Dog - Corneal Ulcers

What is the cornea?

The cornea is the clear part of the front of the eye through which the coloured iris can be seen. Although transparent the cornea is composed of several different layers (a bit like an onion).

What is a corneal ulcer?

A corneal ulcer is an erosion through the outer layer(s) of the corneal cells. If damage is only to the very superficial (shallow) layers it can be called corneal erosion, corneal abrasion or shallow ulcer. Deeper ulcers involve more layers of the cornea (e.g. the stroma) and are potentially very serious.

How do I know if my dog has a corneal ulcer?

Corneal injuries are painful no matter whether it be a superficial abrasion or a deep injury, e.g. a cat scratch. The first sign you are likely to see is a tightly shut eye. Frequently there is an ocular discharge - watering of the eye. If the corneal injury is infected the discharge may be coloured or pus-like. The white of the eye will also appear red due to inflammation.

What causes a corneal ulcer?

Trauma or injury is the most common cause. This may simply be the result of the dog rubbing an itchy eye (i.e. blunt trauma) or be due to a cat scratch, injury from a grass awn or damage from a protruding branch. Irritating shampoo or cigarette smoke can also cause ulceration.

Bacterial and viral infections are other causes. The condition may also be secondary to other ocular problems, e.g. entropion (abnormal eyelid position).

Are some dogs more prone than others?

Dogs with very prominent eyes such as Shih Tzus, Pekingese and Pugs tend to suffer from corneal ulcers. Young dogs playing in undergrowth, and working breeds, are also at risk due to trauma.

In the Boxer, an inherited weakness in the cornea (epithelial dystrophy) can lead to superficial ulcers which are often slow to heal. Similar problems can develop in older dogs of any breed.

The West Highland White Terrier and other breeds can suffer from a condition known as dry eye - Keratoconjunctivitis sicca (KCS) which results in lack of tear secretion. This drying of the cornea increases the risk of ulceration. See handout on Dry eye – keratoconjunctivitis sicca (KCS).

If my dog suddenly keeps his eye tightly shut, is there anything I can do?

Please contact us. It is better to be safe than sorry. Gentle bathing with cold water is a useful first aid measure. Try to part the lids if your dog will allow you, you may be able to identify a foreign body, e.g. grass seed. Sometimes grass seeds and other debris lodge under the lids. The foreign body may be simply removed but although this may relieve the immediate pain, an urgent follow up visit to the vet is still a sensible precaution. We can then check for any corneal damage and prescribe any eye drops if necessary.

What is the treatment for a corneal ulcer?

This depends upon severity. Eye preparations, e.g. ointments or drops are usually prescribed to prevent infection and relieve pain and discomfort. If the ulcer is fairly deep there is always a risk that the eyeball would perforate and surgery may be necessary.

Other treatments involve the use of special contact lenses to protect the ulcer and allow healing. This, however, will be discussed with you after examination of the eye when special dyes may be used in order to show the extent of the ulceration.

Should I expect any side effects from treatment?

Normally there will be no side effects from treatment. However, some of the medications used, e.g. atropine, can be very bitter and since the medication can travel through the tear ducts to the back of the throat they can be tasted by the dog. Occasionally this will cause increased salivation (drooling). If this is excessive, or if any of the eye applications cause discomfort, please contact us. If application of the medication appears to cause discomfort please let us know. Occasionally a dog will be allergic to the drugs prescribed.

Is there any risk that the ulcer can get worse despite treatment?

Superficial abrasions will occasionally continue to progress and deepen and this is the reason why we ask you to come back in a few days. We can then examine the cornea using special instruments and dyes to show up the full extent of the ulcer. Sometimes treatment has to be changed and surgery may be indicated.

As the ulcer heals, what should I look for?

During healing a process called neovascularisation occurs. This involves tiny blood vessels growing across the cornea from the sclera (white of the eye) to aid the healing of the damaged area. This can make the eye appear red and sore. Once healing has occurred these vessels sometimes remain and potentially can obstruct vision. Therefore we may have to alter treatment in order to ensure that this does not become a problem.

These are the reasons why we emphasise that even the mildest injury or discomfort involving your dog’s eye should never be ignored. It is better to be safe than sorry. Let us know if you have any concerns.