Also known as "pinkeye", conjunctivitis is common disease in cats characterised by swelling 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 which cause conjunctival inflammation which 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.
Causes of conjunctivitis:
- Viral infections (Feline Herpesvirus type-1, Calicivirus and reovirus).
- Feline Chlamydophila.
- Bacterial infections.
- Allergies (plants, pollens etc).
- Foreign object (grass seed, hair, eyelash).
- Irritants (eg; smoke, fumes, dust).
- Injury (scratch).
- Keratoconjunctivitis sicca (KCS/dry eye) - This is an inflammation of both the cornea and the conjunctiva and sicca means dry. This is caused by a lack of tears reaching the surface of the eyes which is caused by trauma, inflammation of the conjunctival glands and ducts, scarring etc. 
What are the symptoms of conjunctivitis?
- Ocular (eye) discharge. This will vary depending on the cause of the conjunctivitis. It may either be clear and watery or thick, containing mucus or pus.
- The conjunctiva becomes red and swollen.
- Pawing and rubbing at the eye.
- Third eye protrusion.
- The cat may also show signs of upper respiratory infection such as sneezing, nasal discharge.
This is a mild condition in which the conjunctiva looks pink and swollen. Discharge is clear and watery. Common causes include wind, dust and allergens.
This often starts out as serous conjunctivitis which becomes purulent. Thick secretions crust the lids and the discharge contains mucus or pus. Bacterial infections are often the cause
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. He may be able to diagnose the cause based on signs and symptoms.
He may wish to perform some tests including;
- 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.
- Purulent conjunctivitis requires eye irrigations and warm soaks to loosen crusted eyelids.
- Antibiotics or eye ointment applied several times a day to treat bacterial infections.
- Antiviral eye medications for viral conjunctivitis.
- L-Lysine has been shown to suppress viral replication and inhibit cytopathogenicity.
- If allergy is the cause, anti-inflammatories may be prescribed.
- Once a cat has herpesvirus it 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.
- If a foreign object is the cause, removal should solve the problem.