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Thread: How to measure multifocals?

  1. #1
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    How to measure multifocals?

    I has notice that some ophthalmologist does not know how to measure a multifocal.
    I had one complaining that the lens had a unwanted prism. He was measuring the prisms where the far distance prescription is measures.

    Another complained that the far distance prescription was wrong. He was not measuring it where it has to be measured.

    The real fact is that measuring PAL is not as easy as measuring bifocals. It takes more time to locate the areas where the measurements should be made specially if they do not have the steaker for that multifocal.
    The message i want to send is that if you do not know how a multifocal should be measured or do not want to take the time to do it right then do not do it because you are telling the patient something that is not true.

    Is there a simple and generic guide about how to measure any multifocal made for people that do not know too much about optics ? I am going to talk to them and would like to give them the address where they can find more information that would reinforce my explanation and one of this address should be that guide i am looking for (if exist).

    Here in Panama there are no Opticians. We Optometrist can do by law the job of an Optometrist and the one of a Optician. So we have to deal whith prescritions made by ophthalmologist.

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    Gola,


    What you mentioned sound like classic examples of someone using an autolensometer. You'll get readings all over the board, and if there's a question, the optician will get the blame. After all, how can such an expensive instrument be wrong?

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    Ralph Drew said: "Nothing impresses the prescriber more than a computer print out of the lens specifications." "Doesn't matter whether the print out is accurate or not, just get a lensometer system that prints out the result and send it to the doctor."


    Chip

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    Quote Originally Posted by chip anderson
    Ralph Drew said: "Nothing impresses the prescriber more than a computer print out of the lens specifications." "Doesn't matter whether the print out is accurate or not, just get a lensometer system that prints out the result and send it to the doctor."


    Chip
    We use Humphrey La-350 and i think i could give to the patient a printout so he can show it to the Ophthalmologist.
    It seems to be a good idea. I will try it.

    Thanks

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    Quote Originally Posted by Johns
    Gola,


    What you mentioned sound like classic examples of someone using an autolensometer. You'll get readings all over the board, and if there's a question, the optician will get the blame. After all, how can such an expensive instrument be wrong?
    Johns,

    Don't know about yours, but my auto lensometer automatically locates the exact distance and near "sweet spots". Sorry to say it, but I could have a high school kid read the Rx . Gola's OMD problem sounds more like the Dr. just doesn't know how to read a VFL (probably in a manual lensometer).

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    [QUOTE=fjpod]Johns,

    Don't know about yours, but my auto lensometer automatically locates the exact distance and near "sweet spots". QUOTE]

    Mine too but it is important to check also the prism and this is done in what innovations call MRP or optical center. This spot is in the center of the almost invisible (more invisible the older you get) marks that multifocals has. Most of the time this marks are 34mm apart so in case you do not see one.

    Does you lensometer let you find this spot too.

    By the way, is there a easy way to find this almost invisible marks on the multifocal?
    I am 55 and sometimes need help from a younger person specially if the front surface has scratchs.

  7. #7
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    Quote Originally Posted by fjpod
    Johns,

    Don't know about yours, but my auto lensometer automatically locates the exact distance and near "sweet spots". Sorry to say it, but I could have a high school kid read the Rx . Gola's OMD problem sounds more like the Dr. just doesn't know how to read a VFL (probably in a manual lensometer).

    Ow!! That hurts ! I don't have, use, nor intend to ever own (except to resell) an autolensometer. Unfotunately, many offices use these instruments because their staffs are as well trained as the high school kid you mentioned above.

    And no, I'm not insulting everyone that uses them. Some offices that use them do know how to use manual lensometers, and use them for time savings. I'll put my 35 year old B&L 70 up against any lensometer. When I recently sold one of my offices, I substituted my B&L 70 for a much newer Marco -worth more to some folks, but not to me.

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    Blue Jumper No print..............

    Quote Originally Posted by Johns
    Ow!! That hurts !

    I'll put my 35 year old B&L 70 up against any lensometer. When I recently sold one of my offices, I substituted my B&L 70 for a much newer Marco -worth more to some folks, but not to me.
    I am totally with you...............just too bad the old B&L does not print.

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    Chris,


    The nice thing about them not printing is that you can give your findings in your own handwriting - that is, you are saying what you found, and not the machine. I've had MD tell me "Hey, that's what the lensometer found..."

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    You are right, for a experienced person, there are thinks you can see with the old B&L lensometer that can not see with the automatic one and i use the old one once in a while in some special cases.

    One advantage with automatics is that you have the same measurement no matter who is using it as far as he knows how to measure a lens. With those B&L, you needed to adjust it for each user and sometimes two persons did not came out with the same prescription while measuring the same lens.

