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


Growth on Cornea, Clear Surface of Eye


Growths on the clear surface of the eye are presumed to be tumors until proven otherwise. By far the most common type of corneal tumor is squamous cell carcinoma. This condition is especially common at high altitudes and in horses with pink skin around their eyes (Paints, Appaloosas).

Rarely, inflammatory and infectious conditions appear as a growth. Penetrating wounds through the cornea can allow the colored iris to pop out (prolapse) through the cornea. This can appear suddenly as a dark mass protruding from the clear surface of a painful, inflamed eye.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • If you notice other problems with the eye or the eye seems inflamed and painful.
    • Most eye problems are considered veterinary emergencies.
    • If the mass is large, painful or seems to be growing rapidly.
  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If the eye appears otherwise normal.
    • If the problem is subtle or slowly changing.
    • The eye does not seem painful and the horse does not seem distressed.
You also might be observing
Very Common
Less Common
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your role


What To Do

Given the importance of your horse's sight, do not allow any condition to continue or worsen over time without consulting your vet. Injuries to the eye can be sight-threatening, and require immediate veterinary attention. At minimum, assess your horse's eye and share a photo of the problem with your vet for discussion.

Your vet may advise you to use a fly mask to protect the eye from insects and debris until it can be evaluated.

your vet's role

Vets can usually determine the general nature of an eye mass by examining it. In cases where the cause is unclear, biopsy or cell sampling may be necessary for identification. Once a diagnosis is made, treatment options can be discussed.
Questions Your Vet Might Ask:
  • Does the eye seem irritated?
  • Is the horse showing signs of eye discomfort like squinting or blinking or holding the eye closed?
  • Can you send a photo of the problem?
  • When did you first notice this?
  • What is the horse's age, sex, breed and history?
  • Are one or both eyes affected?
  • Does the horse lack pigment (have pink skin) around the eye?
  • Do you notice the eye watering or any discharge?
  • Can you see anything else going on with the eye(s)?
  • What is the color and appearance of the mass?

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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Treatments Your Vet May Recommend

A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)

Very Common
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further reading & resources

Author: Doug Thal DVM Dipl. ABVP