Lenses, not just frames
Glass vs Polycarbonate Lenses
Glass is harder and heavier. Polycarbonate is lighter and safer when it hits. Almost everyone should start with plastic.
Updated 27 Aug 2026 · 6 min read · glass vs polycarbonate lenses
Weight, smash, scratch
Glass: Mohs-hard, excellent optics, 2.5 index-ish depending on type, heavy, shatters. Polycarbonate: index 1.59, built-in UV, the safety-lens plastic, scratches unless coated, can show more chromatic fringe at the edge of a strong prescription. CR-39: the cheap optical plastic, 1.50, needs UV treatment for sunwear.
For children, sport, and anyone who drops a pair weekly, glass is a bad idea. For a dress sun pair that lives in a case, glass is a luxury texture some people still like.
Sunwear specifics
Mineral glass sun lenses take tints and mirrors beautifully and stay optically calm. They also turn a fall into a face full of crumbs. Polycarbonate sun lenses are what sports frames use because ANSI Z87.1 impact tests exist. Fashion houses still ship glass in $300 pairs; that is heritage, not safety.
| Glass | Polycarbonate | CR-39 | |
|---|---|---|---|
| Weight | Heaviest | Light | Medium |
| Scratch | Best uncoated | Needs hard coat | Needs hard coat |
| Impact | Worst | Best | Middling |
| UV | Needs treatment | Inherent | Needs treatment |
| Kids / sport | No | Yes | Maybe |
What to write on the order form
Poly or Trivex, hard coat, anti-reflective if indoor, UV400 if sun, high-index only if the prescription needs it. Glass as a special request, not a default. $40–$120 for poly sun lenses in a frame you already own is a common optician job.
Questions, answered
- Why do old sunglasses feel ‘clearer’?
- Often they were glass. Also you were younger. A well-coated modern poly is close enough for a car and a pavement.
- Does polycarbonate block UV without a coating?
- Yes, the material absorbs UV. Still look for the UV400 claim on fashion pairs — coatings and tints vary.
- Can I put glass in a nylon sport frame?
- You can. You should not. The frame is designed to flex; glass is not.
