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Thread: Aspheric SV lenses and heights

  1. #1
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    Aspheric SV lenses and heights

    Hi all,

    I am new to Optiboard and Im looking for some help with my technical studies.

    If an aspheric SV lens is dispensed and heights are taken, but upon sending to the manufacturer the heights have to be moved to datum in order to cut out on the largest available diameter...what are the implications of this for the px?

  2. #2
    One eye sees, the other feels. OptiBoard Gold Supporter
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    Quote Originally Posted by Spectacles View Post
    Hi all,

    I am new to Optiboard and Im looking for some help with my technical studies.

    If an aspheric SV lens is dispensed and heights are taken, but upon sending to the manufacturer the heights have to be moved to datum in order to cut out on the largest available diameter...what are the implications of this for the px?
    Welcome to OB.

    Mispositioning will result in oblique astigmatism and power error off-axis, similar to using an incorrect base curve, with the error dependent on the degree of mispositioning, lens power, and the p-value of the asphericity.

    Semi-finished front aspherics should be fit following Martin's Rule for tilt, and free-form back aspheric/atoric designs should be fit according to instructions provided by the lens manufacturer, typically providing the pupil heights on a preadjusted eyeglass frame.

    Workarounds include introducing thinning (yoked) prism , using spherical lenses with higher values for pantoscopic tilt, a different lens brand and/or material, a different frame that positions the lenses optimally, etc.

    Hope this helps,

    Robert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

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