We naturally assume that people who lose an eye would wear an eye patch or use a prosthetic ceramic eye for cosmetic purposes, but few think of how loss of an eye can affect the appearance and career of a prized show horse. Dr. Ralph Hamor, veterinary ophthalmologist at the University of Illinois Veterinary Teaching Hospital in Urbana, explains that there are many cosmetic options available when a valuable horse loses an eye to infection or injury.
Several ophthalmic devices, ranging from colored contact lenses to ceramic prosthetic eyes, can save an animal’s appearance when an eye becomes damaged. The simpler and relatively inexpensive devices are commonly used for pets, but the elaborate prosthetics are almost always used exclusively for horses. Interestingly, some equine performance class show rules state that a horse only needs "the appearance of two eyes," not necessarily two functional eyes, to compete, so such prosthetics can prolong a show horse’s career.
When severely damaged by injury or infection, an eye can become permanently scarred. Corneal scars appear white or cloudy, and veterinary ophthalmologists can use darkly colored contact lenses or tattooing procedures to hide such scars.
Sometimes an eye is so severely ulcerated that it may shrink up into small nub, and the animal loses sight in that eye. In some cases, the eye can be removed via a surgical procedure called an enucleation, in which the eye, the eyelids, its glands, and conjunctiva (the pink tissue covering the eye and eyelids) are removed, and the skin surrounding the eye is sewn together.
For cosmetic purposes, veterinarians may insert an intraorbital prosthesis, which Dr. Hamor describes "like a surgical-grade superball," into the socket during an enucleation surgery before sewing the skin shut. He says, "This prevents the strange ‘crater’ appearance under the eyelids created by the empty eye socket and ends up looking quite nice." This prosthetic is commonly used in dogs, cats, and horses since it is very simple and only adds $20 to $40 to the cost of an enucleation procedure.
If an owner wants its animal to retain the appearance of a normal eye, options, albeit costly ones, are available. One cosmetic procedure is insertion of an intraocular prosthesis. When an eye is injured or infected, a veterinarian can insert a prosthetic ball inside the eye before the eye shrinks. Through an incision in the white part of eye, or sclera, a veterinary ophthalmologist can remove the eye fluid, lens, iris and retina, and insert a darkly colored prosthetic ball. With the white sclera of the eye intact and a dark prosthetic showing through the cornea, Dr. Hamor says, "the eye still has a fairly normal appearance. With this procedure the eyelids, conjunctiva, glands, and eye muscles remain intact, so the horse can still move its eye normally."
A more elaborate and costly option is the ceramic ocular prosthesis, or "glass eye." This type of prosthetic is very similar to those in people; it looks like a real eye, can be removed and reinserted, and is even made by the same ocularists that make ceramic eyes for humans. Veterinary ceramic eyes differ from the human version in that the prosthesis is a single shell and is not connected to any eye muscles.
Since the ceramic ocular prosthesis is not directly attached to eye muscles, a horse must have intact eyelids, eyelid muscles, and conjunctiva to hold the prosthesis in place, so the veterinarian must plan ahead to preserve these structures, especially if an enucleation surgery is performed prior to placing the ocular prosthesis.
Some ceramic prostheses are molded directly over the shriveled eye. In other cases an enucleation surgery is performed to completely remove the eye before a prosthetic is inserted. The latter procedure is more labor-intensive, thus more costly, since an enucleation is an involved procedure and leaves no eye to mold the prosthesis over.
To fit the prosthesis, the veterinarian uses dental alginate (the same material used to mold human dentures) to get a soft but firm impression of the eye socket. This impression is sent to an ocularist, who makes a "rough draft" ceramic eye and sends it back to the veterinarian. The veterinarian can adjust the fit of the prosthesis using dental wax and send it back to the ocularist, who will make a revised version of the prosthesis. The veterinarian and ocularist repeat this process until the fit is just right.
Once the shape of the prosthesis is finalized, the ocularist will send the final "blank" white prosthesis and the veterinarian will trace an outline of the eyelid directly on the prosthesis. The prosthesis will be sent, along with a color photograph of the other eye, back to the ocularist who will paint the details of the conjunctiva, sclera, cornea, iris, and pupil onto the prosthesis and coat it with a clear glaze.
Owners usually get a plain dark brown prosthesis along with the painted version; the brown one can be used for everyday wear, while the more expensive painted one can be saved for shows and special events.
Since the procedure for fitting and creating an ocular prosthesis requires much preparation, time, and money, it is rare and is performed mainly on show horses. Dr. Hamor has performed the procedure mostly on Saddlebreds. The process can take anywhere from three months to over a year to complete, depending on how frequently the horse visits the veterinary ophthalmologist for fittings, and depending on the temperament of the horse.
The procedure can cost between $2,500 and $3,500 (including the cost of the prosthetic), which sounds costly, but may be a worthwhile investment to save a prize horse’s show career. For more information about ocular prosthetics and other cosmetic ophthalmic procedures, contact your equine veterinarian or veterinary ophthalmic specialist.
Original Article: http://www.cvm.uiuc.edu/petcolumns/showarticle.cfm?id=423