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Thread: " Trivex is naturally aspheric "

  1. #26
    What's up? drk's Avatar
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    I look at it this way:

    Trivex for it's mechanical properties: drills on low to medium power lenses.
    Trivex for its optical properties: people who are sensitive to chromatic aberration who's job can't be done in CR39 (very rare).
    Other than that, trivex is not "needed" (but is a great lens).

    1.67 is the "high" high index that we use. You can drill it. It's expensive but not crazy like 1.7+ indices. It's available in a jillion designs.

    1.6 is a "tweener" for me, and though I'm emotionally attached to it, I never use it because:

    Polycarbonate is great for just about everyone else. Any abbe issues (which are extremely rare, IMO) are very power-dependent, and if you switch up to 1.67 you have the same issues.

    So:
    Polycarb for everyone
    1.67 for the super-myopes or for the moderate power lenses in rimless
    1.5 for picky or cheapies
    1.53 for low power rimless or pickies that need a semi-rimless.

  2. #27
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    DrK, why not offer 1.6 to some of your poly patients? Do you forgoe it just to keep things simple?

  3. #28
    sub specie aeternitatis Pete Hanlin's Avatar
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    Again, nothing against Trivex, but wearer studies have found there is no appreciable difference in vision between poly and Trivex (unless you get >4.00D in power, in which case you are probably using 1.67 anyway). In cases where a patient seems to be having a non-adapt to polycarbonate, it usually has more to do with the surface quality of the lens than the material properties- because polycarbonate is the most challenging material to surface. In a finished lens, there should be no difference. Of course, in a FSV application most poly lenses will have some internal stress (because it is a thermal set material- like glass), but internal stress is not an aberration (and is not noticeable UNLESS you are dealing with a polarized lens).

    As mentioned, unless you have a lot of power abbe value isn't going to make much/any difference in your vision. Simply put, you have to have prism to have chromatic aberration (after all, the function of abbe value is to tell you how much chroma you are creating- by dividing the amount of prism by the abbe value). If you do the math (keeping in mind the eye itself has >1.00D of inherent chromatic aberration), there's not much difference between a material with an abbe of 31 and 44 unless you have a lot of power and are looking pretty far away from the OC. Another indication that abbe doesn't matter much is the same practitioner who claims no one can get used to poly will happily dispense 1.67 (which has pretty much the same abbe value) with no issues. When poly fails, it's due to surface quality- not abbe. Personally, I dispensed 1,000s of pairs of poly back when I worked as an optician and can count on two fingers the number of patients who had an issue with chromatic aberration.

    Additionally, Trivex has some disadvantages optically speaking (it has more haze, because the material itself is not as homogeneous as other materials). If you are super concerned with abbe, you should be using 1.50 or crown glass.

    As has also been mentioned, the one truly redeeming quality of Trivex is the fact that it has incredibly high tensile strength (i.e., it is very hard to "tear" Trivex). This makes it super for drill mounts, because it will "hide" poor mounting (even if the lab doesn't chamfer the holes, a Trivex lens isn't going to fail). Of course, 1.60 also has ridiculously high tensile strength- and it will be thinner than Trivex- so 1.60 makes a great material for drill mounts as well. Also, if you properly size and chamfer drill mount holes, you can pretty much use 1.50 and have a durable drill mount (I have a pair of polarized 1.50 drill mounts that I've beat around in for years with no issue).

    I know some practitioners love Trivex- and more power to them. However, optically speaking there's just not much of an argument to be made for the material. Even though PPG positioned it to be an "upgrade to 1.50," the role it ended up playing was to go up against poly (because if you're a manufacturer who has never invested in poly manufacturing capability, it makes a heck of a lot of sense to promote Trivex as an alternative). So dispense the heck out of Trivex- just don't use it for safety applications if you're including AR.
    Pete Hanlin, ABOM
    Vice President Professional Services
    Essilor of America

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

  4. #29
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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.
    +1 a sad reality and has become a frenzy of lies and self survival.

