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Thread: What changes can be made to an Rx?

  1. #1
    Allen Weatherby
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    What changes can be made to an Rx?

    In another thread drk wrote:

    Quote Originally Posted by drk
    Question to the board, and I know the responses will vary according to locale:
    If an Rx includes material, or brand, are you obligated to "dispense as written", or are you allowed to "substitute"? In other words, what constitutes a spectacle Rx in your area, or doesn't anyone know?
    To add to drk's question what are the board members thoughts regarding newer technology lens designs using freeform technology, where frame wrap and pantoscopic tilt actually change the Rx. This change will make it match the as worn position.

    How many O.D.s will object to this change being made to their written prescription. Many Rx's have been wrong in the as worn position since they were correct when measured in a flat plane with a lensometer which does not take wrap or tilt into account.

  2. #2
    ATO Member HarryChiling's Avatar
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    As the optician I suggest the materials lens designs and frames, and the doctor will suggest the Rx. I will make changes to the Rx to compensate for obviuos changes, Vertex Distance and tilts; however when I do something like this I will do the math in the patients file so it becomes part of the documentation and I can always reference why this Rx change was made. The doctors and I have an agreement, I don't write the scripts they won't make the glasses.
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    Allen Weatherby
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    Great logical approach

    Thanks Harry;

    It will be interesting to see how others view this.

    I think your logic is the way O.D.'s and Optician should work together. And keeping the records is a must.

    Do you think that both the prescribed Rx and produced Rx should be provide to the patient?

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    Bad address email on file QDO1's Avatar
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    Quote Originally Posted by AWTECH
    In another thread drk wrote:



    To add to drk's question what are the board members thoughts regarding newer technology lens designs using freeform technology, where frame wrap and pantoscopic tilt actually change the Rx. This change will make it match the as worn position.

    How many O.D.s will object to this change being made to their written prescription. Many Rx's have been wrong in the as worn position since they were correct when measured in a flat plane with a lensometer which does not take wrap or tilt into account.
    you are not changing the RX the patient actually has (in terms of vergance at the pupil) if we compensate for tilt, wrap and BVD. You are actually changing the RX if you do not compensate!

  5. #5
    OptiBoardaholic
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    Changing RX

    Compensating for how the Rx is worn is not changing the Rx it is adjusting it for how the glasses are worn. If you are fitting contact lenses as a fitting optician it is your job to compensate for the change in vertex distance. If you are fitting a strong Rx at a vertex distance other than the refracted distance you need to compensate for how the glasses are being worn.

    When you adjust for any reason record Dr Rx as written and show compensated Rx based on what the reason of the compensation is

    Ed

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    Quote Originally Posted by AWTECH

    How many O.D.s will object to this change being made to their written prescription. Many Rx's have been wrong in the as worn position since they were correct when measured in a flat plane with a lensometer which does not take wrap or tilt into account.
    I would object to changes in my Rx based on wrap or tilt, unless the optician called me and explained what changes he/she was going to make, and why.

    For example, if you change an Rx based on wrap or tilt, you are probably making the based on the patient looking straight ahead. What about when reading? Often the reading position is a tilt=0 situation. And if you correct for wrap, what happens when the patient looks left or right? The amount of wrap similarly goes to zero at some point for each eye, while at that position the other eye is *WAY* wrapped!

  7. #7
    Allen Weatherby
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    Follow up for William Stacy OD

    I am having trouble following your wrap or tilt example.

    If I process the compensation for a Right eye: -4.00 sph, 0 cyl, and 180 axis

    I use the information below.

    Assuming this Rx is to be placed in a wrap frame with an 8 degree pantoscopic tilt with a 20 degree wrap, DBL is 18mm vertex distance is 12mm, A= 55mm, PD 32mm.

    Assuming we use a poly polarized sunlens for index purposes with an 8 base front curve.

    The compensated Rx for this is approximately OD -3.50 sph, -0.37cyl, 027 axis with .32 base in prism. Please comment on what you find incorrect regarding this adjustment.

    One of my main point to this is to consider how often this -4.00 Rx was fitted to a frame with wrap and tilt with an as written -4.00 sph, which I think you will agree would not be appropriate for the frame indicated.

    How do you figure your recommended changes in sph., cyl., and axis for this frame wrap and tilt?

  8. #8
    OptiBoardaholic OptiBoard Silver Supporter Alvaro Cordova's Avatar
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    I agree with Harry and QDO1. I would also like to re-emphasise what QDO1 said. If you don't compensate you are effectively changing the Rx.

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    Quote Originally Posted by AWTECH
    I am having trouble following your wrap or tilt example.

