Conjunctivitis in cats

Conjunctivitis is the inflammation of the conjunctiva, which is the inside of the eyelids and the whites of the eye.  A cat with conjunctivitis will often appear to have a red, swollen and partially or completely closed eye.  The condition is very uncomfortable for the cat and it can progress to problems associated with self-trauma to the area, as well as inflammation inside the eye that is more painful and difficult to treat.  It is vital that you seek veterinary assistance if you notice that your cat’s eye looks to be affected.

Causes

The most common cause of conjunctivitis in cats is due to cat flu.  There are a number of pathogens associated with cat flu, with the most common being feline herpes virus, feline calicivirus and a chlamydial (bacterial) infection.  Herpes viruses re-emerge when cats are stressed or immuno-compromised (eg. have feline AIDS) so often there is an under-lying illness or sometimes a behavioural issue (eg. an anxious cat having a new cat introduced into the household).

Cat flu is transferred in infected discharge from the eyes and nose.  It is very contagious and can be contracted by either direct contact between cats or via infected food bowls or bedding.  Pure breed and shelter cats are more likely to experience cat flu as they have a higher likelihood of exposure.

Conjunctivitis can also be seen when cats have reactions to various allergens such as plant pollens, fleas and foods.  Foreign bodies, such as grass seeds as well as cat scratches to the surface of the eye, can lead to corneal ulcers which then results in conjunctivitis.  The loss of the supporting fat pad behind the eye in cats that lose a lot of weight due to illness, can cause the eyeball to sink into the eye socket and the eyelids to roll under. This causes the fur to rub on the surface of the eye causing irritation which can lead to conjunctivitis.

Signs/Symptoms

The common signs of conjunctivitis include a red, swollen, irritated and painful eye.   The third eyelid that is located on the inside of the eye may protrude as it too becomes inflamed and swollen.  You may notice a white, green or clear discharge from the eye.   If your cat is affected by cat flu you will most likely notice signs such as sneezing, lethargy and inappetence due to ulcers on the tongue and gums.  You may be able to observe some changes to the surface of the eye due to inflammation or ulceration (erosions of the surface of the eye).

Diagnosis

Getting a history

Any information you can give your vet about your cat’s eye, general health and their behaviour will help with the eventual diagnosis.

Some of the questions that you may be asked include:

  • How long has the eye been affected?
  • Has your cat had any previous eye problems or had cat flu in the past?
  • Has there been any contact with cats that may have had cat flu?
  • What is your cat’s vaccination status?
  • Has your cat been in any recent cat fights?
  • Have you noticed if your cat is sneezing, lethargic, lost their appetite or has smelly breath?
  • Are there other cats in the household and are they showing any symptoms?

Clinical examination

The next step is for the vet to examine the eye and determine the cause of the conjunctivitis.

Some of the things your vet will do include:

  • Examining the eye with a light to check how well the pupil constricts (this indicates if the eye is inflamed on the outside or the inside of the eye).
  • Placing local anaesthetic in the eye to allow for a better examination as the eye is more comfortable and can open further.
  • Looking for foreign bodies such as grass seeds under the eyelids (including the third eyelid).
  • Placing an orange coloured stain called fluroscene in the eye to check for corneal ulcers.
  • Checking for other clinical signs such as sneezing, nasal discharge, oral ulceration, inappetence or a high temperature.
  • Further testing including a blood test to check for FIV (feline aids), swabs taken from the eye to check for various bacteria, cells etc.
  • Referral to an eye specialist as required.

Treatment

Depending on the cause of the conjunctivitis one or more of the following may be prescribed or recommended to treat your cat.

  • Oral antibiotics - specifically ones that concentrate well in the tear film and/or the respiratory tract if cat flu is present.
  • Eye medication - antibiotics or anti-viral medications may be selected.
  • Oral anti-inflammatories.
  • Ocular anti-inflammatories.
  • Anti-viral medications such as lysine powder can be used long-term to help prevent recurrence of herpes virus.
  • Surgery- a third eyelid flap (to protect the eye), conjunctival graft (referral procedure to repair a deep, non-resolving corneal ulcer), entropian surgery (to stop the eyelids rubbing on the cornea).
  • Treatment of allergies- medication, food trial etc.


Problems with the eyes are very uncomfortable for your cat and should you notice an inflamed eye it is best to immediately have this checked by your vet.  If cat flu is diagnosed then often there is a long term treatment and management plan established to prevent a recurrence.