What is the difference between polycarbonate, glass or CR-39 plastic lenses?
Glass: Glass offers the best optical clarity, meaning that there is virtually no distortion in glass lenses. This is why it is the material of choice in manufacturers such as Ray-Ban, Revo, Vuarnet, and Serengeti. However, glass is the least impact resistant of all of the material, and may shatter upon impact. Shattering means that the lens will split into small pieces which can easily enter the eye and cause permanent eye injuries or even blindness. Therefore, glass is not recommended for any active sports where a fall or a hit by a ball can shatter the lens. It is also the heaviest of all the materials which may limit the length of time these lenses can be worn. However, glass is the most scratch resistant of all materials. Plastic: CR-39 refers to the type of plastic that is used to make prescription lenses. This is optical plastic and provides very little distortion (more than glass but less than polycarbonate). It is more lightweight and thinner than glass making it comfortable to