Corneal Sequestrums

A corneal sequestrum, a localized area of degenerative corneal tissue, is a manifestation of an ocular disease that most likely occurs in, but is not limited to, Persians and Himalayan cats. A cat owner may first notice squinting, tearing, and /or abnormal eye discharge. The cat may make an effort to rub the eye as well. On closer examination, a brown or black spot may be evident when looking at the front of the eye, the cornea.

When presented to a veterinarian, the observation of this brown spot is diagnostic for the condition. It is possible that a foreign body in the cornea can appear to look like this, so needs to be ruled out. Diagnostic tests may include a Flourescein stain to look for an ulcer and a Schirmer Tear test to check for appropriate tear production. A detailed examination of the eye will include checking for entropion, a folding in of the eye lid, and abnormal eyelashes that may cause irritation. Evaluation for Feline Herpes Virus 1 may also be indicated.

The tests performed will look for a cause of the sequestrum. In some cases, the cause will be unable to be determined. The most common causes are Feline Herpes Virus 1, keratoconjunctivitis sicca (dry eye), trauma, entropion, and corneal irritation or ulcer. Determining the underlying cause is helpful in order to successfully treat a sequestrum. For example, if a cat has dry eye, that problem has to be addressed with medication. Abnormal eyelashes must be removed and entropion must be surgically corrected. Antiviral eye drops are indicated when herpes is suspected.

It is not completely known what causes the formation of a corneal sequestrum. Most likely, a sequestrum is the result of a previous or chronic corneal ulcer. These, in turn, are often linked to herpes or one of the other previously discussed causes. . Management of this condition depends on the underlying cause and the extent of the lesion. All painful chronic sequestrums are likely to benefit from surgery to excise the lesion, called a keratectomy, performed by a veterinary ophthalmologist. Lesions that are not causing pain may be managed by treating the underlying condition as described. Severe cases that progress can lead to rupture of the eye; prompt treatment is imperative to prevent this consequence.

photo  at top courtesy of Rhea Morgan DVM DACVIM DAC VO