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Thread: Problem Solving 101 ...

  1. #1
    Master OptiBoarder Joann Raytar's Avatar
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    Confused Problem Solving 101 ...

    A patient comes in with the following Rx and makes the following frame choice:
    • OD +7.00 -3.75 X 176 4D Base Out 2D Base Up
    • OS +7.00 -3.50 X 003 4D Base Out 2D Base Down
    • Wearing square frame: 45 eye, 64 frame PD, MRP is vertically on center, lens CT is 3.5 mm, power of old Rx only differs by -.25 in sphere power OS
    • Wants rectangular frame: 47 eye, 66 frame PD, MRP is vertically on center
    • Patients PD is 35.0 mm OU
    Problem:

    The patient wants to get as close as possible to the 3.5 CT that he is wearing. He loves the frame he has picked out and doesn't want to try and find something closer in size to what he was wearing. The patient is also a former lab tech so he understands a bit about why this may or may not happen.

    What lens would you folks choose? I decided on Spectralite ASL.

    This post has been edited to fix the typos resulting from typing it after a long week at work.

  2. #2
    opti-tipster harry a saake's Avatar
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    Question pd

    Jo, 37 or is that a typo?

  3. #3
    Master OptiBoarder Joann Raytar's Avatar
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    Doh ...

    actually, it is a typo. His PD is 35.0 mm OU (70mm). Thank you Harry!

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    Master OptiBoarder MVEYES's Avatar
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    Question Jo

    How did the Spectralite ASL work? Did you get your center thickness of 3.5?

    I just had a patient with a +6.50 -2.00 X 10 in a Flexon 84 frame 45-18 and a PD of 57. We got a lens from Pech Optical that was called Airwear Aspheric. It is a poly and has a center thickness of 4.4.



    :cheers: Jerry
    The mighty oak tree was once a little nut that held its ground

  5. #5
    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    Question Huh?

    The frame PD is 66; the patient's PD is 70; the MRP is on center?

    Is this a trick question?

  6. #6
    Master OptiBoarder Joann Raytar's Avatar
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    I didn't get it back yet.

    I figured I couldn't use one of the full aspheric lenses with this amount of prism so I chose Spectralite. Honestly, I didn't even consider poly as one of my choices; that may have worked too.

  7. #7
    Master OptiBoarder Joann Raytar's Avatar
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    Re: Huh?

    shanbaum said:
    The frame PD is 66; the patient's PD is 70; the MRP is on center?

    Is this a trick question?
    No trick here Robert. Our patient is picky and I don't doubt that he will actually pick up a set of calipers and check the CT. I am trying to get his 3.5 CT. I know there isn't a big difference in power or Frame PD but I think there is enough that if he holds frame against frame he will catch a difference in thickness.

  8. #8
    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    Exclamation Aha!

    Oh - VERTICALLY on center. Never mind.

  9. #9
    sub specie aeternitatis Pete Hanlin's Avatar
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    Did you send the frame out to the lab as well? Years ago (when I still worked in the lab side of things), I was amazed at how thin our Gerber SGX could get a Spectralite when we cribbed the lens to the perfect size. I'm sure the job will look as good as possible- hope it comes up to your patient's rather demanding specs!

    One "what if" question, though- wouldn't it help thinness to have a frame with a FPD larger than the patient's (I know that isn't practical in this case)? Even if the p.d. were equal to the f.p.d., the "knife edge" would be on the nasal edge (because of the base out prism). If the p.d. were smaller than the f.p.d., wouldn't the 4 b.o. be like a thinning prism? If the patient's p.d. was about 10-12mm smaller than the f.p.d., wouldn't this result in the thinnest possible lens in given this script?
    Pete Hanlin, ABOM
    Vice President Professional Services
    Essilor of America

    http://linkedin.com/in/pete-hanlin-72a3a74

  10. #10
    RETIRED JRS's Avatar
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    I'm just curious as to why you'd choose Spectralite (1.537 index) instead of a 1.56 or 1.60 lens.
    J. R. Smith


  11. #11
    Master OptiBoarder Joann Raytar's Avatar
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    Pete,

    I sent the frame out to the lab. I figured their tracer would give more accurate measurements before grinding then I could.

