Horse Squinting or Eye Pain: Urgent Causes & What Owners Should Do

Squinting, also called blepharospasm, usually means the eye hurts. In horses, one of the most common urgent causes is a corneal ulcer. Ulcers often happen after trauma from hay, bedding, dust, a branch, or rubbing. Horses with ulcers may tear excessively, keep the eye partly or fully closed, and develop a cloudy or blue-looking cornea. Deep ulcers can perforate, and horses are especially prone to secondary fungal infection after corneal injury.

Another major cause is uveitis, including equine recurrent uveitis. This is inflammation inside the eye and can cause squinting, tearing, light sensitivity, a constricted pupil, corneal haze, and vision loss. Uveitis can be primary, or it can happen as a painful reaction to a corneal ulcer. That distinction matters because some medications used for uveitis, especially topical steroids, can make an ulcer much worse if one is present.

Other important causes include corneal lacerations, foreign bodies, stromal abscesses, eyelid injuries, and less commonly glaucoma or tumors affecting the eyelids or tissues around the eye. If only one eye is affected, trauma is especially likely. If the eye looks white, yellow, or has a visible spot in the cornea, your vet may worry about infection trapped deeper in the cornea.

Because horse eyes can deteriorate quickly, pet parents should treat any painful eye as urgent rather than waiting to see if it clears on its own.

See your vet immediately if your horse is squinting, holding the eye shut, suddenly tearing a lot, acting light-sensitive, or has a red, cloudy, blue, swollen, or injured eye. The same is true if there is blood in or around the eye, a cut eyelid, a visible foreign object, a misshapen pupil, or any recent trauma. These signs can go with corneal ulceration, perforation, uveitis, or infection, and delays can affect comfort and vision.

In real-world terms, there are very few situations where a painful horse eye is safe to monitor without veterinary guidance. Mild watery discharge without squinting may be less urgent, but once pain is present, the situation changes. Horses can worsen fast, especially if a fungal infection or melting ulcer is developing.

While waiting for your vet, move your horse to a shaded stall or dim barn aisle, reduce dust and wind exposure, and prevent rubbing on posts, buckets, or fencing. A soft, well-fitted fly mask can help protect the eye if your horse tolerates it and the mask does not press on the eyelids. Do not patch the eye tightly, and do not rinse aggressively unless your vet specifically tells you to.

If your horse has had repeated episodes of tearing, squinting, or a cloudy eye that seem to come and go, mention that history. Recurrent episodes raise concern for equine recurrent uveitis, which needs a longer-term plan with your vet.

Your vet will start with a careful eye exam and history, including when the squinting started, whether there was trauma, and whether the horse has had previous eye problems. They will usually look for eyelid injuries, foreign material, corneal cloudiness, pupil size changes, discharge, and signs of inflammation inside the eye.

A fluorescein stain is commonly used to check for a corneal ulcer. Your vet may also perform tonometry to measure eye pressure, especially if glaucoma or severe uveitis is a concern. Depending on what they find, they may collect samples for cytology or culture, particularly if a corneal ulcer looks infected or fungal. In adult horses with uveitis, additional workup can include blood testing and inflammatory markers.

Treatment depends on the cause. Your vet may use topical antibiotics, antifungal medication, atropine for pain from ciliary spasm, and systemic anti-inflammatory medication such as flunixin meglumine. Some horses need very frequent eye medications, sometimes every few hours. If the cornea is deep, melting, perforated, or unstable, referral to an equine ophthalmology service may be recommended for a subpalpebral lavage system, advanced imaging, hospitalization, or surgery such as a corneal graft.

Your vet will also decide which drugs to avoid. That is especially important with steroid eye medications, because they can be harmful if an ulcer or infection is present. This is one reason it is risky to use leftover eye drops before the eye has been examined.

Home care for a painful horse eye is mainly about protection and fast follow-through, not home treatment alone. Keep your horse in a dim, low-dust area and limit turnout in bright sun, wind, or heavy fly pressure until your vet advises otherwise. A clean, well-fitted fly mask can reduce irritation from light, wind, and insects, but remove it at least daily to check the eye unless your vet gives different instructions.

Do not use leftover eye medications, especially steroid-containing drops or ointments, unless your vet has examined the eye and told you they are appropriate. Steroids can seriously worsen some ulcers and infections. Avoid touching the eye directly, and do not try to remove embedded material yourself.

If your vet prescribes medication, give it exactly as directed and keep a written schedule. Eye medications for horses may need to be given very frequently, and missed doses can matter. Watch for worsening squinting, more cloudiness, a white or yellow spot on the cornea, more discharge, swelling, colic signs after atropine, or any drop in appetite or behavior, and update your vet promptly.

Longer term, some horses benefit from routine fly-mask use for UV and debris protection, especially horses with light skin around the eyes or a history of recurrent eye disease. If episodes keep returning, ask your vet whether referral or a chronic management plan is appropriate.