Eye injuries and infections are common in horses, given the large size and prominence of their eyes. This is just one of the reasons you should check your horses—and not just from over the pasture fence—at least twice daily.
With prompt treatment, many eye problems can be brought under control within a few days. In most cases, a veterinarian should check the eye, but most management can be done by you, at home.
What Are Eye Infections in Horses?
The most common eye issues in horses include bacterial infections and traumatic wounds.
Untreated eye problems can become nasty very quickly. Minor problems can even result in blindness if left untreated. If the eye becomes badly infected, the structures of the eye can be eroded until the entire eye collapses. Eye problems are also extremely painful, and for animal welfare, should be treated as soon as possible.
Signs of Eye Infections in Horses
Your horse's eyes should be clear and bright, and the lids should be snug around the eyeball, with the inside of the lid pale pink and moist. Tearing should be minimal with perhaps only a droplet at the corner of the eye. Sometimes, if there is dusty, dry wind, a horse’s eyes might run a bit, just as yours would.
Symptoms that require treatment include:
- Cut or torn eyelids
- Swollen eyelids
- Obvious damage to the eye itself
- White film/hazy appearance either over the whole eye or in spots
- Red or inflamed eye or of any surrounding tissue, including the white sclera and lids
- Tears running down the horse's face, which may indicate a blocked tear duct
- Copious discharge other than a thin tear-like stream
- Tumors growing on or around the lid
- In foals, turned under eyelids that cause the eyelashes to rub against the eye
Causes of Eye Infections
Horses can develop an infection after having a foreign object lodged within the eye. If the surface of the eye is scratched, environmental bacteria can quickly cause an infection. This could make the horse's eye appear cloudy and red. The horse will likely squint and tear profusely and may be reluctant to let you take a close look. These types of infections should be seen by a veterinarian, who will prescribe an antibiotic ointment and perhaps other therapies to treat the infection and help heal the eye.
Recurring uveitis is another, much more serious eye infection in horses that can lead to blindness if left untreated. Also known as "moon blindness," this condition may have multiple causes. Research has indicated that a bacterial disease called leptospirosis can be one of the major causes, and other causes are suspected as well.
The signs of uveitis include squinting and hypersensitivity to light, a cloudy eye, and eye pain. Your veterinarian would be able to detect whether other changes have occurred within the eye. Symptoms may flare up and then subside, only to flare repeatedly again.
Infection with the parasite Thelazia, also known as the eyeworm, is also a cause of equine ocular disease. Horses are infected with this parasite via flies. Thin worms can be visualized within the eye. A veterinarian will have to remove the worms from the horse's eye with surgical instruments (usually a forceps) after a local or topical anesthetic has been applied to the eye. In the United States, these parasitic infections may not always show obvious signs in horses.
If your horse has an eye injury or infection, call your veterinarian as soon as you can. Prompt treatment is key to a successful outcome for any eye issue. While waiting for your vet, here are some things you can do to help your horse:
- Eye and face nets may help keep flies away; fly masks or veils should be avoided because they may rub or hit the eye.
- If possible, keep your horse in subdued light, such as its stall, until the veterinarian arrives.
Your veterinarian will likely sedate your horse for a thorough eye inspection. Don't try to force a horse's eye open, as a horse can be extremely head shy if the eye is painful. Rips and tears in the horse's eyelids should be attended to by a veterinarian, so that the lid can be stitched, if necessary. The vet will also check for damage to the cornea and anything that may be lodged in the eye (splinters, awns from grasses, or grit). A vet can assess the overall health of the eye and may be able to see problems that aren't apparent to the untrained eye.
If an infection is diagnosed, your veterinarian will likely give you an ointment or gel to apply to the eye multiple times a day. In some cases, the vet may draw a vial of the horse's blood and extract some components from it, with which you may irrigate the eye; the serum in a horse's own blood acts as a healing agent for eye tissue. With all medications, make sure that you follow the veterinarian's instructions to the letter, and be scrupulously clean as you apply any dressings or ointments.
Just because you may see a marked improvement within a few days, doesn't mean you should stop the medication before the full course is up. Stopping treatment before the infection or injury is completely healed can result in the infection flaring up again and possibly causing more damage. In some cases, the cause of the infection (for example, bacteria) may become resistant to the medication, if the full course is not administered.
When working with a horse with an eye problem, be aware that it may have obscured vision and be a little more jumpy than usual. Talk gently, so you don't surprise your horse if you walk up on a "blind side."
How to Prevent Eye Infections and Injuries
Your horse's environment should be as dust free as possible. If hay is dusty, or bedding is very dry and dusty, dampen it or use other fodder or bedding. Make sure that sharp edges on water troughs, metal buildings, fences, or other obstacles are covered or inaccessible. Pound in or pull any old nails that may be protruding from fences or other structures.
Taking care to make your horse's home as safe as possible will help to prevent accidental eye injury.
Eye Infections in Horses. Texas A&M University Veterinary Medicine & Biomedical Sciences.
Eye Emergencies in Horses. VCA Hospitals.
The Equine Eye. UC Davis School of Veterinary Medicine.
Treating Equine Eye Irritation. Kentucky Equine Research.
Eye Worms in Horses. Kentucky Equine Research.
Eye Injuries. Kentucky Equine Research.