While the most often used plastic eyeglass material, called “CR-39,” is relatively inexpensive and easy to tint, it is not very impact resistant. Thus, it is well suited to those with mild prescriptions who don’t engage in high-impact activities. Because CR-39 lenses can look thick with strong prescriptions, they do not lend themselves well to rimless, drill-mounted frames. Other options include “polycarbonate” lenses that are highly shatter-resistant and thinner than CR-39; they also provide protection from ultraviolet (UV) light. However, polycarbonate isn’t as good optically as other lenses, especially in strong prescriptions. This leads us to “HD” (digital) lenses, which are precision, diamond-cut lenses that provide improved optics, and “high-index” lenses that are thin and lightweight and offer UV protection. Trivex lenses combine the extreme impact resistance of polycarbonate with the optically superior quality of HD lenses and the light weight of high-index lenses.