Leg chestnuts, microchips, branding and lip tattooing of horses soon may be identification methods of the past.
Iris scanning is a 21st century system that will revolutionize the ability to simply and accurately identify horses for registries and practitioners. The iris scan cameras are currently at several large equine hospitals around the United States and in pilot projects in Ireland, Denmark and Italy.
Iris scan technology was developed during a 15-year period, beginning with research in 1996 conducted by Dan Stewart, a designer and the CEO of Iristrac LLC, and his colleagues (the intellectual property was licensed by Global Animal Management). The equine algorithm was then perfected by Sarnoff Corporation.
He began work on horse identification because of his passionate involvement in team roping. He realized that, in most cases, those horses were never registered with the American Quarter Horse Association, and there were some great performance bloodlines that had no previous methodology of identification. "I wanted to see if there was a way, for the first time in history, to simply track the performance of the team-roping horses to allow for the creation of a database to keep track of horse identification and the various parameters of awards within the sport," Stewart recalls.
When compared with other animals, the equine eye's iris shape is quite complicated, so Stewart decided to tackle horse identification first.
"With the USDA's recent concern to microchip all animals, especially horses and livestock for identification, I never wanted to do anything invasive with my horse," says Stewart. So Stewart and his colleagues settled on the iris as being the simplest form of identification. After 10 to 12 months of life, a horse's iris remains stable throughout the rest of the animal's life, and it's essentially unalterable. The iris scan technology can even get an accurate identification with as little as 60 percent of an injured eye.
Iris vs. retinal scan
Nicholas Millichamp, BVSc, PhD, Dipl. DACVO, Dipl. ECVO, says, "You can get some variations in iris pigmentation over time. Since the iris scan photographic image is obtained via infrared light, perhaps you might get more evidence of vascular changes than you would with a normal light photograph where you're just going to see pigmentation."
Otherwise, he notes, corpora nigra, which project from the upper part of the iris, may vary in shape and size. Use of the iris scan "is an interesting thought, because in other species, such as cattle and dogs, retinal photography is used for identification," Millichamp says. "For dogs, there's a lot of variation in pigmentation in irises between breeds, but in other respects, the structures would be similar [to horses]." There's probably a lot more variation in iris pigmentation in dogs, and some horses have much reduced pigmentation.
"It depends what they're looking at—whether it's the vasculature or differences in the folded appearance on the front of the iris—and that's pretty distinctive in horses, which you don't see quite as much of in dogs," says Millichamp. "I guess it depends on exactly what's being picked up with the infrared."
It also depends on what one is going to photograph—the vasculature of the iris, the pigment pattern on the iris surface, or both. "We use infrared photography for horses to look at eyes that have corneal opacities. It allows you to photograph the anterior chamber and the iris to identify corneal edema," says Millichamp. "There is certainly a fairly distinctive appearance to the iris. I think a good part of that is going to be influenced by the vasculature, because it is such a vascular structure. Most of the heat that's generated—the infrared part of the spectrum that's emitted—is due to the blood vessels that are a higher temperature than the anterior chamber. The scan is probably picking up the iris vessels as much as anything. It must be vascular-based."
You can't identify horses based on the retinal vasculature, Millichamp continues, because the vessels are too small. In other species, the retinal vessels are much larger, and that's what people tend to use for imaging and identification purposes. "I would think in the iris, which is a densely vascularized structure, that would be the thing that would give most of the pattern—far more so than pigmentation, which can change significantly over time," he says.
The camera system
The iris scan system registers both the left and right eye because each is different in individual horses, and also in twins and clones. An infrared picture is taken of each eye. "Accuracy is greater than 99.9 percent—far more so than the human fingerprint," says Stewart. As a side note, it's possible to modify a lip tattoo or a microchip, even when it's still implanted in the animal.
The iris scan camera consists of two LED illuminators within the infrared spectrum and a lens. Below the lens system is a handle with a trigger used to gather several images and to automatically feed data to the attached computer, which then constructs the algorithm. Once triggered, the camera essentially takes a very short video, 24 pictures to the shutter-click, which the software automatically analyzes. The software sorts the images and selects the best one for the algorithm. Once done, it converts the algorithm data to a 512-byte code and then to a 15-digit number.
The camera was developed by a company that also developed the color television (RCA Laboratories, which is now Sarnoff Corporation). It's been responsible for refining the algorithms Stewart and his colleagues developed. The LED light and lens system of the battery-operated camera has been continuously improved to its current state of development. The current prototype is being confirmed and tweaked.
The iris scan image is captured with the special camera, allied with client software (EyeSync) and the EyeD processor (the process is similar to downloading onto iTunes or using an iPod or iPhone). The camera interacts with software to gather the horse metadata and iris information. The enrollment (registration) and verification software assembles horse and client information, along with the picture taken of the left and right eye to compute the algorithm.
Whether taking the image initially or verifying the horse, the camera and computer assembly do the work automatically in a few seconds. When an already iris-scanned horse comes to the veterinary practice, its identification is simply verified and retrieved. The technology allows verification in four to five seconds and pulls the animal's information out of the database in three to five seconds.
The procedure is done essentially by photographing the horse's eye with the special digital camera taken at 12 to 14 inches from the eye. Horses seem to tolerate the procedure well.
Consideration should be given to the age of the horse and constancy of its iris image. As noted previously, a horse's iris shape stabilizes after 10 to 12 months of age. Stewart and colleagues have captured images from foals at 12 to 18 hours old, but up until now, the period from that age to 10 to 12 months old has not been studied. They're currently doing so with a group of 100 3- and 4-month-old Thoroughbred foals. It's thought the iris shape may change from when a horse is days old to 10 to 12 months of age, but researchers don't yet know if that change is significant. Even if there is a marked change, the iris identification done at 3 to 4 months old could be redone at 10 to 12 months to bring the original algorithm up to date.
The 15-digit code is the horse identifier. Although a registration number may be different among the various registries, the 15-digit code will be the same for each horse. The various breed registries currently are being consulted for their interest and acceptance to use the iris scan technology for identification purposes, says Craig Markovitz, senior business analyst at Global Animal Management. Use and acceptance by The Jockey Club and the Thoroughbred racing jurisdictions is still in discussion.
Using iris scan technology on Thoroughbreds would be a fairly easy transition for the horse identifier in the racetrack paddock. For example, the iris scan technology would be substituted for lip tattoo visualization. Iris recognition is a rapid process. In terms of software management, on any given day, there would be only about 100 horses to identify (i.e., 10 horses each in 10 races), and the data could be extracted simply, so the paddock identification process would not be adversely impacted. Owners whose horses travel among racing jurisdictions could carry their animals' iris identification with them, which easily could be downloaded into a racetrack's iris scan database.
It appears iris scan identification technology will soon be for horses what retinal scan technology may be for human identification—namely, an innovative move into the future. Someday, using iris scan technology may be just another routine procedure.
Kane is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine with a background in horses, pets and livestock. He is based in Seattle.