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Thread: Original style PALs

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    Original style PALs

    Please confirm my assumption first: original style PALs had their segment on the front side and the back was simply surfaced with a toric and cross curve like a single vision lens.


    Now… from that understanding, if a modern PAL has all of its primary curvature on the backside, then how does cylinder factor in at the reading. Or for that matter, what about cylinders that run directly along the progressive corridor?

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    Master OptiBoarder optical24/7's Avatar
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    1st question, yes, that’s how traditional PAL (and all lenses were surfaced).

    2nd question, it’s all in the software. Watch the video below to see a digital generator cuts a surface (you can skip to the 1:00 minute mark to see it milling/lathing the curve. Welcome to Optiboard.


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    When the progressive design is on the front and you add the Toric curve on the back the patient is looking thru a combination of both sets of curves. When you get a modern free form design the resultant curves that the patient was looking thru are created as a single surface on the back. End result the patient is looking thru the same series of curves. Fortunately you have the ability to offer many more options in design and customization when you are creating the end product.

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    Quote Originally Posted by lauraturner6223 View Post
    Please confirm my assumption first: original style PALs had their segment on the front side and the back was simply surfaced with a toric and cross curve like a single vision lens.
    True.

    Now… from that understanding, if a modern PAL has all of its primary curvature on the backside, then how does cylinder factor in at the reading. Or for that matter, what about cylinders that run directly along the progressive corridor?
    It depends on the orientation of the prescribed astigmatism, but in general it skews or deforms the shape of the progressive optics, and the surface astigmatism surrounding the umbilic, more so for oblique and high cylinder values. Tilt around the vertical and horizontal axes also induces errors. See the third figure in the document link below.

    https://www.2020mag.com/ce/the-optics-of-free-form

    Hope this helps,

    Robert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    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 lauraturner6223 View Post
    Please confirm my assumption first: original style PALs had their segment on the front side and the back was simply surfaced with a toric and cross curve like a single vision lens.


    Now… from that understanding, if a modern PAL has all of its primary curvature on the backside, then how does cylinder factor in at the reading. Or for that matter, what about cylinders that run directly along the progressive corridor?
    Dang!! I have always wondered this myself. It gets even trickier to think about if you consider dual surfaced PALs

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    You know what's interesting Laura? In my career I have met every single type of person (Opticina, OD, MD, ocularist, lab guy, rep, technician, CEOs), but I have never met or ever heard from somebody that has a degree in, I'm assuming, optical engineering. WHO ARE THE PEOPLE THAT ACTUALLY DESIGN THE LENSES AND WHY DO THEY NEVER COME OUT TO PLAY?!?!

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    Quote Originally Posted by Prentice Pro 9000 View Post
    You know what's interesting Laura? In my career I have met every single type of person (Opticina, OD, MD, ocularist, lab guy, rep, technician, CEOs), but I have never met or ever heard from somebody that has a degree in, I'm assuming, optical engineering. WHO ARE THE PEOPLE THAT ACTUALLY DESIGN THE LENSES AND WHY DO THEY NEVER COME OUT TO PLAY?!?!
    They most certainly DO!
    IOT has shared with us at OpticianWorks on numerous occasions and their people wrote the book Modern Ophthalmic Optics a few years ago.
    They have been very open in sharing access all the way to their top level engineers, mathematicians, physics and doctors.

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    Quote Originally Posted by John@OWDC View Post
    They most certainly DO!
    IOT has shared with us at OpticianWorks on numerous occasions and their people wrote the book Modern Ophthalmic Optics a few years ago.
    They have been very open in sharing access all the way to their top level engineers, mathematicians, physics and doctors.
    Thank you John.

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    Quote Originally Posted by Prentice Pro 9000 View Post
    Thank you John.
    Thou art welcome.

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    WHO ARE THE PEOPLE THAT ACTUALLY DESIGN THE LENSES AND WHY DO THEY NEVER COME OUT TO PLAY?!?!
    I think they are busy and as corporate employees would find our sandbox difficult to "play" in, as cats often briefly visit.

    That said try visiting the Hall of Fame thread and read everything by the late Titan of Zeiss Optics Darryl Meister. Be prepared for your head to explode with some of the advanced discussions.

    Meow

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    Quote Originally Posted by Uncle Fester View Post
    I think they are busy and as corporate employees would find our sandbox difficult to "play" in, as cats often briefly visit.

    That said try visiting the Hall of Fame thread and read everything by the late Titan of Zeiss Optics Darryl Meister. Be prepared for your head to explode with some of the advanced discussions.

    Meow
    Damn - Ya said a mouthful there.
    Ain't that the truth.

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    Quote Originally Posted by Uncle Fester View Post
    That said try visiting the Hall of Fame thread and read everything by the late Titan of Zeiss Optics Darryl Meister. Be prepared for your head to explode with some of the advanced discussions.
    I miss him. I learned so much from him. He was so smart and never looked down at anyone and was just happy to help.

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    He worked just down 95 from the school in Richmond. We would go down with each class and visit the Zeiss factory. They used to roll out the red carpet for us. I think I met him once or twice in passing. I have certainly used some of his material for the videos. Yep - I'd certainly place him firmly in the genius department. Or certainly a genius at making very complex concepts a little easier to understand.

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    Quote Originally Posted by John@OWDC View Post
    Or certainly a genius at making very complex concepts a little easier to understand.
    Yes! He was always willing to help and explained things in a way we normal people could understand it. I like to think I'm smart...but people like that make me feel dumb as a box of rocks! Genius. Definitely.

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    Quote Originally Posted by Prentice Pro 9000 View Post
    You know what's interesting Laura? In my career I have met every single type of person (Opticina, OD, MD, ocularist, lab guy, rep, technician, CEOs), but I have never met or ever heard from somebody that has a degree in, I'm assuming, optical engineering. WHO ARE THE PEOPLE THAT ACTUALLY DESIGN THE LENSES AND WHY DO THEY NEVER COME OUT TO PLAY?!?!
    As John said IOT is by far the most forthcoming with their lens design. You can get actual information from them about the lens design other than the marketing fluff. But at a certain point your eyes are going to glaze over with the math. Just looking at something rather simple like tilting a lens involves quite high level mathematics. If you have the knowledge, time, and inclination the material is out there. Even the book John mentioned Modern Ophthalmic Optics, which I own is rather dense for a dispensing optician.

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