Eosinophilic keratitis and eosinophilic conjunctivitis are unique syndromes found in cats (and horses). A particular type of white blood cell (the eosinophil) normally responds when allergy or parasites affect the body. In patients with eosinophilic keratitis, these white blood cells invade the cornea and give the eye a pinkish, white, and/or chalky appearance. In the same fashion, eosinophilic conjunctivitis affects the conjunctival tissues covering the sclera (white part of the eye) and the undersides of the eyelids.
Although the cause in many cases is unknown, there is an association with feline herpesvirus infection of the eye. Treatment for eosinophilic keratitis/conjunctivitis is usually medical and may include one or more of the following types of medications: topical anti-inflammatories, topical antivirals, and/or oral anti-inflammatory medications. Injections of steroids next to the affected eye(s) can be beneficial especially in severe cases or for cats who are difficult to treat topically or consistently. Treatment is usually successful but it may take several weeks or longer for resolution of signs. Recheck examinations are usually advised to determine if the condition is controlled, if additional treatments are required, and when therapy can be discontinued. As recurrences are fairly common with this disease (at least 1/3 of cases), it is important to make sure that the condition is 100% controlled before considering discontinuation of therapy. In some cases where recurrences are a problem, long-term therapy might be advised to try to prevent damage from repeat recurrences.