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.  

 

What's the best lens material  for my prescription? What type of lens should I choose?

What lens material should I use for my glasses is hard to say exactly without knowing all the specifics, but here are some general ideas/rules to keep in mind:

• While plastic is the most popular material to use and will fit most prescriptions, there are some situations where it may be better/recommended to use something else.

• Individuals with prescriptions over -2.00 or +2.00 can expect CR-39 lenses to be somewhat thick

• Plastic frames will cover up some thickness, whereas metal, semi-rimless and rimless do not (and it's not necessarily because the lens is any thinner but that the frame is thicker)

• Plastic and 1.74 high index cannot be used for drilled rimless frames because they crack too easily, so polycarbonate or high index 1.67 must be used.

• Since Polycarbonate is less likely to break or crack than other materials, it is often recommended for children, athletes and individuals with vision in only one eye as a protective measure.

• Rimless and semi-rimless frames show the thickness of a lens the most and in some cases the lens has to actually be made a little thicker so that it can be drilled or grooved.