Most people think that the best use of sunglasses is to disguise your emotions. The theory is obvious, if you can hide your true intentions from your opponents then you gain an edge. Which is why a lot of people believe sunglasses should be banned.

Occasionally I use sunglasses but not for the reason mentioned above. For better or worse I try to manipulate my opponents into doing what I would like them to do, sunglasses take a certain percentage of that away from me. But I do use them occasionally and this is why, my eyes hurt when I play poker, especially tournament poker. If you watch me play poker I have a focus at the poker tables that does not exist in other areas of my life. That focus requires concentration when others are not concentrating. That concentration comes from my eyes.

The theory is obvious, whether it is sunglasses or taking a nap during the dinner break, resting your eyes makes you a better player because it allows you to maintain focus.