There is nothing more peaceful and connecting than gazing into the kind, soulful eyes of a horse. Throughout their history, horses have relied heavily on their nearly 360º range of vision to identify and flee from predators, and find food and water. Today, the vision of our equine athletes is equally critical to navigating the myriad of tricky obstacles we place in front of them ‒ jumps, barrels, a racetrack full of other horses.
In a video about equine eye emergencies with Dr. Claudia Cruz Villagran of the Western College of Veterinary Medicine in Saskatoon, Saskatchewan, she stresses that “any eye problem in the horse is an emergency, period.” Some of the signs that something is amiss with your horse’s eyes include:
- rapid blinking, running tears or a creamy discharge (pus) indicate that something is causing pain and/or irritating the eyeball.
- photophobia, where the horse shuts its eye(s) when brought from the barn outdoors into the sunlight
- swelling or cloudiness inside the corneal surface, which is normally crystal clear, indicates that there is inflammation.
- swelling or redness of the eyelids
- head shaking
Common Eye Problems
The main cause of eye injuries is trauma caused by a kick, or by the horse banging or rubbing its head on a tree or post. Foreign bodies can also enter the eye while the horse is rolling or grazing around bushes or trees and cause a scratch, tear or ulcer on the corneal surface. While many minor scratches and ulcers will resolve on their own, if they become infected it can quickly cause complications.
Treatment for eye trauma injuries are commonly warm or cold compresses applied around the eyelids to help reduce swelling, along with anti-inflammatories, both injectable and topical as eye drops. Infected ulcers will require antibiotic drops or ointments. Dr. Villagran advises, “When we tell you to medicate your horse, we ask you to please wear gloves. Your hands carry bacteria and it’s already infected, so we don’t want you to cause more problems.” To administer ointment, put it on your glove and then apply gently into the horse’s eye by gently pulling down the lower eyelid and depositing it there.
A corneal ulcer generally takes between five to seven days to heal if it’s uncomplicated, but a stubborn one could takes two or three weeks to resolve. Really extreme infections may require insertion of a special catheter and treatment every four hours.
Some penetrating injuries to the eyeball require suturing of the eye performed under general anesthesia; some corneal injuries require tissue grafts or surgical eyelid closure to temporarily protect the wound until it heals.
A worst-case scenario puncture wound can result in perforation or laceration of the cornea, resulting in rupture of the eyeball, which generally necessitates emergency surgical removal of the eye.
Recurrent Uveitis (ERU)
ERU is the most common cause of blindness in horses in the world, characterized by episodes of active intraocular inflammation followed by periods of dormancy. It causes inflammation of the uvea, one of the layers of the eye which contains most of the blood supply and includes three structures: the iris, the ciliary body and the choroid. Some horses experience gradually-worsening ERU causing cataracts, lens luxation (separation), glaucoma, scarring and retinal degeneration. “This happens more commonly in Appaloosa horses; they are genetically predisposed to that,” notes Dr. Villagran. While the cause of ERU is not known, research points to the bacteria leptospira which may play a role.
Non-steroidal anti-inflammatories (bute or flunixin) are used to control inflammation and atropine provides relief of the discomfort of uveitis and prevents complications that can arise when the pupil remains closed for long periods of time. It may take several weeks of treatment to prevent the disease from becoming chronic. Those that do become chronic will see uveitis recur at regular intervals, necessitating treatment with eyedrops. There are surgical options available such as cyclosporine implants or pars plana vitrectomy (removal of the vitreous body) or treatments such as intrachoroidal injections of steroids. Unfortunately, some eyes fail to respond to therapy and require enucleation (surgical removal of the eye) to alleviate the constant source of pain.
Eyelids are an important structure whose job is to protect the eye and distribute lubrication. Similar to eyeball trauma causes, these injuries commonly occur if the horse rubs its eye on a fence, bucket, or sharp object. Eyelid lacerations may bleed profusely and look alarming, but your veterinarian should be able to make surgical repairs and cover the eye to prevent the horse from rubbing the sutures out. Ophthalmic antibiotic ointment, oral antibiotics and non-steroidal anti-inflammatories are usually prescribed.
Corpora Nigra Cysts
While not considered an emergency situation, corpora nigra cysts can impair vision over time as they grow larger. The corpora nigra are structures attached to the iris (the coloured part of the eye); their main function is to shade the pupil from excessive glare. Sometimes the structures become cystic and larger than normal, looking like dark bubbles and affecting vision. Laser surgery can be performed to deflate the cysts.
Eyelids may be affected by sarcoids (nodules below the skin) and conjunctival squamous cell carcinoma (cancerous masses). Treatment for sarcoids depends on whether they are occult, verrucous, nodular, fibroblastic, mixed or malevolent, and include laser surgery, cryotherapy, chemotherapy, hyperthermia, and radiation. Recurrence is common, unfortunately.
Squamous cell carcinoma is more frequently seen in lightly-pigmented or non-pigmented eyelids such as those in Appaloosas. Ultraviolet radiation from excessive sun exposure may also play a role. They grow rapidly (and should be treated quickly) and are commonly found on the horse’s third eyelid. Removal of the affected portion of the third eyelid is the usual procedure. Anticancer drugs, surgery, radiation therapy, hyperthermia and cryotherapy may be employed to control these tumours.
When to Call the Vet (Always!)
If any of the above signs or symptoms are seen in your horse, Dr. Villagran urges, “Call the veterinarian ASAP; please do not wait.” Your vet will first do a manual examination, gently manipulating the eyeball to look for foreign bodies or swelling, and make sure there are no fractures around the orbital bone. A fluorescein strip may be used to stain the corneal surface and a cobalt blue light used to determine if there are any corneal epithelial defects. Sometimes a nerve block is needed to prevent movement of the eyelid “because the muscular tone of the eyelid of the horse is very strong” and it provides some measure of pain relief.
Once a diagnosis is made, a course of treatment or surgical options (see above) will be discussed, and hopefully your horse will be well on its way to a full recovery.
How to avoid eye injuries
- Never fence with barbed wire, as a horse grazing near it could sustain an injury.
- Check surfaces around the farm regularly for sharp or protruding objects such as nails, jagged metal edges, etc.
- Fly masks worn during the spring and summer can prevent irritation. If your horse is pre-disposed to uveitis, use a UV mask.
- Know what is normal for your horse ‒ it’s just another excuse to look into those beautiful eyes every day!