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Thread: Fresnel Press-On prism

  1. #1
    Master OptiBoarder Grubendol's Avatar
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    Idea Fresnel Press-On prism

    Help! I've never worked with Press-On before, and I have a job coming across my bench where I'll have to put 9 base out, OU. I have ordered the prism, but I'm not sure how I put it on the lens so the patient can see properly.


    Any tips/help/suggestions?
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    Master OptiBoarder ikon44's Avatar
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    click on the link to find some tips on applying fresnel prisms



    hp://theoptom.com/viewtopic.php?t=1456&start=0&postdays=0&postorder=asc&highli ghttt=
    To find out what,s happening in the UK optical market:
    http://theOptom.com

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    Master OptiBoarder Grubendol's Avatar
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    thanks for the source, it's definitely helpful.

    I know this is a silly question, but how can you tell which way the prism is correcting by looking at it? I'd hate to do it wrong the first time.
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    OptiBoard Professional Ory's Avatar
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    Quote Originally Posted by Grubendol View Post
    thanks for the source, it's definitely helpful.

    I know this is a silly question, but how can you tell which way the prism is correcting by looking at it? I'd hate to do it wrong the first time.
    The lens carrier will have the word BASE on one side. This is the base! :D

    If you've already cut it, remember that the prism will displace things towards the apex. This should be very apparent when looking through a 9^ prism.

  5. #5
    Master OptiBoarder Grubendol's Avatar
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    Thanks mucho guys!
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    You can "feel" the ribs and figure out the base direction. Take your time. Make sure the lens is very clean, add a small drop of water to the backside of the lens, and apply the smooth side of prism to lens. Slowly work out the air bubbles, working from the center out. Let sit for a while before mounting into frame. I use a NEW straight edge razor and slowly run that around the back edge/circumference of the lens at a slight angle(like a bevel edge). Good luck.


    Fezz
    :cheers:

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    They do have instructions in the package.

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    Master OptiBoarder optigrrl's Avatar
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    First week working for an MD had to put Fresnels on a pt's lenses. Heck, I had only ever seen prism once - through a lensometer! Since then it's been a regular thing and I have it down pat:

    I first look at it thru the lensometer and move it into the correct base direction (and mark it with a pen, 'cause I forget!)

    Take the pt's lens out of the frame and center it on the fresnel. I squish it as flat on the back of the lens as I can, then I take a pair of thin, very sharp scissors and cut the prism to fit the lens.

    note - cut at an angle and try to cut the prism slightly smaller than the lens.

    I then put the lens back into the frame and wash the lens and prism thoroughly with soap and water. Rinse well, stick the prism on the lens and PAT dry with cotton, non-linty towel. While drying, I squish out the air bubbles.

    Viola! Perfect every time with almost no air bubbles or finger prints!

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    Master OptiBoarder LENNY's Avatar
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    Did you order one prism or two?

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    Master OptiBoarder optigrrl's Avatar
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    One. Although we now carry a small stock - 1, 2 and 3 diopters.

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    Ophthalmic Optician
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    It is really helpful to explain to the patient what their lenses, with the mounted prism, will look like, feel like, and how they should maintain them. When you explain to them what a 9D prism would look like if it were not a press on, they usually deal with it easily.

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    Master OptiBoarder optigrrl's Avatar
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    Good point, Johns.

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    Master OptiBoarder Clive Noble's Avatar
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    Hi Grubendol

    Forgive me for asking, and I'm not being critical, but you have written down in your personal title that you are a Dispensing Optician.... Did you not cover the subject of prisms at college.... or was it so long ago that you have forgotten?

    Good luck with the Fresnel and remember, with any prism, when you look through it. an object you are viewing will always be displaced in the opposite direction to the base..... so if you're looking at your computer screen and it appears to have floated upwards, you're holding the prism Base DOWN.

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    Master OptiBoarder optigrrl's Avatar
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    Clive Noble

    Hi Grubendol

    Forgive me for asking, and I'm not being critical, but you have written down in your personal title that you are a Dispensing Optician.... Did you not cover the subject of prisms at college.... or was it so long ago that you have forgotten?

    Hi Clive - we don't have a school for opticianry in AZ so I had to intern for 2 years. I worked in a luxury retail optical shop and can honestly say I never saw an rx for prism. Even though I passed the ABO and am now state licensed my knowledge was not practical. So when I went to work for an ophthalmologist and had to order fresnel I had to call someone to ask what that was...(this was before I discovered OB)

    Anyway, my point is that even though our state is licensed we don't (yet) offer proper instruction. You're basically on your own in terms of education. That's just a sad fact but the good news is that because of learned mentors those of us seeking higher learning can find the answers!

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    Ophthalmic Optician
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    Clive,

    We covered all types of prisms in school, but until you get "down and dirty" with them, you don't really know what to expect.

    Johns

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    Master OptiBoarder Grubendol's Avatar
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    Quote Originally Posted by Clive Noble View Post
    Hi Grubendol

    Forgive me for asking, and I'm not being critical, but you have written down in your personal title that you are a Dispensing Optician.... Did you not cover the subject of prisms at college.... or was it so long ago that you have forgotten?

