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

YOU ARE OBSERVING

Eyeball Seems Enlarged

Summary

Enlargement of the eyeball itself is rare in horses, but can result from a variety of conditions or disease processes. The most important cause of actual eyeball enlargement is glaucoma (a name for conditions causing increased pressure within the eyeball).

Keep in mind that eyes of the same size may look different given their different color, the differences in the surrounding skin, and the different appearance of the "white of the eye." Eyes that have more white around their edges look more bulged, or larger.

Eye size also ranges between different breeds. For example, Appaloosas tend to have smaller eyes. Keep in mind, that the other eye could be abnormally shrunken or small.

  • 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.

  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • The eye does not seem painful and the horse does not seem distressed.
You also might be observing
Very Common
Less Common
Rare
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your role

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What To Do

It can be hard to tell the difference between an eyeball that is abnormally large and an eyeball that is sticking out excessively far from something behind it pushing outward.

In determining whether one eyeball is swollen or enlarged, carefully compare it to the other eyeball. Stand right in front of your horse or try to look down from above to get a better perspective. A good vantage point to make this evaluation is from the saddle.

Using your fingertips, you can press into the eye through the upper lid to get a rough sense of hardness of the eyeball. Certain conditions, notably glaucoma involve increased pressure within the eye, resulting in a larger appearing eyeball.

Assess your horse's general health using the Whole Horse Exam (WHE), looking for any other abnormalities. Assess both eyes, carefully comparing them and look for other abnormalities. Perform the menace response to roughly assess your horse's vision and reflexes.

Given the importance of your horse's sight, share your findings and concerns with your vet.

your vet's role

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Your vet assesses the general health of the eye and may use other diagnostics like tonometry or ultrasound. Referral to a specialist, boarded animal ophthalmologist may be an option.
Questions Your Vet Might Ask:
  • Is the horse showing signs of eye discomfort like squinting or blinking or holding the eye closed?
  • Do you notice the eye watering or any discharge?
  • How does it compare to the other eye?
  • Do you notice the problem in one eye or both?
  • Do the horse's eyes appear different from one another?
  • What is the horse's age, sex, breed and history?
  • Is there any drainage?
  • Is there a difference in the colors of the left and right eye, or the color of the surrounding skin?
  • Do you see an injury or foreign material in the eye?
  • Does your horse seem normal otherwise?
  • Does the horse's vision seem normal to you?
  • What are the results of the Whole Horse Exam (WHE)?
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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
Rare
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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