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


Eye looks Shrunken or Small


What I am describing here is actually the shrinking of one eye versus the other. (Dehydrated horses often appear to have shrunken or small eyes due to the lack of hydration of the surrounding tissues. However, the eyeball itself is a normal size in these cases.)

A small or shrunken eye may be indicative of a chronic eye problem or injury. An eye that has just suffered a penetrating wound leaks its fluid (aqueous humor) and shrinks. Certain severe disease processes of the eye cause the eyeball itself to shrink over time. An eye that has been badly damaged in the past may shrink (phthisis bulbi).

I see shrunken or small eyes in horses that have had penetrating wounds of the eye or have become blind from Equine Recurrent Uveitis (ERU). Eyes that shrink are usually blind. The third eyelid (pink membrane inside corner of the eye) naturally tends to cover over these severely shrunken eyes.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • If this problem seems severe and has come on suddenly.
    • Most eye problems are considered veterinary emergencies.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If the signs are very mild and the eye appears normal otherwise.
    • If you consider this a chronic and relatively mild problem that is not changing rapidly.
You also might be observing
Very Common
Less Common
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your role


What To Do

Assess your horse's eyes carefully. In determining whether one eye is smaller or shrunken, carefully compare it to the other eye. Stand right in front of your horse or look down from above to get a better perspective. A good vantage point to make this evaluation is from the saddle. 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 this eye may seem small because the other eye could be bulging or be larger than normal, so assess both eyes. Check the menace response on both eyes, and feel the eyeball through the lid, which can give an idea of hardness and size of the eyeball. Share your findings and concerns with your vet.

your vet's role

Vets look at the eye in total to try to understand the cause of the shrinking and whether anything can be done to help the horse's quality of life. Vets may also use an instrument called a tonometer to measure fluid pressure inside the eye. Tonometry may require referral to a veterinary ophthalmologist.
Questions Your Vet Might Ask:
  • Is the horse drinking water?
  • Does your horse seem normal otherwise?
  • What are the results of the Whole Horse Exam (WHE)?
  • Is there any drainage?
  • Is the horse showing signs of eye discomfort like squinting or blinking?
  • What is the horse's age, sex, breed and history?
  • Does the horse respond to a menace gesture?
  • Does your horse appear to be blind or partially blind?
  • Does the eye look normal otherwise?
  • Do you see an injury or foreign material in the eye?
  • Do the left and right eye look the same to you?
  • Is the eye watering or swollen?
  • Is there a difference in the colors of the left and right eye, or the color of the surrounding skin?
  • Does your horse seem normal otherwise?
  • Is the horse drinking water?
  • What are the results of the Whole Horse Exam (WHE)?

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