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


Masses, Strands or Floaters within Eyeball


Occasionally, strange bodies appear within the equine eyeball. Normal healthy horses have a projection from the top part of the iris known as the corpora nigra, which might be mistaken for an abnormality. This structure is thought to provide shade to the pupil and reduce glare, similar to a ball cap bill. The corpora nigra takes many shapes and forms in different horses. See the related media record Equine Eye, for a visual reference.

Tumors and cysts can be seen within the eyeball, especially near the colored part of the eye (iris). Strands or webs may be indicative of prior eye disease.

Tiny, moving pale or clear appearing bubbles are known as vitreous floaters. These are fairly common and are usually not considered a problem. Occasionally, parasites can be seen in the front chamber of the 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.
    • If the appearance of the mass seems to be changing rapidly.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If the eye appears otherwise normal.

your role


What To Do

Examine both of your horse's eyes carefully, and compare the affected to unaffected eye. Try to assess vision using the menace gesture.

If you have any difficulty discerning whether an eye-related mass is normal or not, share your findings and concerns with your vet. Take a photo of the suspected abnormality (using good light and close up view) and send it to your vet for discussion.

your vet's role

When it comes to the eye, your vet knows what is normal and what is not. Some subtle abnormalities may be of questionable significance. In that case, they may recommend sharing the images with a veterinary ophthalmologist.
Questions Your Vet Might Ask:
  • Are one or both eyes affected?
  • Can you see anything else going on with the eye(s)?
  • Does the eye look normal otherwise?
  • Is the horse showing signs of eye discomfort like squinting or blinking?
  • Do the left and right eye look the same to you?
  • Do you notice any change in the surface of the eye?
  • Does the horse have a menace response?

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
more treatments

further reading & resources

Author: Doug Thal DVM Dipl. ABVP