Horse Side Vet Guide ®

Equine Health Resource

Eye, Dark Mass Sticking Out, Iris Prolapse

Code Red - Call Your Vet Immediately, Even Outside Business Hours

Code Red - Call Your Vet Immediately, Even Outside Business Hours

    A wound to the cornea can cause the fluid that fills the eyeball to leak out and the eyeball to collapse. When this happens, the colored part of the eye (the iris) can pop out through the wound.

    This often appears to be a strange, usually dark colored mass sticking out of the front surface of a very inflamed (usually gray colored) eye. This observation may also be seen as as result of a tumor, a foreign body, or a deep corneal ulcer (descemetocoele).

    This finding is unfortunately not as rare as it sounds. The odd appearance can be confusing to owners and caretakers. Regardless, this is a sign of a severe eye injury that must be quickly addressed.


    Protect your horse’s eye with a fly mask or emergency bandage until your vet arrives, but ensure that nothing adheres to the surface of the eye causing irritation or additional pain.


    If your vet diagnoses your horse with an iris prolapse, referral to a board certified equine ophthalmologist for emergency surgery should be considered. Although some general veterinary practitioners have confidence repairing this problem, corneal surgery requires specialized skills and equipment.

    Author: Doug Thal DVM Dipl. ABVP


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