Keratitis in Horses
- Keratitis is inflammation of the cornea, the clear front surface of your horse's eye. It may be superficial, deeper within the cornea, ulcerative, fungal, bacterial, viral, or immune-mediated.
- Common signs include squinting, tearing, light sensitivity, a cloudy or blue-looking cornea, redness, discharge, and visible blood vessels on the eye.
- See your vet immediately if your horse has a painful eye. Corneal disease in horses can worsen quickly and may threaten vision within days if infection, a deep ulcer, or corneal melting develops.
- Diagnosis usually includes a full eye exam, fluorescein stain to look for ulcers, and sometimes corneal cytology or culture when infection is suspected.
- Treatment depends on the cause and depth of disease. Options may include topical antibiotics, antifungals, atropine, anti-inflammatory medication, serum, subpalpebral lavage systems, or referral for surgery.
What Is Keratitis in Horses?
Keratitis means inflammation of the cornea, the clear outer layer at the front of the eye. In horses, this problem matters because the cornea is exposed, easily injured, and essential for vision. Keratitis can involve only the surface of the cornea, deeper corneal layers, or an ulcer when the surface has been damaged. Some cases are driven by trauma or infection, while others are immune-mediated and not caused by a germ.
Horses are especially prone to corneal disease because their eyes are large and positioned on the sides of the head, making them more likely to be hit by hay, dust, branches, bedding, or another horse. Once the cornea is injured, bacteria or fungi may take hold. Fungal keratitis is a particular concern in horses and can become serious quickly.
Keratitis is not one single disease. It is a category that includes superficial keratitis, interstitial keratitis, ulcerative keratitis, stromal abscesses, and immune-mediated keratitis. Some horses are very painful and keep the eye tightly shut. Others, especially with some immune-mediated forms, may have more cloudiness than pain.
The good news is that many horses do well when the problem is recognized early and your vet can match treatment to the cause. The outlook becomes more guarded when ulcers are deep, infection is present, the cornea starts to melt, or the inside of the eye is also inflamed.
Symptoms of Keratitis in Horses
- Squinting or tightly closed eyelids, often a sign of significant eye pain
- Excessive tearing or wetness below one eye
- Light sensitivity or avoiding bright sunlight
- Cloudy, blue, white, or hazy appearance of the cornea
- Redness around the eye or inflamed conjunctiva
- Visible blood vessels growing into the cornea
- Mucus, yellow, or green discharge, which can suggest secondary infection
- A rough, irregular, or depressed spot on the corneal surface
- A white, yellow, or tan plaque or spot within the cornea
- Swelling of the cornea or a suddenly enlarged-looking lesion
- Head shyness, rubbing the eye, or resisting handling around the face
- Reduced vision, bumping into objects, or acting startled on one side
Any painful eye should be treated as urgent. Squinting, tearing, a cloudy cornea, or a suddenly closed eye can all happen with keratitis, corneal ulcers, uveitis, or trauma. Deep ulcers and infected corneas can progress fast in horses, especially when fungi are involved.
Call your vet the same day if you notice eye pain, cloudiness, discharge, or a visible spot on the cornea. Seek emergency care right away if the eye looks blue and swollen, has a white or yellow crater, seems to bulge, has blood, or your horse cannot open it at all.
What Causes Keratitis in Horses?
A very common trigger is trauma. Hay stems, dust, sand, bedding, pasture plants, trailer injuries, and rubbing can all damage the corneal surface. Even a tiny scratch can open the door to ulcerative keratitis. Horses can also develop corneal disease when the eye does not blink normally, the tear film is poor, or there is an eyelid problem or facial nerve dysfunction that leaves the cornea exposed.
Infection is another major cause. Bacteria and fungi can invade after corneal injury, and fungal keratitis is especially important in horses. Merck notes that secondary bacterial or fungal infections commonly worsen ulcers, and fungal keratitis is predominantly a problem in horses. Equine herpesvirus can also contribute to corneal ulceration in some cases.
Some horses develop immune-mediated keratitis, where the cornea becomes inflamed without a primary infection. Cornell describes this as non-infectious inflammation that can make the cornea opaque from white blood cells and blood vessel growth. Eosinophilic keratitis is one immune-mediated form that may be associated with allergies or parasites and can create plaques on the cornea.
