Conjunctivitis in dogs

If your dog has a sore or red eye, or there is discharge from the eye, then it is important to contact your vet. Your dog may have an infection in the eye, but a discharge can also be caused by a foreign body (such as a grass seed) caught under the eyelid. It is important that diseases of the eye are treated quickly to prevent any permanent damage being done.

The conjunctiva is the pinkish surface surrounding the eyeball. The third eyelid is an extra protective eyelid in the dog and is also covered by conjunctiva. In normal dogs the conjunctiva is not readily visible. In conjunctivitis this membrane is inflamed and becomes red and swollen. Conjunctivitis can affect one or both eyes.

Dogs with conjunctivitis usually have a discharge from their eye(s). This can be clear and watery or thick and greeny/yellow in colour. The conjunctiva is often more visible and may be swollen, partially covering the eye. The eye(s) may be 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 long term disease which can be more difficult to control.

  1. Irritants, trauma (e.g. a cat scratch) and foreign bodies (e.g. grass seeds) can cause conjunctivitis. In most cases treatment is rapidly effective once the cause has been removed.
  2. Conjunctivitis in dogs usually occurs as a consequence of some other eye problem. In dogs with sagging skin, the deformity of the eyelids can make them more prone to eye infections. In some dogs the eyelids turn inwards and hairs on the eyelid can rub against the eye causing damage and increasing the risk of infection.
  3. A further problem in some dogs is abnormal tear production, inadequate lubrication of the eyes can result in damage to the eye surface.
  4. Disease of the immune system can also cause conjunctivitis. These diseases are not common but can be difficult to treat.

Usually your vet will be able to tell that your dog has conjunctivitis by a simple examination. Your vet will want to examine the eye carefully to be sure there is no damage to the eye itself. If there is no obvious traumatic cause most cases will respond to drops or ointment containing antibiotics and anti-inflammatory drugs.

It is also important to be sure that tear production in the eye is normal. Your vet will be able to do a simple test in the consulting room to check this if necessary. If a foreign body is present then this obviously needs to be removed.

If the signs are not getting better after a few days of treatment, or appear to improve only to get worse again when treatment stops, more investigation is required. Your vet will want to take a swab from the conjunctiva to look for infection. In some cases a blood sample may also be required.

If there is no infection then it can be helpful to look at a sample of cells from the conjunctiva. This sample is obtained by gently scraping the surface of the conjunctiva with a cotton wool swab or spatula. If a larger sample is required, then a section of conjunctiva taken surgically may be necessary.

In most cases conjunctivitis is treated by application of drops or ointments to the eye. Sometimes with particularly stubborn infections antibiotic treatment may also need to be given by injection or tablet.

It is essential to treat any underlying causes of conjunctivitis at the same time – if these are not dealt with the problem will keep coming back. Treatment may be needed to control problems with the immune system and if the eye is too dry then replacement tears may be required. If the tear replacements are needed they are most likely to be required lifelong.

If you are able to treat your dog’s eyes this can be done at home but regular treatment is essential. Most drops or ointments need to be administered at least 3-6 times a day. If you have any doubts as to how to give the medication prescribed, please ask your veterinary practice to give a demonstration. If you are unable to treat your dog appropriately your vet may arrange to keep it in the hospital for a few days to ensure that effective treatment is given.