Glaucoma in Horses
- See your vet immediately if your horse has a cloudy eye, enlarged eye, fixed dilated pupil, eye pain, or sudden vision changes.
- Glaucoma is increased pressure inside the eye. In horses, it is often linked to uveitis, especially equine recurrent uveitis, and can lead to permanent blindness.
- Appaloosas and older horses appear to be affected more often than some other horses.
- Diagnosis usually includes tonometry to measure eye pressure, a full eye exam, and evaluation for underlying uveitis or other eye disease.
- Treatment often needs long-term management and may include pressure-lowering eye medications, anti-inflammatory care, referral to an ophthalmology service, laser procedures, or removal of a blind painful eye.
What Is Glaucoma in Horses?
Glaucoma is a disease in which pressure inside the eye rises high enough to damage delicate structures, especially the retina and optic nerve. That pressure can build gradually or become more obvious over time. In horses, early changes may be subtle, so a horse can have meaningful eye disease before a pet parent notices anything unusual.
Many equine glaucoma cases are secondary glaucoma, meaning another eye problem comes first and disrupts normal fluid drainage. The most common trigger is uveitis, especially equine recurrent uveitis (ERU). As inflammation changes the drainage angle and internal eye tissues, fluid cannot leave the eye normally, pressure rises, and vision may be lost.
This is both a comfort issue and a vision issue. Horses with glaucoma may have a painful eye, a cloudy cornea, a pupil that does not respond normally, or a globe that becomes enlarged over time. Some horses keep partial vision for a while, but untreated or poorly controlled glaucoma can end in permanent blindness.
Symptoms of Glaucoma in Horses
- Cloudy or blue-gray cornea
- Dilated pupil that is slow to respond or does not respond to light
- Redness of the white of the eye
- Eye pain or behavior changes
- Firm-feeling eye or enlarged eyeball
- Vision loss, bumping into objects, or spooking more than usual
- Signs of current or past uveitis
See your vet immediately if your horse has a cloudy eye, a suddenly enlarged eye, obvious pain, or any sign of vision loss. Glaucoma can damage the optic nerve quickly, and some horses hide discomfort well. Even mild redness or a slightly enlarged pupil matters if it is new.
If your horse has a history of uveitis, Appaloosa ancestry, or repeated eye flare-ups, be extra cautious. In these horses, glaucoma may develop as a complication, and early treatment can help preserve comfort and sometimes vision.
What Causes Glaucoma in Horses?
In horses, glaucoma is most often caused by impaired drainage of aqueous humor, the fluid normally produced inside the eye. When that fluid cannot exit normally, pressure rises. The most common reason for this in horses is uveitis, especially chronic or recurrent inflammation such as equine recurrent uveitis.
Inflammation can scar or block the drainage angle, change the position of the lens, and create adhesions inside the eye. Over time, those changes make normal pressure control harder. This is why horses with repeated inflammatory eye episodes need close follow-up, even when they seem comfortable between flare-ups.
Less commonly, glaucoma may be associated with lens luxation, trauma, intraocular tumors, congenital abnormalities, or other structural eye disease. Some horses appear to be at higher risk, including older horses and Appaloosas. Your vet may focus not only on lowering pressure, but also on identifying the underlying eye condition driving the glaucoma.
How Is Glaucoma in Horses Diagnosed?
Diagnosis starts with a careful eye exam, but the key test is tonometry, which measures intraocular pressure. In horses, glaucoma is generally diagnosed when pressure is elevated, often above 25 mm Hg, along with exam findings that fit the condition. Head position, sedation, pressure on the eyelids, and jugular compression can affect readings, so technique matters.
Your vet may also examine the cornea, pupil, lens, retina, and optic nerve, and look for signs of active or previous uveitis. Ophthalmoscopy is important, and some horses benefit from referral for gonioscopy or ocular ultrasound/ultrasonographic biomicroscopy to assess the drainage angle and internal structures when the cornea is too cloudy to see through clearly.
Because many equine cases are secondary glaucoma, diagnosis is really two parts: confirming high eye pressure and identifying the reason it developed. That distinction helps guide treatment choices, expected response, and long-term outlook.
Treatment Options for Glaucoma 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
- Tonometry and fluorescein stain as indicated
- Topical pressure-lowering medications such as dorzolamide or dorzolamide/timolol when appropriate
- Treatment of concurrent uveitis if present, based on your vet's exam
- Short-interval rechecks to monitor comfort and pressure
Recommended Standard Treatment
- Complete ophthalmic exam by your vet or equine ophthalmology referral
- Repeated tonometry and detailed evaluation for uveitis, lens disease, or structural changes
- Combination medical therapy for glaucoma plus anti-inflammatory treatment when indicated
- Ocular ultrasound or additional imaging if the inside of the eye cannot be visualized well
- Structured follow-up plan to track pressure, comfort, and vision
Advanced / Critical Care
- Referral to a veterinary ophthalmologist
- Laser transscleral cyclophotocoagulation or other globe-sparing procedures in selected cases
- Advanced imaging and specialized monitoring
- Hospital-based management for complex or vision-threatening disease
- Enucleation if the eye is blind and painful and comfort is the main goal
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Glaucoma in Horses
Bring these questions to your vet appointment to get the most out of your visit.
- Do you think this is glaucoma, uveitis, or both?
- What was my horse's eye pressure today, and how does that compare with normal for horses?
- Is this likely secondary to equine recurrent uveitis or another underlying eye problem?
- What are our conservative, standard, and advanced treatment options for this horse?
- What signs would mean the eye is becoming more painful or losing vision?
- How often should we recheck eye pressure and the rest of the eye exam?
- Would referral to a veterinary ophthalmologist change the options or prognosis?
- If vision cannot be saved, what is the best plan to keep my horse comfortable?
How to Prevent Glaucoma in Horses
Not every case can be prevented, because glaucoma is often a complication of other eye disease rather than a stand-alone problem. The most practical prevention step is early treatment and close monitoring of uveitis, especially in horses with recurrent episodes. If your horse has had a painful, teary, cloudy, or light-sensitive eye before, follow your vet's recheck plan even after the eye looks better.
Routine eye exams matter. Horses that are older, Appaloosas, or known to have equine recurrent uveitis may benefit from more proactive ophthalmic monitoring. Catching subtle pressure changes or chronic inflammation earlier may improve comfort and preserve vision longer.
Good barn safety also helps reduce preventable eye injury. Minimize sharp edges, manage turnout and trailer risks, and have any eye trauma examined promptly. Most importantly, do not wait on a cloudy or painful eye. Fast veterinary care is the best way to reduce the chance that secondary glaucoma will become a long-term problem.