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Thread: Why do Shamir PALs lower the distance minus so much sometimes AKA NEW YEARS BALL

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    Redhot Jumper Why do Shamir PALs lower the distance minus so much sometimes AKA NEW YEARS BALL

    Hi guys, I use the Auto III and Auto II all the time, or at least more than occasionally. I take great measurements.

    Can anyone explain to me why the minus in this RX was dropped so substantially? What is Shamir thinking here? Patient is complaining of blurry distance.

    OD -2.00
    OS -2.50

    Add 2.00

    BVD:15 PNT 7 Wrap 9.5

    Compensated RX is
    OD -1.89
    OS -2.38
    ADD 193


    What do those measurements have to do with a .12 shift in diopters?

    Granted the patient was seeing with their old glasses
    OD -2.25
    OS -2.75

    OD 20/20
    OS 20/20 -1

    So I'm not sure WHY the prescribing OD decided to drop the distance minus, just to make my life hell. They also prescribed a "Computer RX" of -.25 and -.75, luckily I recalculated THAT one before ordering it.

    If anyone has any reason why shamir would drop the minus bay an 1/8 of a diopter when the lens is sitting FURTHER from the eye than in the exam room what is the deal?

    K THX BYE and happy new year!

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    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    Did you leave off any compensated cyl vales?

    B

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    You say that you are using Auto II and Auto III but no mention of Attitude. Did you provide POW measurements. I would throw an extra -0.25/flipper over the lenses to determine if the distance refraction is the culprit or not. It also sounds like you may require a greater understanding of the product you are selling, I would contact your regional lens rep for assistance.
    I didn't attend the funeral, but I sent a nice letter saying I approved of it. Mark Twain

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    Quote Originally Posted by Tallboy View Post
    Hi guys, I use the Auto III and Auto II all the time, or at least more than occasionally. I take great measurements.

    Can anyone explain to me why the minus in this RX was dropped so substantially? What is Shamir thinking here? Patient is complaining of blurry distance.

    OD -2.00
    OS -2.50

    Add 2.00

    BVD:15 PNT 7 Wrap 9.5

    Compensated RX is
    OD -1.89
    OS -2.38
    ADD 193


    What do those measurements have to do with a .12 shift in diopters?

    Granted the patient was seeing with their old glasses
    OD -2.25
    OS -2.75
    Any tilt and wrap will cause an increase in the Rx(plus or minus) and induce some cylinder.
    Working through Keating's tilt and wrap equations you will find that this compensation is in line, probably with 0.08 induced cylinder, as Barry mentioned.
    Were they wearing a traditional SF lens before?
    My guess is it has to do with the change in Rx from LY.

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    One eye sees, the other feels OptiBoard Silver Supporter
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    From a D. Meister Optiboard post.

    Martin's equations cannot be used directly to determine the compensated prescription necessary to correct for the effects of lens tilt. It can only be used to determine the effective prescription produced by lens tilt. I derived a couple of simple expressions though, for spherical powers anyway, that will give you the compensated prescription (Rx to order):

    Scomp = Srx / [1 + (sin^2 T) / (2 * n)]
    Ccomp = -Scomp * sin^2 T

    where Scomp is the compensated sphere Rx, Ccomp is the compensated cylinider Rx, Srx is the original sphere Rx, T is the angle of lens tilt, and n is the refractive index of the lens material. For pantoscopic (vertical) tilt, the resultant axis would be 180. For face-form (horizontal) tilt, the resultant axis would be 090.

    2. Martin's original expressions cannot be used to determine the prescription changes induced when prescribed cylinder power is present. Though there are forms of these equations that will work with cylinders at either axis 180 or axis 090. More complex mathematics are required for oblique cylinders, or when both pantoscopic and face-form tilts are involved. However, there are several articles available that present these calculations in detail (from authors such as Blendowske and Keating).
    More...

    http://opticampus.com/files/memo_on_...on_of_wear.pdf

    Go to page #6.
    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 Tallboy View Post
    Hi guys, I use the Auto III and Auto II all the time, or at least more than occasionally. I take great measurements.

    Can anyone explain to me why the minus in this RX was dropped so substantially? What is Shamir thinking here? Patient is complaining of blurry distance.

    OD -2.00
    OS -2.50

    Add 2.00

    BVD:15 PNT 7 Wrap 9.5

    Compensated RX is
    OD -1.89
    OS -2.38
    ADD 193


    What do those measurements have to do with a .12 shift in diopters?

    Granted the patient was seeing with their old glasses
    OD -2.25
    OS -2.75

    OD 20/20
    OS 20/20 -1

    So I'm not sure WHY the prescribing OD decided to drop the distance minus, just to make my life hell. They also prescribed a "Computer RX" of -.25 and -.75, luckily I recalculated THAT one before ordering it.

    If anyone has any reason why shamir would drop the minus bay an 1/8 of a diopter when the lens is sitting FURTHER from the eye than in the exam room what is the deal?

