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Thread: optical calculator on aspheric and bi-aspheric lens

  1. #1
    Bad address email on file au's Avatar
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    Question optical calculator on aspheric and bi-aspheric lens

    Hi everyone, lots of optical calculator around, can I calculate the edge
    thickness between aspheric and bi-aspheric lens or freeform lens (single vision) when in different index ?

    Also when using calculator some index like 1.67 have MR8 and MR10, what is that mean ?

    many many thanks for any input !


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    Frances

    I HAVE A 16 YEAR OLD PATIENT WHO CONSTANTLY COMPLAINS OF HER LENSE MATERIAL...I HAVE PUT HER IN POLY AND TRIVEX FOR SAFETY REASONS, YET SHE STILL COMPLAINS OF "BOWL EFFECT". DO YOU HAVE ANY SUGESSTIONS FOR ME...BECAUSE I'M ALL LENSED OUT! THANKS FRANCES

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    Master OptiBoarder
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    Quote Originally Posted by frances View Post
    I HAVE A 16 YEAR OLD PATIENT WHO CONSTANTLY COMPLAINS OF HER LENSE MATERIAL...I HAVE PUT HER IN POLY AND TRIVEX FOR SAFETY REASONS, YET SHE STILL COMPLAINS OF "BOWL EFFECT". DO YOU HAVE ANY SUGESSTIONS FOR ME...BECAUSE I'M ALL LENSED OUT! THANKS FRANCES
    HAVE YOU TRIED...oh sorry, didn't mean to yell...have you tried checking the old base curves or the adjustment of older glasses?

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    ATO Member HarryChiling's Avatar
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    Quote Originally Posted by frances View Post
    I HAVE A 16 YEAR OLD PATIENT WHO CONSTANTLY COMPLAINS OF HER LENSE MATERIAL...I HAVE PUT HER IN POLY AND TRIVEX FOR SAFETY REASONS, YET SHE STILL COMPLAINS OF "BOWL EFFECT". DO YOU HAVE ANY SUGESSTIONS FOR ME...BECAUSE I'M ALL LENSED OUT! THANKS FRANCES
    Bowl effect, this is commonly attributed to distortion, not to be confused with marginal astigmatism that's an effect of progressive lenses that is often referred t as distortion. A lens that exhibits less increase in magnification awasy fom the optical axis would help. Here are some fitting suggestions that may help:

    Lens:

    Aspheric
    Low Base

    Frame:

    Minimal Vertex
    Eye position close to datum
    1st* HTML5 Tracer Software
    1st Mac Compatible Tracer Software
    1st Linux Compatible Tracer Software

    *Dave at OptiVision has a web based tracer integration package that's awesome.

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    Master OptiBoarder Darryl Meister's Avatar
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    Aspheric, Low Base
    Unfortunately, aspheric surfaces will reduce distortion, but flatter base curves will actually increase it, so the net distortion in aspheric lenses is typically comparable to the distortion produced by conventional lenses.

    I HAVE A 16 YEAR OLD PATIENT WHO CONSTANTLY COMPLAINS OF HER LENSE MATERIAL...I HAVE PUT HER IN POLY AND TRIVEX FOR SAFETY REASONS, YET SHE STILL COMPLAINS OF "BOWL EFFECT". DO YOU HAVE ANY SUGESSTIONS FOR ME...BECAUSE I'M ALL LENSED OUT! THANKS FRANCES
    Does she wear contact lenses regularly?

    With some high-index and polycarbonate lenses, the front curves are significantly flattened for cosmetics. If asphericity is used, the change in distortion is minimal. If a spherical lens design is used, however, the distortion can increase by up to 25% or more. In this case, using a spherical lens design with a steeper front curve will reduce distortion. And, as Harry pointed out, shortening the vertex distance and choosing a well fitting frame will also help minimize the effects of distortion.

    Hi everyone, lots of optical calculator around, can I calculate the edge thickness between aspheric and bi-aspheric lens or freeform lens (single vision) when in different index ?
    You might try this program.

    Also when using calculator some index like 1.67 have MR8 and MR10, what is that mean ?
    MR stands for Mitsui Resin, which is a popular line of high-index polyurethanes from Mitsui Chemicals used by many lens manufacturers. The specific technical data for each can be found at Material Reference Table.
    Darryl J. Meister, ABOM

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    Bad address email on file au's Avatar
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    Thank you very much Darryl Meister

    :cheers:

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