Feline Corneal Sequestrum

What is the cornea?
The cornea is the outermost, transparent layer of the eye, less than one millimeter thick. To remain transparent, the cornea contains no blood vessels. However, this makes it prone to infection and slows the healing of injuries.

What is a sequestrum?
A sequestrum is an area of dead corneal tissue that the surrounding healthy cornea tries to get rid of. The lesion has a brownish tint, and in more severe cases may be accompanied by inflammation, which can involve the appearance of blood vessels.

Sequestrum occurs almost exclusively in cats.

Is the sequestrum causing a problem for my cat?
It probably is. Because of the sequestrum:

• Due to the brown lesion, light cannot pass through this area of the eye, which can cause visual impairment.
• The body attempts to remove the dead tissue, which can lead to corneal ulceration.
• The process is painful: the cat may tear up, squint, or rub its eye with its paw.
• In severe cases, the infection can even lead to loss of the eyeball.

Why did my cat develop a sequestrum?
Although research is ongoing, the exact causes are not fully understood. The following factors may predispose a cat to developing a sequestrum:

• Frequent ocular surface trauma – more common in brachycephalic (flat-faced) breeds (e.g., Persian cats), because their eyeballs are more exposed to environmental effects.
• Inward-turning eyelid (entropion), which causes ongoing irritation.
• Inadequate tear production – considered a particular risk factor in Sphynx cats.
• Feline herpesvirus infection.

How can my cat be treated?
There are two main treatment options: conservative and surgical treatment.

Conservative treatment
If the sequestrum is small and not painful:

• Antibiotic treatment
• Continuous lubrication of the eye surface

The goal is for the cornea to remove the dead tissue on its own. However, there is no reliable information on how long this may take.

Surgical treatment
If the sequestrum grows, causes pain, or becomes infected, surgical intervention is required, because the sequestrum can deepen and the eyeball may even perforate.

There are several surgical techniques, which provide differing levels of vision after the procedure:

• Removal of the dead tissue and placement of a contact lens: A soft contact lens is placed on the eye to protect the cornea.
• Pedicle conjunctival flap: After removal of the sequestrum, a conjunctival flap is sutured over the area to bring blood vessels into the cornea and promote healing.
• Graft implantation: After removal of the sequestrum, a corneal replacement material (e.g., amniotic membrane) is sutured over the wound, which promotes healing and improves corneal transparency.
• Corneal flap transposition: When the dead tissue is removed, the defect is filled using the cornea's own tissue, thereby increasing vision after surgery.

Does the surgery carry any risk?
Yes, corneal surgeries are performed under general anesthesia, which carries minimal risk. The most common complications are:

• If the sequestrum is only removed without placing a graft, the condition may recur.
• If a graft is implanted, in rare cases the graft may fail to integrate, and a further surgery may be needed.

What should be done after the surgery?
Following the surgery:

• The cat must wear a protective (Elizabethan) collar for at least 10 days.
• Antibiotic eye drops must be used.
• Oral pain relief may be needed during recovery.

Most patients become pain-free within 2 weeks and can return to their normal life.