Horses have large wide set eyes that allow them nearly 350° of vision. And while this size and position gives them great visual advantages it also makes horses susceptible to the development of corneal ulcers from sticks, branches, dirt and other debris.
The cornea is the outermost surface of the eye, a delicate and extremely sensitive structure containing more nerve endings per square inch than any other part of the body. So when a horse’s cornea is scratched it is very painful. Signs of a corneal ulcer include:
- Swollen eye/eyelids
- Holding eye closed or partially closed
- Excessive tearing (clear or purulent discharge)
- Excessive blinking
- Rubbing face
- Constricted pupil
Some ulcers are large enough to bee seen with the naked eye but the majority of ulcers cannot be seen so easily. Corneal ulcers are diagnosed by your veterinarian with a fluorescein stain. Placing this solution on the eye will highlight damaged areas of the cornea by staining them bright green.
Corneal ulcers are generally treated with topical medications. Because of the dirty environment that they live in, corneal ulcers are always considered contaminated/infected and treated with an antibiotic ointment. This will treat or prevent any infection and allow the cornea to heal itself. Additionally atropine ointment may be added to the treatment regime. The inflammation associated with the ulcer causes constriction of the muscles that control the pupil, leading to a constricted pupil and a painful eye. Atropine ointment will dilate the pupil and make the horse more comfortable. This will also make the horse light sensitive and they should be kept out of direct sunlight or wear a fly mask. Additionally your veterinarian my prescribe an oral anti-inflammatory such as flunixin meglumine (Banamine®) to reduce inflammation and relive pain.
It is very important to avoid putting ointments in the eye that contain a steroid such as dexamethasone. Steroids, while potent anti-inflammatories, act to suppress the immune system. If there is an ulcer present, steroids will allow bacteria and fungus to proliferate in the eye and worsen the corneal ulcer significantly.
Most ulcers heal quickly with simple treatments. However, very large or deep ulcers may require more intensive treatments, even surgery to place a protective flap over the defect. So if your horse develops a painful eye make sure your veterinarian examines it to prescribe the right treatment plan to heal the eye and make your horse more comfortable.