They say eyes are are gateway to soul. When it was said, they were referring to us humans. But truth is, it also refers to horses. Many horse owners don't understand importance and usefulness of horse's eyes while training. That being so, let me share with you some things you may find useful - some you may know...some you may not.
First, there's eye which reveals a little about character of horse you're working with. It may have a kind eye. A kind eye indicates horse will be agreeable to train and will readily respond to your aids while training.
One way to tell if horse is nervous is by noting his eyes. Horses can be very expressive in their looks. And you can tell if a horse is a nervous horse by eyes appearing sort of "worried like."
Obviously, this nervous horse would require more thoughtful handling than would a non-nervous horse.
I have a horse that would get mad after a while of riding. She used to get what I call mad eyes. Her expression was actually a sort of angry expression. Mostly, expression came from her eyes. Here eyes would get red after a while.
Jesse Beery, a famous horse trainer from 1800's, talked a lot about eyes of horse. Even those many years ago he knew about horse's eyes. Beery discovered there were four different disposition types of a horse. Certain characteristics of eyes would tell you much about horse's personality and how much work it would be to train horse.
Berry's classic disposition type 3 was most interesting. Beery said "Where type #2 will allow you to do all work, type 3 will do all work for you. You only need to control its movements."
In all my training experience and many things I've read, I concur with Beery's discovery. The eyes play an enormous role in horse training.
To read more about Beery and his methods, you can go to this web address:
http://www.horsetrainingandtips.com/Jesse_Beery_etips.htm
There is still more to know about horse's eyes.
For one, when you work with a horse, it's advisable to look him in eye a lot. Why? Because horse's an extremely observant animal and they study their surroundings. If you're in their surroundings they are studying you too. If they see you looking at them in eye it sends a message to them about who is in control.