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Thread: What other factors will affect the amount of stress patterns on polarised lenses?

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    What other factors will affect the amount of stress patterns on polarised lenses?

    Hi team!




    I wanted to ask everyone’s opinion on stress marks on polarised lenses.
    We know that stress marks are usually a byproduct of a tight lens mounting on the frame.


    What are some other factors that can affect the amount of stress marks?


    Lens index?
    Manufacturing way?
    Base curve?
    Bevel that was glazed on the lenses?


    Looking forwards to your responses!

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    None, except for tight lens mounting like you said and perhaps if the lens has warped or has been subjected to extremes of heat.

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    OptiBoard Professional Mauro.Airoldi's Avatar
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    there are many elements that cause stress on polarized lenses, certainly an incorrect fit and cut but not only. My experience is related to the construction and treatments of the RX.
    the polarized film is sometimes spread with excessive tension and this can already be seen at the semi-finished level.
    During the hard coat polymerization phases we sometimes have excessive temperatures that lead to tensions on the lens (the polarized film tends to expand in a different way depending on the axis)
    High refractive indices 1.6-1.67 are more sensitive to the defects mentioned above

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    Yes, Mauro is absolutely correct, there are many many issues which can affect the stress of a polarized lens. For example, Trilogy & Trivex typically have lower stress than say Hard Resin. One of the reasons for this is that Trilogy has less shrinkage than H/R during the casting process. The method by which poly polarized lenses are injection molded can also cause stress. Making a polarized lenses is the most difficult lens in the world to make...I am sure Mauro can also attest to that...and minimizing the final amount of the stress within the Mfg. made lens is a constant battle.

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    Guys, thank you very much for your answers, this is truly appreciated.

    Regarding the factors I can influence when glazing:

    Would a different lens to frame BC affect the amount of stress induced on the lens?

    Thanks again for your answers!
    S.

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    Quote Originally Posted by Stress View Post
    Guys, thank you very much for your answers, this is truly appreciated.

    Regarding the factors I can influence when glazing:
    Would a different lens to frame BC affect the amount of stress induced on the lens?
    S.

    The closer you can match lens shape to frame shape coupled with the lens bevel curvature to the frame front curve the better the fit will be both in lens retention while achieving the least amount of stress possible.

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    Quote Originally Posted by Plausible View Post
    The closer you can match lens shape to frame shape coupled with the lens bevel curvature to the frame front curve the better the fit will be both in lens retention while achieving the least amount of stress possible.
    +1

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    Thanks team!

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