We processed 49926 pairs of poly in 2019. 0.08% were returned for cracking.
We processed 49926 pairs of poly in 2019. 0.08% were returned for cracking.
I bend light. That is what I do.
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.
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.
I bend light. That is what I do.
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.
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.
I appreciate the advice, genuinely. Thank you for your suggestions.
But at the same time, if a material is so sensitive that trace amounts of a substance can crack it, that's even more of a reason for me to avoid it. It's actually not fair on the end user, who is surely going to also come into contact with trace amounts of substances like Windex, to be honest.
Poly is stronger than Trivex, especially after AR is applied, in terms of impact resistance at the same thickness. Trivex is more chemical resistant, lighter overall and has higher tensile strength.
In terms of thickness to weight ratio, poly wins with higher RXs. In terms of thickness, weight and chemical resistance, 160 wins.
If optics is your primary concern, fit the best frame first. Then decide on lens materials that best fits the patients’ needs, not yours. This is the opticians’ primary responsibility, otherwise, you are nothing but a frame stylist.
I bend light. That is what I do.
Well, it's sensitive because your are cutting, grinding and polishing. Exposing the raw compound. After you apply the protective coatings, it should not crack at all. Like what lensmanmd said: ~0.08% is normal.
We put poly in our phoropter and I have not seen any of them crack yet. 380,000 lenses shipped.
Poly is 'stronger' in a totally insignificant way. Trivex is less prone to chipping, which is what the customer is most concerned about.
In what way does trivex fit 'my' needs? What a ridiculous comment.
Maybe you should stop trying to defend yourself picking the cheaper and easier option by selecting polycarbonate.
In any scenario where polycarbonate is preferential to trivex, tribrid would be better anyway.
Did I say it happened in the lab? If it did, I would be blaming myself.
But why are offices using trivex instead of cr in low rxs. Trivex is fine. It’s just not that special and I think there is a lot of unjustified snobbery around using it.
UV protection?
Personally, I believe Trivex became obsolete when Tribrid was released. Consider, in order of retail price with selling points:
CR-39: base material, fine optics, no impact resistance
POLY: thinner, lighter, impact resistance, possibly worse optics for some people
Trivex: thicker than poly, impact resistance, optics similar to CR-39
1.60: thinner, better optics, no impact resistance
Tribrid: 1.60 with impact resistance
From the lab I had been using, Tribrid was the same price as Trivex. I don't know about the uncuts. But from a consumer perspective, Trivex serves only to muddy up my options. I can get a lens that's clear, that's impact resistance, or that's thinner. With poly and trivex, I get to pick 2 of those. With Tribrid, you get all three. What's Trivex purpose when Tribrid is available at a similar price? And at that point, it makes sense to have a poly vs tribrid discussion with the patient on price vs quality. It's not just "which two of the three lens features do you value most?"
Well, PPG created CR-39, Trivex, Transitions and Tribrid. So, among these options their marketing materials tell the whole story: http://www.eyemax.co.il/wp-content/u...iew-2-Copy.pdf
Tribrid is the natural evolution of Trivex, Like Windows 10 is the evolution of Windows 7.
Last edited by vfpamp; 02-15-2020 at 12:02 PM.
I agree about tribrid. It's a shame that in the UK it is significantly more expensive...
It is in the US, as well. More than trivex, more than 167.
I bend light. That is what I do.
You do understand that
167 has a higher specific gravity than Poly, fight me.
167 has a higher specific gravity than CR39, fight me.
167 is not much better in terms of ABBE over Poly, fight me.
167 has a higher cost to the patient than poly, fight me.
Unless the frame calls for a groove/drill/safety needs, CR39 is optically better than everything but glass, fight me.
CR39 and Poly are the most cost effective material for the consumer, fight me.
167 is not a miracle material. 174 is not a miracle material. The only miracle? They improve your average sale, in turn, your paycheck. They do not improve the bottom line of any business. They should be used only when the RX calls for it, not for every RX.
Every material has its place in our industry. The key is to understand when and why to advise the patient based on their needs, not yours. Fight me.
I bend light. That is what I do.
I bend light. That is what I do.
Poly is more impact resistant, less prone to heat damage, and when glazed properly, chipping/cracking is minimal. Did I mention that out of close to 50000 pairs that we produced last year, we had 47 returned for this reason? Poly 'non-adapts'? Less than 1 %, of which were mostly poor frame fits to begin with.
Fit your needs? On average, it is more about commissions and revenue. Trivex is more expensive than CR39 and Poly, therefor raises the AVG sale. Higher AVG sale equates to higher spiffs/commissions. Perhaps not you specifically, but true throughout the industry. So, no, it is not a ridiculous statement. It is about fitting the patients' needs.
Defending cheaper and easier option? Again, no. I am just defending the consumers' needs. I am not disagreeing about the merits of Trivex. I am just saying that it is an over-hyped product.
No arguments about tribrid. There needs to be more competition by manufacturers to drive the price down before it can become more affordable to the average consumer.
I bend light. That is what I do.
I agree poly has improved over the decades.
But CR39 has not. In fact, its quality has decreased to the point that I will not use it unless I absolutely have to.
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