DH's old Appaloosa had moon blindness. He had no sight in his right eye though his left eye was fine. Nevertheless, the two were still conditioning for endurance races. We just had to be careful jumping, preferring to go around rather than jump as they lose depth perception. Unfortunately, Orrie got into a nest of ground bees, was stung repeatedly, panicked and bolted, running through a barn wall. He was lacerated up so bad he would have bled to death so he ended up being shot. As a precaution, keep your pasture as bee free as you can
On a happier note, a friend of a friend had a cremello mare who was almost completely blind but they still used her for therapeutic riding. She was housed with a gentle AQHA gelding who was her "leader horse." She would follow him to water, into the stall (they took out their divider) and out in the morning. Blind horses often respond very well to vocal commads
Don't lose hope!