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Thread: ? for a high plus RX with prism...

  1. #1
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    ? for a high plus RX with prism...

    Can anyone let me know why a patient can't see well out of her new bifocal. her rx is a od +13.25 os +12.00-1.00x178 with prism in both eyes as 1base out. she never use to have prism and her old rx was +14.25(od) +13.50-1.00x178(os) with no prism. Is it the prism which she needs to get use to? Doctor is on vacation and I want to know what it could be or what I could tel her. Any suggestions?
    Also we changed lens material from poly to aspheric ultra lite 1.56. Do this have anything to do with it too???
    thanks

  2. #2
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    I would look at the adjustment very closely. An rx like that requires alot of extra care. The prism in that power is rather insignificant.

  3. #3
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    Quote Originally Posted by axomich8481
    Can anyone let me know why a patient can't see well out of her new bifocal. her rx is a od +13.25 os +12.00-1.00x178 with prism in both eyes as 1base out. she never use to have prism and her old rx was +14.25(od) +13.50-1.00x178(os) with no prism. Is it the prism which she needs to get use to? Doctor is on vacation and I want to know what it could be or what I could tel her. Any suggestions?
    Also we changed lens material from poly to aspheric ultra lite 1.56. Do this have anything to do with it too???
    thanks
    My guess is that the new Rx is off. Probably due to the wrong vertex distance of the refractor. It's an aphakic Rx, and a couple of mm off on the vertex distance will make the Rxa way off. If you take the new glasses and pull them away from her eyes a couple of mm she'll probably see just fine. If you can't get away with that kind of adjustment, they will have to be redone. The prism probably has nothing to do with anything. The material change was probably a good thing, with nothing to do with it either. This is probably a good case of trying to fix something that isn't broken.

  4. #4
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    Although the prism isn't much and it is being ground in, I wouldn't recommend using an aspheric lens with prism if you can avoid it. Also, certain progressives work better for hyperopes and others a little better for myopes so it could be the lens design with such a high prescription. The other possibilities that have been posted are worth looking into. The best way to tell is to ask if the distance vision is ok- if yes, then I would look at the lens design a little closer and if no, I would have the doctor take a look at the problem before you get involved in a remake.

    Good Luck!

  5. #5
    One eye sees, the other feels. OptiBoard Gold Supporter
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    Quote Originally Posted by axomich8481
    Can anyone let me know why a patient can't see well out of her new bifocal.
    It depends where she can't see well, far, near, peripheral, or some combination of the above. If it's distance only then refract over the glasses. Start with the RT eye. If the over-refraction is spherical, then the Rx is off or the vertex distance may be different. If there is a cylindrical component then re-check the Rx and if ok look at the OC position, especially the vertical OCs (see Martin's rule).

    I'm really curious as to how this client was wearing a Poly bifocal at +14.25DS. It would have to be bi-convex! Same for a 1.56 bifocal. I would think the off-axis vision (that includes the near) would be very poor, with considerable power error and oblique astigmatism. I would consider using lenses from Rodenstock (Perfstar if still available) Sola (Hi-drop) or the Bristol 5 drop for this power due to their steep base curve availability.

    Hope this helps
    Roberts Optical Ltd.
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    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

    It is easier to fool a man, than to convince a man he has been fooled. -Mark Twain

  6. #6
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    THANK YOU FOR YOUR RESPONSES. This patient is having trouble seeing near with her bifocal. Actually she can't see at all, she says. Also her peripheral is very distorted. If you can, please give me more advice with what I have told you now.

  7. #7
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    Perhaps half of the problem with her near vision is that her doc cut her plus by 1.25 D in the right eye and by 1.25 (spherical equivelent) in the left eye.

    -Steve

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