A horse’s eyesight functions a bit differently from a human’s. Because their eyes are set on the sides of their head rather than at the front of their face the way a human’s are, they see a wider span than we do. While humans see everything through both eyes (binocular vision), horses have monocular vision on either side with a smaller span of binocular vision at the center. They have a bit of a blind spot right in front of their noses. The spectrum of colors that they see differs from what we see.
Understanding equine vision is one way to better understand why horses behave the way they do. For example, the video shows that horses can see better in the dark than humans can, which means when it seems like your horse is shying at a shadow, he might actually be seeing something in the underbrush that you can’t.
For best effect, watch the video full screen on your computer.