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Thread: polycarbonate v. high index lens

  1. #26
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    Quote Originally Posted by nelce
    um. actually i don't. and my prescription ALSO says that i don't. pearle vision is the one who ADDED the prescription for astigmatism in my lens.
    That doesn't make sense. Do you have a copy of your prescription? Why would Pearl add in an astigmatism correction?

  2. #27
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    Quote Originally Posted by Happylady
    That doesn't make sense. Do you have a copy of your prescription? Why would Pearl add in an astigmatism correction?
    yep, i do have a copy of my prescription. and the only thing on it are two numbers: OD & OS. i'm thinking they screwed up...

  3. #28
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    Quote Originally Posted by nelce
    yep, i do have a copy of my prescription. and the only thing on it are two numbers: OD & OS. i'm thinking they screwed up...
    If they really put cylinder in your glasses and its not supposed to be there then take them back right away. Make sure you take a copy of your rx with you.

  4. #29
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    Big Smile get the thinnest lense that also provides good optics ...

    Quote Originally Posted by mirage2k2
    My advice, for what its worth, get the thinnest lense that also provides good optics ... with rx OD -8.75, OS -6.25
    Sadly enough that does not exist.................................

    When you go back in the history of lens curves and their visual performance you can see that lenses progressed from:

    Bi-convex or bi-concave, which made the thinnest and flatest lenses.............

    Plano convex or concave which was the next step in visual quality............

    Meniscus lenses, which were based on base curve of + or - 6.00

    Corrected curve lenses, which provided the best visual effects with the least or none of distortion and aberration off center and towards the edges.
    By going to high index lenses you are compromising the visual quality in favour of the thin cosmetic effect of the lenses.

    Polycarbonate lenses are also high index lenses and higher the index the flatter the lens curves and the worse the optical quality.

    With the newer high index materials you are actually regressing to historic times in quality of vision for a much higher price, but you will have the cosmetic benefit.

  5. #30
    Software Engineer NetPriva.com mirage2k2's Avatar
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    Quote Originally Posted by Chris Ryser
    With the newer high index materials you are actually regressing to historic times in quality of vision for a much higher price, but you will have the cosmetic benefit.
    :D :D :D

  6. #31
    Software Engineer NetPriva.com mirage2k2's Avatar
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    Quote Originally Posted by Chris Ryser
    ... higher the index the flatter the lens curves and the worse the optical quality.
    Doesn't asphericity fix all of the visual errors introduced by the flatter lens form? :D

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    Although I agree with most everything that has been said on this thread, I find it odd that none of you have mentionned the 2.50 anisometropia...I would recommend having equal base curves to minimize image size difference...some patient are that sensitive. Also a smaller frame will minimize the Prentice rule effect and dimish his chances of seeing double in the periphery of the lens. Just an OD's perpective...

  8. #33
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    Quote Originally Posted by francisOD
    Although I agree with most everything that has been said on this thread, I find it odd that none of you have mentionned the 2.50 anisometropia...I would recommend having equal base curves to minimize image size difference...some patient are that sensitive. Also a smaller frame will minimize the Prentice rule effect and dimish his chances of seeing double in the periphery of the lens. Just an OD's perpective...
    I'm sure an iseikonic lens would help but this raises a question that I'm not to sure about. I know that slab off must be prescribed but what about using iseikonic lenses? Is this within the realm of an optician?

  9. #34
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    By iseikonic lenses, if you mean choosing a proper BC for the prescription, I believe it is. As an OD, if a patient asks for his prescription, it never includes BC. Most of the time the labs determine the best BC. In a situation like this, I think it is very reasonable to ask for matching BC. Some labs would do this without you asking for it but as the optician, you are the one that can recommend what is best for the patient to make sure it does not fall through the cracks at you lab. If you specified matching BC, then you protected yourself and your patient. Just my opinion though!