  5. #30
    What's up? drk's Avatar
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    Quote Originally Posted by Tallboy View Post
    DrK, why not offer 1.6 to some of your poly patients? Do you forgoe it just to keep things simple?
    I do believe the better MR-8(?) 1.6 probably kicks polycarbonate's sorry *** to the curb, but it's like you said.

    Generally, polycarb gets the job done, for less.

  6. #31
    Master OptiBoarder AngeHamm's Avatar
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    Quote Originally Posted by drk View Post
    I do believe the better MR-8(?) 1.6 probably kicks polycarbonate's sorry *** to the curb, but it's like you said.

    Generally, polycarb gets the job done, for less.
    And because it's cheaper on the wholesale side, it's the "upgrade" I can throw in for free when patients with no insurance benefit are investing in higher-end lens options like polarization, photochromics, AR, digital lens designs, etc. Instant patient happiness.
    I'm Andrew Hamm and I approve this message.

  7. #32
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    Quote Originally Posted by AngeHamm View Post
    And because it's cheaper on the wholesale side, it's the "upgrade" I can throw in for free when patients with no insurance benefit are investing in higher-end lens options like polarization, photochromics, AR, digital lens designs, etc. Instant patient happiness.
    This is absolutely true - especially for every type of lens other than flat top bifocals the upcharge is minimal. Heck sometimes I offer a "free" upgrade to poly because I don't want to edge CR lenses into a certain frame.I'm making more of an effort to let the patient make that decision to not use 1.6 or trivex these days than I used to though - if I don't offer they won't have the opportunity to say yes and try it.

  8. #33
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    As the founder of LenSync our prices are the same for trivex,1.6 and 1.67 in all lens types to ensure the best overall material is used. We put trivex at the top of the choices and question why you would offer anything else? There is no reason to use trivex if poly is available. Set up your lab for trivex and it is the best overall material that belongs on 90% of the RX's.

  9. #34
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    Quote Originally Posted by Craig View Post
    There is no reason to use trivex if poly is available.
    As the founder of LenSync I know you didn't mean this the way you typed it.

  10. #35
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    Quote Originally Posted by Pete Hanlin View Post
    Additionally, Trivex has some disadvantages optically speaking (it has more haze, because the material itself is not as homogeneous as other materials). If you are super concerned with abbe, you should be using 1.50 or crown glass.
    I meant to respond to this a month ago when I read it but I got busy. What is haze in relation to lenses and how is it different from the light dispersal inherent to low ABBE products?

    I know of Haze in regards to looking through a tube of oil or water, but is there an appreciable amount of this occuring in Trivex? Because Next to the CR39 lenses I cut (digital CR39 kicks ***, for those whom it is appropriate) the Trivex lenses seem awful crisp. Is it a problem that can occcur during casting of lenses - much like the weird junk that can appear in stock poly sometimes?

    Just wondering Pete, thanks!

  11. #36
    Manuf. Lens Surface Treatments
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    Redhot Jumper The manufacturer must perform the test for impact resistance ........................

    The manufacturer must perform the test for impact resistance (21 CFR 801.410(d)(1)). Manufacturer is defined under 21 CFR 820.3(o) and would include the person (or firm) who puts the lens in the form ready for its intended use or who alters the physical or chemical characteristics of the lens by grinding, heat treating, beveling, applying scratch resistant coating, applying anti-reflection coating, cutting, or other pertinent actions. Manufactures of all plastic lenses and non-prescription glass lenses may test at the uncut-finished or finished stage while glass prescription lenses must be tested at the finished stage. Retail laboratories that perform some or all of these processes are manufacturers. For the purpose of 21 CFR 801.410, the term "manufacturer" also includes a company that imports impact resistant lenses for eyeglasses, or who imports finished eyeglasses or sunglasses for resale. (21 CFR 801.410(g)

    See all of it:
    https://www.fda.gov/MedicalDevices/ucm070579.htm
    Last edited by Chris Ryser; 05-25-2017 at 01:32 AM.

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