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Thread: Zeiss 1.74 aspheric !

  1. #1
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    Zeiss 1.74 aspheric !

    just curious to know ,why i see DIFFERENCE IN POWER on my Lensometer when i got my ordered lens from ZEISS !
    I Ordered them -8.75 ( which reads -8.50 on Lensometer ) & -9.00 DS/-0.75 DC ( which reads -8.75 DS/-1.25 on Lensometer )..........The Lens is SV ZEISS 1.74 AS !
    is it because of ASPHERIC DESIGN or this is just A MUFACTURING ERROR ?
    also ,i wann know ...........will it affect the VISION of the person if he will wear this ?

  2. #2
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    Greetings manoj_verma:

    Does your lensometer have capability of reading to nearest .12 or .02 reading? If so what is the reading then?

    As far as I am concerned, an aspheric SV lens should read as ordered.

    What is the lens CT measure at?

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    Underemployed Genius Jacqui's Avatar
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    Daryl Meister would be the "go to" person on this. He is a technician/engineer for Zeiss here in the US.

    Some lensometers have problems reading higher index lenses, I don't know the reason. I would try them on the patient and see if they work.
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  4. #4
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    If the lenses were optimised, the RX change would be included with the order. Otherwise, you probably need to reset the abbe value for you focimeter to match the 1.74 Check out Darryl Meister's website as suggested previously, especially -- http://www.opticampus.com/tools/materials.php

    Good luck

  5. #5
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    As MarySue noted, you should generally receive different "measurement values" with the job if the prescription was compensated or optically optimized at the distance reference point at all. At least in most regions. These are the new sphere, cylinder, and axis values that you should verify in a focimeter.

    While the lenses could indeed be off-power, you may want to confirm that you are using the correct settings on your focimeter before sending the lenses back if they were not compensated. If you are using an automatic focimeter, in particular, you should confirm that you are using the correct Abbe value and reference index settings. In some cases, the type of focimeter will also influence the power readings slightly.

    You should also ensure that you are measuring the lenses at the correct distance reference point. Because of the high power and asphericity of these lenses, measuring the lenses away from the correct power verification point will introduce legitimate power errors.
    Darryl J. Meister, ABOM

  6. #6
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    Most people read the front power with a lensometer, not the true back power. It is the back power that is important to the patient. The lens is within tolerance as you read it. Was it a digitally processed lens?

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