A corneal sequestrum is a brown or gold-colored area of degenerated corneal tissue that is similar to a scab. These tend to affect areas on the cornea where there has been long standing irritation. Corneal sequesta typically occur in cats. Any breed of cat can be affected, however, the Siamese, Persian, Himalayan, and Burmese breeds are particularly susceptible.

Conjunctivitis and keratitis are common eye problems in all ages of cats. Conjunctivitis refers to the inflammation of the pink membranes surrounding the eye whereas keratitis refers to the inflammation of the cornea. Signs of conjunctivitis may be coupled together with keratitis and is then termed keratoconjunctivitis. A number of infectious agents, namely viruses and bacteria have been identified as possible underlying causes of these two conditions. These infections may be contracted as a kitten from the mother or from other cats.

Feline herpesvirus (FHV-1) is a common cause of eye and upper respiratory infection in the cat. This virus is very common in the cat population, but it is not contagious to people and other species of animals such as dogs. Herpesvirus is easily passed from one cat to another through sneezing, coughing, grooming and/or simply being in close contact with an infected cat. Clinical signs associated with infection can vary greatly between cats. Some cats affected with FHV-1 may only have mild conjunctivitis of one or both eyes. Other cats with more severe forms of the disease may show ocular (eye) and nasal (nose) discharge, conjunctivitis (inflammation of the white part of the eye), coughing, sneezing and corneal ulcers. Corneal ulcers can be very painful and serious enough to cause noticeable scarring on the normally clear cornea. An infected corneal ulcer may even progress to cause perforation (rupture) of the eye.

 

Uveitis is an inflammatory process involving the middle of the three layers in the eye. To understand uveitis it is important to know the basic anatomy of the eye. The outer layer enclosing the eye is composed of the clear cornea and the white sclera. The innermost layer is the nerve layer or the retina. The middle layer is the uveal tract, which is rich in blood vessels. It is composed of the iris in the front part of the eye, the ciliary body, which produces the fluid (aqueous humor) inside the eye, and the choroid which nourishes the retina in the back of the eye. Because of its rich blood supply, the uveal tract is a natural target for diseases originating in other parts of the body. When inflammation attacks specific segments of the uveal tract, the disease is further classified as iritis (inflammation of the iris), cyclitis (inflammation of the ciliary body) or choroiditis (inflammation of the choroid), depending on the affected structure. If all the structures are inflamed then it is called panuveitis (inflammation of all uveal structures of the eye).

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 ofinflammatory 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.