The conjunctiva is a mucous membrane, similar to that of the mouth and nose that surrounds the eyeball forming a seal with the inner surface of the eyelids. The third eyelid is also covered by conjunctiva. In normal cats, the conjunctiva is not readily visible and has a pale salmon pink colour. Conjunctivitis is an inflammation of this membrane, which becomes swollen and reddened, often making it more visible. Conjunctivitis can affect one (unilateral) or both (bilateral) eyes.
Cats with conjunctivitis tend to have a discharge from their eye(s) which can be clear or thick and purulent. The conjunctiva is often more visible and reddened, particularly in the corner of the eye and can be swollen, partially covering the eye. Frequently the eye(s) are held half-closed and the third eyelid is more prominent.
A number of different conditions will cause conjunctivitis, many are sudden in onset and easily treatable, others cause a more chronic disease, which can be more difficult to control.
Mechanical and chemical irritants, trauma (e.g. cat fights) and foreign
Bodies tend to cause sudden onset (acute) conjunctivitis. In most cases treatment is rapidly effective once the cause has been removed.
Immune-based diseases can cause conjunctivitis. These diseases are rare in cats but can be difficult to treat, sometimes management of the symptoms is the only realistic option.
The most common causes of conjunctivitis in cats are infectious agents; these can be viruses, bacteria (most commonly Chlamydia) and mycoplasmas (a group of organisms somewhat like bacteria).
In many cases, conjunctivitis will respond to topical symptomatic therapy using drops or ointment containing antibiotics and anti-inflammatory drugs. In some cases, conjunctivitis does not respond to topical therapy or appears to improve and then gets worse again once treatment has ceased. In such cases your veterinarian may feel that a specific diagnosis is required. As infectious diseases are the most common cause of conjunctivitis, the first step is usually to take a swab from the conjunctiva which is sent for culture to a laboratory. In some cases a blood sample to look for evidence of recent infection is preferred.
If the cause of the conjunctivitis is not infectious then a sample of cells from the conjunctiva can be helpful. A small number of cells can be obtained by scraping the conjunctival surface with a cotton wool swab. If a larger number are required, then a surgical biopsy may be necessary.
What treatments are available –
There are two options for treatment:
Local administration using drops or ointment
Systemic treatment given by injection or by mouth is required to effectively treat some diseases e.g. Chlamydiosis.
Discharges from the eyes are more common in long-haired cats due to eyes being prominent and less protected by the eye socket or abnormalities in tear production.
© Forrest Hill Vets (2000) Ltd