3 Facts About Your Horse’s Eyesight to Keep in Mind When Training
Monocular Vision
Humans have binocular vision, meaning that our eyes are placed on the front of our faces, and the lines of sight from each eye overlap and work together to see what is in front of us. Unlike us, horses have monocular vision - their eyes are placed on the sides of their head, which allows for a wider range of sight for each eye separately, but their lines of sight from each eye do not overlap to create one combined image like ours do. Because of this, what they see out of each eye transmits somewhat separately to their brain. For this reason, it is important to work with your horse on both sides of his body and allow him to view any objects or environments out of both eyes.
Poor Depth Perception
Horses have poor depth perception in general. This is why they are often wary about ditches, water crossings, going over/through objects, or stepping up onto trailers. When you are asking a horse to go through or over something, they will often lower their head down so they can see the situation better, or even paw at the water/obstacle/trailer/etc. to evaluate how deep it is or how stable the surface is. It is VERY important to give the horse a chance to investigate like this instead of chastising him for it, or trying to force him into crossing said obstacle/terrain without letting him do this assessment.
Slow Adjustment from Light to Dark
Although horses can see better than humans in the dark, the change from bright light to a dark environment takes the equine eye significantly more time to adapt than the human eye. Entering a dark horse trailer or simply going into an unlit barn or shaded covered arena on a sunny day will leave the horse blinded for a long period of time.