Corneal Ulcers – A review

We have been seeing a lot of corneal injuries or ulcers recently. These scratches to the surface of the eye can be very serious and hard to treat when not acted upon swiftly. Please read on for some very important information about corneal ulcers in horses.

** A special THANK YOU to student Erica Bonthrone who wrote this educational article while externing with Weitz Equine**

What is the cornea?
The cornea is the clear, outermost layer of the eye. It has two main roles: protection (by acting as a barrier against germs, dirt, particles) and object focus (its curved edge bends light that enters the eye). Corneas don’t have a blood supply to provide nourishment or defense against infection; rather, tears and other liquids serve this purpose. Apart from moistening the eye during blinking, tears also assist with wound healing. Fun fact- there are five layers to the cornea!

What is a corneal ulcer?
Corneas can get inflammatory lesions known as ulcers. Horses live in dusty environments with plenty of debris that can cause damage (perforation) to this very thin layer. The horse could have experienced a physical trauma, or the ulcer may have been caused by a stray hair or foreign body. While other parts of the body use blood vessels and lymphatics to aid in the healing process, these are absent in the cornea and so the recovery process is more challenging.

How would I know if my horse has a corneal ulcer?
At least once a day you should scan your horse from head to tail to look for any obvious signs of illness or injury. A horse with a corneal ulcer (check both eyes!) may show the following signs: pain (squinting of the eye), swelling at the eyelid, redness, flowing of tears or discharge from the corner of the eye, or change to the appearance of the cornea. In most cases, owners do not witness their horse’s injury- so it is often hard to tell the how, where, when. If you do recognize the clinical signs above, please do call your vet immediately as this is an emergency. Prompt identification of the injury and initiation of appropriate therapy is KEY! Your horse has only 2 eyes and we certainly want to make sure they stay healthy!

How does the vet determine if my horse has a corneal ulcer?
Your vet probably has an “eye box” in their truck that consists of items used to diagnose and treat ophthalmic conditions. An ophthalmoscope allows the vet to examine the eye under magnification and light. A swab or scraping might need to be collected; this sample may be evaluated on a microscope slide to detect the presence of bacteria and fungi (this will help confirm or change the choice of medication. A stain is often applied to the eye to help locate any injuries to the cornea.

How do we treat a corneal ulcer?

This varies slightly on whether the corneal ulcer is an uncomplicated superficial one or a complicated deep one. However, in general, your horse will be given several drugs: a triple antibiotic, atropine, and an anti-inflammatory. They will show you how to apply/ give the (topical and oral) medications and let you know for how long. It’s important to keep the area around the horse’s eye clean; this may include using an emergency eye mask (there are great examples online of how to make your own) to protect the injury as well as offering your horse feed at a neutral or lowered position so that debris doesn’t fall into the eye. Your horse will need to be re-checked by the vet to ensure they are healing properly. In some very severe cases, referral to a veterinary ophthalmologist may be necessary.

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