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Thread: Design of PALs

  1. #1
    The Hi-End PALs Specialist Bobie's Avatar
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    Design of PALs



    Hard Design
    Soft Design
    Symmetric
    Asymmetric

    Tell me if you like some more! :bbg:
    Last edited by Bobie; 12-09-2006 at 11:49 AM.
    " Life is too short to limit your vision"


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  2. #2
    Master OptiBoarder rinselberg's Avatar
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    I cannot see from the diagrams what it is that distinguishes between a "symmetric" design and an "asymmetric" design. I can see that from one diagram to the other, the power contours are different. But to me, both of those diagrams look equally symmetric or more likely - equally asymmetric - I think - WRT left lens v. right lens.

    Of course, as I often say, I'm just a layman who happens to engage in one of the related professions.


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    Last edited by rinselberg; 12-10-2006 at 01:30 PM.

  3. #3
    ATO Member HarryChiling's Avatar
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    The symetrical design can be used as both a right and a left lens, the progression corridor or umbilic of the lens shoots straight down the lens from the distance to the near. This means that when a optician slightly tilts the axis of the lens to accomadate for the near convergence the surface astigmatism nasally also gets tilted into the patients nasal line of sight. With the asymetric design the lens factors the convergence into the lens design. The symetrical design is a old design and I can't even tell you which ones if any still use that design.
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  4. #4
    sub specie aeternitatis Pete Hanlin's Avatar
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    As Harry noted, the first PALs were single mono-designs which were symmetrical. To produce a left and right lens, the technician would tilt the lens one way or the other (similar to how blended bifocals are currently laid out- there are no left/right- just one design that is rotated to achieve the inset).

    Today, PALs come in distinct left/right designs, but some lens manufacturers use "symmetry" to describe the characteristics of the design intended to produce binocularity. For example, Varilux Panamic was designed around a concept called "Global Design Management" that ensured both eyes viewed through similar optics when looking away from the center of the lens.

    Regarding contour plots in general- while they are intriguing (and may describe the general features of a design), they do not tend to have a correlation to wearer satisfaction with the design. That is, a PAL can "look pretty" on a contour plot and perform poorly in actual wearer tests- and vice versa.
    Pete Hanlin, ABOM
    Vice President Professional Services
    Essilor of America

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

  5. #5
    The Hi-End PALs Specialist Bobie's Avatar
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    Thanks for your comment , Pete
    I would like to learn more about the equalize function of Panamic's patent.
    After fitting many thousands of Panamic , my conclusion = great PALs , but in some case the Comfort wearer like Comfort more than Panamic and most of them are high ADD or high myope or anisometropia over 1.00D.
    Our Varilux Panamic Specialist Shop still open and 90 of PALs we sell is still Panamic.
    I study about Panamic from 2000 until now and it is one of the best semi-finished PALs for the new wearer. :bbg:
    " Life is too short to limit your vision"


    ISOPTIK : The Hi-End Eyeglasses Centre
    494 ERAWAN BANGKOK 4th floor
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    isoptik@gmail.com
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    :cheers:

  6. #6
    Master OptiBoarder Darryl Meister's Avatar
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    Most of those images were pulled from an article I wrote many years ago on the optics of progressive lenses, which explained the features and surface geometry associated with those plots. I have an updated piece available at http://www.optiboard.com/forums/showthread.php?t=20085, which also covers the same type of content.
    Darryl J. Meister, ABOM

  7. #7
    Bad address email on file Freedom's Avatar
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    Darryl , I like you article. THANK YOU.

  8. #8
    The Hi-End PALs Specialist Bobie's Avatar
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    Thank you for great article , Daryyl
    The picture that I post is from http://www.laramyk.com/learn/progressives_1.html
    " Fundamentals of Progressive Addition Lenses " by Daryyl Meister
    , and the updated piece of this article is much better.
    This article have been reference among O.D. in Thailand for many years.
    Great job , Darryl.
    :cheers:
    Last edited by Bobie; 12-12-2006 at 04:29 PM.
    " Life is too short to limit your vision"


    ISOPTIK : The Hi-End Eyeglasses Centre
    494 ERAWAN BANGKOK 4th floor
    Ratchaprasong , Bangkok , Thailand 10330
    isoptik@gmail.com
    www.isoptik.com
    Hotline & SMS : +66 81 538-4200
    Fax. : +66 2 251-3770

    :cheers:

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