Recognizing Vision Problems in Horses
Consider these 8 behaviors that could suggest your horse is struggling to see. Any time a horse owner suspects vision issues, a veterinarian should examine the eyes. | Courtesy Dr. Brett RobinsonYoure 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, Thats ithes 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 thats when you start to wonder: Is my horse still seeing okay?Its 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 Medicines New Bolton Center, in Kennett Square.Its 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 Zurichs Vetsuisse Faculty, in Switzerland.If I had a wish, it would be to look through a horses eyes for a day because its really difficult to know how much they rely on vision, he says.Finding the Behavioral Signs of Vision Loss: a Blind Path?Certainly, vision problems can affect horses behavior, Scherrer says. But the types of behaviors can vary vastly from one individual to another. I dont even think I can give an exhaustive list of them, she explains.Plus, those behaviors can have multiple causes beyond vision issues, McMullen cautions. I used to think it was so cut-and-dried: Theyre shying, theyre bumping into things, they dont like going from light to dark, he says. But there are all kinds of reasons horses do these things. The more cases I see, the more difficult it is to determine what the signs really mean.So, while our sources say its impossible to create a definitive checklist of vision-related behaviors, theyve shared some hints that might suggest your horse is having vision issues. However, they emphasize this list should in no way serve as a diagnostic resource.In general, vision problems affect one eye more than the other, adds Scherrer. So, if any of these behaviors occur more on one side than the other, thats a more convincing sign vision troubles could be at play.1. Spooking or Refusing.Stopping at jumps, especially when its a new behavior, could be a sign of vision issues. | Adobe StockArguably, the most common reasons owners seek vision workups for their horses are spooking and refusing obstacles, our sources say.Its a reasonable assumptionprovided the behavior is a new development, says Scherrer. Growing cataracts, for example, can trigger spooking in previously nonspooking horses, she says. Thats especially true if the horse shies when something or someone approaches from his side, because cataracts can block vision at certain angles. Even so, cataracts in other parts of the eye could also affect forward-facing vision, which might interfere with understanding obstacles, for example.It could be anything, like stopping at jumps, or maybe having trouble finding distances, whereas they used to be seeing distances just fine, she says, adding that some horses with flawed vision even balk at specific colors.That said, many vision-impaired but experienced show jumpers perform very well, notes McMullen. This success is largely due to their ability to draw on previous training and rely on their riders to accomplish what they need to accomplish, he says.Likewise, its important to remember that horses can spook for many reasons, he adds. We get lots of horses referred for spooking, but when we perform a complete ophthalmic examination, we often find no visual defects or refractive errorsmeaning they should be able to process incoming light normally, he says.2. Reacting Differently to Bright vs. Dark Conditions.Horses that react differently to various lighting situations could have vision issues, possibly caused by corpora nigra cystslittle brown balls in the iris that can grow into larger cysts, which interfere with normal vision, says Scherrer. In bright light, when the pupils are smaller, the cysts take up more of horses field of view. These horses tend to be worse on a really sunny day or out on the cross-country course versus working indoors, she says.In addition, vision-impaired horses might not want to move from bright to darker areas, or vice versa, says McMullen. They could also be wary about stepping between brighter and darker surfaces.3. Turning the Head in Unusual or Unexpected Positions.When a horse has particularly uneven vision between his eyes, he might tilt his head or bend his neck to see better view with the stronger eye. This behavior typically occurs only when there is severe or complete vision loss in one eye, Scherrer says.Certain pathologies (disease or damage) can also affect specific areas of the eye, affecting the way horses adjust their head and neck positions, she adds. I had a client horse with a cloudy corneal disease called immune-mediated keratitis, and it was on the bottom half of the cornea, she recalls. The horse couldnt find the carrot during low carrot stretches. But once we treated her and her cornea cleared up, she was able to find the carrot again.4. Bumping Into Things.Horses that dont see well sometimes bump into fences, poles, people, horses, or objectsand then seem surprised about it, McMullen says.Bumping behavior appears early in young horses with congenital vision issues such as severe retinal problems or cataracts, he says. It can also occur in older horses with sudden onset of vision problems.Those with more progressive disease processesmeaning they gradually worsenare less likely to bump into objects due to their training and performance experience, McMullen explains.5. Getting Lost in a New Pasture or When Separated From a Friend.Some vision-challenged horses might struggle to maintain rank in the social hierarchy if they cant see well enough to defend resources such as food and shelter, our sources say. But in general, they adapt smoothly in the pasture.The last thing a horse wants