How do horses see?
The way that horses see is very different to how humans see, so we explore some interesting facts about the limits of their eyesight and how it affects the way they see fences during eventing.
Horses have remarkable vision that is almost panoramic, with small blind spots directly behind and in front. They utilise two forms of vision: a very wide field of monocular vision viewing both sides separately with either eye, and a relatively narrow zone of binocular vision directly ahead, using both eyes. Binocular vision allows the horse to judge distance, monocular vision provides an early warning of approaching threats.
Like all herbivores, the horse has eyes that rotate, so the pupils remain parallel with the ground as the animal lowers or raises the head.
Vision when competing
During the dressage phase, if the horse’s face is vertical, he will predominantly be looking down at the ground. When jumping, the horse switches between binocular and monocular vision.
Professor Josh Slater from the Royal Veterinary College says, “On a cross country course the horse has much more in his field of view than the rider: It is therefore more tempting for the horse to run out. Furthermore, in the final approach, the horse’s ability to judge exact distance from the fence is limited from around two metres away – trust and partnership are vital.”
Adrian Ditcham, cross country course builder and assistant clerk of the course at the Land Rover Burghley Horse Trials, likes to bear in mind the profile of fences in relation to the fact that equines’ eyes are positioned on the side of their heads. “At a curved fence with the highest point in the centre, the horse would naturally see the lower sides. Brush can help here as a filler, as the horse may naturally misjudge the centre.”
Horses do not see the full spectrum of hues seen in show jumping courses. Equines have ‘dichromatic’ vision (‘di’ meaning two, and ‘chroma’ meaning colour) in blue and green. In human terms, horses are said to be red-green colour blind, unable to see reds as we do, probably viewing them as hues of blue-grey.
Light into dark
Course designer Mike Etherington-Smith says that jumping from light into dark can be a concern.
“Horses need time to adjust their eyesight so such fences must be simple and set in the trees, rather than on the shadow’s edge. At least two strides, preferably three, from the time the horse goes into shadow to the fence is ideal,” Mike says.
While the horse only sees the skinny fence out of one eye, and views open space with the other eye, Mike Etherington-Smith says horses do work skinnies out.
“Skinnies are not so much of a challenge if the profile is right; the bigger deal for horses is fences such as ‘pimples’ with narrow, round faces, which horses find hard to read.”
Katie Brickman adds that when approaching any fence, the horse may lift its head to assess fence height and depth, using binocular vision.
DID YOU KNOW? Horses have the largest eyes of any land mammal
Find out more about horses’ vision with this article on what colours horses can see.