    JRS,

    I talked with our lab about it and decided on Spectralite because it was the only lens that they said they had that wasn't a full aspheric.

  12. #12
    RETIRED JRS's Avatar
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    I thought the ASL lens was a 'full' aspheric. By full, I mean aspheric across the whole front surface. I was under the impression that only Bristolite made a semi-aspheric.

    Learn something new here every day.
    J. R. Smith


  13. #13
    Master OptiBoarder Darryl Meister's Avatar
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    ASL comes in several varieties, but all are completely aspheric -- not "semi-aspheric." Regular semi-finished ASL, which covers plus and minus powers, is about a diopter or two flatter than conventional lenses. It is moderately aspheric, meaning that it needs to depart from a sphere by only a marginal amount since the design is not that flat. ASL+, which covers plus powers only, is several diopters flatter than conventional lenses. It is highly aspheric. (Flatter lens designs require more asphericity.) The finished lenses are also highly aspheric. The notion of a "semi-aspheric" is a little ambiguous. A lens surface is either spherical or it isn't. Designs that combine a zone of asphericity with a spherical zone are probably best described by some other term, like "zonal aspheric" or something.

    Best regards,
    Darryl
    Last edited by Darryl Meister; 03-02-2002 at 11:16 PM.

  14. #14
    RETIRED JRS's Avatar
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    That's what Bristolite calls it, right on the box "semi-aspheric". My recollection of the lens is - about 35mm of spherical center (17.5mm's out from GC), then a gradual decrease in curve to almost the edge. I do agree Darryl, zonal aspheric does make more sense.

    Given Jo's power from above, I would think the lab is talking ASL+ series for this job. Which I did believe to be aspheric.
    J. R. Smith


  15. #15
    Master OptiBoarder Darryl Meister's Avatar
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    JRS said:
    That's what Bristolite calls it, right on the box "semi-aspheric".
    Yep. Kind of like those toy boxes that say "some assembly required" on the outside, only for you to find out -- as you dump out 100+ completely unconnected pieces -- that what they really meant to say was, "Okay, you're going to need put the entire thing together, so get three power tools and a mechanical engineer from MIT." ;)

    Best regards,
    Darryl

    PS
    This is in no way meant to belittle Bristol's product, which I'm sure is a fine lens design. Just making a point about the use of more accurate and descriptive language.

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    Blue Jumper Spectralite vs. "hyperindex"

    Although it may be overkill, I'm just that kinka guy. Why not consider Hoya 1.71 with A/R coating?

  17. #17
    Master OptiBoarder Joann Raytar's Avatar
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    Well, the first set of lenses, Spectralite, came out at 5.0 and 5.5 CT. The second set we had made up, Seiko 1.67, came out at 4.0 and 4.5 CT. Combined with a very nice bevel placement by our lab, the second set of lenses were a keeper. The patient was extremely pleased.

    Good call JRS! I am glad I listened to you about using a different lens, albeit I was a bit late. Thank you! I have to learn to come here before ordering lenses.

  18. #18
    Bad address email on file stephanie's Avatar
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    Wink

    Jo I actually love that Seiko 1.67 have used it several times. It yielded some of the best looking gls with high rx's I have seen. Only problem is if you edge it really smells bad...so send em to the lab!! Actually I agree with sending stuff to the lab with rx's that high. You end up just ruining them on these finishing edgers. From what I understand Santinelli's are only supposed to grind +/-8.00D. Is this acurate information? Anyway I am glad you finally made you pt happy. It can be nerve racking sometimes but rewarding in the end. Or not depends on how you look at it!!

    Steph

  19. #19
    Master OptiBoarder Texas Ranger's Avatar
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    I was thinking more along Pete's line about having a frame with the fpd closer to the pt's pd so you weren't having to decenter OUT.

  20. #20
    Master OptiBoarder Joann Raytar's Avatar
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    The patients PD was 70 and the frame PD was 66.

    He loved this frame and begged us to try it even though we let him know that the differences in frame sizes would result in differences in lens thicknesses.

  21. #21
    Ophthalmic Optician
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    Jo,

    Thanks for posting your case. I had a similar situation this morning and hadn't decided which way to go. I think I know now !

    Johns

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