The short answer: CR-39 is an inexpensive standard plastic with excellent optical clarity, best for low prescriptions and everyday glasses. Polycarbonate is lighter, thinner, far more impact-resistant, and blocks UV by default, best for kids, sport, rimless frames and stronger prescriptions. CR-39 gives slightly crisper optics; polycarbonate is the tougher, safer all-rounder.
What each one is
CR-39 is a lightweight plastic (also called allyl diglycol carbonate) that has been the default lens material for decades. It has very good optics and takes coatings well, but it is thicker and can crack or shatter on hard impact. Polycarbonate is a tougher plastic, the same family used in safety goggles and cockpit canopies, that is thinner, lighter and highly impact-resistant, with UV protection built in.
Head to head
| Feature | CR-39 | Polycarbonate |
|---|---|---|
| Optical clarity | Excellent (higher Abbe) | Very good (a touch softer at edges) |
| Impact resistance | Moderate | Very high |
| Weight | Heavier | Lighter |
| Thickness | Thicker | Thinner (index ~1.59) |
| Built-in UV | No (needs coating) | Yes, 100% |
| Best price | Lowest | Slightly higher |
When to choose CR-39
Pick CR-39 for a low prescription in a full-rim frame where you want the crispest optics at the lowest price and impact is not a concern, for example a spare pair or reading glasses. It is a fine, proven everyday choice.
When to choose polycarbonate
Pick polycarbonate for children, sports and safety eyewear, rimless or drilled frames (where CR-39 can crack), higher prescriptions where you want thinner and lighter, and anyone active. The built-in UV and shatter resistance make it the safer default for most people; add anti-reflective coating to sharpen it, see AR coating.
What about high-index and Trivex
For strong prescriptions, high-index lenses (1.67, 1.74) go thinner still than polycarbonate; see high-index lenses explained. Trivex matches polycarbonate for impact and UV but with sharper optics, at a higher price, a great upgrade if you want the toughness without the slight softness; compare in Trivex vs polycarbonate.
From our test bench. For most people we default to polycarbonate: it is lighter, safer, blocks UV and suits rimless frames, and the small optical edge of CR-39 is hard to notice with an anti-reflective coating. We save CR-39 for low-cost, low-power full-rim pairs, and reach for Trivex or high-index when optics or thinness really matter.
FAQ
Is CR-39 or polycarbonate better?
Polycarbonate is better for most people: lighter, thinner, far more impact-resistant and UV-blocking. CR-39 has slightly sharper optics at a lower price and suits low prescriptions in full-rim frames where impact is not a concern.
Does polycarbonate have worse optics than CR-39?
Slightly. CR-39 has a higher Abbe value, so polycarbonate can show a touch more colour fringing at the edges. Most wearers do not notice, especially with an anti-reflective coating. Trivex offers polycarbonate-level toughness with sharper optics.
Which lens is best for kids and sport?
Polycarbonate, because it resists impact and shattering and blocks UV by default. Trivex is an even better, pricier upgrade with the same toughness and clearer optics.
Part of The Complete Guide to Prescription Lenses · Related: high-index lenses · Browse eyeglasses · Last updated: August 9, 2026
