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Thread: Question about plus/minus cyclinder form

  1. #1
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    Question about plus/minus cyclinder form

    Hi Everyone,

    I have a question and I hope someone can help! I have asked many local Opticians here and they are not sure.

    I understand the concept of transposing... but what if one lens was made in minus cyclinder form and the other lens was in plus cylinder form? Would this be acceptable for the patient or cause issues?

    I apperciate your time and I hope this is not too simple of a question to post!

    Kpshann

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    They are still the same Rx no matter what form they are written in. It might confuse the dispenser but the patient would not see any differently.

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    Quote Originally Posted by kpshann View Post
    I have asked many local Opticians here and they are not sure.

    Now you are scaring me.

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    Why?

    Remember, in most states in the US, all it takes to call yourself an Optician is a pulse! Another example of why we MUST tighten up or education and training. A question such as this is simple, basic stuff and we continue to see posts like this. AHHHhHHHHHHHHHHH!

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    ABO-AC, NCLE-AC, LDO-NV bob_f_aboc's Avatar
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    kpshann,

    Check out this post. http://www.optiboard.com/forums/show...8&postcount=49

    Look for the pdf file link at the bottom, click on it, download it, and read it. Free education for opticians by opticians.

    If there is more that you want to know, keep posting on OptiBoard! We have some of the best optical minds in the world on here!

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    Quote Originally Posted by kpshann View Post
    Hi Everyone,

    I have a question and I hope someone can help! I have asked many local Opticians here and they are not sure.

    I understand the concept of transposing... but what if one lens was made in minus cyclinder form and the other lens was in plus cylinder form? Would this be acceptable for the patient or cause issues?

    I apperciate your time and I hope this is not too simple of a question to post!

    Kpshann
    Whether the Rx is written in plus cyl or minus doesn't affect how the lens is ground. Almost all lenses these days are minus cylinder, meaning that the toric curve is on the back (minus) side. Years ago, you saw lenses in plus cylinder form, meaning that the toric curve was on the front (plus) side. How you write it doesn't change how you surface it.

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    ATO Member HarryChiling's Avatar
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    Quote Originally Posted by finefocus View Post
    Whether the Rx is written in plus cyl or minus doesn't affect how the lens is ground. Almost all lenses these days are minus cylinder, meaning that the toric curve is on the back (minus) side. Years ago, you saw lenses in plus cylinder form, meaning that the toric curve was on the front (plus) side. How you write it doesn't change how you surface it.
    Great reply, I was just going to point out that the reason for minus surface form taking on greater acceptance is because the the tool doesn't need to be compensated for different thicknesses and the fact that plastic molded lenses had the segments and progressions on the front surface. Prior to plastic taking over the lions share of the market, glass lenses were traditionally worked on the front in plus cylinder form.

    The question is actually a pretty good one. And no the difference between the two ways of working the surface won't amount to any difference, just a negligible difference in magnification
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    Quote Originally Posted by HarryChiling View Post
    Great reply, I was just going to point out that the reason for minus surface form taking on greater acceptance is because the the tool doesn't need to be compensated for different

    That is the problem right there!

    Too many TOOLS not getting compensated!

    :cheers::cheers::cheers::cheers:;)

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    ATO Member HarryChiling's Avatar
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    Quote Originally Posted by Fezz View Post
    That is the problem right there!

    Too many TOOLS not getting compensated!

    :cheers::cheers::cheers::cheers:;)
    I know I don't get compensated enough but who you calling a tool? :finger::D
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    kpshann, please allow me to answer publicly. Yes, your student should transpose both eyes, but not really for any technical reason. If the OD is +1.00 -1.00 x 180 and the OS Pl +1.00 x 90, that's valid. However, since the refractionist wouldn't have written the Rx that way, everyone would assume a typo had occured. Ambiguity breeds mistakes. Your student probably didn't transpose, but simply set the lensometer axis wheel on 180, and therefore got minus cyl form. On the other lens, the axis wheel ended up at 90, which read in plus cyl form in the above example.

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    Not a problem today. But years ago this would mean that the cylinder was ground on the back of minus cylinder lens and on the front of the plus cylinder lens. Or that the practioner was trained in both, had two trial lens sets and liked a little variety in his life.

    Chip

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    Quote Originally Posted by kpshann View Post
    Hi Everyone,

    I have a question and I hope someone can help! I have asked many local Opticians here and they are not sure.

    I understand the concept of transposing... but what if one lens was made in minus cyclinder form and the other lens was in plus cylinder form? Would this be acceptable for the patient or cause issues?

    I apperciate your time and I hope this is not too simple of a question to post!

    Kpshann
    Plus cyl (front side cyl) lenses haven't been available since the mid-60's, although Zeiss continues to make them on special order.
    Optometrists use -cyl phoropters and Ophthalmologistrs use +cyl phoropters... they can't seem to agree, so the phoropter manufacturers continue to make both types.
    So that leaves a mistake in transposing, or a sloppy Dr.
    No optician should have to deal with an Rx where one eye is written in
    -cyl form while the fellow eye is written in +cyl form. Such a prescriber should be censured for bad form. :finger:

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    Quote Originally Posted by Fezz View Post
    That is the problem right there!

    Too many TOOLS not getting compensated!

    :cheers::cheers::cheers::cheers:;)
    Aren't they paying you enough??
    DragonlensmanWV N.A.O.L.
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    Quote Originally Posted by tmorse View Post
    Plus cyl (front side cyl) lenses haven't been available since the mid-60's, although Zeiss continues to make them on special order.
    Optometrists use -cyl phoropters and Ophthalmologistrs use +cyl phoropters... they can't seem to agree, so the phoropter manufacturers continue to make both types.
    So that leaves a mistake in transposing, or a sloppy Dr.
    No optician should have to deal with an Rx where one eye is written in
    -cyl form while the fellow eye is written in +cyl form. Such a prescriber should be censured for bad form. :finger:

    I've had to use some front side plus cylinder grind when I made some of my specials. Turn a 20D sv aspheric lenticular around, grind a myodisk on the plus side, then turn around and grind plus cyl on what used to be the back of the lens.
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    Quote Originally Posted by DragonLensmanWV View Post
    I've had to use some front side plus cylinder grind when I made some of my specials. Turn a 20D sv aspheric lenticular around, grind a myodisk on the plus side, then turn around and grind plus cyl on what used to be the back of the lens.
    I'm impressed!

    You must have been nervous on the drop ball test.:bbg:

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    ATO Member HarryChiling's Avatar
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    Quote Originally Posted by Uncle Fester View Post
    I'm impressed!

    You must have been nervous on the drop ball test.:bbg:
    Specialty is exempt.
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    Red flag

    Quote Originally Posted by kpshann View Post
    Hi Everyone,

    I have a question and I hope someone can help! I have asked many local Opticians here and they are not sure.

    I understand the concept of transposing... but what if one lens was made in minus cyclinder form and the other lens was in plus cylinder form? Would this be acceptable for the patient or cause issues?

    I apperciate your time and I hope this is not too simple of a question to post!

    Kpshann
    If I saw this on an Rx, I would call the prescriber for verification. Otherwise, I see a redo in the future.

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    Dragon, that's beautiful.

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