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Thread: What's the formula...

  1. #1
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    What's the formula...

    Hi everybody,

    I need help with 2 matters pleaseeee!

    1) I was just wondering if anyone remembers the formula for combining 2 sphero-cylinder lenses which their axises are not 90 to each other, for example:

    +1.00 -2.00 x45
    and
    +2.00 -1.50 x90

    2) why there is usually a prism mounted in most progressive (PAL) lenses.. ? I called the lab today and they said it's usually the outcome of grinding.. is there a better explanation for that?

    Many Thanks everyone

  2. #2
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    Question#1

    Our very own Ultra-Talented, Harry Chiling offered this tid bit in another forum! Great stuff!

    http://www.optiboard.com/forums/showthread.php?t=23751

    Hope that helps.

    You may want to check out a website from one of our other scary smart members, Darryl Meister. It has all sorts of optical calculators.

    www.opticampus.com

    Another great sight with formulas is by another Optiboarder, theDude.

    www.opticiansfreind.com

    TheDude is also part of those ultra smart, way cool, extremely good looking, and gifted group of Opticians over at the Association of Technical Opticians.

    www.technicalopticians.com

    :cheers::cheers::cheers::cheers::cheers:
    Last edited by Fezz; 08-21-2007 at 10:22 AM.

  3. #3
    Ophthalmic Optician OptiBoard Gold Supporter
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    Quote Originally Posted by Fezz View Post
    TheDude is also part of those ultra smart, way cool, extremely good looking, and gifted group of Opticians over at the Association of Technical Opticians.

    www.technicalopticians.com

    :cheers::cheers::cheers::cheers::cheers:
    ...not to mention, a very sharp dresser!
    Ophthalmic Optician, Society to Advance Opticianry

  4. #4
    Master OptiBoarder
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    LOL!!!

    :cheers::cheers::cheers:




    Question#2

    Darryl Meister has a fantastic article on progressives on his website. The part your looking for is at the end of the article, intitled "Prism Thinning"

    http://www.opticampus.com/cecourse.p...essive_lenses/

  5. #5
    Master OptiBoarder OptiBoard Silver Supporter rdcoach5's Avatar
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    Estimate is quicker

    Quote Originally Posted by Berno View Post
    Hi everybody,

    I need help with 2 matters pleaseeee!

    1) I was just wondering if anyone remembers the formula for combining 2 sphero-cylinder lenses which their axises are not 90 to each other, for example:

    +1.00 -2.00 x45
    and
    +2.00 -1.50 x90

    2) why there is usually a prism mounted in most progressive (PAL) lenses.. ? I called the lab today and they said it's usually the outcome of grinding.. is there a better explanation for that?

    Many Thanks everyone
    Right lens power at 45 degrees is +1.00 .The cylinder power is -1.00 at 135 degrees. But at 45 degrees from prescribed axis , the power is half of the prescribed cylinder, or Plano at 90 degrees.Suppose the axis was 67 degrees. The cylinder power is roughly 1/4 of prescribed power or -0.50 Diop. The power at 90 degrees is +0.50. The reason for prism in most progressives is to thin down the lens.

  6. #6
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    not sure but eh

    +1.00 -2.00 x45 and +2.00 -1.50 x90 +1.00 -2.00 x45 [.] +2.00 -1.50 x 90 +150 -1.50 x45 -2.00 +2.00 x90 +2.50 -3.50 x45 pl+.50 x90 not too sure about it but cross cylinders sorta, i never dealt with the sphere park always the cyl. not sure if it helps and im not too sure but i call it cross pollunation.

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