Corneal sequestra in cats

Feline corneal sequestration is a dramatic and unusual corneal disease unique to domestic cats. It refers to the development of an opaque, dark brown to black plaque on the cornea which is a dead piece of corneal tissue. Sequestra are usually oval to round, they can be quite small to quite large, and they can extend deeply into the corneal tissue. Some sequestra have the appearance of a shiny piece of black patent leather on the surface of the eye. Others have a browner, more bronzed appearance. Corneal sequestration can occur in cats of all ages and breeds. The breed with the highest frequency of occurrence is the Persian breed. Other at-risk breeds include Siamese, Burmese, and Himalayan. Sequestra can be painful. The signs of ocular pain may be subtle and include squinting, tearing, and elevation of the third eyelid. Sequestra can remain for months to years and can cause secondary inflammation and/or infection. Additionally, the dead corneal tissue can act as a foreign body, causing the immune system to attack the sequestrum. During this attack, neighbouring healthy corneal tissue is damaged, and the eye can rupture. A sequestra can extrude (slough) from the eye¹s surface and cause eye rupture. If this occurs, the eye unfortunately might need surgical removal (enucleation). 

The exact cause of feline sequestra is unknown. However, the development of a sequestrum is often associated with corneal trauma, dry eye syndrome, abnormal eyelid conformation, and/or Feline Herpes Virus infection. Genetics and conformation may also be involved since there is a definite breed predisposition. A thorough ophthalmic examination is essential to uncover any underlying problems. 

Since sequestra are painful, can remain for months to years, and can lead to eye rupture, early surgical removal of the sequestrum is the treatment of choice. The surgical procedure to remove a sequestrum is called a Partial Lamellar Keratectomy. This surgery is performed using an operating microscope, micro-surgical ophthalmic instruments, and with the patient under general anaesthesia. If the sequestrum is deep, a conjunctival graft or a corneal transplant is sutured into the keratectomy site. 

The prognosis for the eye to be free from pain and to have normal clinical vision is good with surgery, especially if the sequestrum is removed at an early stage. However, the tendency to form a sequestrum is that individual cat's response to corneal irritation, and additional episodes may occur in one or both eyes in the future. To help prevent any recurrences, notify your veterinarian immediately if any new eye injuries occur.