Lens Materials and Lens Thickness
Plastic lenses are the most commonly-used lens material on the market today. Usually referred to as regular or standard plastic, opticians know it as CR-39. Plastic lenses are lighter and more durable than glass, it can be used for nearly any prescription, though many people with higher prescriptions prefer to use a high index type of plastic. The higher the index, the thinner the lenses. Plastic lenses are great for prescription sunglasses due to their tintability factor though they do need to have ultra violet protection added, you can virtually tint a plastic lens to any color and density. Plastic lenses (CR-39) give less chromatic aberration compared to polycarbonate lenses, as measured by the Abbe number.
Polycarbonate lenses are the most-used alternative material for modern ophthalmic lenses. Polycarbonate was the first plastic high index lens and has a high index of refraction of 1.59. Polycarbonate lenses are 10 times more impact resistant than plastic lenses and are highly recommended for children's eyewear, safety glasses, and a must for rimless frames that require drill mounts. Polycarbonate lenses are up to 30% lighter and thinner than standard plastic lenses for greater comfort. Polycarbonate lenses shield your eyes from virtually 100% of the sun's harmful UV rays.
High-Index Lenses, includes but not limited to 1.67 (Super Thin) and 1.74 (Ultra Thin) -
High-Index Lenses are thinner and lighter than the other lenses. Because of their ability to bend light more efficiently, High-index lenses are able to bend light to a stronger degree than a lens with a lower index. High-index lenses for nearsightedness offer thinner edges, require less lens material, which minimizes the overall weight of the lenses than lenses that are made of conventional plastic material with the same prescription power. In general, the stronger the prescription, the greater the difference in thickness between standard plastic and high-index plastic. Therefore, High-index eyeglass lenses are the right choice if you want thinner, lighter lenses and eyeglasses that are as attractive and comfortable as possible