By Sarah Netherton/University of Illinois College of Veterinary Medicine
After suffering repeated episodes of uveitis — an inflammation inside the eye — Chic lost sight in her left eye. Although partial blindness did not stop Chic from being ridden by the young girl who was her owner, the eye did cause the horse pain.
Ralph Hamor, a veterinary ophthalmologist at the University of Illinois Veterinary Teaching Hospital in Urbana, and his colleagues recently performed surgery that provided relief for Chic.
"Equine recurrent uveitis is the most common reason horses go blind," Hamor said. "Sometimes the eye shrinks and the eyelids roll inward, a condition called entropion, which can be uncomfortable."
For Chic, the solution was enucleation, the surgical removal of the globe of the eye and the eyeball itself and the surrounding tissues. This procedure is most often performed when the eye is blind and painful, as in Chic's case.
Before Chic underwent enucleation, as with any surgery, Hamor and the staff of the hospital's equine medicine service performed a physical examination and tested her blood to ensure that the enucleation surgery could be safely performed.
An enucleation can be performed while the horse is sedated and standing in stocks. A regional anesthetic is used to block pain in the eye and surrounding tissues. Antibiotics and anti-inflammatory drugs are given just prior to surgery.
Hamor said two surgical approaches are used for removing an eye.
"In the transconjunctival approach, the surgeon removes the globe by incising through the conjunctival tissues, cutting the extraocular muscles and the optic nerve and then removing all of the conjunctival tissues, the third eyelid and the eyelid margins," he said. "The transpalpebral approach involves making an incision around the eyelids, then the extraocular muscles of the eye and optic nerve are cut, and everything, including the third eyelid, is removed at once within the conjunctival sac and eyelid margins."
An intraorbital prosthetic can be placed within the eye socket to make the shape of the horse's face look more normal; the eyelid margins are sewn shut, so the prosthetic is not seen.
The prosthetic is a surgical ball made of silicone that keeps the empty eye socket from sinking in. Once the prosthetic is placed, the subcutaneous and subcuticular layers are sutured together, the skin incision is sewn shut and the surgery is done.
After the surgery, Chic received anti-inflammatory drugs and antibiotics. Hamor advised Chic's owners that there might be mild swelling of the surgery site. He told the owners to watch for problems, such as excessive drainage and swelling.
Once she was back home, Chic's owners continued giving their horse antibiotics and anti-inflammatories and kept the area of the surgery clean and dry. Hamor said if horses begin rubbing at the surgical site, a fly mask can help protect it.
The sutures were removed about two weeks later, and Chic is now pain-free and back to her old self.
Hamor said it is important to keep in mind an adjustment period after surgery. Precautions should be taken while riding, since there is a potential for the animal to spook if they are no longer visual in both eyes.
An archive of pet columns from the UI College of Veterinary Medicine is available at http://vetmed.illinois.edu/petcolumns/ . Requests for reprints of this article may be directed to Chris Beuoy, firstname.lastname@example.org.