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Thread: " Trivex is naturally aspheric "

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    Master OptiBoarder OptiBoard Silver Supporter ak47's Avatar
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    " Trivex is naturally aspheric "

    I've often seen this quote which I do not understand: "Trivex is naturally aspheric"

    Trivex is a material and aspheric is a design.

    Does anyone care to explain the quote and if it is true why labs offer spherical and aspheric versions?

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    Manuf. Lens Surface Treatments
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    Blue Jumper

    A sphere is a perfectly round geometrical object in three-dimensional space that is the surface ..... Inspherical trigonometry, angles are defined between great circles. Thus spherical trigonometry differs from ordinary trigonometry in many ...


    In photography, a lens assembly that includes an aspheric element is often called an aspherical lens. The asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce other optical aberrations such as astigmatism, compared to a simple lens.

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    Master OptiBoarder OptiBoard Gold Supporter
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    May I ask where you have often seen that quote? That is like saying dough is naturally in the shape of a pizza.

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    My Brain Hurts jpways's Avatar
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    Quote Originally Posted by Chris Ryser View Post
    A sphere is a perfectly round geometrical object in three-dimensional space that is the surface ..... Inspherical trigonometry, angles are defined between great circles. Thus spherical trigonometry differs from ordinary trigonometry in many ...


    In photography, a lens assembly that includes an aspheric element is often called an aspherical lens. The asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce other optical aberrations such as astigmatism, compared to a simple lens.
    That is like answering a question about someone looking for a blue frame and answering: Blue is the color that we associate with light with a wavelength of between 450 and 495 nanometers

    In answer to the actual question I always thought it was just a marketing ploy that allows lens manufacturers (and thus labs) to charge more

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    Eyes eastward... Uilleann's Avatar
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    I've heard the same from countless lens reps and lab rats. Referring to stock SV of course. *shrug*

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    Ghost in the OptiMachine Quince's Avatar
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    I know for certain that I have worked with spherical Trivex. I think Uilleann is on the right track with it being a stock reference though again, it can be made either way. There could be an attribute to the material that has some 'aspheric' property but it must be in reference to something other than the surface curvature.
    Have I told you today how much I hate poly?

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    Master OptiBoarder OptiBoard Gold Supporter
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    Quote Originally Posted by Quince View Post
    I know for certain that I have worked with spherical Trivex. I think Uilleann is on the right track with it being a stock reference though again, it can be made either way. There could be an attribute to the material that has some 'aspheric' property but it must be in reference to something other than the surface curvature.
    Yeah I mean I could order spherical trivex from Younger right now.

    Doesn't Asphericity directly describe an attribute of the surface curvature? This is 100% rep bull**** and I would laugh in their faces.

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    Eyes eastward... Uilleann's Avatar
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    Hey - without rep bullsh**, we wouldn't have any scary blue light "protection" lenses either! ;) Our industry is awash in it sadly. From PALs, to SV, to any manner of filter (FL-41 anyone?!), to frame material and design, to 2 pairs and a "free" eye exam starting at 59.95, to internet glasses being "exactly the same" as a quality pair from a B&M store, etc. etc. The list is, sadly, very long.

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    Master OptiBoarder OptiBoard Silver Supporter ak47's Avatar
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    I only see dough in the shape of pizza. and Benjamins.

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    Ghost in the OptiMachine Quince's Avatar
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    Quote Originally Posted by Uilleann View Post
    Hey - without rep bullsh**, we wouldn't have any scary blue light "protection" lenses either! ;) Our industry is awash in it sadly. From PALs, to SV, to any manner of filter (FL-41 anyone?!), to frame material and design, to 2 pairs and a "free" eye exam starting at 59.95, to internet glasses being "exactly the same" as a quality pair from a B&M store, etc. etc. The list is, sadly, very long.
    Deep breath! It can be discouraging sure, but the reason I decided to stay in optics was the ever changing tech and style. I get pretty upset with my reps when I hear "yada yada nanometers protect blah blah blah" and then the opposite from the other but hey, I'm taking it all with a grain of salt. They got their foot in the door but they are mostly just parakeets. Polly want some blue filter?
    Have I told you today how much I hate poly?

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    sub specie aeternitatis Pete Hanlin's Avatar
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    I hear a lot of good ones on a daily basis, but "Trivex is naturally aspheric" is a fresh one to me.

