Corneal Sequestrum

The cornea is the clear windshield to the eye. A sequestrum is an area of corneal necrosis (dead tissue) which is typically brown or black in color. Corneal sequestra occur in areas of chronic corneal irritation. The irritation can be due to a prominent globe, poor tear film, decreased blink response, a chronic ulceration, or feline herpes virus. Typically, a sequestrum will affect the superficial layers of the cornea; however, they can extend into the deeper layers of the cornea and even lead to corneal perforation and vision loss. Persians, Himalayans, and Burmese cats appear predisposed to corneal sequestrum formation, but any breed may be affected.

Symptoms

The first symptom of a sequestrum may be a brown or black tinge developing in the cornea. This may only be visible in certain light. Usually, cats will also exhibit squinting, tearing, and redness in the affected eye.

Diagnosis

The diagnosis of a corneal sequestrum is made during the slit lamp examination. Fluorescein stain may also be applied to the cornea to evaluate the health of the tear film and diagnosis any corneal ulcers.

Treatment

The treatment of choice for corneal sequestra is a superficial keratectomy. The affected portion of cornea is surgically removed leaving only clear cornea behind. The procedure is performed with the aid of an operating microscope and microsurgical instruments. Surgery alleviates the discomfort associated with corneal sequestra, prevents the sequestrum from progressing, and shortens the overall healing time of the cornea. In some cases, a conjunctival or synthetic tissue graft is placed over the surgical site.

In cases where surgery is not an option, medical therapy will be prescribed, and will be long term. Antibiotics, artificial tear lubricants, and anti-viral medications may be prescribed. Without surgery, corneal sequestra typically require prolonged medical therapy.

Prognosis

Prognosis for a corneal sequestrum is typically very good with surgery. Rare complications can occur with surgery to include: infection at the surgical site, corneal scarring, graft dehiscence, corneal mineralization, and (rarely) recurrence of the sequestrum.