Lens Materials:
Plastic - Also known as CR-39, this lens has been the standard material for eyeglasses for many years. It is half the weight of glass and less prone to shatter. Plastic material is easily tinted, and UV protection can be added to this lens.
Polycarbonate - Polycarbonate was the first "thinner, lighter" lens material. Polycarbonate is 10 times more impact resistant than glass and CR-39. Polycarbonate lenses are the preferred choice for safety eyeglasses and children's eyeglasses. The lens material also provides UV protection.
Trivex - Trivex lenses are thin, lightweight and impact resistant. This lens is another preferred choice for safety eyeglasses and children's eyeglasses. This lens material also provides UV protection.
High Index (Hi) - High index lenses are thinner and lighter weight than are plastic, polycarbonate, or Trivex. There are a wide variety of high index lenses such as Hi 1.60, Hi 1.67 and Hi 1.74. The optician will help you decide which high index lens would work the best for you. For stronger prescriptions, a higher index will help keep the lenses thinner. This material also has UV protection.
Glass - Glass offers superior optics and is the most scratch-resistant material available for eyeglasses. However, glass must be specially treated for impact resistance. Glass is also much heavier in weight and not offered in many designs. Glass lenses can only be put into specific frames.