    Lets take advantage of boths.

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    Quote Originally Posted by Johns
    Ow!! That hurts ! I don't have, use, nor intend to ever own (except to resell) an autolensometer. Unfotunately, many offices use these instruments because their staffs are as well trained as the high school kid you mentioned above.

    And no, I'm not insulting everyone that uses them. Some offices that use them do know how to use manual lensometers, and use them for time savings. I'll put my 35 year old B&L 70 up against any lensometer. When I recently sold one of my offices, I substituted my B&L 70 for a much newer Marco -worth more to some folks, but not to me.
    We mark up on manuals.
    But for checking lens powers we have the auto reading 100ths of a dioptre.
    Not that we work to a hundredth of a dioptre but it is nice to see exactly what we are making.

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    I had a lab that used an autolensometer and would send out the print outs. Problem is that the lab was doing really poor work. My jobs I was getting in were up to 10 degrees off axis. We had to always send the stuff back and get them to do it again (of course we do not deal with them anymore).

    Anyways, it made me furious when they sent the print out and my B&L was saying it was wrong.

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    Quote Originally Posted by For-Life
    I had a lab that used an autolensometer and would send out the print outs. Problem is that the lab was doing really poor work. My jobs I was getting in were up to 10 degrees off axis. We had to always send the stuff back and get them to do it again (of course we do not deal with them anymore).

    Anyways, it made me furious when they sent the print out and my B&L was saying it was wrong.
    They must have been turning the job til the foci was reading what they wanted it to say, probably hoping that you would take their word for it. Rather bad form.

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    Quote Originally Posted by For-Life
    I had a lab that used an autolensometer and would send out the print outs. Problem is that the lab was doing really poor work. My jobs I was getting in were up to 10 degrees off axis. We had to always send the stuff back and get them to do it again (of course we do not deal with them anymore).

    Anyways, it made me furious when they sent the print out and my B&L was saying it was wrong.
    its called seeing what you want to see, it is a widespread practice. If the operator does it long enough they believe the results too

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    Quote Originally Posted by QDO1
    its called seeing what you want to see, it is a widespread practice. If the operator does it long enough they believe the results too
    I would only trust the print from an auto if the prism is displayed and is 0.

    You can move the lens around and eventually you will see what you want to see. If the prism isnt displayed then the foci isn't necessarily reading the centre of the lens.

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    Quote Originally Posted by rsandr
    They must have been turning the job til the foci was reading what they wanted it to say, probably hoping that you would take their word for it. Rather bad form.
    the sad part about it all is how many stores do not check their work.

    Our store and another were talking about how bad this lab was, and another one was saying that they have not seen a problem. They get the slip so they assume it is right.

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    Okay...I went from an office that I did not have to use a lensometer to an office with a Humphrey lens analysor. I can use the old lensometer, but am at loss with this new one, any suggestions?:hammer:

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    Quote Originally Posted by Karenrp1956
    Okay...I went from an office that I did not have to use a lensometer to an office with a Humphrey lens analysor. I can use the old lensometer, but am at loss with this new one, any suggestions?:hammer:
    Did you ask for the manual of the lens analizer? If it is a La350 or La360, the manual is very descriptive.
    What is what you want to know specifically?

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    Checking a progressive, how do you notice a prism? The simple things are okay.

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    Your meaure prism at aproximately 3mm below the distance visual axis, if markings are still on the lens this would be at the cross(+).

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    Quote Originally Posted by chip anderson
    Your meaure prism at aproximately 3mm below the distance visual axis, if markings are still on the lens this would be at the cross(+).


    http://www.essilorha.com/fitting_guide.htm

    Here you have some instructions for the essilor panamic that may be valid for others too.
    3 is the optical center (meassure prism there) this spot is in the middle between lasser engraved circles 2 and 6. 17mm from 2 or 6 in case one of the
    lasser marks (2,6) are not present due to the descentration needed on a small frame size.


    The correct areas for readings are shown on this diagram. To recreate these markings, dot the laser engraved circles and trace over the lens diagram on the back of this guide - or use dispensing decal. Check engraved markings to verify lens product. 1 Fitting cross 2,6 Engraved circle 3 Optical Center 4 Abbreviated Add Power 5 Checking Distance Power 7 Engraved Logo

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    Standard Terms

    Referring to the graphic in the post below:

    1) Layout Reference Point (the fitting cross, in the case of a PAL).

    3) Prism Reference Point (the answer to the question at hand).

    5) Distance Reference Point

    and not labeled, the Near Reference Point (the circle identifying the area in which the near power should be measured).

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