    Of course, I'd rather have a rep make the mistake of calling Trivex aspheric than have them make the mistake of calling it a safety lens.
    (Although uncoated Trivex is basically as impact resistant as poly, once you hard coat- and especially if you AR coat- it, it can lose quite a bit of its impact resistance...)
    Pete Hanlin, ABOM
    Vice President Professional Services
    Essilor of America

    http://linkedin.com/in/pete-hanlin-72a3a74

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    Master OptiBoarder OptiBoard Silver Supporter ak47's Avatar
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    Sorry Pete, this quote was mainly used 5-8 years ago before Essilor could go through their inventory of a trillion poly blanks and introduce Varilux in trivex...but I heard it again recently and got me thinking...

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    Quote Originally Posted by Pete Hanlin View Post
    Of course, I'd rather have a rep make the mistake of calling Trivex aspheric than have them make the mistake of calling it a safety lens.
    (Although uncoated Trivex is basically as impact resistant as poly, once you hard coat- and especially if you AR coat- it, it can lose quite a bit of its impact resistance...)
    I'd love to see some numbers on that, comparative to poly. Have a citation handy you can give us?

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    Ghost in the OptiMachine Quince's Avatar
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    I had not heard that before either... How much resistance does it lose? As in- should a safety trivex be thicker than poly?
    Have I told you today how much I hate poly?

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    Eyes eastward... Uilleann's Avatar
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    Safety CR (in a minus power) is a 3.0 center. Poly is a 2.0. Trivex is basically a blend of the two anyway right? So perhaps a 2.5 center? Not a massive difference at all for the majority of safety SRx's it would seem if so?

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    Ghost in the OptiMachine Quince's Avatar
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    I've always done 2.0 poly and trivex- 3.0 CR39 and mid-high index.

    http://www.esafetyinc.com/store/news...cement&nTerms=

    I also didn't know Rx over +3.00 only requires 2.5mm in low-impact materials.

    This has been a very educational thread! Lol
    Have I told you today how much I hate poly?

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    sub specie aeternitatis Pete Hanlin's Avatar
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    Just a disclaimer, Essilor manufactures lenses made of both Trivex (TREXA) and polycarbonate- and I'm happy to sell either material. However, safety lenses that have a MAR (multi-layer AR) should be made of polycarbonate- not Trivex.

    I base this on a study conducted at the University of Waterloo School of Optometry that was sponsored by a competitor (who at the time manufactured Trivex but not polycarbonate). The study concluded safety lenses should be made of poly if the wearer desires ARC. To be sure, Trivex lenses do meet the FDA standard for impact resistance and are safe at 3mm thick (and they are also less likely to "oilcan" than poly lenses). However, when Trivex lenses are AR coated they lose a significant % of impact resistance.

    The full version of the study to which I refer can be found at this link: http://onlinelibrary.wiley.com/doi/1...6.00013.x/full

    A quote from the study:
    The average impact speed for failure of the Phoenix [Trivex] lenses ranged from 50 to 62 m/s, which indicates that its impact resistance was closer to that of 3 mm uncoated CR39 than the 180 to 270 m/s range often quoted for polycarbonate.1,2 We confirmed qualitatively that polycarbonate lenses have a much higher impact resistance in that we were unable to break any 2 mm polycarbonate lenses with blunt missiles at the maximum speed of the apparatus, which was approximately 100 m/s.2

    And a quote from the conclusion:
    Our data confirm that multiple antireflection coatings significantly reduce the impact resistance of Phoenix [Trivex] lenses at both dress and industrial thicknesses. Phoenix spectacle lenses are a better alternative to CR39, however, multiple antireflection coated lenses should not be used in eye protectors for industry or sports, particularly at 2 mm centre thickness, in situations where there is a high risk of exposure to high energy impacts. If antireflection coated lenses are preferred by the patient, the best option remains polycarbonate despite its poorer Abbé number.

    Pete Hanlin, ABOM
    Vice President Professional Services
    Essilor of America

    http://linkedin.com/in/pete-hanlin-72a3a74

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    Quote Originally Posted by Pete Hanlin View Post

    Of course, I'd rather have a rep make the mistake of calling Trivex aspheric than have them make the mistake of calling it a safety lens.
    (Although uncoated Trivex is basically as impact resistant as poly, once you hard coat- and especially if you AR coat- it, it can lose quite a bit of its impact resistance...)
    So how does Trivex with AR compare with CR39 and high index lenses on impact resistance? I had assumed it was about as impact resistant as poly.

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    I've got to admit that our whole office "drank the kool-aid" on Trivex ~6 years ago. Now I'm starting to wonder how much of an appreciable difference there really is between it and poly and how much of the apparent benefits were just confirmation bias and halo effect.

