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Thread: PD Tolerance chart

  1. #1
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    Question PD Tolerance chart

    Hello professionals, I want information about pd tolerance chart. I try find this search engine but dont work. I have questions about because lab supplier write somethings that I believe that is not good. ex. sphere 0.25 13.5mm +/- is in standars. Can you tell where I can find this chart of standars?


    Thanks,


    Melvin

  2. #2
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    Don't know about a chart but you can easily compute:

    1mm @ 10diopters of power=1 diopter prism
    10mm @ 1 diopter of power=1 diopter of prism
    5mm @ 5 diopter of power= 2.5 diopters of prism.
    10mm @ 2 diopters of power=2 diopters of prism
    1mm @ 2 diopters of prism =.2 diopters of prism
    horizontal prism, patient might tolerate a diopter.
    verticle prism, none is good, patient might tolerate 1/2 diopter.

    Chip

    Also do not confuse diopters of prism (which our stuff is measured in) with degrees of prism which we do not use in the opthalmic business and they are similar but not quite the same.

  3. #3
    Rising Star
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    Hi,


    I'm not sure where to find a copy of this....Opticians Association of Canada may help www.opticians.ca

    In Canada we use an ANZI Standards Tolerance Chart.....states how much prism is allowed horizontally

    ie <-0.75 cyl allowed (0.25 ??) diopters of prism(? chart not infront of me ?)

    therefore you would use your prism formula to calculate

    prism = Fxc

    F= power at 180
    C= amount of cm off by ie. want od. 30 mm, receive 28 mm = 2 mm = .2 cm

    I think this is correct (someone correct me if i'm wrong.....haven't been doing optical formulas in a long while)

  4. #4
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    Tolerance

    The American National Standards Institute will probvide those answers. It is based on prism, and can be found using Prentice's Rule. The ANSI standards can be purchased on line (a general search will provide the URL), or your lab should be able tp provide one for you. The downloaded version from ANSI costs about $15.00.

    Good luck!

  5. #5
    It also involves total power in the given meridian... hence it is hard to make a chart for

    -0.50 -5.00 x 80

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