risk breeds, and Siamese cats are also mentioned in some sources. Flat-faced facial structure tends to increase corneal exposure and chronic irritation, which raises the overall risk.

How much does treatment usually cost?
Costs vary widely depending on lesion depth and whether surgery or grafting is needed. A basic exam and medical management sit at the lower end of the cost range, surgical removal (keratectomy) falls in the middle, and complex cases needing a corneal or conjunctival graft cost more. Your vet can give you a specific estimate after examining your cat's eye.