Corneal Ulcers in Horses Leave a comment

Corneal Ulceration in Horses

Corneal ulcers — injuries to the outermost layer of the eye — are usually the outcome of some type of trauma to the eye. It may have come about as the result of running into something, violent contact with another horse, a foreign object entering the eye, fungus or bacteria in the surrounding environment, and harsh dust entering the eyes. All of these can be considered traumatic incidents.

Once the eye has an ulcer, it can easily become infected, and these infections have the potential to turn a corneal ulcer into a serious health issue, sometimes breaking down the corneal tissue and leading to a defect of the eye that needs more invasive treatment than if it had been given immediate treatment.

Symptoms and Types

  • Redness in the eye
  • Severe eye pain (squinting or closing the eye)
  • Swollen eye lids
  • Tears running down the face
  • Eye infection(s)
  • Inflamed lining of the eye (conjunctivitis)
  • Dull corneal surface (i.e., cloudy in appearance)
  • Blood vessel development through the cornea
  • Ocular discharge


Corneal ulcers are often due to eye trauma, whereby foreign objects come into contact with the eye. Other secondary issues include bacterial, viral, and fungal infections.


Your veterinarian will perform a thorough ophthalmological exam on your horse, taking into account the background history of symptoms and possible incidents that might have led to this condition. A fluorescein stain, a non-invasive dye that shows details of the eye under light, will be used to identify the presence of an ulcer and its location on the eye’s surface. Fluorescein stain adheres to the underlying ocular connective tissue that is exposed by the ulcer, staining this area bright green. If there is no ulcer, no stain will adhere to the eye.

An ulcer, after staining, should be easily visible, as well as the side effects to the condition itself. If it appears that an infection is present, your veterinarian will need to take samples from the cornea by scraping away some of the tissue for laboratory testing. Any discharge or fluid will also be collected for testing. A specific diagnosis is essential, as not all drugs are appropriate for treating an injured eye, and some may in fact do more harm.


Treatment varies based on the severity of the corneal ulcer. In all cases, it is vital that the horse be removed from bright light. This means keeping the horse inside during the time of day when the sun is high and covering the eyes with blinders or shades to protect them from light.

Leaving corneal ulcers untreated can create a potential risk for loss of sight. Untreated ulcers may cause scar formation on the cornea, and if deep enough, may actually cause rupture of the eyeball, resulting in loss of that eye. This is a very painful process. For these reasons, immediate and effective treatment of even the smallest ulcer is highly important. Your veterinarian, once alerted to the possibility of an eye injury, will treat the injury with the serious attention that is required.

A secondary infection is one of the more common side effects of a corneal ulcer, and this is the main reason for immediate treatment. Based on the laboratory results from the corneal scrapings, an antibiotic or antifungal ointment or drops may be administered to help clear up the infection. Even without clinical signs of infection, your veterinarian will prescribe an antibacterial ophthalmic ointment to administer multiple times a day to aid in healing of the eye.

Sometimes, the ulcer is so large or deep that the horse will require medication several times a day. In this case, or a case where the horse is unwilling to allow you to put ointment in its eye at all, your veterinarian may choose to place a subpalpebral lavage system in the horse’s eye. This simple medical device is a small, thin, flexible tube that is sutured underneath the eyelid. The tube is then wound back behind the horse’s head and down its neck where there is port where the medication is administered. This prevents you from having to get close to the horse’s eye to deliver medication. After the ulcer has healed, the subpalpebral lavage system is easily removed by your veterinarian.

In very severe cases or cases where the ulcer is not healing, surgical treatment may be needed, with unhealthy tissue removed from the eye. In the most severe cases, a corneal transplant may be called for.

Living and Management

Enough time should be given to the horse to allow for full healing of the eye after a corneal ulcer. Care will need to be taken to ensure that further damage is not done to the eye, either the surrounding environment — such as with dust, flies, etc. — by contact with other horses or while being exercised. Some horses will become spooky on the side where they had the corneal ulcer. Take time to work with your horse so he regains confidence and overcomes this behavioral side effect.


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