PixelOptics has developed a bifocal lens that can change its viewing properties with the push of a button.
The top part of the glasses function with a far-focusing prescription lens, but the bottom half has an electro-active liquid crystal that can change its refraction index as the wearer requires.
The “manual off” setting disables the current and the lens then acts like a low-power progressive lens. The “manual on” setting sends an electric current through the lens, in effect freezing them in place to optimize near focus.
The “active on” setting, however, uses motion-detection sensors that read where the wearer is looking and adjusts the focus of the lens accordingly.