b'of clearness of vision) and color per-ception; Bullet-hole lesions on the fundus, at the back of the eye, have been associated with significant visual disability; Older horses with senile retinal degen-eration show decreased vision in dim lighting conditions; and Dense opacities on the lens can disrupt the passage of light, creating blind spots.Looking Beyond What We SeeThe reason identifying impaired vision can be tricky is because horses might be able to adapt their behavior when faced with ocular dysfunction, especially when vision loss occurs gradually. Owners, together with their veterinarians, can use these three tests to help assess equine vision:LAURA PALAZZOLO1.The dazzle reflexThis reflex involves the horses involuntary aversion response (e.g., blinking, globe retraction, third eyelid protrusion, and/or head movement) to intenseVisually impaired horses typically dont do well in herds and instead thrive with a calm companion. illumination of the eye. This 21-year-old blind mares seeing-eye pony helps guide her around their small \x03eld.2.The menace responseThis test is con-ducted by making a small, threateningowners of blind/visually impaired horses,Check all fencing, windows, footing, hand gesture toward the horses eye. Aand several owner-friendly publicationshooks for hanging, and feed and water horse that can see should blink.are readily available (see box on page 28).buckets, etc. for sharp edges to avoid 3.Obstacle course testingAlso referredIn a nutshell, Dwyer suggests owners fo- injury. to as maze testing, this is a prettycus on the following key areas when deal- Blind horses tend to use their muzzles reliable method of assessing vision ing with a horse affected by vision loss: to read their environment, much like probably more so than the menacehumans read braille, says Dwyer. We response, which is known to bewant to be certain their sensitive muzzles somewhat subjective. If a horse thatBlind horses tend towill not be injured when navigating their is unilaterally blind has the other eyeenvironment.blindfolded and is presented with ause their muzzles toAdditionally, horses with visual maze of buckets or other solid objects,read their environ- dysfunction benefit from cues that it will either freeze or stumble intoment, much likeindicate where certain objects are in a the obstacles, says Dwyer. When thepasture. Such cues include stone footing visual eye is uncovered the horse willhumans read braille. near gates, rubber mats near feed/water be able to navigate the maze.sources, and rubber tires around trees, to DR. ANN DWYER name a few.Supporting Horses With DecreasedIn addition to simply keeping blindVision/BlindnessSocial interactionsVisually impairedor partially blind horses as pasture pets,So, the question now remains: Howhorses typically dont do well in herdsome owners continue to actively trainsafe is a blind 1,000-pound domesticatedsituations. They are often relegatedthese animals. Again, horses tend to rely prey species with a flight instinct? Ourto the hollows of the pecking order,more heavily on other sensory cues, such sources agree that attitudes have changedfrequently being excluded from foodas hearing, smell, and touch. Along within terms of managing aging equids,and water. The majority thrive with aauditory cues, owners need to reassure and that owners of blind or visuallypasture buddy, be it a calm compan- their horses frequently with touch, con-impaired horses should avoid jumpingion horse, goat, or other friend. Somesistently approaching the horse from the to conclusions regarding the functionalprefer to live in solitude.same side each time (e.g., at the front of consequences of ocular disease or Environmental organizationOnce set upthe left shoulder). damage. appropriately for safety, try not to moveReligiously following training and Many organizations exist to supportanything in a blind horses enclosures.handling routines will help visually TheHorse.com | The HorseNovember 201827'