    K THX BYE and happy new year!
    I would reject/reorder this job again..........I'll wager the result will be different, the second time around.

    You are dealing with enough drop in minus with this person, which needs coaching(if it's their first drop in myopia) as it stands. Lab result interference is the last thing you need.
    Eyes wide open

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    Quote Originally Posted by Paul Smith LDO View Post
    You say that you are using Auto II and Auto III but no mention of Attitude. Did you provide POW measurements. I would throw an extra -0.25/flipper over the lenses to determine if the distance refraction is the culprit or not. It also sounds like you may require a greater understanding of the product you are selling, I would contact your regional lens rep for assistance.
    I didn't mention Attitude because the lens was ordered as I mentioned. I do use Attitudes for some wrap jobs.
    I provided the POW measurements I listed in my post.

    My understanding of the product is just fine - and the Optical Minds of Optiboard are MUCH better informed than Shamir Reps when it comes to Opthalmic optics. I use a compensated IOT lens as my main lens and never had this issue before.

    I also believe it is the drop in myopia that is the issue. I am not sure why the OD would alter the DVO RX when the patient sees 20/20 out of it... that is a huge red flag to me - Do any ODs on here know why a DR would alter an RX for a patient who is seeing 20/20 out of it? After this post I went and calculated the wrap and tilt and the RX was similar... so maybe it is definitely the Drs. RX

    Quote Originally Posted by Barry Santini View Post
    Did you leave off any compensated cyl vales?

    B
    There were no compensated cyl values provided RX

    Quote Originally Posted by lensgrinder View Post
    Any tilt and wrap will cause an increase in the Rx(plus or minus) and induce some cylinder.
    Working through Keating's tilt and wrap equations you will find that this compensation is in line, probably with 0.08 induced cylinder, as Barry mentioned.
    Were they wearing a traditional SF lens before?
    My guess is it has to do with the change in Rx from LY.
    You are probably right... this OD habitually seems to underminus presbyopic patients. Should I just stay away from compensated lenses for this OD's RXs? This happens to me with him much more than other ODs.

    Quote Originally Posted by uncut View Post
    I would reject/reorder this job again..........I'll wager the result will be different, the second time around.

    You are dealing with enough drop in minus with this person, which needs coaching(if it's their first drop in myopia) as it stands. Lab result interference is the last thing you need.
    This is how I feel... how can I celebrate POW compensated lenses when they give me results like this?


    PS thanks to Daryl Meister's teachings I learned all about this stuff, as well as Barry and Robert et al. I just hate when it backfires. Its like the symptoms caused by the lessened RX power are worsened when compensated, where they would have been fine if not compensated. UGH.

  8. #8
    One eye sees, the other feels OptiBoard Silver Supporter
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    Quote Originally Posted by Tallboy View Post
    ... this OD habitually seems to underminus presbyopic patients. Should I just stay away from compensated lenses for this OD's RXs? This happens to me with him much more than other ODs.
    That could be due to equipment malfunction, or an improperly configured lane. Give the prescriber a heads-up.

    Keep in mind that one of the goals of compensation is to match the intended powers of the prescribed Rx when the lenses in the frame are not oriented in the same as they are in the phoropter, that is, tilted around the horizontal or vertical axis. The differences are small though, unless there are high tilts values along with moderate to high dioptric values.
    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 Tallboy View Post
    I didn't mention Attitude because the lens was ordered as I mentioned. I do use Attitudes for some wrap jobs.
    I provided the POW measurements I listed in my post.

    My understanding of the product is just fine - and the Optical Minds of Optiboard are MUCH better informed than Shamir Reps when it comes to Opthalmic optics. I use a compensated IOT lens as my main lens and never had this issue before.

    I also believe it is the drop in myopia that is the issue. I am not sure why the OD would alter the DVO RX when the patient sees 20/20 out of it... that is a huge red flag to me - Do any ODs on here know why a DR would alter an RX for a patient who is seeing 20/20 out of it? After this post I went and calculated the wrap and tilt and the RX was similar... so maybe it is definitely the Drs. RX


    There were no compensated cyl values provided RX


    You are probably right... this OD habitually seems to underminus presbyopic patients. Should I just stay away from compensated lenses for this OD's RXs? This happens to me with him much more than other ODs.


    This is how I feel... how can I celebrate POW compensated lenses when they give me results like this?


    PS thanks to Daryl Meister's teachings I learned all about this stuff, as well as Barry and Robert et al. I just hate when it backfires. Its like the symptoms caused by the lessened RX power are worsened when compensated, where they would have been fine if not compensated. UGH.
    Practice fluidity.......POW is not a selfie....but a moving target with variables.

    Ask yourself........what if?
    1)what if I have to increase vertex for eyelash touch.
    2)what if I have to increase/decrease panto by 3 or more degrees.......or with a variable panto frame like Adidas shield temple products.
    3 what is the wearer's preferential wear position is different than measured.("I want to wear it here!)
    4)what if the Rx is drastically changed over previous.
    About the Rx: my opinion is.........


