During spring training last year, Corey Brown was sure his eyes were the reason he kept striking out. The Washington Nationals outfielder had 20/15 vision and never needed contact lenses or glasses, but he couldn’t always pick up off-speed pitches out of pitchers’ hands and react while batting. The communication between his eyes and brain just wasn’t happening fast enough.

The team’s consulting eye doctor, Keith Smithson, recommended Brown do a variety of drills to improve the problem: toss around colored balls, field a ball with corners that made it roll unpredictably, and catch a tennis ball on one leg while wearing a pair of glasses that make it harder to see by creating a strobe-like effect.