Tuesday, August 21, 2012

Eye Surgery at Cornell

During their June teeth floating, three of the horses here at the farm were diagnosed with Uveal Cysts-- growths of tissue at the lower edges of their irises.  In two of the horses, these were compounded by overgrowths of the corpora nigra, the little fringe at the top of the iris that functions as a "sun shade" for the horse in a normal eye.

While these growths are fairly common, and do not pose a generalized health threat (such as cancer or other disease process), they do form a barrier to light (and thus all sight) getting into the eye.  In bright light conditions, when the iris closes down naturally in response to light, these cysts and overgrowths can cause a partial, or in some cases, complete, blindness as they block the very small opening left in a constricted pupil.  Left untreated, these cysts can eventually grow together and fuse top-to-bottom and cause permanent blindness (partial or complete) in all light conditions.

Sherman's full brother, Sonny, and half-sister, Twinkle, had very serious growths of both sorts in both  eyes.  Sherman had a small uveal cyst noticeable in the right eye only.

In mid-July, Sonny and Twinkle traveled to Cornell to have laser eye surgery, which involves a simple ablation of the fluid-filled cysts, which the vets describe as similar to popping a water balloon. Sonny's eyes both looked like this pre-surgery:
Uveal Cysts at bottom

After 10 zaps with the laser, both eyes looked like this:

Cysts deflated

The change in tissue in his eyes was pretty dramatic.  Surgery took about an hour, and then the doctors at Cornell monitored the eye pressures (like we test for glaucoma) for several hours.  In the first hour after surgery, pressure normally rises as the eye responds to the fluids from the ruptured cysts being encountered and reabsorbed by the eye.  After that initial spike, the pressures should fall again, and the doctors look for three successive readings of lower pressures before the horse is released to go home.

Aftercare involves banamine and pain-relieving eyedrops for three days and one week, respectively, along with confinement away from sunlight from dawn-dusk for a week.  After that, life resumes as normal for the horse, only with an enhanced field of vision!

Some owners report that formerly spooky, tense horses go through this procedure and those negative behaviors disappear almost instantly.  None of our horses were terribly spooky, though Sonny could be tense and (hindsight causes us to speculate) was perhaps struggling to see a bit.

Sherm himself never behaved as though his eyes were bothering him, or he was trying to see anything, but he's pretty much afraid of nothing, so it's difficult to tell whether he was bothered or not.  It was recommended that he have this surgery particularly because of this family history-- his sire was eventually completely blinded by these cysts in the days before laser surgery was so readily available, and the older siblings' cases were dramatic, which led the vets to suggest he was headed in the same direction.  So even though his cysts were small, dealing with them now was the right course of action.

His procedure went normally, and dilation at the clinic revealed cysts in both eyes, so he got zapped on each side.  He was a good patient, but not quite good enough to stop the action and get photos of his eyes, like his big brother allowed.  His experience was textbook, and his recovery was normal.

The surgery was so uneventful, in fact, that the two major take-home messages from the trip had nothing to do with his eyes!  The first was that Sherm is teetering on dangerously fat, and that Sherm's parents need a bigger truck to haul his fat butt around with.

Neither was great news, but I am perfectly happy with having all the laser stuff go so well that we could focus on other issues.


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