Conjunctivitis in cats
Conjunctivitis is an inflammation of the eye. To be more precise it is an inflammation of the mucous surface of the eye, which is called the conjunctiva. This conjunctiva is a layer of mucus which surrounds the eyeball. This creates a seal with the inner surface of the cat's eyelids and the nictitating membrane (which is sometimes called the 'third eye'). A healthy conjunctiva is pale, and slightly pink. When infected it swells and become red. This is why cats with conjunctivitis are often referred to as 'red-eyed'. Conjunctivitis is the most common disease of the eye affecting cats.
The most common causes of conjunctivitis are a viral infection, e.g. feline herpes virus type I; or a bacterial infection e.g. chlamydia. However, conjunctivitis can also result from injury to the eye by - for example - a chemical irritant or something getting stuck in the eyelid. There are some immune diseases which can also cause conjunctivitis, but there are relatively rare in cats. Because they are so rare, these causes of conjunctivitis are the most difficult to diagnose and treat.
Diagnosis and treatment
Conjunctivitis in a cat can affect either one eye or both together. It is also possible for an infection in one eye to spread to the other if it is not treated. Cats with conjunctivitis usually have a discharge from one or both eyes. This discharge can be clear, or thick and cloudy. Because the infected eye is sore, and the conjunctiva may be swollen, a cat with conjunctivitis tends to keep an affected eye half-closed. The infected conjunctiva is often red and swollen.
If the conjunctivitis is cased by a chemical irritant or foreign body, improvement is rapid once the original cause has been removed. If you suspect that your cat's eye is infected get the vet to collect a swab from the infected eye for culture analysis. This will tell you what is causing the infection. The vet might also take a blood sample to check whether the cat has an infection elsewhere in her system.
Eye drops or ointments are usually the drugs of choice for treating conjunctivitis and most cats will respond quickly to the treatment. The eye drops are watery solutions that must be applied every few hours, while ointments last longer and are usually only applied two to three times per day. How the cat responds to these drops being administered depends on the character of the cat, but as these drops bring relief, even defensive cats soon learn that the application is not some diabolical torture on the human's part.
It is important that conjunctivitis is treated as soon as possible. Although conjunctivitis is not life threatening, if the infection is not treated it can spread from the conjunctiva and damage other parts of the eye and damage the cat's eyesight. Furthermore, infections or foreign bodies may cause corneal ulcers which is a very serious condition. In any case, conjunctivitis is painful and unpleasant for your cat and should be treated as soon as possible.
Note: This information is for guidance only. It is not intended to replace consultation with a licensed practitioner.