eye problems in old horses

You’ve owned your senior horse for a long time. You’ve been through ups and downs with him, and it’s clear as day when he’s not feeling his best. But do you know how well he can see? Recent study results suggest it’s not easy for owners to spot eye problems in old horses: Owners reported that fewer than 4% of the study horses had some sort of ocular disease, but, in fact, researchers determined that nearly 90% of them did.

“Horses are prey animals in the wild and are, therefore, good at hiding any signs of discomfort or any potential weakness that would made them more vulnerable,” said Fernando Malalana, DVM, GPCert(EqP), DipECEIM, FHEA, MRCVS, RCVS, European specialist in equine internal medicine, of the University of Liverpool Philip Leverhulme Equine Hospital, Leahurst, in the U.K.

“A lot of chronic eye disorders can go unnoticed while the disease process and discomfort continue on in the background,” he said.

Malalana and colleagues analyzed survey results from nearly 1,000 horse owners in Queensland, Australia, about their horses’ eye health. They only accepted data about horses 15 years and older. Then, their research team carried out clinical eye examinations on about a third of those horses using a diopter and/or an ophthalmoscope to assess for lesions outside or inside the eye.

Owners reported that 3.3% of the 974 study horses had vision problems, eye pain, discharge, or lesions, Malalana said. But when the clinical team investigated 327 of these horses themselves, they found that 87.8% had eye abnormalities ranging from mild to severe.

About a third of the horses had cataracts in at least one eye, he said. Nearly 14% had lesions on the cornea (although many had healed, scarring remained and could affect vision or cause discomfort). And almost 85% had “posterior segment” lesions—those deep within the eye, including problems with the retina and/or optic nerve.

Fortunately, Malalana said, most of these lesions didn’t have a significant bearing on vision. Fewer than 6% of the horses had reduced vision on clinical exam (measured by menace response—the horse’s blink response to an approaching hand). Still, that percentage was much greater than that of the owner-reported vision problems—at only 1.1%. And interestingly, most of those 1.1% weren’t part of the 5.5% group of horses reported by the scientists. So the horses with true vision problems weren’t reported as such by their owners.

The low reporting rates don’t appear to be from a lack of care or observation by the owners, Malalana said. On the contrary, it’s possible that the 3.3% reporting rate is high compared to the general population of horse owners, since the owners from their surveys were recruited from equestrian associations that encourage attentive observation at home, he said.

The low reporting rate is probably due to the simple fact that equine eye disorders are difficult for people to pick up without specific skills and tools, said Malalana.

“The best thing to do to determine if there is any discomfort in an eye is to face the horse from the front and look at the angles of the eyelashes,” he said. “Both sets of eyelashes should be symmetrical and parallel or almost parallel to the ground. If an eye is painful, the angle of the eyelashes in that side will drop.”

Owners should also contact their veterinarians if an eye appears more closed than normal, if there’s any discharge, or if they just have a concern or get the feeling there’s a problem, he added, as eye issues can worsen rapidly.

Picking up ocular disease early can improve horse and human safety while protecting equine welfare, said Malalana.

“Although horses tend to cope well with limited vision, a blind horse poses an increased danger to itself and its handlers,” he said. “A lot of blind horses can cope well, but the owners need to be aware … so they can implement safety measures for the horse and all handlers. If an owner is unaware that the horse has reduced vision and is continuing to exercise that horse, this could also lead to accidents.”

As far as painful lesions are concerned, Malalana said identifying them can facilitate early treatment and, hence, earlier pain relief.

“Some of these conditions can cause chronic discomfort that may not be immediately evident to us but that for sure affects the horse’s welfare,” he said.

Early identification not only allows for faster initiation of treatment but also possibly more effective treatment, Malalana said.

The study, “Prevalence of owner‐reported ocular problems and veterinary ocular findings in a population of horses aged ≥15 years,” was published in the Equine Veterinary Journal