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The eyes of our domestic pets have a structure and function very similar to our own eyes. This means they can have the same eye problems that humans can develop including cataracts, glaucoma and corneal ulceration.

The eye is a complex organ that constantly adjusts to provide a clear image to the brain. If any part of the eye is not functioning well it can affect sight.

The cornea is the transparent domed outermost part of the eye. Its primary function is to work with the lens to focus the light on to the light sensing cells in the retina, but also for protection of the rest of the eye structures. It has to be incredibly thin (its four layers are less than one millimetre thick!) and the cells are very specifically aligned to allow light to pass through unimpeded.

Three main points to remember

Please read through our frequently asked questions and be aware of these three main points:

  1. Know the signs of ulceration.
  2. Speed of diagnosis is crucial to success, so if in doubt come see us!
  3. Successful treatment can take a reasonable amount of time, so be patient!
Frequently Asked Questions

What is a corneal ulcer?

A corneal ulcer (known as ulcerative keratitis) is an erosion of the layers of the front surface of the eye.

Ulcers are very sore (it feels like something constantly stuck in your eye!) and need to be treated quickly to alleviate pain and to avoid permanent damage to the eye.
There are three classes of ulceration:

Superficial ulcer

A shallow (superficial) ulcer is a disruption and inflammation of the top layer (epithelium) of the cornea. Superficial ulcers are painful and irritating and can progress to become deeper ulcers without treatment.

Deep ulcer

A deep ulcer occurs with deeper erosion (descemetocele) of the corneal layers (epithelium and stroma) that exposes the membrane lining the inside of the cornea. This is a very serious condition that can easily progress to a perforation if not managed carefully.

Full thickness ulcer (perforation)

Once the inner membrane of the cornea is perforated then there is nothing to protect the front chamber of the eye. This is a surgical emergency and needs swift treatment to save the eye.

What are the signs of ulceration?

  • Pain
  • Tightly closed eyelids
  • Rubbing/scratching at eye/head
  • Small pupil
  • Opacity to surface of eye (due to disruption of the layering)
  • Redness to the white part of the eye (inflammation)
  • Discharge from the eye (either watery or pus)

How does the vet examine my dog's eye?

Physical examination with an ophthalmoscope:

The vet will visually assess both eyes and compare the two, looking for evidence of the signs of disease. An ophthalmoscope is used to provide a light source and allow the vet to focus on different portions of the eyeball all the way from the cornea to the retina.

Fluorescein dye

This is a very useful tool in evaluating corneal ulcers. This is an orange dye that when applied to the surface of the eye will turn green if there is an ulcer present. This provides an indication of how wide the ulcer is and how deep it is. The deep and perforated ulcers will only glow green around the edges.


This is a tool to measure the pressure inside the eye. It can be useful in evaluating secondary problems associated with ulcerations, particularly glaucoma, but is not commonly used in this situation as the eye is more fragile than normal.

Tear production test

  • The amount of tear production can be measured to help determine if a condition called “dry eye” is present that makes corneal ulceration more likely
  • It is performed by using a small piece of special paper placed under the eyelids to absorb the tears and measure their production. This condition is common in some terrier and spaniel breeds.
  • This test is not routinely performed unless this condition is suspected.

How are corneal ulcers treated?

Ulceration of the eye can be slow and difficult to treat. This is mainly because of a poor blood supply to the area.

All ulcers will benefit from treatment to varying degrees depending on the severity.

The earlier an ulcer is treated the more likely a good outcome will be achieved.

Topical eye medications:

  • There are a variety of eye drops (including antibiotics and anti-inflammatories) that provide the mainstay of treatment.
  • They are applied directly to the surface of the eye; you will be shown how to do this when these medications are dispensed. If you are unsure how to apply them, then please call us for further explanation.
  • Some (but not all) medications need to be kept in the fridge, so look out for this on the label!
  • Often a cone collar will be needed to prevent self-trauma exacerbating the situation.

Systemic medications

Sometimes oral antibiotics and pain relief is needed to supplement the treatment of an ulcer.


Sometimes the dead corneal tissue needs to be removed to allow new cells to take their place. This is usually needed when the ulcer edges form a ridge or become underrun, or when an ulcer is not healing at the desired rate.

It can be performed in two ways:

  1. Local anaesthetic drops applied to the eye, then a sterile cotton bud is used to gently remove the excess material

  2. More severe ulcerations can benefit from a procedure called a “Grid Keratotomy” under general anaesthetic. This is a procedure to remove the dead tissue and then using a needle to place a grid pattern of tiny scratches on the surface of the cornea to provide a network for the normal healing process. Often a contact lens is placed to help protect the eye along with a suture in the eyelid to help hold this in place.

Surgical management

Ulcers at risk of perforation require surgical management to assist healing and to protect the eye. This usually takes the form of a conjunctival graft, to provide a good blood supply to the cornea to allow the body’s natural healing process to work more effectively.

Unfortunately, sometimes corneal ulceration can be so serious that the eye cannot be saved, and removal of the eye (enucleation) needs to be performed to keep the animal comfortable. Dogs and cats with only one eye can still function very well indeed and we have many happy patients with us years after this procedure has been performed.

What can I expect while the eye heals?

Once treatment is started, we will need to re-examine your pet frequently to make sure that healing is going according to plan and make adjustments to treatments accordingly.

If deterioration is not picked up it can have a very negative outcome.

Severe ulcerations can sometimes leave a white scarring on the surface of the cornea.

These usually are cosmetic only and do not adversely affect functional vision.

What are the common causes of corneal ulcers?

Trauma is probably the most common cause of an ulcer, usually from a claw of a fellow furry friend, or from anything sharp that can scratch the eye.

Other eye conditions can cause corneal ulcers, such as entropion (rolling in of the eyelids), distichiasis (abnormal eyelash growth) and keratoconjunctivitis sicca (dry eye).

Are any breeds predisposed to corneal ulcers?

Ulceration can occur in any breed of dog!

However, they are more likely to occur in breeds where the eyes protrude from the surrounding facial features, where they are more exposed to traumatic damage.

Some breeds (especially boxer breeds) are slower to heal ulcers than normal and commonly need more intensive management than other breeds.

Dog breeds that are particularly predisposed to ulcers include (but are not exclusive to):

  • Boxer
  • Pug
  • Shih Tzu
  • Bulldog breeds
  • Terrier Breeds (especially West Highland)
  • Shar Pei
  • Chihuahua


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