DSO Eyewear has Prismatic Elimination System (PES) Polycarbonate lenses. The PES lens gives prism free viewing (longer wear with less eye weakness). The PES lens system furnishes optical clarity while eliminating all harmful Ultra-Violet light. Natural traits of Polycarbonate make the material lighter than glass and up to 10X more impact resistant. Superb for ski, snowboarding, or any outdoor sport..