Shape
It is usually important for an artist 
to consider not only the directions that the eye will follow as it explores the artwork, but to also orchestrate the speed, flow and cadence of its movement.  Sharp changes in the direction of the visual flow cause us to slow down, while curving, continuous paths encourage our eye to move along quickly.  A wealth of detail or the relative importance of an object can cause our eye to pause.  The spacing and duration of these pauses creates the visual rhythm 
of the piece.