Consider these 8 behaviors that could suggest your horse is struggling to see.

You’re walking peacefully along a quiet trail in the woods with your trusty equine friend when, suddenly, you find yourself clinging to the side of the saddle, with your heart beating out of your chest.

Your horse, meanwhile, stands under you, stiff-backed with ears perked, snorting at a stump.

A stump. A measly, graying, run-of-the-mill stump, the likes of which you and your horse have certainly crossed paths at least a dozen times.

You tell yourself, “That’s it—he’s gone completely berserk.” But over time, you start connecting the dots. You realize this spookiness has taken on a pattern.

Indeed, your steed only seems to spook at objects on his left side, for example, and generally on days and during hours when trees cast dark shadows, contrasting the otherwise general brightness of daylight. And that’s when you start to wonder: Is my horse still seeing okay?

It’s a question horse owners regularly pose to equine vision specialist Nicole Scherrer, BA, DVM, Dipl. ACVO, associate professor of clinical large animal ophthalmology at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center, in Kennett Square.

It’s also a mysterious issue equine ophthalmologist Richard McMullen, Dr. med. vet., Dipl. ACVO/ECVO has been studying in-depth in his role as a senior veterinarian in the equine ophthalmology service at the University of Zurich’s Vetsuisse Faculty, in Switzerland.

“If I had a wish, it would be to look through a horse’s eyes for a day because it’s really difficult to know how much they rely on vision,” he says