A new device may be joining smartphones, iPads and music players that you have to charge overnight: electronic eyeglasses. These glasses have tiny batteries, microchips and assorted electronics to turn reading power on when you need it and off when you don't.

People who hit their 40s often need extra optical help as farsightedness sets in. They may buy bifocals or no-line progressive lenses.

But such glasses have a drawback: the lenses that magnify fine print also blur objects more than an arm's length away when a wearer looks down, distorting the view when on a staircase, for example, or when swinging at a golf ball.