Polycarbonate vs Trivex
Two materials sold as near-equivalents, with one genuine difference between them that almost nobody mentions at the counter. Both are tough enough for children and sport; only one of them is pleasant to look through.
The short answer. Trivex, if you can get it and the price difference is small. It is lighter, it has a far better Abbe number (45 against 30) and the thickness penalty is 0.33 mm at −4.00 — nothing. Polycarbonate wins on price and availability, and that is a real argument for a child's prescription that will change next year.
The question this page answers: which impact-resistant lens material should I choose?
The one difference that matters
Polycarbonate and Trivex sit almost on top of each other in refractive index — 1.59 against 1.53 — so they produce lenses of near-identical thickness. They are both impact-resistant enough to be the standard recommendation for children, for sport, and for anyone working near flying debris. On the two things people usually compare lenses on, they are the same material.
Where they part company is dispersion, measured by the Abbe number. Lower numbers mean more chromatic aberration: a faint coloured fringe around high-contrast edges, visible when you look through the outer parts of the lens rather than straight through the middle. Polycarbonate scores 30, which is the lowest figure of any lens material in common use — lower than 1.74, the thinnest and most aggressive high-index plastic available. Trivex scores 45.
Put plainly. Polycarbonate has worse optics than the material people are warned about having worse optics. Trivex has noticeably better ones, at the same thickness and a lower weight. If the price gap is small, there is very little case for polycarbonate in an adult's everyday glasses.
Side by side
| Trivex | Polycarbonate | CR-39 | |
|---|---|---|---|
| Refractive index | 1.53 | 1.59 | 1.5 |
| Abbe number | 45 | 30 | 58 |
| Density, g/cm³ | 1.11 | 1.2 | 1.32 |
| Impact resistance | High | High | Standard |
| Suitable rimless | Yes, best in class | Yes | Not generally |
| Relative cost | Higher | Lowest | Low |
Weight is the underrated column
Trivex is the lightest lens material in general use, by a margin that is not close. At 1.11 g/cm³ it is 7% lighter than polycarbonate per unit volume and 16% lighter than CR-39. Since the two materials make lenses of almost the same thickness, that density advantage passes through directly to the finished pair.
| Prescription | Trivex | Polycarbonate | Edge difference |
|---|---|---|---|
| −2.00 | 6.0 g | 6.2 g | 0.16 mm |
| −4.00 | 7.4 g | 7.6 g | 0.33 mm |
| −6.00 | 9.4 g | 9.5 g | 0.51 mm |
| +2.00 | 4.6 g | 4.7 g | 0.23 mm |
| +4.00 | 7.4 g | 7.4 g | 0.48 mm |
A gram or two per lens sounds like nothing written down, and it is the difference between glasses you stop noticing by eleven in the morning and glasses that leave marks on your nose. Weight is the complaint people bring back to a dispenser most often, and it is the one the thickness conversation never addresses — a thinner high-index lens in a denser material can easily weigh more than a thicker Trivex one.
Impact resistance: both, differently
Polycarbonate's reputation was built on impact resistance, and it earned it. It is the material used for safety eyewear and for riot visors, and it will take a direct high-velocity strike better than anything else here. Trivex passes the same standards with margin to spare.
The difference between them is in how they fail rather than whether. Polycarbonate is softer and scratches more readily, which is why it is almost always supplied with a hard coat applied. Trivex is more resistant to cracking around a drilled hole, which is why dispensers reach for it on rimless and half-rim frames where the lens is held by a screw through the material itself. If you are choosing a rimless frame, that single property is usually enough to decide the question.
For a child, either material is a correct answer and the safety question is closed by choosing either one. What remains is cost against optics, and for a prescription that will be replaced within eighteen months, polycarbonate's price is a reasonable argument. For an adult expecting to wear the same lenses for three years, it is a weaker one.
Where neither is the answer
Both are 1.59-ish materials, and neither comes in a thinner version. Above about four dioptres their thickness becomes the thing people complain about, and the sensible conversation moves to 1.60 or 1.67. That is a real trade: at 1.67 the Abbe number is 32, which is back down near polycarbonate's, so you buy thinness with the optical quality Trivex was protecting.
The rule of thumb that follows from the arithmetic: under four dioptres, pick on optics and weight, which means Trivex. Over six, pick on thickness, which means high index. Between the two, see what the frame can do first — a smaller frame changes edge thickness more than a material step does, and it does not cost you an Abbe number.
What to ask for
- Ask which material is being quoted, by name. "Impact-resistant" covers both and is the word a quote will use if it does not want to say polycarbonate.
- Ask for the price difference as a number. If Trivex is a few pounds or dollars more, take it. If it is a large multiple, polycarbonate with a good anti-reflective coating is a perfectly sound pair of glasses.
- Insist on anti-reflective coating on polycarbonate. Its dispersion is worst in exactly the conditions — night driving, high contrast — where surface reflections also hurt most, and the two problems compound.
- For rimless, ask for Trivex specifically and say why. A dispenser who mounts rimless regularly will agree with you.
Run it on your own prescription
The figures above are a 52 mm frame on a 63 mm pupillary distance. The lens thickness calculator runs both materials, and the four high-index options, on your own numbers — and draws the cross-sections to scale so you can see whether any of the differences would be visible on your face.
Material properties are the published figures for each class of material; individual products vary. Thickness and weight are calculated from lens geometry and will differ from a finished pair depending on the lab's minimums, base curve and lens shape. This is not a substitute for an optician's advice.
Questions people ask
- Is Trivex better than polycarbonate?
- Optically, clearly: Trivex scores 45 on the Abbe scale against polycarbonate's 30, which is the worst figure in common use. Trivex is also lighter, at 1.11 g/cm³ against 1.2. Polycarbonate's advantages are that it is cheaper, available everywhere, and very slightly thinner at the same power.
- Which is more impact-resistant?
- Both pass the same impact standards, and both are far tougher than standard plastic or glass. Polycarbonate is marginally better at resisting a high-speed impact; Trivex resists being pulled out of a rimless mounting better, because it is less brittle at a drilled hole. For practical purposes, treat them as equally safe.
- Is Trivex worth the extra cost?
- At a −4.00 prescription in a 52 mm frame the thickness difference is 0.33 mm — invisible. What you are buying is the Abbe number and 0.2 g per lens. If you have noticed colour fringing at the edges of polycarbonate lenses, or wear glasses all day, it is usually worth it.
- Which should children wear?
- Either. Both meet the impact standards that make them the right class of material for children, and the choice between them comes down to cost and optics rather than safety. Polycarbonate's lower price makes it the common answer for a prescription that will change in a year.
- Can I get Trivex in a high index?
- No. Trivex is a 1.53 material and does not come in a thinner version — that is the trade. Above about four dioptres its thickness becomes the dominant complaint, and the conversation moves to 1.60 or 1.67, where the Abbe numbers are back down near polycarbonate's anyway.