  10. #35
    One eye sees, the other feels OptiBoard Silver Supporter
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    Francis,

    I'm looking at the shape factor formula for spectacle magnification and I believe we would want to increase the base curve on the left lens instead of decreasing the curve to match the right lens. My feelings are that if there are no symptoms it's usually best to leave well enough alone, considering the appearance and poor off-axis optics of lenses optimized for image size.

    Optidonn,

    Single vision wearers usually posture and hold objects higher, decreasing the reading depth, minimizing the vertical imbalance. However, multifocal wearers who perform frequent and/or prolonged close tasks would certainly benefit from a slabbed lens.

    Regards,
    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.



  11. #36
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    Quote Originally Posted by francisOD
    By iseikonic lenses, if you mean choosing a proper BC for the prescription, I believe it is. As an OD, if a patient asks for his prescription, it never includes BC. Most of the time the labs determine the best BC. In a situation like this, I think it is very reasonable to ask for matching BC. Some labs would do this without you asking for it but as the optician, you are the one that can recommend what is best for the patient to make sure it does not fall through the cracks at you lab. If you specified matching BC, then you protected yourself and your patient. Just my opinion though!
    A specific base curve should be chosen based on how it will effect aberrations not image size. If you begin to change the lenses parameters ie, thickness, base curve, vertex distance, all with the intent of changing retinal image size then you have an iseikonic lens. I can see if an optician changes a few things here and there to increase patient adaptability but is making a full blown iseikonic lens within the real of an optician? Or should it be prescribed?

  12. #37
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    OptiDon,

    From what I remember about this portion of optics, over 80% of image size is related to BC. If both BC are equal, you will minimize image size disparity. The BC selection in a case like this I am not sure on. I would talk to my guy at my surfacing lab and get feedback from him before deciding. :cheers:

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    Robert, I agree with you...I was just wondering if anyone had taken this into consideration. If there is no symptomatology in a case like this then there is no cure needed. However if patient has adaptation issues, increased headaches or other vague complaints, this would need to be considered as a source of those complaints. Cheers!!

  14. #39
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    Quote Originally Posted by francisOD
    OptiDon,

    From what I remember about this portion of optics, over 80% of image size is related to BC. If both BC are equal, you will minimize image size disparity. The BC selection in a case like this I am not sure on. I would talk to my guy at my surfacing lab and get feedback from him before deciding. :cheers:
    OK! My mind is some where else right now:hammer:

    I was assuming that you were basing correct base curve selection on image size and not the corrected curve theory to minimize lens aberrations. But in a case like this if you were to regulate image size one of the first places to start would be base curve! Duh! This is what happens when crazy kids keep you up all night! You start reading things that aren't even there!:(

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    Optidon, I have a 2 and 4 year old (2 girls)...I now how it feels. No damage done. Happy to see you agree. Cheers!!

  16. #41
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    I've got a two year old and a 9mo. old both girls too! I think its rough now I'll be in a straight jacket when they are teens:hammer:

  17. #42
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    I'll I can say Optidon is may the force be with both of us...:cheers:

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    Old Dead Thread of the Week:: Since it seems on here that a terribly old thread gets dug up every 2 weeks or so, and a mess of people comment on it before they realize the folly...

    Admins, many forum software and groups will auto-lock a thread if its over a certain time without a reply. I don't know if that is possible with the software Optiboard uses, but it would held promote new discussions, and shorter threads that don't exist over the course of decades. It should be based on last comment, not when it was started. It would still be visible.

    Some discussions simply need to die. What say ye?

  19. #44
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    Consumer thread, consider it dead.

  20. #45
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    You should be going to a reliable doctor's office with a good optician and asking them these questions and probably ordering from them too. Costco? pearle? really? just my two cents. chains give too much pressure to employees to make that cash money.
    "what i need is a strong drink and a peer group." ... Douglas Adams - Hitchikers Guide to the Galaxy

  21. #46
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    Quote Originally Posted by sharpstick777 View Post
    Old Dead Thread of the Week:: Since it seems on here that a terribly old thread gets dug up every 2 weeks or so, and a mess of people comment on it before they realize the folly...
    This thread was dead for 8 years until you revived it, and now see what happened when you did that !!!

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