Traditional bifocals could become a thing of the past with the invention of electronic glasses that automatically adjust to let their wearer view objects at different distances.The spectacles, which are due to be launched in the US this year and the UK next year, use lenses that change their strength when a small electrical current passes through them. A layer of liquid crystal sandwiched inside each lens alters its refractive properties according to the current applied, adapting the focal length according to where the wearer is looking. Traditional bifocals, which use two lenses of different strengths in front of each...