Barn Kitten with conjunctivitis - photo Lee (Flickr). I have used this sad picture before.
Feline conjunctivitis is inflammation of the conjunctiva. The conjunctiva is a clear mucous membrane consisting of cells and underlying basement membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids1. "Itis" means inflammed in medical parlance. It is one of the most common health problems that cats have with their eyes3.
What causes the inflammation? Usually viral or bacterial infections. Other non-infectious agents that can cause inflammation are: tumors, dermoids (cysts of mature skin and hair and other tissue), trauma, foreign bodies, allergic disease, fungal infection (rare) and pre-corneal tear film abnormalities.
The most common viral infectious agent is Feline Herpes Virus (FHV). A common baterial infection is caused by Chlamydia psittaci (30% of cases perhaps). The Feline calicivirus can also cause feline conjunctivitis. When one eye is first inflamed and then a second this indicates a bacterial infection (Chlamydia or Mycoplasma). Conversely if both eyes are involved a viral infection is indicated3.
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The inflamed eye will look red and swollen. There is usually a watery discharge "as a result of pain"2. If the discharge is yellow and sticky it indicates a bacterial infection. Feline conjunctivitis is not painful to the cat (this conflicts with the above)3. The eye is irritated and may itch. The cat may paw at the eye for this reason. If the eye is painful to touch the condition might be: keratitis (the eye's cornea, the front part of the eye, becomes inflamed1), uveitis (inflammation of the middle layer of the eye1) or glaucoma (a disease in which the optic nerve is damaged, leading to progressive, irreversible loss of vision1).
Treatment for bacterial infections is administering antibiotics which is effective in for individual cats. An ointment is applied to the eye at regular intervals. Multi-cat households are harder to treat. Antiviral eye medication will be prescribed by a vet if needed.
Mild forms can be treated at home. The eye(s) should be cleaned with a dilute solution of boric acid for ophthalmic use or a sterile ophthalmic irrigating solution for people (buy over the counter). Improvement should occur within 24 hours and if not a trip to the vet is needed3.
New born kittens can contract feline conjunctivitis before their eyes open after 10-12 days. Infectious agents or bacteria can enter the closed eye. FHV can also affect a new born kitten by being transmitted through the mother's milk or at birth.
Feline Conjunctivitis - associated pages:
Feline Eye Disease (new window)
Feline Herpes Virus (new window)
1. Verbatim quote Wikipedia authors
2. Veterinary Notes for Cat Owners by Trevor Turner DVM and Jean Turner VN
3. Cat Owner's Home Veterinary Handbook by Drs Carlson and Giffin