The lenses of prescription sunglasses can be made from various kinds of materials, for example, glasses. But many people don’t like it for they are too heavy can be easily broken. Today the new materials like the polycarbonate and the photochromic have made wearing eyeglasses much more comfortable. The photochromic lenses can change their colors when people are in different environment. Thus people don’t need to remove the sunglasses even when they enter into the room.