Visual concentration is the ability to screen out distractions and stay focused on an opponent. To improve visual concentration, have other students stand around the sparring area while you are sparring waving their arms and moving in and out of your field of vision. You also can spar in a darkened room with a slowly pulsating strobe light (be very careful).
Eye tracking helps you keep your balance and react quickly. You must be able to follow movement without much head movement. To improve eye tracking, have two people stand about ten feet apart and toss a ball back and forth. Stand between them, centered and to the side, with a book balanced on your head, and follow the ball movement without the book falling. You can also train by keeping track of a small ball rolling inside a Frisbee. Change the ball size and rolling speed as you improve.
Visualization is seeing yourself do one thing well in your mind's "eye" while your eyes are seeing and concentrating on something else, such as a moving ball. Research as shown that picturing yourself perform well at something, such as sparring or performing a hyung, can actually improve your ability.