    If I process the compensation for a Right eye: -4.00 sph, 0 cyl, and 180 axis

    I use the information below.

    Assuming this Rx is to be placed in a wrap frame with an 8 degree pantoscopic tilt with a 20 degree wrap, DBL is 18mm vertex distance is 12mm, A= 55mm, PD 32mm.

    Assuming we use a poly polarized sunlens for index purposes with an 8 base front curve.

    The compensated Rx for this is approximately OD -3.50 sph, -0.37cyl, 027 axis with .32 base in prism. Please comment on what you find incorrect regarding this adjustment.

    One of my main point to this is to consider how often this -4.00 Rx was fitted to a frame with wrap and tilt with an as written -4.00 sph, which I think you will agree would not be appropriate for the frame indicated.

    How do you figure your recommended changes in sph., cyl., and axis for this frame wrap and tilt?
    My point was you are making certain assumptions about the patient's direction of gaze, the Rx's vertex distance, and the vertical position of the line of sight in the frame. I'll bet when the patient is reading with those glasses, he is looking through a portion of the lens that doesn't need or want that cyl. because his "tilt" at that direction of gaze is probably zero or actually negative (it will be negative if his reading material is more than 8 degrees downward from the primary position), in which case the "compensation" will be counterproductive, to say the least. Re the wrap, could you show the calcs without the panto calc, and with a more normal 10 deg wrap, in a CR39 material, just for my benefit? Thanks

  10. #10
    Allen Weatherby
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    Reply to William Stacy OD

    Re the wrap, could you show the calcs without the panto calc, and with a more normal 10 deg wrap, in a CR39 material, just for my benefit? Thanks
    Here they are for -4.00, 0, 0 with no panto and CR-39 for material (all other information is the same:

    -3.58 sph, -0.30 cyl, 180 0.30 base in prism

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    Bad address email on file Rich R's Avatar
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    Not to get off the wrap and tilt compensation, my question is regarding patient needing a slaboff, would we need the rx written for a slab off.

    I would make the point that with certain rxs not doing a slab is giving patient vertical prism at reading, however I always call the OD and ask the rx be written for the slab before we do that.

    What do you think?
    Rich R.

  12. #12
    OptiBoardaholic OptiBoard Silver Supporter Alvaro Cordova's Avatar
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    I think that is unnecessary. Most ODs are not looking for anisometropia per se they are trying to diagnose diseases and get a working Rx. If there is vertical imbalance, I correct it without hesitation. That's what I'm there for. I also do iseikonic lenses too. I'm very much a function before form kind of guy.

  13. #13
    ATO Member HarryChiling's Avatar
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    theDude nailed it on the head, we as opticians are the ones that should have the knowledge to put the doctors Rx into a frame and essentially make it work, that is our job. Most of the doctors I work with learned optics at one point in school and then forgot it, because that's what I am there for.

    Quote Originally Posted by AWTECH
    Do you think that both the prescribed Rx and produced Rx should be provide to the patient?
    I will not provide the patient with the compensated Rx, every time we do any calculations on a Rx we have to round the numbers off to make them work and this could lead to compounded errors. Plus if the patient needs the Rx compensated for in another frame I am not guarenteed that the parameters are going to stay the same and I know that in order to get the same level of service that I have provided they will have to visit a quality optical shop, wich are mostly the independents.
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    Bad address email on file QDO1's Avatar
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    What I say to a patient is: "here are your new spectacles. I have compensated the prescription for position of wear. I have altered the numbers in the glasses we made, to take into account the way the frame fits. This means that if somone checks your spectacles against your prescription, the numbers will differ. This actually means you are given the same prescription as the practitioner prescribed, who tested you with a trial frame which was in a different position to your spectacles. The compensation means we actually give you exactly what the practitione asked for. If I made a different pair of spectacles for you, with a different fitting, there will be a different compensation. If you happen to get somone else to measure them, and they do not comprehend the compensation, then you are probrably in front of the wrong person, nether-the-less ask them to call me and I will walk them through the compensation"

  15. #15
    ATO Member HarryChiling's Avatar
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    Quote Originally Posted by QDO1
    ...then you are probrably in front of the wrong person...
    Sweet :bbg:
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    What's up? drk's Avatar
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    I think most O.D.'s/O.M.D.'s egos (profit hunger?) would prevent them from the following, but if a careful relationship were fostered then I think it would be best that inter-office communication would flow freely when complex things like slab-off needs to be recommended, or when a dispenser/lens designer has questions on the wearability of the given Rx.

    I think adjusting for position of wear is absolutely OK, but a lot of O.D.s (most!) would have no idea what that really means, so I'd be careful to phrase that gingerly. Same with designing occupational lenses.

