Also known as "pinkeye", conjunctivitis is a common disease in cats characterised by inflammation and pinkness of the conjunctiva (the pink membrane which covers the front of the eyeball and the inside of the eyelids). Conjunctivitis can affect one eye (unilateral) or both eyes (bilateral) and covers a broad range of possible conditions. Conjunctival inflammation can be acute or chronic, infectious or non-infectious. It is extremely important to seek veterinary care when it comes to eye conditions. Failure to do so could result in loss of vision.
What causes conjunctivitis in cats?
There are many possible causes of conjunctivitis in cats which can loosely be divided into infectious or non-infectious. The most common causes of conjunctivitis in cats are FHV-1, Calicivirus and Feline Chlamydophilia. All of which produce flu-like symptoms.
Most bacterial infections occur secondary to viral infections when irritation or damage to the sensitive tissues of the eyes expose them to opportunistic bacterial infections, common pathogens include Streptococci and Staphylococci.
What are the symptoms of conjunctivitis?
The most common symptoms of conjunctivitis in cats are eye discharge along with a meaty like appearance to the eye (as you can see in the image above).
- Ocular (eye) discharge. This will vary depending on the cause of conjunctivitis. It may either be clear and watery or thick, containing mucus or pus. Thick and purulent discharge are more often due to bacterial infection (primary or secondary), watery discharge is more likely to be due to allergy or irritants.
- The conjunctiva becomes red and swollen.
- Pawing and rubbing at the eye.
- Third eye protrusion.
- Ulceration of the eye may also occur in cats infected with FHV-1.
Other symptoms may also be present depending on the underlying disease. The most common causes of conjunctivitis are feline herpes virus and chlamydopilia, both of which typically produce flu-like symptoms such as fever, nasal discharge, and sneezing along with conjunctivitis.
Cats with chlamydophilia may develop conjunctivitis in one eye which then progresses to the second eye a few days later.
How is conjunctivitis diagnosed?
Your veterinarian will perform a physical examination including looking closely at the eyes and type of discharge (watery, thick etc.) and obtain a history from you including how long your cat's eye(s) have been like this, his vaccination history, other symptoms you may have noticed. He may be able to diagnose the cause based on signs and symptoms.
He may wish to perform some tests including:
- Thorough examination of your cat's eye to look for foreign body.
- Conjunctival swab - Your veterinarian may take an eye swab from an infected cat which will be sent to a laboratory for testing. There are several tests which can be performed, including PCR (polymerase chain reaction), Immunofluorescent assay (IFA) or bacterial culture.
- Fluorescein staining - This is a dye which is used to stain and demonstrate ulcerations of the cornea.
How is feline conjunctivitis treated?
Treatment depends on the cause of conjunctivitis. Mild cases of conjunctivitis may only require flushing of the eye with a saline solution. Ideally the causative agent will have been determined.
- Purulent conjunctivitis requires eye irrigations and warm saline soaks to loosen crusted eyelids.
- Antibiotic eye ointment (usually topical tetracyclins) applied several times a day to treat bacterial infections.
- Systemic antibiotics may also be prescribed if your cat has Chlamydophila as recent research has revealed the pathogen may hide away in non-ocular sites.
- Antiviral eye medications for viral conjunctivitis. Even if the cause is viral, your veterinarian may prescribe broad spectrum antibiotics to treat or prevent secondary bacterial infections.
- L-Lysine has been shown to suppress viral replication and inhibit cytopathogenicity for cats with feline herpes.
- Other treatments for cats with chronic FHV-1 conjunctivitis may include topical or systemic interferon and systemic anti-virals such as aciclovor.
- If allergy is the cause, anti-inflammatories may be prescribed as well as removal of the allergen if possible.
- If a foreign object is the cause, removal should solve the problem. This usually involves irrigating the eye with a saline solution to dislodge the object.
- Artificial tears will be used to keep eyes moist for cats with dry eye along with Cyclosporine which is an immune modulating medication which can help suppress immune system inflammation of the tear glands.
- Surgery may be required to correct entropion.
Once a cat has herpesvirus he has it for life. After an outbreak it will lie dormant and be shed intermittently. Shedding is precipitated by stress, and as such, the cat should be kept as stress free as possible. Cats who have conjunctivitis due to infectious causes should be isolated from other cats until they have recovered to avoid spreading the infection.
- Remove discharge from the eyes with a cotton ball gently soaked in warm water.
- Administer all medications as prescribed by your veterinarian.
- Wash hands with warm soapy water before and after handling a cat with conjunctivitis.
- Keep your cat indoors while he is receiving treatment.
Preventing conjunctivitis in cats:
There are routine vaccinations available for FHV-1, Calicivirus and Feline Chlamydophila.
Image courtesy of Nottingham Vet School