Lens material sets the ceiling on what a pair of sunglasses can do. Tint and coatings are chosen afterwards; the material decides how sharp the view is, how much the lens weighs, how easily it scratches, and what happens when something hits it.
There are four in common use, and no best one – the trade-offs genuinely point in different directions.
The number nobody mentions: Abbe value
Different wavelengths bend by slightly different amounts as they pass through a lens. The more a material separates them, the more you see colour fringing – a faint rainbow edge on high-contrast boundaries, most visible toward the periphery.
Abbe value measures that dispersion. Higher is better. Roughly: glass and CR-39 sit around the high fifties, Trivex in the mid forties, polycarbonate around the low thirties.
It rarely appears on packaging, and it explains more real-world complaints about lens quality than any other specification. If edges look soft or colours fringe when you glance sideways, this is usually why.
CR-39
The original optical plastic and still the default for non-prescription and light-duty lenses. Optically excellent, tints evenly and predictably, and inexpensive.
Its weaknesses are hardness and impact resistance. It scratches readily without a hard coat, and it is not the material for anything that might take a knock. It is also thicker and heavier than modern alternatives at the same prescription.
Choose it for everyday sunglasses where optical quality matters and impact does not.
Polycarbonate
The impact-resistant option, by a wide margin. It is also light, thin, and blocks essentially all UV as a property of the material rather than a treatment.
The cost is optical. Its Abbe value is the lowest in common use, so peripheral colour fringing is more noticeable than in any other material here. It is soft, too – a hard coat is not optional on polycarbonate.
Choose it for sport, cycling, anything around children, and safety contexts. It is the correct answer whenever a lens might be struck.
Trivex
Developed later, and it resolves most of polycarbonate’s compromise. Comparable impact resistance, inherent UV blocking, noticeably better optics, and it is the lightest of the four.
It costs more and is stocked less widely, so it is often not offered unless you ask. It is also a good choice for rimless mounts, because it resists cracking around drill holes better than polycarbonate.
Choose it for the best balance available, if the price difference is acceptable.
Glass
Optically the best, and the most scratch-resistant by a distance. A glass lens looks the same after years of the kind of handling that leaves plastic hazy.
Two serious drawbacks. It is heavy, which is felt over a long day and puts more load on the frame and nose. And it can shatter – which is why it is unsuitable for sport and why it is rare in children’s eyewear.
Choose it for maximum clarity and durability in relaxed use, where weight is acceptable and impact is unlikely.
Matching material to use
- Driving and general wear – CR-39 or Trivex. Good optics matter here, impact does not.
- Cycling, running, watersports – polycarbonate or Trivex. Not glass, ever.
- All-day wear where weight matters – Trivex.
- A pair you intend to keep for a decade – glass, if you will accept the weight.
- Rimless frames – Trivex or polycarbonate. CR-39 and glass crack at drill holes.
What to ask
Sellers describe lenses by tint and features far more often than by material, so it usually takes a direct question: what is the lens material, is there a hard coat, and what is the UV rating.
An answer of premium or high-quality is not an answer. Any of these four is a legitimate choice for the right use, and knowing which one you are buying is the difference between a lens that suits what you do and one that quietly does not.