Horses have the largest eyes of all land mammals. Combined with their active outdoor lifestyle, it’s no wonder they’re prone to eye issues. Those big, beautiful eyes are especially vulnerable to infection, injury, and irritation.
When your horse greets you with swelling present in one or both eyes, it’s crucial to be able to distinguish between a mild, acute issue and something that could pose a serious risk to their vision. Here are some indicators to watch out for.

Why Horses Get Swollen Eyes
In the springtime, conjunctivitis tends to crop up more frequently in horses. Conjunctivitis, also known as “pink eye,” is an infection of mucous membrane surrounding the eye, or the inner eyelids. Along with swelling, you’ll also notice whitish or yellowish gunk. The eye itself should be clear and free of cloudiness.
As pink eye can be a sign of another issue, such as a corneal ulcer, it’s important to see your veterinarian for treatment. Your vet will usually prescribe antibiotic ointment and/or eye drops to soothe irritation and eliminate the infection.
You may also notice swelling if your horse has an issue that directly affects the eye itself. Common eye conditions such as a corneal ulcer, uveitis, foreign body, and blunt force trauma can cause swelling that may also be concurrent with squinting, light sensitivity, spasms, excessive tearing, and/or a bloodshot sclera.
Any time your horse has an eye issue, it’s important to seek veterinary help. Even acute issues like pink eye can cause permanent damage if left untreated. Before you call your vet, see if your horse’s symptoms affect one eye or both. Take note of any other unexplained symptoms such as fever, lethargy, hives, or anorexia.
Your veterinarian can use a fluorescein stain to look for issues or injuries of the cornea that may not be obvious upon first inspection. They may also swab the eye to perform a culture to check for infection. Always follow your vet’s aftercare instructions and use prescription medications exactly as prescribed.

Preventing Eye Issues In Horses
During spring and summer months, a fly mask is a great way to protect your horse’s eyes from flies as well as pollen and debris. For horses prone to mild eye irritation due to allergies, your veterinarian may recommend flushing with saline solution on high pollen days.
As conjunctivitis is sometimes caused by a contagious virus or bacteria, horses with pink eye should be isolated to avoid spreading the infection via direct contact with other horses.
Protect eyes from scratches and trauma by regularly checking the stables and turnout areas for protruding nails, hooks, and overgrown branches. If your horse likes to rub up against doors, posts, or trees, it can be helpful to put up a scratching post so they can safely scratch an itch without risking an eye injury.
Examine your horse’s eyes often to get them used to handling with low-stress husbandry techniques. Daily practice and tasty treats go a long way in preparing your horse to accept medical care in the future.