CONDITION
Corneal Sequestrum in Cats
A corneal sequestrum is a discrete area of dead tissue that forms on the surface of a cat's eye, most often appearing as a dark brown or black patch on the cornea. The tissue becomes isolated from the healthy cornea around it, and over time the body treats it as foreign material. This condition is almost exclusive to cats and tends to occur following injury, chronic irritation, or certain viral infections affecting the eye. Owners often first notice a dark spot on the eye itself, sometimes accompanied by squinting, tearing, or a change in how the eye looks. The appearance can be striking—a small brown or black island on the clear part of the eye—and it may prompt worry about whether the eye is damaged or infected. In some cases the area causes discomfort, while in others the cat shows few outward signs. This page explores what signals may accompany a corneal sequestrum, what is happening in the tissue of the cornea, how the condition is investigated and confirmed, and what approaches exist for managing it. The course and outlook vary depending on the underlying cause, the size and location of the affected area, and how the eye responds over time.
Why this matters now
Corneal sequestra tend to develop in young to middle-aged cats, though they can appear at any life stage. Certain breeds—particularly Persians, Himalayans, and other brachycephalic cats with prominent eyes—appear more prone, likely because their eye shape makes the cornea more vulnerable to drying and minor trauma. The condition often follows a period of irritation: a scratch from another cat, persistent dust or pollen exposure, or a flare of feline herpesvirus affecting the eye. In some cases no clear trigger is identified, and the sequestrum forms gradually over weeks or months.
Once the patch of dead tissue appears, it typically remains stable in size or expands slowly over weeks to months. The sequestrum may loosen at the edges as the surrounding cornea begins to wall it off, and in some cases the body gradually extrudes the fragment, leaving an ulcer beneath. In other cats the sequestrum remains adherent for months or years, and the degree of discomfort can vary—some cats show persistent squinting and tearing, while others tolerate the lesion with minimal outward signs. The course is difficult to predict for any individual animal.
Signals & patterns
Early signals
Dark spot on the eye
Owners often notice a small brown or amber-coloured patch on the clear surface of the eye, usually near the centre or slightly to one side. The colour can deepen over days to weeks, becoming darker brown or black as the tissue dies and oxidises.
Squinting or holding the eye partly closed
The affected eye may be held narrower than the other, or the cat may blink more frequently. This can signal discomfort from the rough surface of the sequestrum or from inflammation in the tissues around it.
Clear or slightly cloudy discharge
A small amount of watery tearing is common, and the fur below the eye may become damp or stained. The discharge tends to be clear or faintly cloudy rather than thick or coloured, unless a secondary infection has developed.
Redness around the edge of the eye
The conjunctiva—the pink tissue lining the eyelids—may appear pinker or more prominent than usual. This reflects mild inflammation in response to the irritation on the cornea.
Later signals
Deepening or enlargement of the dark area
Over weeks to months, the sequestrum may expand in diameter or develop a more irregular shape. The tissue can become jet black and raised slightly above the surrounding cornea.
Cloudiness around the dark patch
The cornea surrounding the sequestrum may lose some of its clarity, appearing hazy or milky. This represents swelling or scarring in the tissue as the eye attempts to isolate the dead area.
Persistent pawing at the face
Some cats begin to rub or paw at the affected side of the face, particularly if the sequestrum has loosened or if an ulcer has formed beneath it. This can increase the risk of further injury to the eye.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
Last reviewed: Invalid Date ·