Corneal ulcers – a sore eye

The basic structure of a dog’s eye is much the same as a human’s eye. Consequently dogs can suffer a similar range of eye diseases to humans. Because the eye is complicated, delicate and easily damaged, all eye problems require immediate veterinary attention.

A corneal ulcer is a hole in the clear covering of the front of the eyeball (the cornea). Sometimes only the top layer of the cornea (the epithelium) is affected but in some cases the damage may go deeper and become more difficult to treat. On rare occasions a corneal ulcer can become infected with bacteria that may produce toxins. These toxins can destroy the surrounding normal tissue, leading to a rapid deepening of the ulcer that can cause loss of the eye unless treated quickly and appropriately.

Common causes include:

  • External trauma (e.g. by a thorn or cat claw).
  • A foreign body such as a piece of grit or grass seed caught under the eyelid.
  • Eyelashes or hairs growing in the wrong place on the eyelid.
  • Inherited/ breed-related problems such as in-turning of the eyelids (entropion).
  • Some bacterial or viral infections can also cause corneal ulceration, or exacerbate an existing ulcer.
  • If your dog is unable to produce tears (a condition known as ‘dry eye‘) the eye may also be more susceptible to corneal ulcers. In some cases the cause of the ulcer is uncertain.

Ulcers can be very painful and your dog may resent being touched around the affected eye. Your dog may blink frequently, keep the eye partially closed, or rub at the eye. There may be a watery discharge from the eye (if the corneal ulcer becomes infected this discharge may become purulent).

The white of the eye may become reddened and if the ulcer is particularly painful the third eyelid (a protective membrane under the main eyelids) may cover the surface of the eye when the eye is open (this can give the appearance of the eye ‘rolling up into its socket’).

Your vet will try to identify the cause of the ulcer in order to choose the best treatment. The eye must be examined carefully to make sure there is nothing rubbing against the eye. Your vet may check for ‘dry eye’ by using a small strip of filter paper placed inside the lower eyelid in order to check tear production. Local anaesthetic drops may be put in the eye to make your dog more comfortable whilst the eye is examined.

Your vet will then put a few drops of dye into the eye. This green dye sticks to the damaged areas and will show your vet how far the corneal ulcer extends.

The choice of treatment depends on the type of injury and how far it extends. If there is an underlying cause (such as a foreign body, eyelid abnormality, or dry eye) then it must be identified and treated.

For minor corneal ulcers your vet may prescribe antibiotic eyedrops or ointment. The aim of this is to prevent the ulcer becoming infected whilst it is healing. Uncomplicated corneal ulcers should heal within 5-7 days. If the ulcer takes longer than this to heal, there may be an underlying cause or complication that should be investigated.

More severe ulcers may require additional treatment and in some cases this may include surgery. Various surgical procedures are possible, depending on the type and severity of the ulcer. In difficult or protracted cases your vet may recommend referral to a specialist veterinary ophthalmologist.

During treatment, an Elizabethan collar may be necessary to prevent your dog rubbing the eye and causing further damage. As the eye heals, the area around the ulcer may become redder and small blood vessels start to grow across the eye surface to help the healing process.

When the ulcer has healed there may be a small indentation or scar left on the eye surface, but in the majority of cases this is unlikely to affect your dog’s eyesight.

Your vet is likely to ask you to put drops or ointment into your dog’s eye during the healing stage. This is relatively straightforward in most dogs with a bit of practice.

  1. Hold your dog firmly and tilt its head upwards.
  2. With the thumb and finger of the holding hand, the eyelids should be pulled gently apart and the medication given with the other hand.
  3. The tip of the tube should be held parallel with eye surface, not pointed directly at it.
  4. Expel a single drop onto the surface of the eye, taking care not to touch the surface of the eye with the tip of the dropper because this may damage the eye or spread bacteria from the eye back into the contents of the bottle.

Almost all corneal ulcers are treatable, as long as the cause and type of ulcer is identified and the correct treatment is given. Early treatment gives the best chance of a good recovery. If your dog’s eyes appear sore or red or if any abnormal discharges are present you should make an appointment to see your vet immediately.