Underlying disease also matters. Your vet may look for conjunctival foreign bodies, low tear production, poor corneal sensation, uveitis, or systemic conditions that make healing harder. In practice, more than one factor may be involved at the same time, which is why a full eye exam is so important.
How Is Keratitis in Horses Diagnosed?
Diagnosis starts with a careful history and a complete ophthalmic exam. Your vet will look at the eyelids, tear film, conjunctiva, cornea, anterior chamber, pupil, and deeper eye structures. Because horses with eye pain often clamp the eyelids shut, sedation and local nerve blocks may be needed to safely examine the eye.
A fluorescein stain is one of the most useful first tests. This dye sticks to areas where the corneal surface is missing, helping your vet confirm whether an ulcer is present and how large it is. Your vet may also use magnification, focal light, and sometimes tonometry or other tests to check for related problems such as uveitis or glaucoma.
If infection is suspected, your vet may collect corneal cytology or culture from the lesion. This can help identify bacteria, fungi, or inflammatory cell patterns and guide medication choices. In referral settings, additional tools such as corneal confocal microscopy, ultrasound, or specialist ophthalmology consultation may be used for deep, nonhealing, or complicated cases.
One important safety point for pet parents: do not put leftover steroid eye medication into a painful horse eye unless your vet has examined it and confirmed there is no ulcer. Steroids can delay healing and can make some corneal problems much worse.
Treatment Options for Keratitis in Horses
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Same-day farm call or clinic exam
- Basic ophthalmic exam with fluorescein stain
- Topical broad-spectrum antibiotic when an uncomplicated ulcer is suspected
- Atropine if your vet feels it is appropriate for pain from secondary uveitis
- Systemic anti-inflammatory medication as directed by your vet
- Protective fly mask, reduced dust exposure, and close recheck
Recommended Standard Treatment
- Complete eye exam with fluorescein stain and pain assessment
- Corneal cytology and/or culture when infection is suspected
- Targeted topical therapy such as antibiotic, antifungal, or other medication based on exam findings
- Atropine and systemic anti-inflammatory medication when indicated
- Autologous serum or anticollagenase support for melting ulcers when appropriate
- Repeated rechecks and medication adjustments, sometimes with hospitalization or intensive nursing
Advanced / Critical Care
- Referral to an equine ophthalmology service
- Subpalpebral lavage system for frequent medication delivery
- Hospitalization for around-the-clock treatment
- Advanced diagnostics and specialist monitoring
- Surgical options such as conjunctival grafting, keratectomy, or other corneal procedures when medically indicated
- Management of severe fungal keratitis, stromal abscess, corneal perforation, or vision-threatening disease
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Keratitis in Horses
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look like superficial keratitis, an ulcer, fungal keratitis, or an immune-mediated problem?
- How deep is the corneal lesion, and is my horse at risk for perforation or vision loss?
- Should we do fluorescein stain, cytology, or culture today?
- Are there signs of uveitis or pain inside the eye that also need treatment?
- What medications are most important, how often do they need to be given, and what side effects should I watch for?
- Would my horse benefit from serum, a subpalpebral lavage system, or referral to an ophthalmology specialist?
- What changes would mean the eye is getting worse and needs emergency recheck?
- What is the expected cost range for the next 48 hours, the full treatment course, and possible referral care?
How to Prevent Keratitis in Horses
Not every case can be prevented, but you can lower risk by reducing eye trauma and irritation. Keep hay feeders, fencing, trailer interiors, and stall hardware as safe as possible. Limit dusty bedding and feed when you can, and use a well-fitted fly mask for horses that are prone to eye irritation or spend time in bright sun and windy conditions.
Daily observation matters. Check for tearing, squinting, discharge, cloudiness, or a horse that suddenly dislikes light. Early treatment is one of the best ways to prevent a small corneal problem from becoming a sight-threatening one. If your horse has had previous eye disease, ask your vet what changes should trigger a same-day exam.
Manage underlying issues that can set the stage for keratitis. Eyelid abnormalities, poor tear production, facial nerve problems, recurrent uveitis, and chronic rubbing all increase risk. Horses with a history of ocular surface disease may need more frequent rechecks, especially during dusty seasons or fly season.
Finally, avoid using leftover eye medications without guidance from your vet. This is especially important with steroid drops or ointments, which can worsen some ulcers. A prompt exam, the right stain test, and treatment matched to the cause are far safer than guessing.