Poly for the win?

[pneese]

I think the vast majority of patients are fine with poly. Trivex, is nothing magical, and is over used by people who think it's a must to be a high end optical. Its abbe value is no where near CR and will be thicker than poly, plus it is a nightmare to work with. I say use poly unless you have very good reason to think a specific patient has an issue with it.

I will politely and respectfully disagree.

Trivex has a better abbe value, it does not have the CA issues that polycarbonate has, it has better tensile strength (more ideal for half-eyes and rimless frames), it has slightly better light transmittance, and like someone earlier mentioned it has a lower center of gravity.

If a customer is fitted correctly (ideally I know) where there is not a significant amount of decentration than the fact that it's 10% more thicker won't mean much. By the time we are getting into higher prescriptions CYL or SPH where the difference will matter we should be fitting people with a Hi-Index lens anyway.

[Kwill212]

Top-notch poly is better than Trivex.

Where would one source "top-notch poly", specifically what manufacturer makes it? What makes it objectively "better" than trivex? Again specifics would be great.

[ak47]

I will less than respectfully disagree. Whoever is selling that information is either clueless or full of sh*t. Poly has its place, and is the best choice in a few, select situations. Nine times out of ten it is absolutely not the BEST choice. But, if you want your clientele to become frustrated when their lenses chip and crack, please use poly. They will then become your former clientele.

[vfpamp]

Where would one source "top-notch poly", specifically what manufacturer makes it? What makes it objectively "better" than trivex? Again specifics would be great.

I wouldn't know which US optical labs are working with good poly. We work more closely to the precision optics folks in China that make lenses for scientific equipment (microscopes, telescopes, etc). But, the samples I have achieve Abbe of 43-47, at indexes of refraction of 1.55–1.56 and better scratch resistance than Trivex at a slightly higher UV protection on our tests. What attracted us to this particular technology was the fact that the remaining chromatic aberration was concentrated in the 400-500nm range (violet). The material's index of refraction is 1.56+/-0.5 from 500nm to 830nm but 158 at 400nm. This is particularly good for green/red calibration of devices. To the best of my understanding, the property comes from the use of carbonyl sulfide instead of the usual thiols and phosgene polymerization method. Looks like it's also a "greener" option to the manufacturing of polycarbonate (at least, that's what they sell).

The Abbe number (more precisely, the index of refraction per wavelength of the material) is what makes it "objectively better" for me. But I expect every optician to have their own usually-contrasting notions of "better".

[Kwill212]

I wouldn't know which US optical labs are working with good poly. We work more closely to the precision optics folks in China that make lenses for scientific equipment (microscopes, telescopes, etc). But, the samples I have achieve Abbe of 43-47, at indexes of refraction of 1.55–1.56 and better scratch resistance than Trivex at a slightly higher UV protection on our tests. What attracted us to this particular technology was the fact that the remaining chromatic aberration was concentrated in the 400-500nm range (violet). The material's index of refraction is 1.56+/-0.5 from 500nm to 830nm but 158 at 400nm. This is particularly good for green/red calibration of devices. To the best of my understanding, the property comes from the use of carbonyl sulfide instead of the usual thiols and phosgene polymerization method. Looks like it's also a "greener" option to the manufacturing of polycarbonate (at least, that's what they sell).

The Abbe number (more precisely, the index of refraction per wavelength of the material) is what makes it "objectively better" for me. But I expect every optician to have their own usually-contrasting notions of "better".

I appreciate the detailed response. Is anyone using this material in eyeglasses? Is it called polycarbonate by the manufacturer? Seems like you are talking about a completely different material than what opticians would call Polycarbonate. Do you have a link to the Precision Optics folk in China?

[Uilleann]

The sheer amount of fear-mongering and misunderstood facts about poly, and CA in this thread are laughable! But keep on pushing that trivex folks. PPG thanks you from the bottom of their pocket book. LOL

[ePii]

Anyone who swears by Trivex should first have to work in a lab for a year then say how they feel. Trivex is fine but Poly is better when all things factors are considered and compared, i.e price, ease, thickness, weight and even abbe value. Btw CR is still optically the best organic material we have. Most people just get indoctrinated by their Hoya or Younger rep, most patients can't tell the difference.

[Kwill212]

Anyone who swears by Trivex should first have to work in a lab for a year then say how they feel.

Why, that makes no sense. If you run the lab and think Trivex is too hard to process, or wears out the equipment too much, either don't offer it or charge accordingly for it.

[Robert_S]

We use poly for a tiny, tiny amount of jobs because our company considers other materials better in most situations. I would say we have more issues with the few jobs we sell in poly than we do with the majority of jobs we sell in trivex. It cracks and stars, something I've never seen happen with trivex. And we don't buy 'cheap' poly.

[ePii]

It's not that Trixex is too hard to work with, it's that it's notably harder to work than other materials without offering significant benefits. I'd rather have optical professionals be a bit more critical about the information that they get indoctrinated with. The fear mongering and propaganda in this industry is truly destructive, and very few people even know when they're being lied to by the oligarchs.

[lensmanmd]

We processed 49926 pairs of poly in 2019. 0.08% were returned for cracking.

[pneese]

It's not that Trixex is too hard to work with, it's that it's notably harder to work than other materials without offering significant benefits. I'd rather have optical professionals be a bit more critical about the information that they get indoctrinated with. The fear mongering and propaganda in this industry is truly destructive, and very few people even know when they're being lied to by the oligarchs.

There is no fear mongering, polycarbonate clearly is a worse lens material. I've never heard any specs or facts that have convinced me otherwise. Do you have sources you can link for us?

Don't get me wrong, I sympathize when you say its a pain to work with but I am more worried about my customer's sight than how much more work we would have to do.

[lensmanmd]

Why, that makes no sense. If you run the lab and think Trivex is too hard to process, or wears out the equipment too much, either don't offer it or charge accordingly for it.

I run a full service lab. Trivex is no more difficult to work with than poly. Surface macros are basically poly macros. Edged settings are basically poly setting.
Trivex is tougher on wet edger roughing wheels. Generator diamonds and turning tips wear a little quicker, sure, but not by large numbers. Labs do charge more for Trivex due to lens and consumables costs.
My gripe with Trivex is not processing costs. It lies specifically with those that do not know when to or how to properly sell it.

[vfpamp]

We use poly for a tiny, tiny amount of jobs because our company considers other materials better in most situations. I would say we have more issues with the few jobs we sell in poly than we do with the majority of jobs we sell in trivex. It cracks and stars, something I've never seen happen with trivex. And we don't buy 'cheap' poly.

Have you study the reasons for the cracks? Most of the time is a chemical compound that's being used to clean or to lubricate the machines. Tiny amounts of ester-based additives can easily crack the lens. Ammonia (Windex or 409) will damage. And obviously you should avoid all types for solvents, propanol, etc. Here's a starting point for your research: https://www.calpaclab.com/polycarbon...ibility-chart/ :)

Your poly source should be able to give you a list that is more appropriate to the specific mixture he is using to create the lens.

[Robert_S]

What is fear mongering about stating facts? Trivex is optically better, lighter, less chemically reactive and stronger than poly and therefore preferential in almost all cases. Doesn't mean poly is going to kill anyone, but then neither is not having AR.

Part of our role as optical professionals is to drive the standard of our industry forward.