Few things alarm a cat owner faster than spotting a brown or black patch on a pet’s eye. When that dark spot sits on the normally crystal-clear cornea and the cat squints or waters, one possible cause is corneal sequestrum, a condition seen almost exclusively in cats. It develops slowly, can be genuinely painful, and always deserves a professional eye exam. Flat-faced breeds such as Persians, Himalayans, Exotic Shorthairs, and Burmese are diagnosed more often, but any cat, including ordinary house cats, can develop one.
What a Corneal Sequestrum Is
The cornea is the transparent window at the front of the eye. In this condition, a small area of corneal tissue dies and turns tan, brown, or black, forming a plaque that looks like a scab stuck to the eye surface. The dark color is thought to come from pigments in the tear film. Sequestra usually appear where the cornea has endured ongoing irritation or repeated injury: chronic ulcers, eyelid abnormalities that rub the surface, incomplete blinking in flat-faced cats, tear film problems, or feline herpesvirus infection, which is common in cats and frequently flares up in the eyes. The dead tissue typically does not heal over on its own, and every blink over the rough surface is uncomfortable for the cat.
Symptoms to Watch For
- A dark spot: a tan to black area on the clear surface of the eye, sometimes visible only in good light.
- Squinting or holding the eye shut: discomfort is the most consistent sign.
- Watery or thick discharge: tearing that may become yellow or green if infection develops.
- A raised third eyelid or redness.
- Eye rubbing: pawing at the face or rubbing against furniture.
- Behavior changes: hiding, reduced appetite, or irritability because of chronic eye pain.
When to See a Vet
Any dark spot, persistent squint, or ongoing discharge from a cat’s eye calls for a veterinary exam within a day or two rather than a wait-and-see approach, because eye problems in cats can progress quickly. The veterinarian will examine the eye with magnification and staining dyes, check tear production, and measure eye pressure to rule out other diseases. Go urgently rather than routinely if the eye suddenly swells shut, the cat cannot be consoled, the cornea looks cloudy all over, or there is a history of trauma. Complex cases are usually referred to a veterinary eye specialist, who can judge how deep the lesion runs.
Common Vet-Directed Treatments
Management depends on the depth of the sequestrum and how much pain the cat is in. Very shallow lesions are sometimes managed medically with lubricating drops, protective ointments, and treatment of any underlying herpesvirus, then monitored as the body slowly sheds the dead tissue over weeks or months. More often, because these lesions stay painful and can deepen, the recommended treatment is microsurgery: the surgeon removes the dead corneal tissue and, when the defect is deep, reinforces the area with a graft of conjunctival or donor tissue. Surgery relieves discomfort, prevents the lesion from deepening toward a perforation, and generally shortens healing time. After surgery, cats wear an Elizabethan collar, receive antibiotic and antiviral eye drops as prescribed, and return for rechecks over the following weeks. Recurrence happens in a minority of cats, especially where herpesvirus or eyelid problems are not also addressed.
Home Care and Prevention
- Never apply leftover or human eye medication. Some products that are safe for other uses can worsen a cat’s eye; use only what your vet prescribes.
- Keep the collar on. A few days of frustration prevents permanent damage from rubbing.
- Keep flat-faced cats’ eyes clean and dry by gently wiping discharge with a damp cloth, and have eyelid issues assessed early.
- Manage herpesvirus flare-ups promptly. Treating recurrent conjunctivitis and ulcers quickly reduces the chronic irritation from which sequestra develop.
- Book regular rechecks after any eye ulcer, and monitor the previously unaffected eye, since some cats eventually develop a sequestrum in the other one.
Because the exact cause is not fully understood, prevention is mainly about minimizing chronic corneal irritation: prompt treatment of ulcers and infections, and early evaluation of squinting in predisposed breeds.
This article is educational content only and is not a substitute for professional veterinary advice. Any suspected eye problem in a cat should be examined by a veterinarian promptly.