Corneal sequestrum

Corneal sequestrum is a condition unique to cats, especially Persian, Siamese, Burmese and Himalayan, Colorpoints and Abbysinians breeds. It can affect any age of cat except the neonate. The sequestrum is a result of corneal necrosis (death of the corneal cells). The dead tissue becomes pigmented and then usually sloughs (falls out), leaving a pigmented ulcer.

The signs usually consist of a history of blepharospasm (eyelid spasm), third eyelid protrusion and lacrimation (tears). The condition is normally unilateral (one eye) and may appear amber, brown or black and oval to circular in shape. The edges are often slightly elevated and usually only the periphery of the ulcer will stain with flourescein (a dye that stains ulcers a deep green color). The edges of the sequestrum may have fine blood vessels growing into it. Corneal sequestrum occurs in the central or paracentral (near the centre) cornea.

The cause of corneal seuqestrum is not known, but there is usually a history of some form of irritation to the cornea. Feline Herpes virus has also been suggested as a potential factor.

The appearance and location of this condition is quite unique and is often enough for diagnosis. Specialised blood tests or conjunctival scrapings can be used to evaluate cats for herpes virus infection.

The treatment of choice is surgery primarily because the condition is uncomfortable and will take months to years to heal on its own. The affected cornea is removed using an operating microscope to visualise the cornea. The third eyelid is then pulled over the eye and temporarily sutured in order to protect wound and allow it to heal. If the sequestrum is deep or recurs then a conjunctival graft is used. This involves cutting a small flap of the conjunctiva and moving it over the defect, suturing it in place. Antibiotics may be required if secondary infections become a problem.