What you see. The starting point for addressing any equine health related issue is your observation.


Eye has Ulcer or Scratch on Surface


You notice that there is an erosion of the smooth, glassy surface of the clear part of the eye (the cornea). In most cases, these wounds to the surface are very hard to see without staining of the eye with a special dye.

Erosions and ulcers on the surface of a horse's eye are common. In fact, corneal ulcers and abrasions should always be suspected whenever there is any eye injury. Ulcers can worsen fast and threaten the entire eye.

Contact your vet immediately with any eye injury because delay in diagnosis or treatment can have sight-threatening consequences.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • Most eye problems are considered veterinary emergencies.
You also might be observing
Very Common
Less Common
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your role


What To Do

Assess the eye, taking note of other expected signs including squinting, swelling, drooping lid, tearing, reddening and grayness of the cornea.

What Not To Do

Do not "wait and see" in this case. Corneal ulcers often become infected, and worsen without treatment. Within hours, the process can spread or deepen and become much harder to treat.

Do not use eye ointments or drops without your vet's guidance. Many contain steroids, which are likely to severely worsen a corneal ulcer.

your vet's role

Your vet will assess the overall health of the horse and health of the eye, and then determine the severity of the ulcer, often using fluorescein dye. Fluorescein is a bright green dye which adheres to areas of the cornea (clear front part of the eye) in which the surface layer has been lost. In this way, it illuminates and maps the extent of the damage, which can be hard to see without it.
Questions Your Vet Might Ask:
  • Do you see grayness to the cornea or an actual area of ulceration or erosion?
  • Is the horse's eye tearing or watering?
  • Is the horse showing signs of eye discomfort like squinting or blinking or holding the eye closed?
  • Does the other eye look normal?
  • What exactly do you see?
  • What are the results of the Whole Horse Exam (WHE)?

Diagnoses Your Vet May Consider

The cause of the problem. These are conditions or ailments that are the cause of the observations you make.

Very Common
Less Common
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further reading & resources

Author: Doug Thal DVM Dipl. ABVP