Managing the blue eye blues: Equine corneal disease
Changes in the equine eye certainly get attention. For example, it is hard to miss when a normally brown-eyed horse suddenly develops a uniformly whitish-blue eye — or when a horse gets on the track with a bright open eye and finishes its workout with a tearing, squinting eye.
Eye trauma in the horse is a common event. The equine eye is the largest of any land mammal, and its side-facing position and relatively shallow socket (allowing horses to have a nearly 360-degree visual field) combine to make bumps, scrapes and other damage routine
Cynthia Cook, DVM, PhD, of Veterinary Vision Inc. in California explains, "The equine cornea, which is the transparent covering of the globe of the eye, is a common site for injury and disease and, as such, is a cause for many calls to equine practitioners. The most common cause of corneal disease is trauma, and racehorses are especially prone because of debris thrown up by the hooves of other horses during racing and training."Causes
There are many causes of equine ocular damage and disease, and many of the common conditions can lead to a dramatic discoloration. The cornea is normally transparent to allow light passage for normal vision. When the cornea is damaged, regardless of the cause, it responds by swelling. It is this intense swelling that creates a blue or cloudy eye.
Corneal scratches are painful, and squinting (blepharospasm) and tearing are almost always noted. Initially, these corneal scratches are not visible on the surface of the eye, and there is no clouding of the cornea. Blunt trauma to the eye with a closed eyelid may result in a blue eye without any corneal scrape or visible damage.
A number of other serious ocular diseases can present as a blue eye as well. Keratitis is inflammation of the cornea (this part of the eye is largely made up of keratin cell types). The cause of keratitis is often infectious, viral, bacterial or fungal, but in some cases the cause is unknown. All types of keratitis are associated with a blue discoloration of the cornea.
Glaucoma is another disease with multiple causes and is characterized by increased pressure within the eye. Typically, the horse's eye is enlarged, blue and painful. Measurements of ocular pressure can be taken, which will help you formulate a diagnosis.