Eyeglasses

Lens Materials

Glass

Oldest lens material (although archeological findings have discovered emerald and ruby lenses in ancient cultures- we'll just stick to modern times). Has superior optical qualities (clarity) to plastic lenses, yet are very heavy and are a safety concern due to shattering into small sharp fragments when impacted.

 

 
Basic Plastic (CR-39) Like the name implies, these lenses are, well, basic. The cheapest lens available, but prone to shattering upon impact, and chipping when placed into a drill-mount or semi-rimpless frame.
 

 
Polycarbonate The most impact-resistant material available- these lenses exceed ANSI safety standards at less than 1/3 the required thickness! Polycarbonate lenses also have the added benefit of being lighter and thinner than basic plastic lenses. Recommended for safety, sports and children's glasses.
 

 
Trivex Trivex has optical qualities (degree of clarity) nearly identical to glass. Due to manufacturing processes, it is even less likely to crack than polycarbonate, although it is less impact resistant (more prone to shattering than polycarbonate, yet less likely to crack? strange but true- anyways, both are much safer than basic plastic or glass). Recommended for drill-mounted frames.
 

 
Hi-Index Hi-index lenses fall between basic plastic and polycarbonate in their degree of safety, but offer the benefit of creating the thinnest lens possible. Hi-Index lenses include 1.60, 1.67, 1.70, and 1.74. Basically the higher the number, the thinner the lens (but also the higher the cost).