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Thread: Understanding fitting guide for verifying progressives

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    Understanding fitting guide for verifying progressives

    I'm having difficulty verifying Zeiss HDV progressive lenses. (these are also transition lenses) When I verify the distance portion of these lenses should I find the focus of the lens when looking in the lensometer somewhere in the distance circle provided by the fitting guide for these lenses? The literature makes it clear to check the distance portion of the lens in this area but it doesn't specify where this will be when using the lensometer. I'm finding it much higher and considerably out from the fitting cross, or at "10:00" so to speak. Does this mean that progressives add intended prism in order to achieve their progressive power? There is no prescribed prism in the Rx.

    The cyl is a quarter diopter less than the Rx in both left and right lens. Does it make any difference at this stage when verifying if the lenses are HD or traditionally created? The guide I'm using is for this lens design.

    the original Rx : OD -.75 -1.00 172; OS -.75 -1.50 160 OC and mono PD both taken. 19 31.5 and 33 respectively
    Many thanks!

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    http://www.optiboard.com/forums/show...572#post529572

    Use the prescriber's written/typed Rx for verifying if the lab doesn't supply a compensated Rx.

    Hope this helps,

    Robert Martellaro
    Science is a way of trying not to fool yourself. - Richard P. Feynman

    Experience is the hardest teacher. She gives the test before the lesson.



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    I'm finding that the mires cross at a location way above the distance circle and off to the right on the right lens. Is that expected?
    Thanks for your input!

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    Quote Originally Posted by iokuok2 View Post
    I'm finding that the mires cross at a location way above the distance circle and off to the right on the right lens. Is that expected?
    Thanks for your input!
    It should be above the reference circle on a lens with minus power, maybe offset somewhat if the lens needed base down prism thinning. Very low dioptric values with oblique axes may move the mires in or out slightly at the distance reference point and is normal. There may be a small amount of prism at an oblique axis if it is a compensated lens, but that value should be under 0.50∆.

    When you verify minus lenses with much greater power in the 90 meridian, you'll need to use a prism ring to acquire the mires, and with low Abbe value materials, to make them clearer and distinct. Make sure you didn't leave a prism ring in place from a previous verification.

    In summary, with the Rx you posted, the mires should be slightly above the distance reference point and possibly decentered slightly but not significantly.

    Hope this helps,

    Robert Martellaro
    Science is a way of trying not to fool yourself. - Richard P. Feynman

    Experience is the hardest teacher. She gives the test before the lesson.



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    Master OptiBoarder lensgrinder's Avatar
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    Quote Originally Posted by iokuok2 View Post
    I'm having difficulty verifying Zeiss HDV progressive lenses. (these are also transition lenses) When I verify the distance portion of these lenses should I find the focus of the lens when looking in the lensometer somewhere in the distance circle provided by the fitting guide for these lenses? The literature makes it clear to check the distance portion of the lens in this area but it doesn't specify where this will be when using the lensometer. I'm finding it much higher and considerably out from the fitting cross, or at "10:00" so to speak. Does this mean that progressives add intended prism in order to achieve their progressive power? There is no prescribed prism in the Rx.

    The cyl is a quarter diopter less than the Rx in both left and right lens. Does it make any difference at this stage when verifying if the lenses are HD or traditionally created? The guide I'm using is for this lens design.

    the original Rx : OD -.75 -1.00 172; OS -.75 -1.50 160 OC and mono PD both taken. 19 31.5 and 33 respectively
    Many thanks!

    Keep in mind that the DRP is located about 9mm above the PRP. So prism will be induced when checking the distance power, the amount and direction will be dependent on the power. So where the mires end up in the lensmeter will be different for every Rx. I am not sure what you mean by considerably out from the fitting cross. Do you mean you see BO prism at the DRP? Do you see prism at the PRP?

    Did you receive a compensated ticket? Did you provide PoW measurements? 0.25 difference seem like a lot for that Rx in regards to compensation. That being said if you are able to induce about 1.0 D of prism in your lensmeter then you can get the mires clearer.

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    I know you said you are using the fitting guide but are you remarking the lenses with Zeiss's marking chart? Their lenses have a 6 drop which can be quite different than many other companies

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    As I recall all our lensometers reticle are also too large to get a truly accurate reading from the compensated ticket. But we can't see a .01D difference anyway!!!

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    Quote Originally Posted by lensgrinder View Post
    Keep in mind that the DRP is located about 9mm above the PRP. So prism will be induced when checking the distance power, the amount and direction will be dependent on the power. So where the mires end up in the lensmeter will be different for every Rx. I am not sure what you mean by considerably out from the fitting cross. Do you mean you see BO prism at the DRP? Do you see prism at the PRP?

    Did you receive a compensated ticket? Did you provide PoW measurements? 0.25 difference seem like a lot for that Rx in regards to compensation. That being said if you are able to induce about 1.0 D of prism in your lensmeter then you can get the mires clearer.
    Thank you for sharing this. It is very helpful.

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