Vision is used in every aspect of life. It is used for everything from reading a book to walking to your car. Vision is not just made up of how well you can see; it is made up of how well you can move your eyes, focus your eyes, interpret what you see, and use your vision to direct your movements. These are learned skills, and as such can be improved upon with practice. As you can imagine, visual skills play a huge role in sports performance.
One of the visual skills used in sports is tracking. Every sport has a tracking aspect to it, whether it is tracking your surroundings while you move, tracking a ball as it moves, or tracking a straight line to tell where you want the ball to go. There are two ways to track movement: using central or peripheral vision. At times, it is more beneficial to use central tracking, as it is generally more precise. At other times, using central vision, looking where you are going to pass the ball, gives away your move and peripheral vision would be the better option, if you are able to accurately use your peripheral vision to tell where your teammates are. Wayne Gretzky was one of the best hockey players when it came to peripheral vision tracking, allowing him to always know where his teammates were and making it very difficult for the opposing team to predict his moves.
Another visual skill used in sports is visual attention. Visual attention is the ability to maintain focus despite peripheral distractions, while still maintaining a high level of awareness of your surroundings. Losing visual attention while dribbling a ball may make you fumble the ball. Being distracted by a waving flag may cause you to miss your target. Visual attention is what allows you to literally and figuratively keep your eye on the ball. Other visual skills commonly used in sports include hand-eye coordination, accommodation (focusing), vergence (where your eyes are pointing relative to each other), visual reaction speed, depth perception, spatial awareness, and visual perception (interpreting what you see).
These visual skills are learned, and given the appropriate stimuli and environment, they can be improved upon at any age. That appropriate stimuli and environment are provided by vision therapy, a doctor-supervised program tailored to your skill level, designed to improve your visual skills. Because of the advantage gained by increasing visual skills, it is common for high level athletes to have visual skills training by doing vision therapy. Many international level sports teams have a vision therapist on their coaching staff. So if you want an edge in your game, consider fine tuning your visual skills and giving yourself the increased accuracy and extra seconds of better, faster visual skills.