To date prescription eye glasses can be made with glass, plastic, hi-index plastic, polycarbonate and trivex. Before I go into the new lens I will let you know what my take is on the current options.
Glass: AKA Crown Glass. Optical clearity is super, scratch resistance is great, although tempered it will shatter into shards if luck is not on your side, but the real doozy is the weight. This material is heavy. While european and asian opticians will produce ultra thin glass lenses to minimize the wight issue, we are bound by some safety laws that require thicker glass lenses. All in all this lens is filled rarely at best.
Plastic: AKA CR39. Optical clearity is good, scratch resistance is so-so, not shatter-proof but much less likely than glass, will get thick in moderate to high prescriptions. Decent work horse lens.
Hi-Index Plastic: Optical clearity is not the best and the higher the index the worse it gets. The higher the index the thinner it gets. All in all this lens is well tolerated and is recommended with higher prescriptions.
Polycarbonate: The poorest optical clearity, the most impact resistance, the easiest to scratch, fairly light and thin. All in all my least favorite lens other that glass.
Trivex: Best optics, lightest, equal impact resistance to polycarbonate, but not the thinnest. All in all I would choose this lens if thickness was not an issue.
Now from the scientists at PPG Industries, Tribrid.
Think Trivex hybrid Hi-Index: Best optics, lightest, thin but not the thinnest, most impact resistance, also very scratch resistant. All in all I think this will be my new favorite lens.
Here is a link to learn more:http://www.ppg.com/en/newsroom/news/Pages/20130316A.aspx