    Myopes may read 20/13 with proper correction, and merely20/20 or average if they are farsighted(over-plussed).
    Eyes wide open

  10. #10
    Master OptiBoarder lensgrinder's Avatar
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    Quote Originally Posted by Tallboy View Post
    There were no compensated cyl values provided RX
    That is a little odd.

    Quote Originally Posted by Tallboy View Post
    Should I just stay away from compensated lenses for this OD's RXs? This happens to me with him much more than other ODs.
    I would not stay away from compensated lenses.

    Quote Originally Posted by Tallboy View Post
    This is how I feel... how can I celebrate POW compensated lenses when they give me results like this?
    More dispensers and refractionists need to be educated on getting a proper history on the lenses that were used in the past. A patient walks in with a traditional SF lens, someone reads the Rx and that is the baseline for the new Rx. No one took into account the effective change in power that the SF lenses will create. This is less of an issue with distance powers and more of an issue with hyperopic presbyopes.
    How many times has a patient come in with a distance Rx of +2.00 with a +1.00 add we use a SF progressive and a year later they get a new Rx +2.00 +1.25 add. This time they decide to get a newer FF, digital, compensated, etc lens. When they pick them up they cannot read. We blame the drop, the manufacturer, the compensation, etc.
    A SF progressive (+2.00 +1.00 add) with an average PoW and a 30 degree eye rotation(15 mm) will create an effective add power of roughly +1.21
    The new compensated Rx will give you the prescribed +1.25 add power, so the patient feels like the Rx is the same.

    Quote Originally Posted by Tallboy View Post
    PS thanks to Daryl Meister's teachings I learned all about this stuff, as well as Barry and Robert et al. I just hate when it backfires. Its like the symptoms caused by the lessened RX power are worsened when compensated, where they would have been fine if not compensated. UGH.
    I still think it is the new Rx and not the compensation.

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    In case anyone cares - I have had 2 more "remakes" since this one from the same OD, both for underminusing the patient. It must be a habitual thing he does, because I've probably had 30 remakes from him in the last year, almost all are overplussed by .50 to .25 diopters in the DVO.

    Uggh. Oh well what can I do, I'm not stopping making his patients lenses.

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    OptiBoard Novice cecelia77's Avatar
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    I am having a similar issue with one of my px. Only difference is there is no change in rx but yet cx perceives that his distance vision is worse than his old pair. Shamir have told me that it is my measurements but yet the new pair is a complete duplicate
    Cecelia

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    Quote Originally Posted by cecelia77 View Post
    I am having a similar issue with one of my px. Only difference is there is no change in rx but yet cx perceives that his distance vision is worse than his old pair. Shamir have told me that it is my measurements but yet the new pair is a complete duplicate
    I would analyze both pairs for OC(prism thinning) position and base curvature, first. Secondly, what variables in fit exist that can create enough perceived visual difference?

    What are the measurements that you supplied(according to Shamir) that were different that previous?
    Eyes wide open

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    looking up the answers smallworld's Avatar
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    I've only seen myopic shifting lower with cataracts forming. But usually there is induced cylinder along with the myopic shift. I think a talk with the OD is in order. Remakes are my personal bane.
    What is reality but a concept unique to each of us? Can anything be classed as real when our perceptions differ greatly on so many things? Just because we see something a particular way does not make it so.

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    cecelia post your RXs and measurements and we may be of better service.

    I ended up getting the distance bumped up back to the original DVO, then after my measurements and Shamir's calcs everything was honkey dory.

    Lens Grinders points above are also good to listen too. That being said I've started having issues with Auto III's lately, and they never used to give me issues. Switching to a non-compensated design has solved the issue both times. 70% of the PALs I sell are compensated so its kind of odd, but I just "let it go" and put them in something that "works". I hate undefined gray areas though.

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    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    Assuming the POW values are accurate and the calc/design engine is performing correctly, the most probable reason compensated lenses will have a problem is that your starting Rx is inappropriate
    B

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    We trial frame all MD rx's and we now have the Eyenetra to self check; it works great and gives a wearable RX almost everytime. We have never seen an autorefractor that gives a usable RX!
    Time to let the patient decide?

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    Most ODs when faced offering the question, what is better one or two? Face the answer that they both look the same. In most of those cases they use the lower power (and they should) that achieves the desired VA. The Free-form lens also reduces the power, voila, they are a 1/4 off.

    Technically this could be solved by prescribing in 1/8 increments. But its common that with high compensated FF lenses the Rx power has to be bumped.

    Quote Originally Posted by Tallboy View Post
    In case anyone cares - I have had 2 more "remakes" since this one from the same OD, both for underminusing the patient. It must be a habitual thing he does, because I've probably had 30 remakes from him in the last year, almost all are overplussed by .50 to .25 diopters in the DVO.

    Uggh. Oh well what can I do, I'm not stopping making his patients lenses.

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