Equine Health – Common eye injuries
Your horse’s eye swelling, weeping, squinting, or bleeding is almost always an emergency
Our horses’ eyes can give us clues, minute by minute, about their moods and health status. Is he bright, alert, and engaged or dull and aloof? Is she at ease or under stress? Our horses’ eyes also draw the unwelcome attention of tree branches, walls, buckets, sharp objects, dust, sand, insects, and more.
Eye injuries represent as many as 10% of emergency calls that equine veterinarians receive, says Ann Dwyer, DVM, an equine practitioner at Genesee Valley Equine Clinic, in Scottsville, New York, who has a special interest in ophthalmology.
When a horse shows signs of eye injury, whether that’s tearing up, bleeding, or just an inability to keep both eyes open to the same extent, your first reaction should be to call your veterinarian.
“Don’t mess around with eye injuries; the wisest course of action is to call your vet immediately,” says Caryn Plummer, DVM, Dipl. ACVO, assistant professor of comparative ophthalmology at the University of Florida, in Gainesville.
Common Signs of Eye Injuries
Horses can show us they’ve injured an eye in a variety of ways that range from very obvious to very subtle. In extreme cases a horse might have a serious traumatic injury to the side of his face, damaging the eye as well as the bones around it. The resulting swelling, bleeding, and deformation will be fairly obvious, says Dominic Alexander, BVMS, MRCVS, director of Belmont Farm & Equine Vets and a member of XLVets in Hereford, U.K., who has an interest in equine ocular disease.
On the flip side, a horse might show signs as slight as a difference in eyelash height, Dwyer says. Or horses might become “averse to the bright light from a cell phone flashlight, making them wince,” she says.
Between these two extremes are the horses with weepy eyes or eye discharge that’s a creamy pus, says Alexander.
“In a healthy eye the lids will be nice and open, the cornea (outer layer of the eye) will glisten, and there won’t be any tears,” he says, adding that the pupils will be of equal size if they’re exposed to the same amount of light; inflamed eyes will have constricted (smaller than normal) pupils.
With an injured eye, the sclera (the white of the eye) might be red, Dwyer says. The normally transparent cornea might also change color, becoming red, brown, blue, or even yellow.
Another possible sign of an eye issue is a nose bleed, Dwyer adds. “This could indicate a trauma to the sinuses, which could lead to damage and restriction of drainage through the nasolacrimal (tear) ducts or a serious infection in the orbit, the space behind the globe (that is framed by a fragile bony ridge),” she says.
In rare cases, such as with glaucoma (increased pressure within the eye due to inflammation), the pressure can build up in the eye so much that the globe itself appears bigger, says Plummer.
Different types of eye damage can cause similar symptoms, our sources say, giving little indication about the actual injury.
No. 1 Eye Injury: Corneal Ulcers
By far the most common eye injury is a corneal ulcer, says Alexander. While the word ulcer might conjure images of open sores, in the eye it simply means the cornea has been damaged.
“The cornea can get scratched or cut from (the horse) rolling, getting sand or dirt in the eye, brushing against a twig—there are all sorts of things that can set off a problem,” he says.
Horses are particularly prone to corneal damage because their eyes are so prominent, says Dwyer. “Those eyes are just sticking out there, and they can get ulcers from galloping through the bushes or just hitting their face against a stack of hay,” she says.
Ulcers that only affect the top, or epithelial, part of the cornea are superficial and usually heal quickly, she says. But if they’re deep enough to get into the stroma, which makes up 85% of the cornea, healing is slow and complicated.
“The seriousness of the ulcer is usually related to the depth,” she says. “In the stroma there’s a whole cascade of wound healing that goes on, and if you get infection on top of that, then it becomes an even greater challenge.”
Corneal ulcers are particularly prone to secondary infections, easily trapping bacteria or fungi from the environment, says Plummer. “This can cause the ulcer to get deeper and worse, even leading to perforation or rupture of the globe,” she says.
Perforation, which is extremely painful, causes the aqueous humor (the fluid in the eye) to leak out. With a rupture, the eye’s internal contents become exposed. In severe perforation or rupture cases veterinarians often can’t save the eye and must remove it using a procedure known as enucleation.
One factor that can contribute to impaired corneal ulcer healing is a dry eye, Alexander says. If damage to the cranial, facial, or lacrimal nerves or sinuses affects tear production and a horse’s ability to blink, his eye can become dry. When that happens, the eyelid can scratch the cornea and create or exacerbate an ulcer.
Common but Preventable: Eyelid Tears
If a horse gets an eyelid trapped on a hard, pointy object, such as a metal hook on a bucket handle or a nail sticking out of a stall door, it can rip when he pulls his head back. “Eyelid tears are common, but mostly preventable,” Dwyer says.
Manufacturers usually cover the J-shaped hooks on bucket handles with plastic caps, but they can break and fall off. Worse, the hooks tend to gap over time, opening a space just wide enough to trap the eyelid margin if the horse rubs on the handle. To make sure buckets stay safe for equine eyes, owners can crimp the hooks back together and seal the remaining gap with duct or electrical tape. “Handlers need to be on regular bucket patrol,” Dwyer says.
Our sources say veterinarians need to repair torn eyelids immediately—and correctly—to preserve their function. If the eyelid heals improperly, skin, hair, or eyelashes can traumatize the cornea every time the horse blinks, causing an endless cycle of painful ulcers that could eventually lead to enucleation.
A Damaging Force: Blunt Trauma
Horses occasionally fall or run directly into objects, leading to blunt trauma of the head and/or periocular (around the eyes) areas, says Alexander.
