Most pool players are neither binocular (vision center between the eyes) nor monocular (vision center under one eye). They perform best with the cue stick positioned underneath a point on their face between the nose and one eye.
The vision center, in part, refers to a perfectly straight shot that appears straight when lined up correctly. If you align the shot and then move your head off-line, it will give the impression of a cut shot. This means that all your shots will be off-target unless the vision center is accurately aligned.