Corneal Ulcers in Horses
- See your vet immediately if your horse is squinting, tearing, holding an eye closed, or has a cloudy blue-white spot on the cornea.
- A corneal ulcer is a break in the clear surface of the eye. In horses, even small ulcers can worsen quickly because trauma, bacteria, and fungal infection are common.
- Diagnosis usually includes an eye exam and fluorescein stain. Deeper or infected ulcers may also need culture, sedation, pain control, and repeat rechecks.
- Treatment often involves frequent eye medication, pain relief, and protection from rubbing. Some horses need a subpalpebral lavage system or surgery.
- Early superficial ulcers often heal well, while deep, infected, or melting ulcers can threaten vision and may become emergencies within hours to days.
What Is Corneal Ulcers in Horses?
A corneal ulcer is a defect or open sore in the cornea, the clear outer surface at the front of your horse's eye. The cornea has several layers, and ulcers can range from a shallow scratch on the surface to a deep injury that weakens the eye. Because horses have large, prominent eyes, they are especially prone to corneal trauma.
These ulcers are painful. Many horses squint hard, tear excessively, and avoid bright light. A simple superficial ulcer may heal with prompt treatment, but horses are also at meaningful risk for secondary bacterial or fungal infection. That matters because an ulcer that starts small can become deeper, infected, or "melting," which means the corneal tissue is breaking down.
This is why eye problems in horses should be treated as urgent. Fast evaluation by your vet helps confirm whether the problem is a corneal ulcer, a deeper corneal abscess, uveitis, or another eye condition that can look similar at first.
Symptoms of Corneal Ulcers in Horses
- Squinting or holding the eye closed
- Excessive tearing
- Red or inflamed tissues around the eye
- Swollen eyelids
- Cloudy, bluish, or white-looking cornea
- Eye discharge, especially yellow or green discharge
- Sensitivity to light
- Small, constricted pupil
- Visible spot, divot, or irregular area on the eye surface
- Rubbing the eye or face
When to worry? With horse eye problems, the safest rule is to worry early. Squinting alone is enough reason to call your vet the same day. A cloudy cornea, worsening pain, discharge, or a horse that keeps rubbing the eye raises concern for a deeper ulcer, infection, or uveitis. If the eye looks sunken, bulging, very white-blue, or your horse seems suddenly unable to see, treat it as an emergency.
What Causes Corneal Ulcers in Horses?
Most corneal ulcers in horses start with trauma. Common triggers include hay stems, bedding, dust, sand, branches, trailer injuries, pasture accidents, or another horse's hoof or head. Even a tiny scratch can disrupt the corneal surface enough to cause significant pain.
After that first injury, infection can complicate the picture. Horses are particularly vulnerable to fungal involvement of the cornea, especially after plant-related trauma or when an ulcer is not healing as expected. Bacteria can also invade damaged tissue. In more severe cases, enzymes released during inflammation and infection can cause a "melting" ulcer, where the cornea softens and breaks down.
Other eye problems can set the stage for ulcers too. Abnormal eyelid position, poor tear film, foreign material trapped under the eyelid, and painful inflammatory eye disease such as uveitis may contribute. Because several conditions can overlap, your vet needs to examine the whole eye rather than assuming every painful eye is a simple scratch.
How Is Corneal Ulcers in Horses Diagnosed?
Your vet usually starts with a careful eye exam, often in a dim area, to assess pain, eyelid swelling, discharge, corneal clarity, pupil size, and whether there may be deeper eye inflammation. Sedation or local nerve blocks may be needed in some horses so the eye can be examined safely and thoroughly.
A fluorescein stain is one of the most important tests. This dye sticks to exposed deeper corneal tissue, helping your vet confirm that the surface layer is missing. The stain can also help estimate the size and shape of the ulcer and track healing over time. Repeat staining at rechecks is common.
If the ulcer is deep, infected, slow to heal, or has a suspicious white-yellow plaque or stromal appearance, your vet may recommend additional testing such as corneal cytology, culture, or referral to an equine ophthalmology service. These cases may need more intensive treatment because fungal keratitis, stromal abscesses, and melting ulcers can threaten vision and even the integrity of the eye.
Treatment Options for Corneal Ulcers in Horses
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent farm-call or clinic exam with fluorescein stain
- Topical antibiotic selected by your vet for a superficial uncomplicated ulcer
- Pain control such as oral anti-inflammatory medication if appropriate
- Atropine eye medication when indicated for painful spasm or uveitis
- Fly mask, stall rest or turnout modification, and strict no-rub management
- Short-interval recheck to confirm healing
Recommended Standard Treatment
- Complete eye exam with fluorescein stain and repeat rechecks
- Topical antibiotic therapy and pain control tailored to exam findings
- Atropine and anti-inflammatory treatment when appropriate
- Evaluation for fungal involvement, melting, or uveitis
- Corneal cytology and/or culture for infected, deep, or nonhealing ulcers
- Subpalpebral lavage system placement when frequent medication is needed
- Referral discussion if the ulcer is deep or vision-threatening
Advanced / Critical Care
- Referral to an equine ophthalmology or hospital service
- Intensive topical therapy for bacterial or fungal keratitis, often every few hours
- Subpalpebral lavage management and hospitalization when needed
- Advanced diagnostics including cytology, culture, and deeper corneal assessment
- Surgical procedures such as debridement, conjunctival graft, or other corneal stabilization techniques
- Management of severe pain, uveitis, stromal abscess, or melting ulcer complications
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Corneal Ulcers in Horses
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look like a superficial ulcer, a deep ulcer, or something more complicated such as fungal keratitis or a stromal abscess?
- Was fluorescein stain positive, and how large or deep does the ulcer appear right now?
- What signs would mean the ulcer is worsening and my horse needs to be seen again immediately?
- How often do the eye medications need to be given, and would a subpalpebral lavage system make treatment safer or more realistic?
- Is there concern for uveitis, melting, or infection that changes the treatment plan?
- Should we do cytology, culture, or referral now, or is it reasonable to start treatment and recheck first?
- What level of scarring is likely, and could this affect vision or future performance?
- What is the expected cost range for the next 48 to 72 hours if the eye improves versus if it does not?
How to Prevent Corneal Ulcers in Horses
You cannot prevent every eye injury, but you can lower risk. Walk stalls, paddocks, and trailers regularly for sharp edges, protruding nails, splintered boards, rough feeders, and thorny plants. Reduce dusty hay and bedding when possible, and be careful during transport, turnout changes, and herd introductions when facial trauma can happen.
Daily observation matters. A horse with mild tearing or brief squinting can look "not too bad" early on, but eye problems can change fast. Checking both eyes in good light helps you notice asymmetry, discharge, swelling, or cloudiness sooner. Prompt vet attention for any painful eye is one of the best ways to prevent a small ulcer from becoming a vision-threatening one.
Good medication technique also helps prevent setbacks. If your horse is being treated for any eye condition, follow your vet's instructions closely and avoid touching the eye with the bottle tip. Do not use leftover eye medications unless your vet tells you to. Steroid-containing eye medications can be harmful when a corneal ulcer is present, so every painful eye should be examined before treatment choices are made.