version 0.0 2 TONOMETRY FOR HORSES by Dr. Ann E. Dwyer the horse is an “at risk” breed for uveitis or multiple congenital ocular anomaly, or already has had an ocular problem like a corneal ulcer or immune mediated keratitis? Horses are athletes as well as treasured members of the family — it is logical that good vision and eye health is critical. • Tonometry is a valuable addition to pre-purchase (PP) examinations. Orthopedic problems like arthritis or tendon/ligament inflammation are the number one issue that affects purchase decisions in PP exams, but ocular issues present a frequent “sticking point” as well. In my experience, eye concerns are #2 behind orthopedic problems as horses commonly present with ophthalmic abnormalities like corneal stria, cataracts, or scars on the fundus. Veterinarians who are excellent “leg detectives” may not possess strong ophthalmic examination skills, and very few offer tonometry as part of the PP exam. Again, practices can differentiate their services by doing a baseline measurement of IOP at their PP exams. • Rebound tonometers are great instruments for measuring IOP on a wide range of species including dogs, cats, rabbits, birds, reptiles and pocket pets. If an equine practitioner balks at investing in a tonometer for their practice, I advise that they talk to their small animal colleagues. Proposing an arrangement where either practice share in the purchase of the tool, or one practice purchases the instrument and rents it to the other on a regular basis may be mutually beneficial. Similarly, the instrument may be of value for rental to a local zoo or other animal care facility. • Here is what I say in my lectures about what horses benefit from tonometry: o ANY horse undergoing a thorough eye evaluation! Owners are GRATEFUL to have the baseline IOP documented once the process is explained. The world equine population is aging. Just as Baby Boomers are screened annually for glaucoma and other eye disease, tonometry and thorough eye exams are important parts of care of our geriatric equines. o Pre-purchase examination — IOP is one more health metric, just like heart rate or temperature. o Glaucoma suspects, breeds at risk for glaucoma, particularly Appaloosas and other spotted breeds like Knabstruppers, Pony of the Americas, Nez Pierce, etc. o Uveitis cases. o Any horse that presents with a cloudy area on the cornea or “immune mediated keratitis”, or a “red eye”. o Any horse with ocular pain or aversion to ocular examination. o Horses that show signs of MCOA (Multiple congenital ocular anomaly) —prevalent in horses with silver dapple coat color, but also common in miniatures, some gaited breeds. o Any horse that is blind, or showing any sign of ocular disease including synechia, cataract, lens luxation, intraocular masses, periocular trauma, etc. o Any horse where one eye is not symmetric with the other (either smaller appearance or protruding/enlarged appearance). THE LEARNING CURVE As noted above, there is “art” to tonometry as well as science, and practice makes perfect. I suggest that clinicians new to tonometry practice the technique by doing a “free screening test” on all the horses they do dental exams on for the first 4 weeks after purchase (or whatever interval makes sense
