The team ultimately concluded that the superficial keratectomy and Gundersen inlay flap procedure can provide a surgical alternative to long-term medical treatment of severe corneal edema in some horses. | Photo: Kevin Thompson/The Horse

For a horse to see well, all layers of the cornea—the transparent layer that forms the front of the eye—must be free of cloudy or opaque areas. A healthy cornea is a clear and relatively dehydrated structure. When fluid accumulates in the cornea, however, swelling and a bluish haze appears. This condition is called corneal edema.

“There are many reasons for corneal edema,” explained researcher Nikki Scherrer, DVM, ophthalmology resident at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center. One of those is endothelial disease.

The endothelium is one of three layers of the cornea; specifically, it’s the thin innermost layer that plays an important role in keeping the cornea clear. When the endothelial cells are missing or not functioning correctly, fluid can move from the inside of the eye into the cornea, creating edema