- Equine Eye - Uveal Cysts
Wednesday, January 11, 2012 at 12:14AM
Stacey Sofia Clarke in Anatomy

Credit: EquineOutreach.com


The Equine eye is beautiful.  Large, loving, and soulful, it feels like when they look at you, they just know.  But have you really looked at your horse's eye?  What you find may surprise you.

My Cyst Story

A Normal Equine EyeA few years ago the sun hit my mare Sahara's eyes just right and sort of lit them up.  I looked closely into them and noticed what looked to be a large brown bubble in her right eye.

Somewhat concerned, I checked the left eye, but nope, it was only in the right.  At the time I had no idea what it was, but it didn't look normal, so I showed my trainer. She too was stumped (and wanted to know how I even found it), so I talked to my vet. 

After an exam my vet explained that my mare had a uveal cyst.  He didn’t think it was affecting her vision or causing pain, so at that time recommended that we keep an eye on it (no pun intended) and see if it got any worse.  I followed that advice for a couple of years, keeping careful watch over the size of the cyst, occasionally checking to see if her range of vision was affected, and generally making sure the eye didn’t look abnormal.

That worked for awhile, but then over fall of 2010 the cyst appeared to suddenly almost double in size, and I had noticed Sahara was starting to look hard at things on the side where the cyst was.  She never really became full-on “spooky”, but she was turning her head around and back to look at things lower to the ground, and occasionally stopping or running out on a fence when approaching from that side.  She has never been a stopper, and since she would jump fine on re-approach, it seemed more and more likely she might not be seeing it well at certain angles.

An Equine Eye with Uveal Cyst

Right about that time I attended a seminar given by eye specialist Dr. Brendan Mangan on the Equine Eye at Sporthorse Veterinary Services in San Marcos, CA.  Part of the lecture focused on uveal cysts, and I was able to discuss the topic a bit with Dr. Mangan.  We decided he should look at Sahara's eye, and after he completed his initial exam of the eye he confirmed what I already knew (it was a uveal cyst), but what I didn’t realize is that he estimated that when in bright light, and the pupil was most constricted, the cyst was blocking about 50% of  Sahara’s range of vision.  No wonder she was having trouble seeing!

The recommended treatment was to shrink the cyst with a diode laser.  It was an outpatient procedure that was covered by my veterinary services insurance, and I’m happy to report there were were no complications, the cyst shrank and disappeared, and Sahara’s sometimes odd behavior on her right side also cleared up.

Who Cares?

I bring this up because I recently noticed what appear to be uveal cysts in the eyes of some of my massage clients.  After having gone through the steps with Sahara, I tend to be extra-observant of the eyes of all horses I work with, so I almost notice it unintentionally.  I let the owners know what I think I saw, and suggested they ask their vets about it.   They were as surprised as I was when I first found the cyst in my mare's eye; these things are hard to spot if you aren't looking for them!

Here are a few things I learned from my vets during my personal experience with uveal cysts:

  1.  A uveal cyst, also known as an “iris cyst”, is a thin fluid-filled pouch of epithelium, is not necessarily uncommon in horses, and it is usually treatable if necessary
  2. The “if necessary” part refers to if the cyst is causing pain, discomfort, interfering with vision, or otherwise adversely affecting the eye.  If the cyst is there but not seeming to cause any of these issues, your vet may recommend not doing anything due to the fact it is best not to mess with the eyes if you don’t have to.
  3. Uveal cysts are often treated with a diode laser to shrink them. 
  4. Uveal cysts can be free-floating in the eye or attached to the eye structure at the iris or ciliary body epithelium
  5. The location of the cyst in the eye can determine how much it affects range of vision
  6. The size of the cyst can determine how much it affects range of vision
  7. If the cyst becomes large enough to bump up against the inside of the cornea, it can cause other more serious eye problems.

There are many factors to these cysts as to whether or not a vet will recommend treatment, so if you notice it in your horse the best thing is to have your vet (and possibly a specialist) check it out, but you can’t do anything about it if you don’t know it’s there.   So next time you’re at your barn, take a close look at your horse’s eyes, and get to know what is “normal” for your particular horse so that you can more easily recognize potential problems when they arise.

Article originally appeared on Planet Equus - Horses Forever (http://www.planetequus.com/).
See website for complete article licensing information.