    I think the "add power thing" is particularly prickly. How many new +3.25D adds have you seen, and the patient refuses a trifocal? That needs a call, IMO.

    The absolute worst is the "OS: same" "OD: pl-2.50x62 +3.00 add" after cataract extraction when the other lens is +2.50/ +2.50 add. Those kill me.

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    Quote Originally Posted by AWTECH
    Here they are for -4.00, 0, 0 with no panto and CR-39 for material (all other information is the same:

    -3.58 sph, -0.30 cyl, 180 0.30 base in prism
    So was that with a 20 deg wrap, or a 10 deg? I don't have the formulas you use, so pardon my insistence. I suspected that the amounts of such compensating are small and that is why we o.d.s generally ignore them. As an old school o.d., I DO understand this stuff (am not to sure about what they are teaching these days and would not be surprised if it's not taught all that much), and it is probably a good trend in general. However, at this point in the development of it, I think you'd be smart to communicate with the o.d. esp. if you suspect he/she might be asked to verify the Rx by the patient.

    Re slab off, I DO prescribe it when I think it's necessary, and I think that should remain part of the Rx. If the optician thinks slab off is a good idea for the patient, the doc should be advised on that as well. I hope to heaven they are still teaching o.d.s about slab off.

  18. #18
    Allen Weatherby
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    Followup to William StacyOD

    So was that with a 20 deg wrap, or a 10 deg?
    The wrap angle was 20 degrees. The lens wrap angle will be different than the frame angle due to the PD and A size calculations (see original below)

    If I process the compensation for a Right eye: -4.00 sph, 0 cyl, and 180 axis

    I use the information below.

    Assuming this Rx is to be placed in a wrap frame with an 8 degree pantoscopic tilt with a 20 degree wrap, DBL is 18mm vertex distance is 12mm, A= 55mm, PD 32mm.

    Assuming we use a poly polarized sunlens for index purposes with an 8 base front curve.

    The compensated Rx for this is approximately OD -3.50 sph, -0.37cyl, 027 axis with .32 base in prism. Please comment on what you find incorrect regarding this adjustment.
    I am neither a practicing OD or Optician, my company has developed specialized lens surfacing technology for making wrap around sunglasses for strong presdriptions. We have an excellent adapation rate (over 98% during our beta testing). We use this type of calculation to properly correct the lens for wrap and tilt.

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    Bad address email on file QDO1's Avatar
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    Quote Originally Posted by HarryChiling
    Sweet :bbg:
    but too friggin true

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    Quote Originally Posted by AWTECH
    The wrap angle was 20 degrees. The lens wrap angle will be different than the frame angle due to the PD and A size calculations (see original below)

    I am neither a practicing OD or Optician, my company has developed specialized lens surfacing technology for making wrap around sunglasses for strong presdriptions. We have an excellent adapation rate (over 98% during our beta testing). We use this type of calculation to properly correct the lens for wrap and tilt.
    OK I don't speak for all o.d.s, obviously, but I think most of them would go along with the idea of such corrections, especially in deeper curves, wierd tilts and huge wraps. Just make sure the prescribing O.D. knows they are doing it and they will be accepted. I'd guess the neutralizing would be pretty much on Rx if the frame were held in the lensometer approximately how it will be worn, no?

  21. #21
    OptiBoard Professional William Walker's Avatar
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    It should be close, if not on if you can simulate the wearing position. I don't know the vertex distance simulated when having a lens against the stop in the varying types of lensometer, though.
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  22. #22
    Allen Weatherby
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    Lensometer adjustment measurement

    The problem here is the vertex distance. If this was easily adjustable on the lensometer you could move the lens to the as worn position to check the modified Rx for as worn.

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    Bad address email on file QDO1's Avatar
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    Quote Originally Posted by AWTECH
    The problem here is the vertex distance. If this was easily adjustable on the lensometer you could move the lens to the as worn position to check the modified Rx for as worn.
    well a BVD adjustment is a pretty simple enough equation to do on the fly?

  24. #24
    Allen Weatherby
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    Easy adjustment?

    Yes if the OD is familiar with this, however I think Dr. Stacey had a point that with the frame held in the as worn position an O.D. could check the Rx without any additonal calculations. The fact is the vertex distance correction would be necessary so some calculations are required.

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    Bad address email on file QDO1's Avatar
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    Quote Originally Posted by AWTECH
    Yes if the OD is familiar with this, however I think Dr. Stacey had a point that with the frame held in the as worn position an O.D. could check the Rx without any additonal calculations. The fact is the vertex distance correction would be necessary so some calculations are required.
    that makes the assumption a focimeter works like the eye, and it does not

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