Why does usher always wear sunglasses?

In 1975 Hank Williams jr. Fell 500 feet coming down from Ajax mountain in Montana. He hit a boulder face first crushing part of his face, knocking several teeth out, and almost losing his right eye. He had to undergo several facial reconstructive surgeries. As a result his right eye does not move as quick as his left and he grew a beard to cover the scars and started wearing sunglasses.