Glass eye
Wall eye
China eye
Clydesdale eye
Cotton eye

“When horsemen speak of a glass-eyed horse, they refer to an eye that is any color other than normal [brown], but the eye is usually some shade of blue.  A ‘china eye’ is blue, a ‘wall eye’ is part blue and part white, and a ‘watch eye’ is a mixture of yellow and blue.” From The Revised Health Problems of the Horse by Robert M. Miller