Prescription Eyeglasses Bifocal Lenses Bifocals are lenses with two distinct viewing areas to help correct vision that fails at two or even three distances. High Index and Aspheric Lenses Manufactured to be thinner at the edges of the lens and lighter in weight overall—a good choice for people with stronger prescriptions. Photochromic Lenses Photochromic lenses change from clear to dark based on the intensity of UV radiation. Polycarbonate Lenses Progressive Lenses Progressive lenses allow multiple vision fields to be incorporated into a single lens without any clear distinction between the fields themselves. This is why progressive lenses are often referred to as “no-line” bifocals or trifocals. Caring for Lenses These lens care and maintenance tips will go a long way toward maintaining your healthy sight. Eyeglass Frame Materials Which frame material is right for you? Learn about the different types of metal and plastic, and the advantages of each. Frame Maintenance Tips for Keeping Your Frames Properly Maintained.