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Thread: How do I use a Fresnel stick-on prism?

  1. #1
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    How do I use a Fresnel stick-on prism?

    I figured it would come with directions, but the only directions were for how to clean the lens! I have absolutely no idea how I'm supposed to use it. My customer is already wearing progressives with 3.5 base out o.u. and his doctor wants to see if he can tolerate an additional 3 base out on the left eye. The package shows a picture of someone cutting the lens to the shape of the frame and applying it with water, but surely there's more to it than that.

    This is a first for me in forty years in the business! I will greatly appreciate your help!

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    Cut the prism how you want it. Typically the size of a ft 28 bifocal area.

    Get a bowl of warm water and dip the prism piece into the water for a few minutes. Place it on the backside of the lens and squeeze it down.

    It should stay in place.
    Last edited by TylerOpticians; 11-06-2015 at 06:54 PM.

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    So it doesn't cover the whole lens? How do I know where to put it? I'm sorry to sound so stupid!

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    It depends on the patient and the prism you are wanting to induce and which lens you are doing.

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    Quote Originally Posted by VHB View Post
    So it doesn't cover the whole lens? How do I know where to put it? I'm sorry to sound so stupid!
    Disregard the 7x28 bifocal comment (really, there is no such thing as a 7x28 bifocal, and if the poster would read your post, nothing at all about a multifocal). From your description, it should cover the whole lens. Remove the recieving lens from the frame and clean it THOROUGHLY and make sure the Fresnel is clean as well. Submerge both in water and simply press them together (smooth side of Fresnel against back side of lens), making sure the prism base is OUT and the lines are completely vertical, not tilted. Remove them from water and squeeze out any air bubbles. Then take a sharp blade, scalpel or xacto knife and carefully trim the excess material from the Fresnel, angling the blade to make a nice bevel cut that's thinnest on the outer edge. Then take it off and reinsert the lens into the frame, submerge the whole thing again and squeegie it again, and there you have it, just like Hillary did after her concussion.

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    The base of the prism is marked on the side align the lines so they are perpendicular to the 180 line, the base going out on the entire inside surface of the lens. I take the lens out to do this. Cut around the edge of the lens with a slight angle, do that none of the prism overhangs the lens edge. Then take the cleaned lens and prism and dunk into warm water, squeeze out all of the air bubbles and let it set. Dab the lenses dry and it should be good to go.

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    Master OptiBoarder rbaker's Avatar
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    Follow directions on packaging.

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    Quote Originally Posted by rbaker View Post
    Follow directions on packaging.
    True, and those will probably include a warning about being careful not to slice your fingers...

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    Master OptiBoarder OptiBoard Silver Supporter SharonB's Avatar
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    I have found it more valuable to use CL (rigid) wetting solution rather than water.... it makes the Fresnel adhere better.
    Lost and confused in an optical wonderland!

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    rbaker: that's my point--there were no directions!

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    CME4SPECS and Dr. Bill Stacy--Thank you both so much! That's exactly the information that I needed! Hugs and kisses to you both!

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    1. Determine which eye has better acuity. If both have the same, determine which eye is dominant. You'll want to apply it to the opposite eye. (Prism by itself, along with the material Fresnel's are made of induce higher LCA's and will drop acuity in that eye. Don't take it away from the better eye.)

    2. If you have compound prism (both vertical and horizontal components ) Do not use two Fresnel's. (one direction in one eye, the other direction in the other eye) for the same reason listed in #1.

    3. With compound prism, figure the resultant prism ( P² = H² +V ² √) then it's orientation/axis ( Tan ¹ = V/H )

    4. Once you have the prism direction, place your lens on a protractor and make two marks on the lens front 90 degrees opposite the direction of prism orientation. ( by marking the lens 90 degrees opposite of direction you can use the lines on the Fresnel to align with your marks on the lens front.)

    5. Clean both lens back and Fresnel's smooth side, dry. Orient the Fresnel on the back lens surface. (do this dry so the Fresnel doesn't move around).

    6. Use scissors to trim around the lens, cutting about 2-3mm's from the lens edge.

    7. While still dry, hold the lens and Fresnel together in the middle tightly while you use a new razor to trim excess off. tilt the razor about 45 degrees. If the lens go into a plastic or metal frame you'll want to make sure you trim it well away from the bevel. If the frame contacts the Fresnel it will usually want to lift off the lens at that point.

    8. Once fully trimmed dry, it's time to apply it. There are several ways, one is to submerge both lens and Fresnel fully into a bowl of water, brush any small air bubbles off the two, press together, remove from the water and keep compressing with a paper towel or cleaning cloth. The Fresnel my have moved while doing all of this so check it prior to fully drying it. You can still move it slightly until it is centered and away from the lens edge or bevel.

