Procedure for an Equine Eye Exam

At some stage we've all been faced with a horse that has an eye injury and it can be a very worrying situation.

Sometimes a problem is obvious: your horse's normally bright eye is swollen shut and draining profusely. Other times, trouble is more subtle: you notice your horse's pupil is constricted, despite the fact he's inside a dimly lit barn, as slow tears stain his face. Whatever the reason, once your veterinarian arrives, chances are he or she will perform an ocular exam.

TheHorse.com reports that at the 2012 American Association of Equine Practitioners' Focus on Ophthalmology conference, held 6-8 September, Dennis Brooks, DVM, PhD, Dipl ACVO, professor of ophthalmology at the University of Florida's College of Veterinary Medicine, reviewed the following current standards of care for equine eye exams with veterinary attendees.

What's First?

"The standards of care for doing eye exams on horses have changed," Brooks began.

First, he said, a veterinarian should "stand back and look at the horse." Signs of pain or discomfort can be identified easily during an ophthalmic exam by evaluating:

• The eye lash position ("The first sign of a painful eye often is the eyelashes of the upper eyelid pointing downward," he said, as opposed to them being perpendicular to the eye's surface as seen in healthy horses.);
• If the horse is squinting (which typically is a sign of eye pain);
• The presence of tearing;
• Ocular discharge (If present, Brooks noted it means that "either there's an increased production of tears or the tears are not draining properly.");
• The drainage angle (the gray band on the outer portion of the eye, which contain tiny holes; if these holes collapse and appear solid, or "closed," there is an increased risk of glaucoma.)
• Any color changes of the iris or cornea;
• The pupil size (constricted pupils are a sign of pain);
• The clarity of the aqueous humor (clear eye fluid that, if cloudy in appearance, could indicate uveitis);
• Eye blood vessel symmetry (Thicker spots of red mean more inflammation in one area, Brooks said.)
• Lens and cornea clarity; and
• The anatomy of the eye via an ophthalmoscope, transilluminator, or slit lamp.

Although it's not possible to test how well a horse sees, it is possible to ensure the retina is functional, Brooks said. Depending on the diagnosis, a functional or nonfunctional retina can help decide treatment protocol. Brooks recommends veterinarians use either the dazzle response or the indirect pupilary light reflex (PLR) test to find out if an eye has the potential to see.

Source: TheHorse.com

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