Any medical term that ends in itis means nflammation of. Conjunctivitis is defined as inflammation of the conjunctiva, the membrane that covers the eyeball and lines the eyelids. The cat has a third eyelid, or nictitating membrane, in the inner corner of the eye. This is also covered by conjunctiva. In normal cats the conjunctiva of the eyelids is not readily visible and has a pale, pink color. With conjunctivitis the membranes become swollen and bulge from the lids, take on a deep red color and the tears may become cloudy. Conjunctivitis can affect one (unilateral) or both (bilateral) eyes.
How will I recognize conjunctivitis in my cat?
If you see excessive tearing from one or both eyes, cloudy, yellow or even greenish discharge, and prominent and reddened conjunctival membranes, your cat may have conjunctivitis and should be seen by a veterinarian. Your cat may avoid direct light (photophobia), close or squint its eyes, or the swelling of the conjunctiva may partially close one or both eyes. The third eyelid may protrude and cover the eyeball. The cat may rub its eye.
How is conjunctivitis diagnosed?
A diagnosis of conjunctivitis is made by ruling out conditions such as a foreign object in the eye, blocked tear ducts preventing normal drainage of tears, or injury to the eye surface (cornea) or deeper structures. Because there are many causes of conjunctivitis that do not directly involve the eye, a specific diagnosis may involve cultures and/or blood tests.
What are some of the causes of conjunctivitis?
Causes of conjunctivitis can be roughly divided into two categories: infections from bacteria, viruses or other infectious organisms and non-infectious causes.
What are some of the non-infectious causes?
Breeds such as Persians, Himalayans and other long-haired breeds may be born with a turning in of the eyelids called entropion. Entropion causes corneal irritation when the eyelashes constantly rub against the eyeball. Foreign bodies such as dust or sand may become trapped inside the eyelids, or exposure to irritant chemicals may initiate conjunctivitis that then becomes infected. Allergies are believed to be a common cause of conjunctivitis because the allergens are difficult to pinpoint and avoid.
What are some of the infectious causes of conjunctivitis?
Infectious agents (bacteria, viruses, etc.) are the most common causes of conjunctivitis in cats. In many cases virus infections such as Feline Viral Rhinotracheitis (FVR), Feline Calicivirus (of which there are many different strains) are the initial cause of inflammation. This allows a variety of bacteria such as Streptococci and Staphylococci to move in and cause a secondary infection. Two special organisms, Chlamydia and Mycoplasma can also cause conjunctivitis.
These infections may be contagious between cats, so infected cats should be kept separated from healthy cats to avoid contamination. While viruses are usually species-specific, bacteria can contaminate wounds of any organism. Always wash your hands after handling a cat with conjunctivitis or any suspected bacterial infection.
How can these causes of conjunctivitis be diagnosed?
Because most cases of conjunctivitis have a bacterial component causing much of the symptoms and because there is a need to reduce the immediate pain and inflammation, treatment is usually begun without a specific diagnosis. In cases that are not improving or where there is need to make a definitive diagnosis, swab samples may be taken from the eyes and sent away for specialized laboratory culturing and microscopic examination. Blood samples may be tested for infectious diseases such as feline leukemia or FIV, which may suppress the immune system and leave the cat more susceptible to infections.
What treatments are used?
The general approach is to use preparations containing antibiotics to control the bacteria and anti-inflammatory drugs to reduce the inflammation and encourage healing. These preparations come as either drops or ointment for instilling into the eyes. Systemic treatment with injections or oral medication may be added if there is significant swelling or evidence of accompanying upper respiratory disease, as occurs with some feline viral complexes.
How should eye medication be administered?
Regular and frequent treatment is essential. Most ophthalmic drops need to be administered at least 4-6 times a day. Ointments may require less frequent administration but may be more difficult to administer. Two people may be necessary: one to hold the cat and the other to administer the ointment, at least until the discomfort and sensitivity of the eyes has decreased. Apply 1/4 to 1/2 inch of ointment to each eye and then close the lids to smear the ointment across the eyeball. Liquid preparations can be applied directly onto the surface of the eye; one or two drops per eye are usually sufficient.
When should I expect a response?
Normally you will expect a rapid improvement after a few days. But even if the conjunctivitis has resolved, do not stop treatment until the end of the prescribed period. Stopping your cats medication early may allow a resurgence of the infection and make it harder to eliminate the next time.
Can the conjunctivitis recur?
With some non-infectious causes, if the underlying cause is not removed the conjunctivitis will recur. Some of the viruses that cause infectious conjunctivitis may persist in a hidden form or as chronic infections and flare up from time to time, especially during periods of stress or illness.
If the conjunctivitis was caused by a simple irritant or one-time exposure to a bacterial contaminant, it should resolve with treatment and cause no further problems.