Eosinophilic keratitis is an inﬂammatory condition that affects the cornea and/or conjunctiva. The characteristic appearance is white, tan or pink roughened plaques on the corneal surface. These plaques are composed of inﬂammatory cells known as eosinophils. The cause of eosinophilic keratitis is believed to be related to an underlying feline herpesvirus infection. This disease is progressive and can grow to involve the entire surface of the eye causing blindness and discomfort. Often it is initially detected in one eye; however, the disease often progresses to involve both eyes.
Superficial corneal scraping is usually adequate to obtain a diagnosis, which is confirmed by the presence of eosinophils under light microscopy. Occasionally, microscopic examination is not sufficient for diagnosis and further diagnostics may be recommended.
Due to its suspected association with feline herpes virus (FHV-1), diagnostic testing and/or empirical treatment for herpes virus may also be indicated. Treatment for eosinophilic keratoconjunctivitis consists of topical anti-inﬂammatory medications and/or systemic hormonal modification. Ovaban (megestrol acetate) is a synthetic progesterone (hormone) used to treat this disease. It is very effective but does have possible side effects, which may include transient diabetes mellitus, enlargement or (rarely) cancer of the mammary gland, and liver toxicity. The length of treatment is variable and some cats may have disease recurrence when medications are discontinued. The majority of patients can remain comfortable and visual when there is client compliance with respect to the medication schedule.