    Good luck with the Fresnel and remember, with any prism, when you look through it. an object you are viewing will always be displaced in the opposite direction to the base..... so if you're looking at your computer screen and it appears to have floated upwards, you're holding the prism Base DOWN.

    I've been working in optical on and off since I was a junior in high school. I have a bachelors in Biology, but did not go to school to be a dispensing optician. I have about 12 years of experience in the industry, but have only been working in the lab regularly (managing it actually) since April of this year.

    I'm planning on taking the ABO either in November or May (probably May since I"m getting married in 5 weeks and don't have the time to devote to studying right now).
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    A few clues for those abissmaly ignorat on fresnel pasters

    Note:
    The product is a fresnel paster not fresnel prism.
    2nd. if the direction of the prism is lost in trimming, one can look at the edge of the paster, the fat side of the little triangles (prism) will be pointed toward the base (it is the base).
    Don't try to final mounting or eliminating all the bubbles until you have them trimmed and the spectacle lenses back in the frame, other wise you will ruin all your hard work when you re-assemble everything.
    Quality: No bubbles is accept able, a few here and there are not.
    3M who makes the things recommeds bubble elimination under water.
    If the paster is not smaller than the eyewire, you will get more bubbles as you try to smooth things out.
    Heat at least thus far in my experience doesn't help.
    You must have the lens, the paster, the frame and your hands immaculately clean, it's a ****** to try to get rid of small dirt particles under the lens, or small particles of the "trimmings".

    And that's Fresnel 101.

    Chip

    If the frame is very small you can sometimes get two lenses covered from one paster (still charge for two) if the prism required is equal on both sides of the job. And yes, still charge for two because you will mess enough of them up to eat the profit and labor time anyway.
    Last edited by chip anderson; 09-05-2006 at 01:35 PM. Reason: Another Tip

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    Practice makes perfect

    Hey Grubendol! I see all the info. you will need posted here so 'nuff said. This is something that will have to come with experience, try to get ahold of some "seconds" or partially used prisms from Fresnel to experiment with. Just remember the smooth side of the prism goes against the backside of the lens. Also, you may not get a request for the same power again but depending on the size of the frame and how you cut it you may have enough left over to use on another job some day, good luck, Chris.

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    Master OptiBoarder Grubendol's Avatar
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    Well the RX from the doctor calls for the fresnel only on the bottom half of the lens, so I should have extra, but I ordered two pairs just to be safe, considering it's my first.

    Thanks for all the excellent tips, thanks Chip for the 101. You guys have all been an incredibly resource in my relatively short time here.
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  20. #20
    Old Optician to New OD Aarlan's Avatar
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    Quote Originally Posted by chip anderson View Post
    Note:
    The product is a fresnel paster not fresnel prism. .

    chip,

    sorry for digging up an old thread, but I was searching for an unrelated topic and I came across your quote. I've never heard of the term fresnel paster, nor have I ever heard of anyone else using the term. Where did you get the term?

    I've seen the manufacturers (3M, and some old ones by OSG) refer to all the press ons as 'press on Optics', with prism, bifocals and aspheric lenses as options, but nowhere can I find that they're referred to as 'pasters'. The only exception is a few MD books where they refer to them as fresnel 'paste-on' prism...but it sounds as if a misguided concept by MDs that the prism must be pasted on the lens, as opposed to pressed on.

    When they were first applied, before some of the more advanced plastics was there a need to actually apply optical paste or adhesive? If so, then the term 'paster' would have been more appropriate, but now there is no adhesive necessary, so it seems that 'press-on prism' is in fact the more appropriate term.



    AA

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    Quote Originally Posted by Fezz View Post
    You can "feel" the ribs and figure out the base direction. Take your time. Make sure the lens is very clean, add a small drop of water to the backside of the lens, and apply the smooth side of prism to lens. Slowly work out the air bubbles, working from the center out. Let sit for a while before mounting into frame. I use a NEW straight edge razor and slowly run that around the back edge/circumference of the lens at a slight angle(like a bevel edge). Good luck.


    Fezz
    :cheers:
    I like a disposable scalpel - even sharper, and a handle which makes it easy to cut the edge of the press-on INSIDE the edge of the lens, which is to say, SLIGHTLY smaller - you can't beat a telephone book as a cutting platform - plop down the press-on, ridges down, lay the lens on top and slice away.

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    For the term Fresnel Paster you have to be old. When first introduced they were Fresnel Pasters.

    Somewhat like the front of an ophthalmic frame is a chassis, not a "front part."

    For trimming them industrial single edge razor blades are excellent, just don't use a dull one. They come in packages of a hundred for a reason.


    Chip

  23. #23
    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    I align it to the proper direction, stick it on the front of the lens, then hit it with the hand edger to cut it exactly the shape of the lens. Then I hold it all under water for final application. Can't get a bubble under it if it's all underwater.
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    Only problem with an exact fit (as opposed to somewhat undersize) is you are going to bump the edge on the frame and get air.

    Chip

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    Master OptiBoarder Ginster's Avatar
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    Wave

    I gotta try doing the submersion technique, always just rubbed out the air bubbles. I have to use the lensometer as well, I always get turned around wth the directions, don't know why, my brain is missing something.:hammer:

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