Corneal Ulcer

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.

What is a corneal ulcer?
A corneal ulcer is an erosion through the outer layer of epithelial cells.  If damage is only to the very superficial layers it can be called corneal erosion or corneal abrasion as well as a 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 such as a cat scratch.  The first sign you are likely to see is the eye being kept tightly shut.  Frequently there is an ocular discharge – watering of the eye and sometimes if the corneal injury is infected the discharge may be coloured or pus like.

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 can follow from a cat scratch or injury from a grass seed or damage from a protruding branch.  Irritating shampoo or cigarette smoke can also cause ulceration.
Other causes include bacterial and viral infections and secondary to other ocular problems such as abnormal eyelid position (entropion).

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 the undergrowth, and working breeds, also develop traumatic ulcers quite frequently.
Other breeds such as the Boxer, can inherit conditions such as epithelial dystrophy which leads to weakening of the cornea and the formation of painful ulcers. Older dogs commonly develop superficial ulcers which can be slow to heal.
Breeds such as the West Highland White Terrier can suffer from a condition known as dry eye –  keratoconjunctivitis sicca  (KCS) which results in lack of tear secretion and the lack of lubrication increases the risk of ulceration.

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

It is better to be safe than sorry so an early visit to the veterinary surgeon is a wise precaution.  However gently bathing with cold water is a useful first aid measure, also it is worthwhile endeavouring to part the lids if your dog will allow you, just to see if there is a foreign body (such as a piece of twig) in the eye.  Sometimes grass seeds lodge under the lids and can be simply removed but nevertheless although this may relieve the immediate pain, an urgent follow up visit to the vet is still a sensible precaution.

What is the treatment for a corneal ulcer?
This depends upon the severity.  Eye preparations in the form of ointments or drops are usually prescribed to prevent infection and relieve the pain and discomfort.  If the ulcer is fairly deep there is always a risk that the eyeball could be perforated in which case your vet may suggest surgery.
Other treatments involve a procedure called a ‘grid keratotomy’. This is preformed under anaesthesia and allows for better  healing.  This, however, will be discussed with you after examination of the eye when special dyes may be applied to the eye 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.  Occasionally this will cause increased salivation (drooling).  If this is excessive, contact us without delay.  If application of the medication appears to cause any discomfort, again contact us since occasionally a dog will be allergic to some of the drugs and we will want to know of this as soon as possible.

Is there any risk that the ulcer can get worse despite treatment?
Occasionally superficial abrasions will sometimes continue to progress and deepen and this is the reason why we ask you to come back in a few days so that we can 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 have to be recommended.

As the ulcer heals, what should I look for?
During the healing a process called neovascularisation occurs.  This involves tiny blood vessels growing across the cornea from the sclera or white of the eye to aid the healing of the damaged area. This can make the eye appear more red.   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.