E-Glasses or the electronic eyeglasses: a new device that may join smartphones, iPads, and MP3s among devices that must be charged overnight. The electronic eyeglasses have tiny batteries, microchips, and assorted electronics to turn reading power on when it’s needed and off when it’s not.

People who hit their 40’s 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.

The electronic spectacles, called emPower, place liquid crystals, cousins to the familiar ones in TVs, in the bottom part of the lenses. The crystals change how the lenses bend light, just as varying levels of thickness do in traditional glasses.

To call up reading power, users touch the side of the frame. Batteries in the frame send along a current that changes the orientation of molecules in the crystals. When the wearer touches the side of the frame again, the reading power vanishes.

The glasses, made by PixelOptics in Roanoke, Va., will be on the market this spring — first in Virginia and North Carolina, and later in the year nationwide, Dr. Ronald Blum, an optometrist and the firm’s president, said. The estimated price, $1,000 to $1,200, will include frames, lenses, coatings, and a charger. Unlike traditional glasses, you’ll have to recharge them that lasts two to three days. Although the glasses are loaded with electronics, they look just like ordinary high-end glasses.

Thirty-six frame styles made by Aspex Eyewear will be offered initially. The lenses are manufactured by Panasonic Healthcare Co. in Japan and can be popped out and replaced if a prescription changes. The process of bringing the glasses to market in a stylish form took 12 years and about 275 patents.