Corneal Sequestrum

Corneal Sequestrum
Christina Korb

What is a corneal sequestrum?
A corneal sequestrum is an unusual disease unique to our feline patients. It appears as a tan to dark brown-black area of corneal discoloration. It can vary in size, shape, and depth, and it is usually accompanied by corneal inflammation and vascularization (blood vessels). The sequestrum is an area of necrosis, or dead tissue, and is commonly associated with chronic, non-healing corneal ulcers. The exact cause for sequestra is unknown, and it can occur in cats of all ages and breeds. Predisposing factors include breed, including Persian, Himalayan, and Burmese, corneal trauma, entropion (rolling inward of the eyelid), and feline herpes virus. A sequestrum can also develop after inappropriate use of a grid keratotomy, which is contraindicated in cats with chronic corneal ulcers.

How is a sequestrum diagnosed?
A corneal sequestrum can be easily diagnosed by your veterinary ophthalmologist with a full ophthalmic exam. The appearance, especially with concurrent ulceration, is diagnostic. Most owners notice signs of ocular pain, including squinting, tearing, and elevation of the third eyelid.

How is a sequestrum treated?
Some sequestra can be managed medically, but most often, they require surgery. Since sequestra are commonly painful and can persist for months to years, surgery is the treatment of choice. After surgical removal of the diseased cornea with a lamellar keratectomy, corneal and conjunctival grafts are typically utilized for stabilization and healing. This surgery requires specialized training, microsurgical instruments, and an operating microscope. Postoperative treatments include topical antibiotics and antiviral medication, as well as use of an e-collar.

What is the prognosis for a sequestrum?
When a sequestrum is diagnosed and treated early in the disease process, prognosis is good. If not properly identified or left untreated, sequestra can lead to deep corneal infection, corneal perforation (a full thickness hole in the eye), and even loss of the eye. Many cats do need long-term treatment with antiviral medication for their concurrent feline herpes virus.