If you know and love horses, you probably quickly figured out that they are giant—but lovable—disaster magnets. They will likely find any creative way to injure themselves, at the least opportune time. “I see you are packing the trailer so we can leave for a show. This would be the perfect time to run my eyeball into something and give myself a corneal ulcer,” they seem to think. Yet we love them, and wouldn’t trade them for anything—most days at least. Whether your horse currently has a corneal ulcer, or hasn’t checked that one off their injury to-do list yet, anyone whose heart belongs to a horse could benefit from a corneal ulcer review.

Equine corneal ulcers explained

If you have spent any time looking at eyes—your horse’s or your own—you probably noticed a clear portion in the front of the eye, which is called the cornea, and lets light pass into the eye. When the microscopic layers of cells and nerve fibers making up the cornea are disrupted, a corneal ulcer occurs and, in many cases, the bacteria and fungi from the environment attach to the broken area and cause further complications. The end result is a painful, cloudy eye, and the potential for permanent eye damage.

Causes of equine corneal ulcers

Corneal ulcers commonly occur when a foreign substance (e.g., hair or plant material) gets into the eye, abnormal eyelashes rub the eye, or the eye is scratched by an object or the horse’s attempts to rub their painful or itchy eye. Although less common, horses can also have ulcers from herpesvirus, a lack of tear production, or an inability to blink. Compared with dogs and cats, horses are more likely to have bacterial or fungal invasion of the ulcer, with potentially sight-threatening consequences. In some cases, enzymes secreted by bacteria, or released due the resulting inflammation, may start to break down the cornea, creating an aptly named melting ulcer. These ulcers have a gelatinous appearance, and if left unchecked, can create a full thickness hole in the cornea, exposing the eye’s inner contents to the outside world.

Signs your horse may have a corneal ulcer

Horse with corneal ulcers typically have an abrupt onset of the following signs:

  • Squinting or holding the eye completely closed
  • Cloudy blue cornea
  • Light sensitivity
  • Excessive tearing
  • Painful, swollen, red eye

If you notice any of these corneal ulcer signs, immediately contact our Veterinary Vision Center, as ulcers can rapidly progress from a simple, superficial ulcer to a sight-altering deep or melting ulcer. 

Methods to diagnose equine corneal ulcers

If you have ever tried to pry your horse’s eyelids open when they wish to keep them closed, you understand how difficult that can be. To allow a full eye inspection, and reduce the amount of pressure applied to the eye during the exam, Dr. Pierce will inject a local anesthetic in several locations around your horse’s eye. This allows him to hold your horse’s eyelids open to check for foreign material, view the cornea with a handheld microscope, and apply fluorescein and/or rose bengal dye to the eye. The fluorescein dye will attach only to areas of disrupted cornea, and can be used to delineate the location, size, and shape of the ulcer, should one be present, and the rose bengal dye can help detect early fungal ulcers. Depending on the ulcer’s appearance, Dr. Pierce may also collect corneal cells for laboratory examination or culture, to diagnose and effectively treat bacterial or fungal infections. 

Treatment of equine corneal ulcers

Most corneal ulcers can be managed using topical and/or systemic antibiotics, antifungals, or anti-inflammatories. The liquid portion of the horse’s own blood (i.e., serum) may be applied to a melting ulcer, to inhibit the damaging enzymes produced by the bacteria or the inflammatory process. As already established, prying a horses’ eye open to administer medication isn’t easy, so sometimes Dr. Pierce will place a subpalpebral lavage system, which consists of a thin tube that goes through the eyelid, to allow administering medication directly to the eye’s surface. If the ulcer is large, deep, or melting, and unresponsive to medical therapy, or the eye is already ruptured, surgery may be needed to patch the defect and encourage healing. 

If your horse is showing signs of a corneal ulcer, or a previously diagnosed ulcer is not healing as expected, don’t hesitate to contact us. The Veterinary Vision Center team is committed to aggressively managing corneal ulcers, to ensure the best possible outcome for you and your horse, so they can continue to bring you joy—as well as chagrin—despite their next disaster.