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    Ghost in the OptiMachine Quince's Avatar
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    Quote Originally Posted by Browman View Post
    I've got to admit that our whole office "drank the kool-aid" on Trivex ~6 years ago. Now I'm starting to wonder how much of an appreciable difference there really is between it and poly and how much of the apparent benefits were just confirmation bias and halo effect.
    Poly=30 Abbe value
    Trivex=44 Abbe value

    No bias there, just stats.
    Have I told you today how much I hate poly?

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    Thank you Pete!

    (ak47, sorry for hijacking your thread---the OP has been put to bed, I think? Otherwise 30% of my business wouldn't even exist....)


    I assume Table 3 refers to 3mm CR-39. I wonder if there's a similar chart for CR-39s impact degradation with MAR as well? If it tracks with Trivex on this table, then I'm confused how industry articles published years after this study assert Trivex is at the top of the field with regard to impact resistance? Begs the question of industry production variables, if not the original PPG data.
    It is uncertain whether unmodified Trivex material has the same impact resistance characteristics. There may be slight differences in the performance of virgin Trivex compared to Phoenix. We anticipate that different coating materials and procedures have a larger effect on the impact resistance of finished lenses. This hypothesis is based on previous results with CR39 that showed considerable variability in impact speeds with different SR coatings....We anticipate that the Phoenix lenses will show a similar variability with different SR coatings.

    The study here addresses Ullian's intuition:
    Nevertheless, the 3 mm SR-MAR has an impact resistance that is essentially identical to that of the 2 mm SR lenses, suggesting that a decrease in impact resistance due to the addition of the MAR can be offset by a reasonable increase in centre thickness.
    But this study suggests Pheonix's best reach for poly performance is just to go 3mm uncoated.

    When I dispensed safety specs, I almost never let a patient opt for AR. The ARs available weren't too fancy anyway and never worth the effort. Trivex wasn't even on the menu, either.

    However, for general population use, sports use concerns me here. What's poly's performance range within the industry production array, for that matter? With which coats? Is there a difference per blank size & base curves?

    This thread mentions the same study. I'd hope someday we get to see the chart that OP was asking for.

    (Maybe ak would appreciate it if we took the discussion to that thread instead of loitering in his....) :P
    Last edited by Hayde; 04-27-2017 at 11:33 AM. Reason: grammar

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    Quote Originally Posted by Quince View Post
    Poly=30 Abbe value
    Trivex=44 Abbe value

    No bias there, just stats.
    Oh, I mean, I know about the properties of the lens... Just not certain, from a patient's perspective, how much of a difference there is. I mean, theoretically, if I took, say, 100 patients, and gave them each two pairs of identical frames to try on-- one with poly, one with trivex-- and asked them if they preferred one over the other or if there was no difference, how many would say "no difference"?

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    Ghost in the OptiMachine Quince's Avatar
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    Quote Originally Posted by Browman View Post
    Oh, I mean, I know about the properties of the lens... Just not certain, from a patient's perspective, how much of a difference there is. I mean, theoretically, if I took, say, 100 patients, and gave them each two pairs of identical frames to try on-- one with poly, one with trivex-- and asked them if they preferred one over the other or if there was no difference, how many would say "no difference"?
    That's valid. I couldn't tell you what percent would notice the difference. I've always been under the impression that the high the power (especially cyl) the more likely they can tell. But sure, if a lower power script wants a groove, I'm not going to push Trivex unless they have a history of not liking poly for whatever reason.

    I guess the same study could be preformed for 1.6 vs. 1.67- so on and so forth...
    Have I told you today how much I hate poly?

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    OptiWizard
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    Quote Originally Posted by Browman View Post
    I've got to admit that our whole office "drank the kool-aid" on Trivex ~6 years ago. Now I'm starting to wonder how much of an appreciable difference there really is between it and poly and how much of the apparent benefits were just confirmation bias and halo effect.
    We were in a similar situation. Trivex definitely has its place but most people aren't sensitive to the lower abbe of poly.

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    Master OptiBoarder OptiBoard Gold Supporter
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    I took a wait and see approach to trivex and now reccomend it to anyone who sits down and wants "the best lens" between -1.00 and -3.00 and +1.00 to about +5.00 or 6 frame dependent.

    Always use on drillmounts if possible cosmetically. I do a lot of 1.60 also and a decent amount of poly. I find trivex is the best lens for plus prescriptions, you can really make a super thin knife edge. If I don't offer 1.60 or Trivex it then I don't know if people want it, many more say yes than I originally thought.

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