With a moderate prescription like yours, CR-39 is certainly thin enough, unless you want giant width frames. It's the best plastic for optical quality. It's also the least expensive option when it's offered. It's index (of refraction) is 1.5. If some vendor is offering something they call CR-39, but with a higher index, either the index or the name of the plastic is incorrect.
It's scratch resistant enough that scratch-coating isn't essential, though many places offer it at no extra charge. If you buy it at a local store, and they charge a lot for scratch-coating, don't get it; it may even already have scratch-coating! If you don't have scratch- coating, or if you don't know, don't use paper to clean your lenses unless it's especially made for the purpose. (Have you even seen how easy it is to put tiny scratches on a [polycarbonate] CD or DVD? That's what I'm talking about. CR-39 is not as bad, but you still want to be careful.) --~--~---------~--~----~------------~-------~--~----~ Check us out at the oft-updated http://glassyeyes.blogspot.com! You received this message because you are subscribed to the Google Groups "GlassyEyes" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/glassyeyes?hl=en -~----------~----~----~----~------~----~------~--~---
