Eye injuries in the horse

Horses have very prominent eyes, and seem to frequently injure them. If you find your horse has swollen eyelids, is squinting, tearing excessively, has a laceration near the eye, or has a cloudy eye please call your veterinarian immediately for proper treatment. You can roll the dice with the wait and see approach, but it is frustrating how many horses eyes could have been saved with timely treatment. Most horses are never the same with one eye, and can be a hazard to human safety as well.

Eyelid lacerations

Eyelid lacerations are extremely important to repair, even if it has been 12+ hours since the injury. There is excellent blood supply, so with proper surgical repair, most lacerations heal and maintain an intact eyelid margin. If a portion of the eyelid margin is destroyed, the surface of the eye is at risk for future disease due to lack of protection from the eyelids and lack of tear film covering the eye.

Corneal ulcers

Corneal ulcers are a defect in the surface of the eye (the cornea), that usually begin from a simple scratch to the surface of the eye. They frequently become infected either with bacteria or fungus, which can lead to severe scarring or even rupture of the cornea.

The first sign of a small corneal ulcer can be a slightly squinted, light-sensitive eye, with increased tear production. Larger ulcers can be easily seen as a scratch or even a hole in the surface of the eye, which may be surrounded by a bluish haze. The blue haze or cloudiness is corneal edema or swelling of the surface of the eye. To diagnose an ulcer, your veterinarian will examine the eye in a dark area by shining a bright light source at the eye, as well as staining the eye with fluorescein, a bright green stain that will highlight the damaged areas of the cornea. Rose Bengal dye is also used to diagnose fungal ulcers. A corneal culture and cytology may also be taken to identify the infectious agents growing on the eye.

Treatment will include a systemic NSAID such as Banamine for pain management, topical antibiotics, topical antifungals if appropriate, atropine to dilate the eye, serum to decrease the activity of corneal proteases (enzymes that destroy proteins making up the cornea) as well as other medications that may be appropriate for the particular case. These medications may be administered topically in the form of an ointment or drop, or your veterinarian may choose to place a sub-palpebral lavage system, or “eye catheter” to allow for easier treatment. Depending on the type and severity of the ulcer, medications may be given as frequently as every two hours. Steroids (dexamethasone, hydrocortisone, etc) ARE NEVER indicated for the treatment of a corneal ulcer. If you do not keep the inflammation under control with NSAIDS such as banamine and use atropine to keep the eye dilated your horse is at a greater risk for iris adhesions and blindness. The iris, which is the brown part of the eye, will get sticky and adhere to the lens or cornea resulting in permanent adhesion formation. Serum is obtained by drawing your own horses blood, and spinning it down in a centrifuge to use for topical administration. Most corneal ulcers heal with a white spot remaining, which is scarring, and will sometimes go away completely with time.

Stromal abscesses

Abscesses in the layers of the cornea can develop from a small puncture or ulcer that the surface cells heal over, leaving infectious agents within the corneal stroma. Medical treatment is similar to that of corneal ulcers, but may also require systemic antibiotics as well.

Blunt trauma to the eye

With blunt trauma to the eye, the surface of the cornea may not be damaged, but fractures of the orbit (the bony encasement of the eye) can occur, as well as a ruptured eye, detached retina, damaged optic nerve, or lens luxation. The horse may simply present with a severely swollen eyelid. Some injuries may lead to an eye that is so damaged, that it needs to be removed. Other injuries may lead to permanent blindness. After the swelling is addressed, vision is assessed through a variety of methods. Depending on the type of injury, appropriate therapy is initiated.

Conclusion

Any time you have a concern about an injury to your horse’s eye, please contact your veterinarian. With some equine injuries you may be able to take the wait and see approach, but timing is everything with ocular traumas.

Dr. Darin Peterson, DVM, was born and raised on a horse and cattle ranch in Rosholt, S.D., and received his B.S. in Animal Science from SDSU. He concentrates most of his work time with large animals. He can be reached at 701-347-5496 or dpeterson@cassvetservice.com.