think of physical therapy, but for the eye(s)....
As you may have noticed, I don't know much about it, but it is often used to help someone who is strabismic(?) straighten their weak eye (before of after sugery) and to get that eye working with its companion and to also get the brain processing the visual info from the weak/lazy eye once again, since the afferent signals from such an eye tend to get ingnored.
It is also used to get people with eye coordination problems (ie. not tracking an object with both eyes completely) or people that are having problems with their vision and even headaches when using a computer extensively.