Corneal Sequestrum

A corneal sequestrum is a dense, black spot on the cornea (the clear front part of the eye). This condition appears to be unique to cats as there are only a few reports of suspected sequestra in other species. The development of a sequestrum follows this sequence: A cat suffers trauma, exposure or infection of the cornea, usually resulting in a corneal ulcer (a defect in the surface layers of the cornea). Sometimes, for reasons that are not understood, these corneal ulcers fail to heal and the exposed layers become sequestered from the healthy adjacent cornea and undergo cell death. Pigments or other substances in the tear film may accumulate in the affected tissue, coloring the ulcerated area black. This dark, discolored area is called a corneal sequestrum. A corneal sequestrum is thus an area of dead, discolored cornea, almost like a "scab".

A sequestrum may eventually slough from the cornea after a long period of time; alternatively, it may remain in the cornea and progress deeper through this tissue. Surgery is recommended if cats are painful or if the sequestrum persists for longer than a few months. The reason is that if a sequestrum is present for a long time, it may progress more deeply into the cornea and the area surrounding it may become infected. Removal of a deep sequestrum is more difficult than removal of a superficial one, and if it is very deep, then there is a risk of perforation of the eye.

Following removal of the sequestrum, we recommend placing a conjunctival graft or a corneoconjunctival transpositional graft into the area where the sequestrum was removed. If a sequestrum is removed and the cornea is then left uncovered there is a significantly higher risk of the sequestrum recurring. Placement of either type of graft helps to prevent recurrence of the sequestrum. The surgical area may always retain somewhat of a scar, but it will become clearer over time.