Blunt periocular trauma can damage the sinuses, nerves, and orbit, which can affect the eye’s function and vision, Dwyer says. Sometimes the globe itself gets crushed or damaged in an accident.
“We put horses in trailers and starting gates, send them through narrow pasture gates and stall openings, and house them in ways that could be dangerous if horses get rough with each other,” she says. “All it takes is for them to startle, and then it’s not unusual for them to hit their eye on something.”
Blunt trauma can also lead to bleeding and retinal detachment, says Plummer. “There’s little you can do in horses for retinal detachment, which can cause blindness,” she says. “You hope it resolves, but usually it doesn’t.”
Horses can also sustain penetrating or puncture injuries directly into the globe, says Dwyer.
What Can You Do?
Our sources agree that every eye injury merits immediate veterinary attention.
“I can’t tell how many times I’ve had to manage cases where the horse had already been treated on farm, or the owner had used salve from last time, and it was the wrong combination for that particular injury, and have had to try to undo what went wrong,” Plummer says.
For example, an eye ointment that contains steroids can be very useful in some cases but catastrophic in others, causing the eye to “melt”—meaning an ulcer becomes much deeper, further compromising the integrity of the corneal surface. “It’s really dangerous to use the wrong drugs in these cases,” she says.
Even experienced owners should avoid home treatments with eye injuries, especially because it’s so challenging to know exactly what the problem is based on clinical signs alone. “Owners just don’t have the skills or equipment to see what’s going on inside the eye,” Dwyer says. “Eye examination takes veterinary skill as well as diagnostic tools.”
Horses rarely let you treat a painful eye anyway, she adds. “They have very strong muscles in their eyelids and just won’t allow inspection of the globe without the help of sedatives and short-term regional nerve blocks,” says Dwyer.
One thing owners can do is take photos of the horse’s eyes, being careful to put the camera’s focus on the eye itself, and send those to the vet, Alexander says. “This can be helpful right away and also helps monitor progression of the signs, before and after treatment,” he says.
Handlers can help reduce discomfort while waiting for veterinary examination by keeping horses stalled and/or using fly masks to protect injured eyes from light and insects, says Dwyer. “Horses get sensitive to light with an eye injury just like we do,” she says.
Otherwise, call the veterinarian and wait patiently for him or her to come out to conduct an exam. “Whatever you do, don’t just go to your medicine cabinet and reach for an old tube of eye ointment,” says Dwyer.
Eye Injury Examinations
Veterinarians begin with a general examination of the whole horse for signs of a systemic illness such as an endocrine problem, says Dwyer. Then they’ll look closely around the eye and slowly move toward the globe itself, looking for signs of periocular trauma.
Veterinarians check the structure, transparency, and color of each part of the eye, she says. They perform functional reflex tests such as evaluating the horse’s response to a light flash or an object moving suddenly toward the eye. If the horse has impaired vision, his reactions will be diminished or absent. Again, the pupils should constrict the same way in response to light in both eyes, so the veterinarian will make this comparison.
Depending on the vet’s training and toolkit, he or she might use specialized equipment to examine the eye. Most veterinarians use an ophthalmoscope to look into the eye to see the lens and the retina, says Alexander. This stage of the exam usually requires sedation and nerve blocks because the horse’s eye is too painful to open completely.
Fluorescein dye applied to the ocular surface can reveal information about ulcer depth, Dwyer says. If the ulcer is deep enough to reach the stroma, the veterinarian will see bright green spots on the ocular surface after applying the dye to the tear film. Veterinarians might also perform a Schirmer tear test that involves using a paper strip to measure tear production, Alexander adds.
When vets suspect a secondary infection, they often take a sample of the cells and material on the corneal surface to submit for culture and cytology analysis, Dwyer says. They can examine samples under a microscope to check for foreign materials on the cornea, such as bits of plants or mineral (which might have caused an ulcer), inflammatory cells, or pathogenic (disease-causing) organisms.
If necessary, the veterinarian might ultrasound the eye or radiograph (X ray) the periocular region. In severe cases the horse might be admitted to the hospital for a CT scan or an MRI, says Alexander.
Treatment and Follow-Up
After the veterinarian has examined and diagnosed your horse, you can treat most eye injuries at home with a prescribed medication, says Alexander.
Home eye treatment isn’t an easy task, but recent developments are making it easier, he says. In some cases the veterinarian can insert a tube through the upper or lower eyelid and attach it to the horse’s mane so you can inject the medicine directly onto the eye surface from a distance. This is particularly useful for horses that are head-shy or clamp their eyelids shut, he says. Practitioners can also place bandage contact lenses, which are porous, onto the cornea to protect it and make it more comfortable, while still allowing medications to pass through.
“There’s a lot we can do to make life easier for the horse and owner,” Alexander says.
Eyelid tears require immediate and skilled surgery, whether at the farm or in the clinic, Dwyer says. In severe cases veterinarians might have to repair the globe or even enucleate it.
Photography allows for some of the best follow-up, Alexander says. By taking photos from the same angle and with the same lighting every day, owners can track healing progress while keeping their veterinarians in the loop.
Horses have big eyes—which can lead to big problems. Trouble is even more likely when they spook or roughhouse. When this leads to bleeding, swelling, weeping, or squinting, the horse might have sustained an eye injury. If this happens, don’t treat it yourself, and don’t wait to call the vet. A prompt vet visit can set your horse on the road to recovery without complications such as infection.