I have a hard time judging the location of a ball as it moves toward me.

Your first phone call, according to Andrew Iwach, M.D., Assistant Clinical professor of ophthalmology at the University of California, should be to your ophthalmologist. "That way, you can make sure both eyes are working properly," he explains. Anything from astigmatism to a misalignment of the eyes—known colloquially as lazy eye—can contribute to problems with depth perception. There are a number of vision-training programs aimed at improving athletic performance; Dr. Iwach suggests approaching them with healthy skepticism. "These are interesting and worth further study," he says, "but it's difficult to determine if the training is making a difference or if it's a placebo effect." One of the best ways to improve your performance in a sport is simply to do it; your binocular vision may not improve, but your ability to judge the ball will. "Adults who lose an eye can do a very good job of judging distance by making use of the secondary visual cues," adds Dr. Iwach.