As horse owners, we often worry about the hooves and legs of our animals and routinely check for swelling or signs of lameness, but it is easy to overlook how important the horse’s eyes are. Dr. Chantale Pinard, a professor at the Ontario Veterinary College who specializes in eye problems in dogs and horses, suggests some strategies to keep your horse’s eyes as healthy as possible:
Know your horse: By spending time with and observing your horse, you’ll know how he looks and behaves when he’s healthy, and be able to more quickly pick up signs of problems. Pinard suggests taking some close-up photos of your horse’s eyes so that you have something to refer to if there are any changes over time.
Prevent eye irritation: Dust in a horse’s eye can cause inflammation, so take steps to keep dust down in your arena and barn. If you are sweeping barn hallways, be sure to sweep away from the horses. If you are mucking out the stall – which inevitably means bits of manure and bedding will be in the air – it’s safer to move the horse elsewhere.
If your horse is out in the pasture during windy weather, a fly mask will protect him from wind-blown particles, as well as protecting his eyes from irritation and disease spread by flies.
Protect from ultra-violet rays: Certain breeds, such as Paints and Appaloosas with white eyelids, and some breeds of draft horses, are more susceptible to squamous cell carcinoma of the eyelids, explains Pinard. The latter can also get this particular cancer on the nictitating membrane, or third eyelid – a pink membrane which moves across the cornea from the inside corner to help protect the eye from trauma. For these horses, wearing a fly mask with protection against UVA and UVB radiation can significantly reduce their risk. “They should wear the fly mask even if it is cloudy – the radiation is still there even when you can’t see the sun,” adds Pinard. She points out that horses with dark eyelids, while their risk is lower, can still get UV radiation-linked cancers and can benefit from the protective fly masks as well.
Check with your vet: “A problem with a horse’s eyes can go bad very quickly,” warns Pinard. Sometimes if a horse has had previous eye problems which were treated, and then displays similar symptoms again, the horse owner may assume it’s the same issue. Not necessarily! As Pinard points out, a symptom such as a red, inflamed eye or an eye with yellowish discharge can mean a multitude of different issues. “What worked the last time isn’t necessarily what is needed this time,” explains Pinard, “and sometimes it can make things worse.” She encourages horse owners to get veterinary care promptly, and to ask for a referral to a specialist in equine ophthalmology if needed.
Symptoms of eye problems
“Winky-blinky”: While your horse will naturally blink if you bring him outside into daylight from a dark barn, if rapid blinking (or winking, if just one eye is affected) persists, this may be a sign of a problem. Pinard reiterates that this is when knowing your horse can really help – some horses do normally blink more than others, but an observant owner will notice when something has changed. Excessive squinting is another warning sign.
Pinard says that sometimes all this eye movement is just the horse’s attempt to flush a speck of dirt or dust from his eye. If the blinking continues for more than a few hours – and definitely if the symptoms persist for more than 24 hours – it could be a sign of a more serious problem such as inflammation, corneal lacerations, or other trauma.
Tearing: Tear production in the eyes can be prevalent in any horse outdoors on a windy day, or one which has some dust or a particle of dirt in his eye. But if the tearing continues when the horse is indoors or in a shelter, and lasts for more than a short period of time, Pinard recommends contacting your veterinarian. Also, if rather than clear, watery tears you are seeing a greenish or yellowish discharge, this should be seen by your vet. Because the tear ducts are connected to the horse’s nose (just as they are in humans), you may also see this discharge from the nostrils when there is a problem with the eyes or tear ducts.
Swelling of eyelids: If you think one or both of the horse’s eyelids may be swollen, refer to the photo you took for comparison. This symptom can be caused by many different conditions: an insect bite, an allergic reaction, exposure to an irritant, or more serious problems such as lacerations, trauma or even parasitic infestation. Pinard suggests that if it lasts more than a couple of hours, it’s time to call the vet.
Third eyelid prominence: Normally, says Pinard, you should just barely see the margin of the third eyelid at the edge of your horse’s eye. (There are individual variations on this – again, it’s important to know the usual appearance.) If the third eyelid becomes more prominent, this could be a sign that the horse is experiencing pain, or that perhaps a tumour is pushing on the eyelid.
Cloudiness of the cornea: In a healthy horse, the cornea (the outer surface of the eyeball) is clear, and the iris (the coloured part, either blue or brown) is easily visible. If there is cloudiness – either one dense spot, or throughout the cornea – this is “extremely concerning” according to Pinard. Causes of cloudiness can include squamous cell carcinoma (tumour), immune-mediated keratitis (inflammation of the cornea), fibrosis (scarring of the cornea), and glaucoma (increased fluid pressure within the eye). Very serious vision-threatening causes of cloudiness include abscesses, eosinophilic keratitis (invasion of the cornea by white blood cells) and uveitis (moon blindness).
Other eye changes: If the eye appears sunken into the eye socket (possibly Horner’s syndrome or dehydration), or if the eyeball seems to be protruding or bulging out (possibly glaucoma or orbital injury), these should signal a call to the vet. Another thing to watch for is a change in the size, shape or position of the pupil (the dark line in the middle of the iris), especially if it is no longer horizontal, but appears to be diagonally placed in the iris.
Protecting your horse’s vision and keeping his eyes healthy involves management to avoid potential hazards and being observant so you can catch any changes that might signal problems. “Know your horse,” Pinard repeats. “That puts you in the best position to identify any concerns.”
