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Thread: Revising Seg Adjustments for Anisometrope with Vertical Prism

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    Revising Seg Adjustments for Anisometrope with Vertical Prism

    Hail, paragons of wizardry and virtue! Would you please double check me?

    Rx:
    -0.25 +0.25 105 1.50D BI/6.00D BU 20/30-2
    -5.00 +0.75 160 1.50D BI/6.00D BD 20/60
    Add: +3.00


    Line bifocals FT28
    OS slab off
    Raw seg measurements: 12.5/13.0

    My bible tells me to adjust segs .3mm per diopter of vertical prism towards the apex, so ordinarily I’d order segs at 10.7/14.8 (or 11/15 and tap the nosepads up at dispense.)

    Say the OS FT segment line shares the demarcation line the slab-off, then shouldn’t I leave that calculation alone?

    Or do I need to be nervous that the image in the seg is getting some 4D of Base-Up treatment and I need to shove that OS seg back down to a 10.7/13.6 (or 11/14 with the bilateral nosepad adjustment?)

    Or is it some arcane bit of quantum entanglement that gives me a whole new number in between?

    Thanks for your help!
    Last edited by Hayde; 05-20-2016 at 01:53 PM. Reason: clarity

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    Quote Originally Posted by Hayde View Post
    Hail, paragons of wizardry and virtue! Would you please double check me?

    Rx:
    -0.25 +0.25 105 1.50D BI/6.00D BU 20/30-2
    -5.00 +0.75 160 1.50D BI/6.00D BD 20/60
    Add: +3.00


    Line bifocals FT28
    OS slab off
    Raw seg measurements: 12.5/13.0

    My bible tells me to adjust segs .3mm per diopter of vertical prism towards the apex, so ordinarily I’d order segs at 10.7/14.8 (or 11/15 and tap the nosepads up at dispense.)

    Say the OS FT segment line shares the demarcation line the slab-off, then shouldn’t I leave that calculation alone?

    Or do I need to be nervous that the image in the seg is getting some 4D of Base-Up treatment and I need to shove that OS seg back down to a 10.7/13.6 (or 11/14 with the bilateral nosepad adjustment?)

    Or is it some arcane bit of quantum entanglement that gives me a whole new number in between?

    Thanks for your help!
    Hello Hayde. I see a lot of these types of RXs also. Hopefully this resolves your client's diplopia.

    .3mm is a good rule of thumb; lowering the right segment to 11mm and raising the left to 15mm looks good. One might want to mark the lens and confirm with a 12∆ (8 + 4) trial lens(es). Place the OCs on the primary gaze, or 1mm to at the most 2mm below.


    The slab line should be coincident with the left segment. Use a little less prism than the calculations called for, that is, if you calculate 4.5∆, order 4∆ BU in the left, and use Trivex for safety (right eye) and for less chromatic aberration. Moreover, one might also decide to put more of the prescribed prism in the left eye to keep the chromatic aberration from disturbing the vision in the right eye, although it will probably make little difference with 20/30-. I had some concern that we might be introducing VI with the segment height disparity, but I now think that the OC and segment will travel together, along with the eye's visual axis. I'll have to think about that one some more! Cheers.
    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
    Hello Hayde. I see a lot of these types of RXs also. Hopefully this resolves your client's diplopia.

    .3mm is a good rule of thumb; lowering the right segment to 11mm and raising the left to 15mm looks good. One might want to mark the lens and confirm with a 12∆ (8 + 4) trial lens(es). Place the OCs on the primary gaze, or 1mm to at the most 2mm below.


    The slab line should be coincident with the left segment. Use a little less prism than the calculations called for, that is, if you calculate 4.5∆, order 4∆ BU in the left, and use Trivex for safety (right eye) and for less chromatic aberration. Moreover, one might also decide to put more of the prescribed prism in the left eye to keep the chromatic aberration from disturbing the vision in the right eye, although it will probably make little difference with 20/30-. I had some concern that we might be introducing VI with the segment height disparity, but I now think that the OC and segment will travel together, along with the eye's visual axis. I'll have to think about that one some more! Cheers.
    Good to chat again Robert, thanks for all your help. I'm looking forward to hearing any thoughts you come up with.

    Agreed that Trivex is ideal for this patient. (It's such a default choice for me I forget to even mention it!)

    I'll keep you posted on the results.

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    Master OptiBoarder MakeOptics's Avatar
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    I'll add a quick and dirty trick to avoid parallax when blocking, flip your lenses over and mark them on the back surface, for FT's and PAL's mark the engravings or the edges of the flat top with a marker. Now when blocking you can just block to your marks and the lenses will line up on inspection.
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    Quote Originally Posted by MakeOptics View Post
    I'll add a quick and dirty trick to avoid parallax when blocking, flip your lenses over and mark them on the back surface, for FT's and PAL's mark the engravings or the edges of the flat top with a marker. Now when blocking you can just block to your marks and the lenses will line up on inspection.
    Reminds me of an embarrassing, tangential story I'll now share with the world!

    I got a pair of polarized PALs back from the lab. Dotted them up as fastidiously as ever. I color in the whole circle very carefully so when I dot the cross there's no drift based on clumsy mis-sized dots bouncing around inside the fitting chart circles. High wrap lenses--so I carefully place each lens on the fitting chart so the reference circles are equidistant from it. Steady check of alignment from each dot...Bang--got the crosses. Flip the lenses back to the front size so I can carefully place the pd stick on the lens to measure again avoiding parallax. I'm a hot-snot optician, don't you know?

