Corneal ulcers – a sore eye

Although cat’s eyes have a number of differences which improve night vision, the basic structure is much the same as a human. Consequently cats 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. One of the most common eye problems in cats is a corneal ulcer.

©Keith Barnett

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 is affected but the damage may go deeper and be more difficult to treat. There will often be a layer of dead tissue over the wound and the surface of the eye may appear cloudy. Usually ulcers increase in size slowly but on rare occasions the wound can become infected with dangerous bacteria. These bacteria can produce chemicals which eat away at the surrounding normal tissue causing permanent blindness within a few hours.

In many cases the cause of the ulcer is uncertain. Most are caused by a scratch from another cat during a fight or something rubbing on the eye such as a piece of grit or grass seed caught under the eyelid or eyelashes or hairs growing in the wrong place on the eyelid. Bacterial or viral infections can cause damage to a normal eye as well as making problems worse following physical injury. If your cat is unable to produce tears (a condition known as ‘dry eye’) the eye may be prone to damage.

Ulcers can be very painful and your cat may hide or become unusually aggressive if it has one. The affected eye is usually very watery unless the ulcer is caused by a lack of tears. Your cat may blink frequently and the membranes around the eye may appear red and inflamed. Sometimes the third eyelid (a protective membrane under the main eyelids) will cover the surface of the eye when the eye is open.

Your veterinarian 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. Local anesthetic drops can be put in the eye to make your cat more comfortable while the eye is examined.

Your veterinarian will then put a few drops of dye into the eye. This dye sticks to the damaged areas and will show how far the injury extends.

The choice of treatment depends on the type of injury and how far it extends. A foreign body (like a grass seed) in the eye can be removed.

For minor ulcers you may be given a cream or eyedrops to speed up the healing process.

If the damage is more severe your vet may need to keep your cat so that an anesthetic can be given. During the operation any dead tissue will be cut away and a protective layer put over the wound to encourage it to heal. The third eyelid may be sewn across the eye until the ulcer has healed or a clear soft contact lens can be fitted.

An Elizabethan collar may be necessary to prevent your cat rubbing the eye and causing further damage. Antibiotic drops or cream help tackle any infection and other drugs may be used to reduce the inflammation. 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.

Your veterinarian may ask you to put drops or cream into your cat’s eye to help with healing. This is relatively straightforward in most cats with a bit of practice. You will need someone to help you hold your cat firmly. Then you should grasp your cat’s head with your left hand and tilt it upwards. With the thumb and finger of the holding hand the eyelids should be pulled gently apart and the medication given with the other hand. The tip of the tube should be held parallel with eye surface not pointed directly at it. A squirt of cream or a few drops of fluid are carefully placed on the surface of the eye, the eyelids closed and rubbed gently to spread the medication over the whole surface of the eyeball. Be careful not to touch the surface of the eye with the tip of the dropper or tube because this may damage the eye or spread bacteria from the eye back into the contents of the bottle.

The likelihood of successful treatment depends on the type of ulcer and how advanced the condition has become. Early treatment gives the best chance of a good recovery. When the ulcer has healed there may be a small indentation or white scar left on the eye surface, but this is unlikely to affect your cat’s eyesight.

If your cat’s eyes appear sore or red or if any abnormal discharges are present you should make an appointment to see your vet immediately.