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Thread: Help with high prism Rx

  1. #1
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    Question Help with high prism Rx

    Good afternoon,

    We have a customer in our Port Adelaide practice who has been prescribed a total of 36 dioptres of base in prism for near only (split equally between both eyes).

    Her full Rx is as follows:

    R.E. +2.00 / -1.25 X 180 2 base in distance

    L.E. +1.75 / -1.00 X 175 2 base in distance

    18 dioptres base in R & L for near only.

    Add +3.50

    Customer presently wears Franklin bi-focal with Fresnel prism on near portion, however this is not terribly successful as the Fresnel keeps peeling off.

    Can anyone suggest a lens design or a manufacturer that can produce such a prescription????


    Many thanks!

  2. #2
    Master OptiBoarder optical24/7's Avatar
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    IF you were to fabricate this it would still require a franklin design. Even if you were able to fit this patient in a 40mm dia. lens the add portion would be extremely thick at the nasal. This would create a huge ledge inducing a lot of reflection. I would personally use a FT 35 with 2 diopters base in, then (still) use a fresnel of 16 in the near only. If the patient is dislodging the fresnel they need better instructions on cleaning (or there may be a problem with the size of the prism. i.e. partially touching the frame upon application creating a gap in the seal.)

    If you wanted the fresnel to adhere more permantently you may experiment with a UV curing glue. (though I've never heard of this technique for fresnel's.)

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    @rsmith: Welcome to the forum!

    A question....Are you putting the fresnel on the front, or back of the lens?

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    Find someone that can make an inlaid prism seg for you. You should be able to get all the prism and a lot less thick. The only place I know of here in the US is Epic Lab. I was making them, but quit when I left the business.

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    One eye sees, the other feels. OptiBoard Gold Supporter
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    If you can saw one of these in half...

    http://www.fresnel-prism.com/product...cclusion-lens/

    Is there any chance that the near prism would be reduced if the near work was closer to the primary/straight ahead gaze? That might make in-the-lens prism practical, using SV readers or a high set segmented multifocal. Objects could be elevated with a reading stand. A separate distance/general purpose pair would be required.
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  6. #6
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    Wafer

    E. Mail me and I will send you pictures on how to make this as a Franklin bifocal.
    It's gonna be Ugly, Heavy and thick no matter what you do.
    Unless you can find a very old lab man optician who can make you a wafer prism segment and you use glass.

    Chip
    Last edited by chip anderson; 03-21-2011 at 06:03 PM. Reason: Alternative solution

  7. #7
    Underemployed Genius Jacqui's Avatar
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    Quote Originally Posted by chip anderson View Post
    Unless you can find a very old lab man optician who can make you a wafer prism segment and you use glass.

    Chip
    Could be a fun project :) :)

    The inlaid prism seg is shaped like a D seg and is inlaid into the lens. Even at 28 mm wide it is still gonna be thick.

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    Long time no post - Here's pair I did years ago...

    http://www.optiboard.com/forums/show...ighlight=mbabc

    Mark Babcock
    Krebs Optical
    Louisville, Ky

  9. #9
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    High prism

    Many thanks to all who replied to my query. My sincere apologies for not replying sooner but I'm still trying to find my way around the forum.

    We'll probably stick with the Franklin design + Fresnel stick-ons. We've done Franklins a few times over the years with good results. I agree with optical24/7 that better patient education is probably the key point here.

    As for front or back attachment of the Fresnels, I'm not sure as I haven't personally seen this customer. In the past I've always put them on the back, so I assume that's where it'll be.

    Thanks again!

    rsmith

  10. #10
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    Thanks Chip. I've been around for 30 years myself, and agree that if you need something unusual these days the modern labs either don't know what you're talking about or their machinery is unable to fabricate it. Says a lot about progress in our industry, doesn't it ??

    I'd love to see the pictures you have. Please forward them to me at rsmith@fsma.com.au

    Thanks again!

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