Conjunctivitis – “Pink Eye”

Feline conjunctivitis is most frequently caused by an infectious agent, such as those explained below. Other causes include tear dysfunction, drug sensitivities, allergies, etc. Conjunctivitis - feline - three kittens

The conjunctiva consists of the pink tissue, which surrounds the eye and lines the underside of the eyelids. When this tissue becomes irritated and inflamed it becomes much more prominent and noticeable (chemosis). Other signs of ocular irritation may be seen with conjunctivitis including increased tearing, more frequent blinking, and holding the eye partially closed. These symptoms may be present in one or both eyes. Many cats being presented for evaluation of conjunctivitis have a history of upper respiratory tract infections.

Feline Herpesvirus
Feline herpesvirus is the most common infectious cause of feline conjunctivitis. This virus is often acquired as a kitten and remains in an inactive state in nerves until times of stress. During times of stress, when the body’s immune defense is decreased, the virus is able to reactivate and replicate causing unilateral or bilateral conjunctivitis, ocular discharge, and occasionally superficial ulcers on the cornea. This virus is also able to cause concurrent cold symptoms such as sneezing and nasal discharge. Typically, the clinical signs are the most severe during the initial infection with the virus (usually as a kitten). The level of stress that causes reactivation of the virus varies greatly between individuals. Treatment is aimed at minimizing stress and giving supportive care (e.g. keeping the eyes and nose clean and clear of discharge). For individuals that do have frequent recurrence of symptoms, the amino acid L-lysine may be recommended as a dietary supplement. This amino acid does not treat acute outbreaks of the disease but has been shown to decrease the frequency of recurrences.

Eosinophilic Keratitis/Conjunctivitis
This disease has no known cause, but it has been associated with herpesvirus infection and allergies. Aside from conjunctivitis this disease may cause cells to infiltrate the cornea giving it a cloudy appearance. Diagnosis is made based on cytology of corneal and/or conjunctival swabs. The appearance of a certain cell type (eosinophils) on cytology confirms the diagnosis. Treatment is aimed at decreasing the immune response using topical medications. Long-term treatment is usually necessary.

These bacteria may not be able to cause disease on their own; however, they may be a more important cause of conjunctivitis in cats that have concurrent herpesvirus infection or have weakened immune systems. Treatment involves topical and possibly systemic antibiotics.

These are bacteria that may cause mild upper respiratory signs and severe conjunctivitis. The conjunctivitis may begin in one eye, but usually spreads to the other eye within 7 to 14 days if no treatment is initiated. Cats with long-standing Chlamydophila conjunctivitis may develop a nodular appearance to their third eyelid. Diagnosis of Chlamydophila conjunctivitis is made based on clinical signs and cytology. Treatment involves applying topical antibiotics to the eye.

· Schirmer tear test

· Fluorescein staining to look for corneal ulcers

· Intraocular pressure

· Slit-lamp examination and indirect ophthalmoscopy

· Cytology or culture/sensitivity may be recommended

For more information on this subject, speak to the veterinarian who is treating your pet.