    9. Alternative to water is alcohol. You don't need to submerge it, just pour some into the concave side up. Press the Fresnel down from the center letting the alcohol run off as doing so. Press and dry and orient the same as #8.


    10. Re-insert lens in frame. Carefully clean the lens (pat dry only the Fresnel side.) Be sure to go over cleaning instructions with your patient. Until the water between the Fresnel and lens evaporates, the prism can become dislodged easily. Let the patient know that tiny air bubbles may show up over the 1st day or so. It's just the water evaporating and will go away soon.


    That's why I prefer to use alcohol applying Fresnel's. It dehydrates faster than water. I hope this helps, good luck!

  13. #13
    Master OptiBoarder rbaker's Avatar
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    Quote Originally Posted by VHB View Post
    rbaker: that's my point--there were no directions!
    "The package shows a picture of someone cutting the lens to the shape of the frame and applying it with water, but surely there's more to it than that."

    No, that's all there is to it. It is that simple, particularly for someone with forty years in the trenches!

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    Quote Originally Posted by optical24/7 View Post
    1. Determine which eye has better acuity. If both have the same, determine which eye is dominant. You'll want to apply it to the opposite eye. (Prism by itself, along with the material Fresnel's are made of induce higher LCA's and will drop acuity in that eye. Don't take it away from the better eye.)

    10. Re-insert lens in frame.
    On # 1 if you are going to switch the prism from the prescribed side to the other, if it's got any vertical component, don't forget to change that vertical prism by 90 degrees.

    On #10, I like to insert the lens alone first into the frame esp if any heat is involved, but also because you might need to do a little more trimming if the Fresnel contacts any part of the frame.

    Otherwise, a good recipe.

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    Quote Originally Posted by Dr. Bill Stacy View Post
    On # 1 if you are going to switch the prism from the prescribed side to the other, if it's got any vertical component, don't forget to change that vertical prism by 90 degrees.

    .
    Yep, failed to mention that if it's prescribed BU-OD you'd apply BD of putting the prism on the OS. Good catch!

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    Thanks, everyone. The doctor specified using the Fresnel on the left lens. And, mercifully, it isn't a compound prism!

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    Quote Originally Posted by SharonB View Post
    I have found it more valuable to use CL (rigid) wetting solution rather than water.... it makes the Fresnel adhere better.
    +1

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    Quote Originally Posted by VHB View Post
    Thanks, everyone. The doctor specified using the Fresnel on the left lens. And, mercifully, it isn't a compound prism!
    http://www.opticampus.com/tools/compounding.php

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    Master OptiBoarder optical24/7's Avatar
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    Quote Originally Posted by Uncle Fester View Post

    That's cheating!

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    Quote Originally Posted by SharonB View Post
    I have found it more valuable to use CL (rigid) wetting solution rather than water.... it makes the Fresnel adhere better.
    I was taught 40 years ago to clean them this way, but water to apply. When I switched from a bead heater to a hilco air, I put it in there on air only to dry it.

  21. #21
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    The instructions from 3M/Fresnel that I remember was to clean both surfaces with a hard lens cleaner, typically LC65 or Lobob, then a light, steady stream of water between surfaces as it's applied from corner to corner or nasal to temporal depending on the ocular curve, or as desired. Don't forget to check the final product before dispense. Consider surfacing the prism for better optics.
    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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    Quote Originally Posted by Robert Martellaro View Post
    . Consider surfacing the prism for better optics.
    Of course. The only possible reason for a Fresnel is a temporary reduction/elimination of diplopia and/or a test run to see if it actually works. I recommend no more than 1 or 2 weeks. If still good at that point, grind it in...

    Oh, and sorry, I think a permanent Fresnel is probably warranted in high prisms, like 10 P.D. or more, although in a small frame more than 10 might be successfully surfaced.

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    Master OptiBoarder CCGREEN's Avatar
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    I'm amazed that VHB got 40 years in before ever touching a fresnel. Hats off to you.
    I have spent half my 35 years with OMD's so I have done a few fresnel's.
    And I prefer to use alcohol on them.

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    Quote Originally Posted by optical24/7 View Post
    That's cheating!
    If you ain't cheatin' you ain't tryin'!

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    Quote Originally Posted by CCGREEN View Post
    I'm amazed that VHB got 40 years in before ever touching a fresnel. Hats off to you.
    I have spent half my 35 years with OMD's so I have done a few fresnel's.
    And I prefer to use alcohol on them.

    In my 40 + years, one thing has amazed me is how little O.D.s and M.D.s seem to prescribe prism at all. I'm thinking maybe they don't quite get the binocular vision coursework we got back in the day. One doc I know decided to take out the prism (4^ base out o.u.) because he didn't think it was doing much.

    Of course the patient who had been happy as a clam got instant diplopia that persisted for the entire time he was encouraged to "give it a try". What part of binocular vision aren't they getting taught?

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