As an underdog with a great story — and a Twitter account — Patch is easy to pull for, and he’s proving to be a fan favorite in the days leading up to the race on Saturday. But as a one-eyed racehorse, he’s neither unique nor even the first to run in the Kentucky Derby: One ran in 1982, another in 2004, and another in 2007.
“We very commonly have situations where racehorses have to have their eyes removed, and the majority of racehorse trainers don’t even think twice about it,” said Nicole M. Scherrer, a clinical assistant professor of ophthalmology at the New Bolton Center of University of Pennsylvania School of Veterinary Medicine.
Sports fans will recall human athletes who have competed successfully with less-than-complete vision. Orioles pitcher Chris Lee is legally blind in one eye, as was Wesley Walker, a New York Jets wide receiver in the 1970s and ’80s. Bryan Berard, a former NHL member, lost his eye playing hockey and came back to the ice.
Because of how a horse’s vision works, losing an eye likewise doesn’t have to end their athletic careers. We humans have small, round pupils that allow us to see very well front and center. But we don’t have very good peripheral vision. Horses, by contrast, have the largest eyes of any land mammals, and their long, horizontal pupils allow them to get an enormous view from side to side, said Janet L. Jones, a cognitive scientist who trains horses and has written about how horses see the world.
Additionally, while human eyes move in tandem and give us a view of 140 or 150 degrees, horses can move their eyes separately for a view of about 350 degrees.
Jones says to imagine you are holding up a piece of cardboard with two small pinholes, centered to each of your eyes. You would easily see what’s directly in front of you, but nothing of what’s behind you or to the side. To correspond to where a horse’s eyes would be located, you would crease the cardboard down the middle, and add two long slots on either side.
“You can see that you would get a totally different view of the world,” she said. “And if you were just to imagine covering up the left slot on your horse cardboards, and then run in great big circles to the left, you would have an idea of what this horse is attempting to do.”
So how does Patch do it? Scherrer said it has to do with that extraordinary side vision.
“Just because the one eye was removed doesn’t mean that they can’t see anything on that side,” she says. “So if the left eye is removed, the right eye looks out in front, and can actually see a little bit to the left as well.”
Patch’s impairment could present a problem, Scherrer said, “if a horse came out of nowhere and bumped him from the left side.” That’s unlikely to happen, because bumping another horse during a race constitutes a foul. Also, Patch’s residual vision — and his jockey’s guidance — should prevent contact.
“And after a couple weeks we were like, ‘This horse is fine,'” Pletcher said. “I mean, there is common sense stuff, like I don’t come up to him without letting him know I’m there. You don’t want to startle him, things like that. But really, you really wouldn’t know it and you don’t really have to do anything special with him either from a rider standpoint on the track or around the barn.”
Patch doesn’t wear a prosthesis, but some one-eyed horses do. There are two kinds for equine eyes, Scherrer said. One is an implant that a surgeon puts in the sunken hole, and then closes skin over it. That gives the horse sort of a permanently mid-blink look that makes eyelessness tough to detect. Surgeons can also place a false eye in the socket, to give a horse the appearance of having two eyes, more along the lines of a human glass eye. Scherrer said those are usually used in horses “that have a job based on their appearance,” such as show horses competing in a class in which the animals and riders are judged on looks as well as performance.
“Sometimes it just creeps people out to have the socket, but obviously the horse doesn’t care either way,” she said.
What’s more important is patience, said Scherrer, adding that horses that have lost an eye adjust better when in familiar surroundings and with known companions. Scherrer has her own one-eyed horse, a former patient, and she initially rode his best friend and led her horse along from the saddle. Now they compete over jumps.
“I couldn’t ask for a better horse,” she said. “He is better than the majority of two-eyed horses.”
Scherrer cited a retrospective study based out of New Bolton that followed up with horses that had had their eyes removed. The majority, she said, went back to doing the same thing they were doing before they lost the eye. Those that didn’t were stymied by a perception that they’d be too changed to do the same job, not because of any evidence that they couldn’t.
“It definitely makes me very happy for [Patch] to go out and do this successfully and show people that horses with one eye adjust amazingly,” Scherrer said. “They’re so much more adjustable than humans.”
Correction: An earlier version of this story provided inaccurate information about the size of horses’ eyes. It has been corrected.