[September 29, 2010; Kennett Square, PA] – It was 8:30 on a Friday night when a call came in to the New Bolton Center emergency services. "I have a 29 year old pony that appears to have a Descemetocele,” said the Sock’s primary care veterinarian, “and his owner would like to do anything possible to save the eye.” About three hours later, this aged but still handsome Arabian-Haflinger cross pony gelding unloaded spryly from the trailer and trotted into the exam room of the George D. Widener Hospital for Large Animals at New Bolton Center with his left eye open half way. His apparent comfort level was misleading. The ulceration in his eye had progressed to a depth beyond that at which the cornea is well innervated, to the depth of Descemet's membrane, the deepest layer of the cornea and the last barrier to perforation of the globe.
Socks arrived at New Bolton Center, University of Pennsylvania School of Veterinary Medicine’s large animal campus, accompanied by three generations of his family: 16-year-old Emily Geedy, who had ridden this pony when they both were younger, her parents, and the grandfather who had purchased Socks as Emily’s first pony. On ophthalmic examination by Mary Utter DVM, the pony's left eye did not have a menace response (a blink in response to movement) but the dazzle reflex (a blink in response to bright light) and indirect pupillary light reflex from the left to the right eye were both positive, suggesting that although the cornea had a deep wound, structures in the back of the eye were intact. The left pupil was constricted and there were other signs of uveitis, or inflammation, in the left eye, including corneal edema, vascularization extending from the periphery of the globe toward the lesion, and hypopyon (white blood cells in the anterior chamber).
Dr. Utter explained that this was a surgical emergency, and discussed the options for treatment which included corneal surgery to repair the deep ulcer, medical therapy to support the eye while it healed without surgery (which carried with it a poor prognosis for survival of the globe) and enucleation, or removal of the eye, as an economic alternative to corneal surgery or extended medical therapy. The pony's family declared without hesitation that, while they were sure he would do well with only one eye, they had no reservations about giving him his best opportunity to keep a visual left eye. “He has always been like a puppy, very sweet and easy to keep,” says Emily’s father, Tim Geedy. Socks went into surgery that night.
One of only approximately 320 board-certified veterinary ophthalmologists in the country, Dr. Utter has performed eye exams or surgery on a broad range of species including pit viper, crocodile, Siberian tiger, hyacinth macaw, kangaroo, zebra, chinchilla, as well as the domestic pets and farm stock. Since 2006 she has been practicing exclusively at New Bolton Center, where she has operated on horses, cows and alpacas.
After collecting samples for bacterial and fungal culture, both of which turned out to be negative, and therapeutically removing the margin of the Descemetocele to ensure that the subsequent transplant would have a healthy bed to which to adhere, the transplant was prepared and placed in the pony's cornea. Corneal transplantation is the most common tissue transplant in people, and is performed in horses and other animals as well. Corneas are harvested from donor horses that are humanely euthanized for non-ocular reasons such as a fracture that cannot be repaired or a lameness that precludes a good quality of life, and frozen for use as needed. In the pony's case, the corneal transplant was donated by a 12-year-old Thoroughbred gelding with acute abdominal pain for whom surgery was not an option, but who was otherwise systemically healthy.
The corneal transplant was covered with a layer of conjunctiva, the pink tissue that lines the eyelid and a catheter placed under the eyelid to facilitate treatment of the eye. The eyelid was then temporarily sutured closed to protect the transplant postoperatively. Following the one hour surgery, Socks recovered well from general anesthesia. A routine course of postoperative therapy, including treatment with topical antibiotics, antifungals and a pain reliever as well as a systemic nonsteroidal anti-inflammatory, was happily uneventful. This lucky pony retained a visual, comfortable left eye, thanks to the final gift of a horse who donated his cornea after he lost his life. “Everyone on the team at New Bolton Center feels very gratified to have been able to help this obviously very well-loved pony. His quality of life will no doubt be better with vision in both eyes.”