It's not as scary as the evil "glare of death" your cat occasionally fixes you with, but it is dangerous -- for your cat, anyway. When your cat's eyes are barely open or slitted, and wet matter is seeping out, it's a cause for real concern.
What Is It?
Conjunctivitis is just a big word for swelling of the tissues around the eye. It can have many causes, such as a loose hair caught in the eye, an accidental scratch or a bacterial infection. In cats, conjunctivitis is often the result of feline herpesvirus.
Don't panic just yet: Herpes does not pass between cats and humans, and a large portion of the cat population carries the feline herpes virus without any symptoms. Most of the time, in fact, it is dormant. But when a cat suffers injury or endures stress, herpes can attack. In kittens, herpesvirus infection will often look like a cold or upper respiratory infection, but in adults it often just shows up in the eyes. The type of medication your cat will need for his eyes depends on the cause of the conjunctivitis.
Triple-antibiotic ointment, containing neomycin, bacitracin and polymyxin, is usually the standard first line of attack in clearing up conjunctivitis. It's inexpensive and doesn't have any serious side effects. The biggest drawbacks are that it can be difficult to apply if the cat is unwilling, and it has to be applied on a regular basis to be effective. The antibiotic kills any bacteria in the eye, regardless of why it is there. The ointment also helps relieve discomfort from dryness and itching. Antibiotic ointment won't kill off the herpesvirus, but it will clear up an infection that is the result of herpes.
If the infection is serious enough that the eye could be permanently damaged, your vet will probably prescribe an anti-viral ointment or drops. Ulcers on the cornea, for example, might make an anti-viral medication necessary. These ointments and drops are typically expensive, and you must apply them several times throughout the day, sometimes up to five times a day. Unless your cat is unusually sedate, it can be hard to put the drops or ointment in his eyes so many times. Anti-viral drops won't eliminate the herpes virus, but it will stop the damage it can cause.
L-lysine fights off the effects of feline herpesvirus. It can be useful for speeding up recovery or fighting off early signs of infection. L-lysine is available over-the-counter inexpensively and is given orally, making it easier than eye ointments and drops. You can give L-lysine to your cat even when he's not showing signs of eye irritation to prevent future infections. A home treatment like this should be given after consulting with your veterinarian to make sure it done safely.
Normal vaccines serve to prevent diseases, but a nasal feline herpes vaccine can actually speed up healing, too. If your cat has a severe herpes infection in his eyes or gets them over and over again, your vet may give him a vaccination in the form of a nasal spray. Not only will it help with the existing infection, but it can make any future cases of conjunctivitis less severe.