to do is draw attention to itself and change its status within the herd, McMullen says. So if they become visually compromised, that could be a huge problem for themand it might be part of the reason theyre so good at adapting and covering up those changes.Their whole drive is to not let anyone see that they have a problem, Scherrer adds. They do a really good job of pretending that everythings okay.That all changes, though, if these horses lose familiar elements in their environment. Maybe theyre moved to a different field, or a friend dies, and then all of a sudden they look like theyve gone acutely blind, she says.Thats also the case with vision-impaired horses moving to a new facility or competing in an unknown venue, McMullen adds.When I see these horses come in for evaluation, I usually find chronic changes, Scherrer continues. So its not something recentits just that theyd been really good at hiding their disabilities up to then.But even in new environments, visually impaired horses adapt remarkably well, she adds. Her own ponywhose eye troubles eventually led to surgical removal of both eyeswas galloping in a new field within weeks of surgery. By the second week, you would never have known that that pony was blind, given how she negotiated around the property, Scherrer says, adding that the mare appeared to memorize the location and depend on her herdmates.Horses might blink or squint when pain is involved with a vision issue. | Adobe stock6. Headshaking, Increased Blinking, or Squinting.Headshaking can have multiple causes, but Scherrer says vision problems are certainly worth considering. Specifically, horses with floating structures in the field of view can find their movement irritating, prompting them to shake their heads. That can also be the case with corpa nigra cysts, which can be somewhat mobile, she says.If the vision issues involve pain, horses might blink more often than usual or seem to squintmeaning any downward deviation of the upper eyelashes. Standing in front of the horse can allow you to easily compare the eyelash angle on one eye to the other, she says.Unlike humans, however, horses rarely have issues with eye focus that lead to squinting or blinking, she adds.7. Grumpiness, Stubbornness, or Any Recent Behavior Change.Importantly, behavior problems could reflect vision issues truly upsetting and confusing for the horse, our sources say.Indeed, horses reactions to vision loss can be so broad and varied its often impossible to associate specific behaviors with specific vision problems, McMullen says. We often find really significant lesions during an exam, but they are often not associated with behavioral patterns matching that kind of vision loss, he explains.Even so, any abrupt new behavior can be an important clue. Acute behavior changes are always a good indication to look to see if theres something going on in the eyes, he says.The biggest thing, especially if theyve had the horse for a while, is any type of change, Scherrer seconds. Most of the time when we find an actual eye problem as the cause of a behavior issue, its something that the horse had started doing over the last six months to a year or so.Some horsesespecially stoic breeds such as stock horsesmight simply act a little grumpier or more stubborn than they used to, she explains.Every time I see something in the horses eye, my job is to ask myself, Okay, do these clinical signs meet what Im seeing in the eye? she says. If theres any question of a behavior change, its just a good idea to get an eye exam.Owners can request basic exams from their treating veterinarians during regular checkups or get a specialist referral for more advanced testing. Its always worthwhile to mention these things to your vet, she says.McMullen agrees. Its fairly easy to thoroughly look at the eyes, he says. And then if there are no findings, you can start looking for other issues that might explain the problem.8. No Unusual Behavior at All.Because horses have evolved to hide their weaknesses from predators and herdmates, many show no signs of vision loss at all, says Scherrer.Theres not necessarily a red flag that goes up for these animals, McMullen says. They just tend to adjust really well and accommodate for vision lossoften to the point where theyre completely blind in one or both eyes, and nobody knows it.Ive even seen horses come in to the clinic who are close to blindness, with disease thats clearly been going on for years, and theirvery goodowners have never even seen them squint, adds Scherrer, who in a recent study of more than 500 horses found that well-meaning owners frequently noticed no signs whatsoever of minor cataracts.It can be really hard to interpret when you have a tricky horse like that, she says.Take-Home Message Horses can cope remarkably well with vision issueseven extreme cases involving blindnessmaking it difficult for owners to pick up on behavioral signs that their horses are struggling to see well. Still, careful observation can sometimes pick on possible signs meriting a vision workup, at least to rule out sight as a cause. For optimal equine health and welfare, our sources recommend having your veterinarian investigate any new behavioral problems in horses for vision and other health issues, our sources say.This article is from the Older Horse 2025 issue ofThe Horse: Your Guide to Equine Health Care. We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Your subscription helps The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels. To access current issues included in your subscription, please sign in to theAppleorGoogleapps ORclick herefor the desktop version.
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