A Prosthetic Eye for the Horse

When Brian Gilger, DVM, MS, Dipl. ACVO, associate professor of ophthalmology at North Carolina State University (NCSU), examined a Thoroughbred gelding referred to NCSU's College of Veterinary Medicine, he discovered thick, cloudy material throughout the anterior chamber of the right eye that obscured his view of the inner eye. Using ocular ultrasonography, he was able to diagnose complete retinal detachment with a large retinal tear. Because of the grave prognosis for recovery of vision, enucleation (removal of the eye) was recommended.

The owner of the gelding agreed to the procedure, but wanted the horse to return to competition. A prosthetic eye would be needed--one with increased stability, optimum mobility, low risk of loosening of the eye, and best overall cosmetic appearance.

The decision was made to place a prosthesis composed of hydroxyapatite, a natural material derived from marine coral that is the most common material used for human prosthetic eyes. Hydroxyapatite has the advantage of being lightweight, porous, and biocompatible with living tissue, allowing small blood vessels and fibrous tissues to grow within its pores.

The implant was fitted using the sclera (outer white covering of the eye) of a horse euthanized for an unrelated reason. A donor eye bank is maintained at NCSU with eyes donated from euthanized horses. "The corneas are used for transplant, and the sclera are used for this procedure," says Gilger.

The donor sclera was filled with a sterile hydroxyapatite sphere and placed into the eye socket. It was sutured to the remnants of the ocular muscles, allowing some movement of the prosthesis. Six weeks later, a custom-made external prosthesis was fitted to the sphere. Gilger describes this piece as similar to "a shell." It is made of methylmethacrylate, and is remarkably life-like. Six months later, the horse was comfortable with the prosthesis, and the owner could easily remove it for daily cleaning.

Next in prosthetic research will be a series of case studies comparing complication rate and long-term results after placement of hydroxyapatite ocular implants.

Gilger's other research interests include equine recurrent uveitis, or moon blindness. He and others are studying the immunosuppressant cyclosporine-A, delivered through in a slow-release device into the lens of the eye to combat uveitis. To learn more, visit www.cvm.ncsu.edu:8110/docs/opthaleru.html.

Gilger, B.C.; Pizzirani, S.; Johnston, L.C.; et al. Journal of the American Veterinary Medical Association, 222 (3), 343-345, 2003.

About the Author

Susan Piscopo, DVM, PhD

Susan Piscopo, DVM, PhD, is a free-lance writer in the biomedical sciences. She practiced veterinary medicine in North Carolina before accepting a fellowship to pursue a PhD in physiology at North Carolina State University. She lives in northern New Jersey with her husband and two sons.

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