Corneal Sequestrum in Cats

Corneal sequestrum is a painful eye condition in which part of the cornea, the clear front surface of the eye, becomes brown to black and dies. It is considered a feline-specific problem, meaning it is seen primarily in cats. The lesion often appears in the center or just off-center of the cornea and may begin as a small dark spot before becoming denser, rougher, or more raised over time.

Many cats show signs of discomfort such as squinting, tearing, blinking more than usual, or keeping the eye partly closed. Some cats also develop discharge, redness, or visible blood vessels growing across the cornea. In mild cases the lesion can remain stable for a while, but it can also worsen suddenly. Because the cornea is delicate, ongoing pain and deeper tissue damage are real concerns.

Corneal sequestra are often linked with chronic irritation rather than one single cause. Common contributors include prior corneal ulcers, feline herpesvirus-1, eyelid abnormalities like entropion, poor tear film quality, and facial shape in brachycephalic breeds. Persian and Himalayan cats are often mentioned as higher-risk breeds, though any cat can develop this condition.

Your vet may recommend medical management, surgery, or referral to a veterinary ophthalmologist depending on how deep the lesion is and how painful the eye appears. Surgical removal, called a superficial keratectomy or lamellar keratectomy, is commonly recommended when the sequestrum is painful, deep, nonhealing, or threatening the strength of the cornea.

Diagnosis starts with a full eye exam. Your vet will look at the cornea closely, often using magnification and special lighting. Fluorescein stain may be used to check for an ulcer or exposed corneal defect, although a sequestrum may stain only faintly or not in a typical pattern. Tear testing, eyelid evaluation, and checking for concurrent irritation are also important.

In more complicated cases, your vet may recommend referral to a veterinary ophthalmologist. A specialist can better judge how deep the sequestrum extends into the cornea and whether the eye is at risk of rupture. Depth matters because it helps guide whether medical management is reasonable or whether surgery is the safer option.

Your vet will also look for underlying problems that may have led to the lesion. These can include feline herpesvirus-associated keratitis, chronic corneal ulceration, dry eye or poor tear film quality, entropion, abnormal eyelashes, or incomplete blinking. If these issues are missed, the eye may stay painful or the lesion may recur.

Differential diagnoses can include corneal pigmentation, a foreign body, a corneal ulcer, or less commonly a corneal mass. The goal is not only to identify the dark lesion, but to understand the whole eye environment around it. That broader view helps your vet discuss realistic treatment options and recovery expectations.

The exact cause of corneal sequestrum is not fully settled, but most sources describe it as a response to chronic corneal irritation or injury. Repeated surface damage can interfere with normal corneal healing and lead to necrosis of the corneal stroma. In plain terms, part of the cornea becomes unhealthy enough that it dies and turns dark.

Common risk factors include chronic corneal ulcers, trauma such as a scratch, eyelid abnormalities, poor tear film quality, and exposure-related irritation in cats with prominent eyes. Feline herpesvirus-1 is frequently discussed because it can cause recurrent corneal disease and delayed healing. Some cats also have a history of previous eye surgery or long-standing inflammation before the sequestrum appears.

Breed and facial shape matter. Persian and Himalayan cats are often listed as predisposed, and Merck also notes increased frequency in Siamese and Persian cats. Flat-faced cats may have more corneal exposure, incomplete blinking, or tear film problems, all of which can increase irritation over time.

This condition is not something pet parents cause by routine care. Still, delayed evaluation of chronic squinting, discharge, or recurrent ulcers can allow the cornea to stay inflamed longer. That is why ongoing eye symptoms, even if they seem mild, deserve a veterinary exam rather than watchful waiting at home.

Not every case can be prevented, because some cats have breed-related anatomy or viral eye disease that makes them more vulnerable. Still, early attention to eye irritation can lower the chance of chronic corneal damage. If your cat squints, tears excessively, develops discharge, or seems sensitive to light, schedule an exam promptly instead of waiting to see if it clears 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 treatment plans from your vet. Addressing those issues early may reduce repeated corneal injury that can set the stage for sequestrum formation.

Home care should stay gentle. Do not use leftover eye drops, especially steroid products, unless your vet specifically prescribed them for the current problem. Human eye medications can be unsafe or inappropriate. Keep the eye area clean with materials your vet recommends, and prevent rubbing if your cat is already showing discomfort.

Routine observation helps, especially in flat-faced breeds. During grooming or daily interaction, look for cloudiness, dark discoloration, tearing, crusting, or one eye that seems more closed than the other. Small changes can be easy to miss at first, but catching them early can make treatment simpler and recovery smoother.

The outlook is often good when the lesion is treated before the cornea becomes dangerously thin. Many cats are much more comfortable once the sequestrum is removed or the eye is otherwise stabilized. Vision can remain functional, although some degree of corneal scar may persist, especially if the lesion was deep or central.

Recovery depends on lesion depth, whether surgery was needed, and whether an underlying cause is still active. After keratectomy, rechecks are commonly scheduled every 7 to 10 days at first, then spaced out as healing progresses. Your vet may recommend an e-collar, several eye medications, and strict instructions to avoid rubbing or trauma during healing.

Recurrence is possible. Cats with low tear production, thick lesions, chronic irritation, or incomplete removal of affected tissue may be more likely to have future problems. That does not mean treatment failed. It means the eye may need longer-term management and closer follow-up.

Pet parents should call their vet right away if the eye becomes more painful, more cloudy, more swollen, or develops heavier discharge during recovery. Sudden changes can signal ulceration, graft problems, or deeper inflammation. Fast reassessment gives the best chance to protect comfort and vision.