As your horse gets older, his graceful figure may give way to a swayback and potbelly, and his joints may get stiff and creaky, but, unlike elderly people and old dogs, he's not all that likely to lose his eyesight. Horses do undergo age-associated vision changes but rarely to the point of blindness.
"We don't see a lot of older horses presented with vision problems," says Claire Latimer, DVM, an equine ophthalmologist in Lexington, Kentucky. "Typically, deterioration does not progress to the point where it causes a change of behavior that the owner notices." Horses with compromised vision, Latimer notes, often mask their condition by adhering so well to the familiar in their environment and their routine that they don't appear disabled.
Cataracts, a common thief of vision in other species, do affect horses but usually not to an obstructive degree. "When you say 'cataracts,' people think that means a completely cloudy lens," says Latimer. "By definition, it's any focal opacity in the lens. Under magnification, I may see little cataract changes, but they are relatively insignificant."
Age-related immune changes may increase horses' susceptibility to eye maladies. In her studies of older horses at New Jersey's Rutgers University, Karyn Malinowski, PhD, has noted a propensity for corneal ulcers among the school's over-20 herd.
"The ulcers form near the lower lid," she says, "and they are treated with an antibiotic ointment. They clear up, then they come back."
Robert Holland, DVM, PhD, a Lexington, Kentucky, practitioner, says that he has seen more than a few cases of moon blindness -- a recurring immune-mediated inflammation of the eye -- in geriatric horses. "They act like they can see, but not exactly," he says. "If you change their field or stall, they may have problems seeing the wall, or they may bang a hip on the stall door."
Because significant vision loss is rare in the species, most veterinarians do not consider eye examinations to be a must for all older horses, except as part of a general physical exam. Behavioral changes suggesting disorientation are cause for a closer look at the eyes, however.
"If the horse is suddenly spooking, knocking into things, tripping or having trouble keeping his footing with slight changes in elevation," says Latimer, "then vision should be checked."