    Big flunk--narrow PD. Send it back to lab. They call me back the next day to politely and professionally tell me that while they're willing to remake it, they think it's already pretty darn close to perfect. I scratch my head and take their word for it--have 'em send it back so I can take a second look.

    Job returns, I re-dot the PALs, and then it dawns on me...these high wrap lenses have some significant thickness. Significant enough that the dots I put on the back side of the lens are inset from where the fitting cross would be on the Front side of the lens, had I bothered to dot the Fronts looking straight down the lens centers after I dotted the backs of lenses!

    I write a contrite email apology to the lab acknowledging my error and painfully detailing my omission.

    It seems to me the embarrassing stories are the lessons I learn the best! Deep impact craters of the ego make the best shrines of learning....


    We now resume waiting for the patient of this thread to report in....

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    Master OptiBoarder MakeOptics's Avatar
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    Quote Originally Posted by Hayde View Post
    Reminds me of an embarrassing, tangential story I'll now share with the world!

    I got a pair of polarized PALs back from the lab. Dotted them up as fastidiously as ever. I color in the whole circle very carefully so when I dot the cross there's no drift based on clumsy mis-sized dots bouncing around inside the fitting chart circles. High wrap lenses--so I carefully place each lens on the fitting chart so the reference circles are equidistant from it. Steady check of alignment from each dot...Bang--got the crosses. Flip the lenses back to the front size so I can carefully place the pd stick on the lens to measure again avoiding parallax. I'm a hot-snot optician, don't you know?

    Big flunk--narrow PD. Send it back to lab. They call me back the next day to politely and professionally tell me that while they're willing to remake it, they think it's already pretty darn close to perfect. I scratch my head and take their word for it--have 'em send it back so I can take a second look.

    Job returns, I re-dot the PALs, and then it dawns on me...these high wrap lenses have some significant thickness. Significant enough that the dots I put on the back side of the lens are inset from where the fitting cross would be on the Front side of the lens, had I bothered to dot the Fronts looking straight down the lens centers after I dotted the backs of lenses!

    I write a contrite email apology to the lab acknowledging my error and painfully detailing my omission.

    It seems to me the embarrassing stories are the lessons I learn the best! Deep impact craters of the ego make the best shrines of learning....


    We now resume waiting for the patient of this thread to report in....
    I love that story, I make lot's of mistakes too. We take risks, we make mistakes, and the world goes round. I appreciate hearing you admitted to it and learned from it. I have been discouraged from admitting mistakes, the vast majority view mistakes as a fault but like you I take that as learning experiences. The more I admit to the more vigilant I become and the better intuition I have for the next scenario. Best this I read this morning.
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    Quote Originally Posted by MakeOptics View Post
    I love that story, I make lot's of mistakes too. We take risks, we make mistakes, and the world goes round. I appreciate hearing you admitted to it and learned from it. I have been discouraged from admitting mistakes, the vast majority view mistakes as a fault but like you I take that as learning experiences. The more I admit to the more vigilant I become and the better intuition I have for the next scenario. Best this I read this morning.
    I agree completely! (Even Spock learns by doing.) I was told by my first boss in Optics, 'if you strive for excellence and fail, you're only mediocre. So strive for perfection, and when you fail you might still be excellent.' Haven't met a decent colleague who didn't suffer from perfectionism, but the pretense of being perfect makes for a rather silly professional culture. Average opticians learn from their own mistakes, good ones also try their best to learn from the mistakes of others, the best ones are effective educators who make good opticians better.

    Speaking of...

    Robert, after 3 weeks of successful wear, the patient is very happy. Thanks for the assist! I am amazed he's good to go without an Rx revision considering the difficulty of his refraction navigating through compound medical conditions. Clearly, the patient was blessed with an amazing doc (MD even!) who took a considerable amount of time nailing it down. Even if success like this on the first draft probably required a little luck, I'm very pleased the lens fulfillment was up to the task.

    I really appreciate y'all taking the time to comb through the order with me.

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    Your welcome, and a huge thanks for the follow-up.

    BTW, check out my new signature line- it's one that I've used it in the past, and pretty much sums up what you and MakeOptics have been saying.
    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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    Master OptiBoarder RIMLESS's Avatar
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    Quote Originally Posted by Hayde View Post
    I agree completely! (Even Spock learns by doing.) I was told by my first boss in Optics, 'if you strive for excellence and fail, you're only mediocre. So strive for perfection, and when you fail you might still be excellent.' Haven't met a decent colleague who didn't suffer from perfectionism, but the pretense of being perfect makes for a rather silly professional culture

    Nice concept but theses days I say " don't let perfect ruin good enough"
    90% of everything is crap...except for crap, because crap is 100% crap

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    Quote Originally Posted by RIMLESS View Post
    Nice concept but theses days I say " don't let perfect ruin good enough"
    One of my engineer clients said: "Robert, perfect is good enough." He was kidding of course. Mostly.
    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
    One of my engineer clients said: "Robert, perfect is good enough." He was kidding of course. Mostly.

    Gotta love the engineers :)
    90% of everything is crap...except for crap, because crap is 100% crap

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    I mark the center of the block so I can double check parallax before I cut it. Brooks and Riley study reccomends .3 mm adjustment for every diopter of vertical prism prescribed opposite the base direction. I've used it and it works.

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    And engineers are the worst.

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    The other days I googled "why are engineers so..." and the results were boring, weird, arrogant, and cheap. I almost fell off my stool.

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    Quote Originally Posted by ThePinkRanger View Post
    The other days I googled "why are engineers so..." and the results were boring, weird, arrogant, and cheap. I almost fell off my stool.
    Bahahahaha

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