This work is a synthesis of the ideas of 3 swordsmen of the 16th in to the 17th Centuries, Hidetsuna, Muneyoshi and Munenori
"Give special attention to the movement of your opponent's eyes. It is even said that you must make it your own. Unless you can follow your opponent's eye movements with absolute calm, whatever you may have learned about sword handling will be of no use."
While one could apply a more open or vague interpretation to this, for me the intent is pretty clear.