The distinction between hunters and jumpers is important. Top jumpers–judged by the size of obstacles and the speed of their rounds– are often selected because their necks are set high on the withers, with head position proportionately higher.
pleasure, depth perception is not so critical. But consider cutting, barrel racing or jumping. The horse needs to know how far away relevant objects are and the speed with which those distances are changing as she moves. A horse can improve depth perception slightly by raising her head or lifting her nose, but this often complicates her task. In cutting, for instance, the horse needs to keep her eyes down on the cow and her head low to make quick turns. In jumping, she needs impulsion from her hindquarters to power off the ground and abdominal tuck to lift her legs. The physics of such movements require that the horse maintains a round back for core strength, which often precludes the high-headed position that aids depth perception.
The distinction between hunters and jumpers is also important. Top jumpers ---judged by the size of obstacles and the speed of their rounds---are often selected because their necks are set high on the withers, with head position proportionately higher. Those without that conformation are often trained to approach jumps with their heads raised. If you watch a jumper approaching a fence, you will see her head lift in the last stride or two. This natural form provides both eyes with a brief view of the jump, so that the equine brain can determine its height and width. But the view is fleeting---fractions of a second--and it’s late.
Depth perception is easier for hunters. These horses are judged on the quiet beauty of their jumping form and are taught to maintain a long frame with hindquarters engaged, necks arched long, heads low and faces near vertical to form a strong topline. This position can be preserved over fences because hunters are given a long approach with which to see jumps without raising their heads much. Good hunter riders encourage horses to look at a fence while rounding a distant corner. This supplies the horse with a better side view, a longer front view and more time for the brain to compute distance to the jump.