By Dennis E. Brooks, DVM, PhD, Dipl. ACVO
A corneal ulcer (ulcerative keratitis), is the most serious eye disease that veterinarians treat. Defined as a lesion in which the outer layer and some of the middle layer of the cornea have been lost, even simple ulcers can quickly progress to larger, more complicated ones if not diagnosed and treated promptly. A corneal ulcer can even lead to an infection of inner structures of the eye.
Corneal ulcers can be classified by their cause. There can be mechanical causes such as abrasions, foreign objects, or ingrown eyelashes. Some corneal ulcers are caused by infectious organisms like bacteria, fungi or viruses. If the horse has a paralyzed nerve on the face, he may not be able to blink properly or close the eye to protect it. There is even a disease where horses cannot make tears, causing the eyes to become dry and prone to damage.
As an owner, you should contact your veterinarian immediately if your horse shows any of these signs:
- Unable to tolerate bright sunlight
- A cloudy or blue eye
- A red, swollen eye
Your veterinarian will perform a complete ophthalmological examination of both of your horse’s eyes, including staining the corneas to check for an ulcer. Abrasions to the cornea are often difficult to see without specific dyes, even with the proper lighting and equipment. Defects in the outer layer of the cornea allow the dye to diffuse into the middle layer, and appear bright, fluorescent green.
If the cornea takes up this stain, the next step is to determine how serious the ulcer is. A small, shallow defect that just appeared that day should heal rapidly with simple, straight-forward treatment. However, a deep or infected ulcer may need additional diagnostic tests and more aggressive treatment. Your veterinarian may need to take a culture of the eye and samples of affected eye tissue to look for infectious organisms or unusual white blood cells. Additional stains may also be required.
The goal of treatment is to remove the cause, prevent the eye from getting worse, and provide support to the eye while it heals. This support may include ointment for pain and a separate ointment for infection (NOT a steroid!). In the case of more serious ulcers, this medication may be given in liquid form through a tube sutured underneath the upper eyelid. Also, an eyelid flap or even contact lens may be used to cover and protect the defect while it heals.
Noticing that your horse has a problem with its eye is the most important step in healing corneal ulcers. The sooner that a diagnosis can be made and treatment started the better your horse’s chances for a smooth recovery. Especially when treating eyes, it’s best to let your veterinarian figure out what is wrong and prescribe the right medicine, since no medicine or the wrong medicine could cause permanent damage.
Dr. Dennis Brooks, Professor of Ophthalmology at the University of Florida College of Veterinary Medicine in Gainesville, is a past President of the American College of Veterinary Ophthalmologists, and an expert in the medical and surgical treatment of corneal diseases of the horse.
Reviewed by original author in 2016.