ADVICE
Conjunctivitis
Conjunctivitis is an inflammation of the conjunctiva. The conjunctiva is a mucous membrane similar to the lining of the mouth and nose. It is a layer of epithelial cells with mucus-secreting cells that covers the eyeball and lines the eyelids. Cats and dogs have a third eyelid, or nictitating membrane, in the inner corner of the eye. This is also covered by conjunctiva.
Conjunctivitis often involves both eyes, but one eye may be affected in certain conditions.
What are the signs?
- Excessive tearing
- Cloudy yellow or even greenish discharge
- Prominent or reddened conjunctival membranes
- Your pet may squint, keep its eyes closed, rub at its eyes or paw at its face, either because of a reluctance to being in bright light or because of pain
- In severe cases, the third eyelid or conjunctival tissue may be so swollen that it may partially or fully cover the eye
- Conjunctivitis may occur alongside other clinical signs, including nasal discharge, sneezing or coughing.
Causes of conjunctivitis
Infectious causes of conjunctivitis
Infectious agents such as bacteria, viruses, and fungi are the most common causes of conjunctivitis in dogs and cats.
In cats, virus infections such as feline viral rhinotracheitis (FVR), also known as feline herpesvirus or feline calicivirus, are the initial cause of inflammation. Primary viral infections are often complicated by secondary bacterial infections with a variety of bacteria, including Streptococci and Staphylococci. Two special organisms, chlamydia and mycoplasma, are also capable of initiating primary conjunctivitis.
Non-infectious causes of conjunctivitis
Some dog breeds may be born with a turning in of the eyelids called entropion. Entropion causes corneal irritation when the eyelashes constantly rub against the eyeball. Foreign bodies, such as dust or sand, may become trapped inside the eyelids. Exposure to irritant chemicals may initiate conjunctivitis that may become secondarily infected.
Allergies are believed to be a common cause of conjunctivitis because the allergens are difficult to pinpoint and avoid.
Diagnosis
A diagnosis of simple conjunctivitis is made after conditions such as a foreign body in the eye, blocked tear ducts preventing normal drainage of tears, or injury to the eye and cornea are ruled out.
Specific tests will be performed, based on the medical history and results of the eye examination. A conjunctival scrapings or biopsy sample may be obtained and sent to a diagnostic laboratory for specialised testing. The nasolacrimal ducts, or tear ducts, may be flushed to ensure proper drainage. Blood tests may be performed to determine if the conjunctivitis is related to a systemic condition.
Since secondary bacterial infections cause many of the symptoms in most cases of conjunctivitis, and because there is a need to reduce the immediate pain and inflammation, a symptomatic treatment is usually begun without a specific diagnosis.
What are the treatment options?
The general approach to non-specific conjunctivitis is to use ophthalmic preparations containing antibiotics to control the bacteria and anti-inflammatory drugs to reduce the inflammation. These preparations come as either drops or ointment for application into the eyes. Local treatment may need to be supplemented with oral medications.