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Thread: More anisometropia woes...

  1. #1
    OptiBoard Apprentice Trevor D's Avatar
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    Crier More anisometropia woes...

    Hey guys,

    Haven't posted here in a while but I've been lurking often! I normally find an answer to any problem I have just with the use of the search function ;)

    We have a client with this rx:

    R +2.00 -2.00 x 60

    L -3.50 Sph

    Add is about +2.00

    Someone has dispensed her a pair of Varilux Comforts (progressives were called for on the doc's rx) but she cannot see well, which is no surprise to me.

    I want to change her into SV distance but I cannot find a way to reduce the disparity in image size she will experience. After punching different combinations of front curves and CTs etc into the different online calculators, it seems as if the only way to reduce the aniseikonic effect in this case is to minimise the vertex distance as much as possible.

    I suppose the doctor has a reason why a contact lens could not be worn in the left eye (the right eye has had a corneal graft and is unstable) hence the progressives called for on his script.

    Anyone have an idea how to manage this rx?

    Thanks :hammer:

  2. #2
    ATO Member HarryChiling's Avatar
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    Try playing around with the online calculators, but instead of making the VD the same between both eyes, try a 1 - 2mm disparity between them. Then when your cutting the lenses put a front bevel on one (minimizing the VD) and a back bevel on the other (increaseing the VD). Just another tool to pack away in your tool belt.
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  3. #3
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    Quote Originally Posted by HarryChiling View Post
    Try playing around with the online calculators, but instead of making the VD the same between both eyes, try a 1 - 2mm disparity between them. Then when your cutting the lenses put a front bevel on one (minimizing the VD) and a back bevel on the other (increaseing the VD). Just another tool to pack away in your tool belt.
    That's genius!! It never dawned on me to utilize the bevel to accomodate for VD....thank you...thank you!

  4. #4
    OptiBoard Apprentice Trevor D's Avatar
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    Because the right lens is plus (through one meridian) and the left is minus, can increasing the VD on one lens and decreasing on the other still work? I think this creates a higher % of magnification difference. I might have to call the doc on Monday and ask if there is another solution.

  5. #5
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    If the graft is unstable I would be supprised if the va was any good or consistant anyway.
    An ancient cure is a frosted lens for the eye with the worst acuity.

    Chip

  6. #6
    Optician Extraordinaire
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    You could do a slab off. They can be done on progressives, too, but of course there will be a fine line on the one lens.

  7. #7
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    Commenting only on the functional side of this problem.

    1. What is the problems with the sight? Blurry vision. Distortion? Diplopia?
    2 What is the relative visual acuities of the eyes?

  8. #8
    OptiBoardaholic
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    slab off adresses the prismatic imbalance, but not the eikonic. dissimilar vertex, base curves and thickness are normally used in various combinations to acheive desired results. npdr is also correct, it is important to know the corrected acuities, since anisemetropia is often associated with reduced acuities, usually monocularly. Other important considerations are whether the disparity is recent onset, such as post-op, or if the disparity is long term, and allows a suppression reflex. If the image disparity is likely to cause some discomfort over time, Harry's suggestion to use an online calculator is your best bet. My preference was to give the lab the rx, and let them work out the numbers using their own eikonic program.

  9. #9
    Doh! braheem24's Avatar
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    Contact the Dr, find out the VAs in the surgical eye with and without correction.

    In a healthy eye the +2.00-2.00 would improve VAs by 4 lines at most, in this situation it's probably not making much of a difference.

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    Uphill battle at best...

    check with the prescribing doctor for other options. Monocular corneal graft, +/_ 50 yo pat with probably BVA OD of 20/40 or less at best, 5D aniso, progressive lens mandate...not good. You need to know exactly where you are with this patient as far as visual needs and recommend an appropriate course. A progressive lens would not be my choice with this info. Although too many assumptions without more complete info... info you need to know. Good luck.

    Scout

  11. #11
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    I just got more instructed

    My mainmost expert was just in to pick up some new glasses and I presented him with the problem.
    My question: How much image size disparity can a patient live with.
    His answer (in addittion to telling me he would send me lots of information and a book on the subject next weeK): If the disparity is axial (due to difference in eyeball length) they can tolerate: "A hell of a lot."
    If the difference is refractive (Due to shape of cornea or lens) not much.

    Will share more as I get re-indoctrinated.

    Chip

  12. #12
    What's up? drk's Avatar
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    (This case is presumably 100% refractive due to the graft OD. Any cylinder anisometropia is refractive.)

    This case is really the province of an OD, and it's discouraging that the "prescriber" has cut this patient loose with apparently nothing more than monocular refractive findings. A consult with an OD would have been in order. (I hope it wasn't an OD prescriber:().

    At least you're trying to pick up the slack, and you should be commended for your initiative. This is a perfect example of optician's professional services that should be directly remunerated.

    My take: What would be needed is eisekonic lens design if the patient is experiencing symptoms of anisekonia, which hasn't exactly been established, and is difficut to establish in the average clinic.

    So you are putting the cart before the horse. An inexpensive pair of SVDO lenses is a good trial run. Merely order equal BC and CTs to keep the shape factor aspect of spectacle magnification minimized.

    If she has debilitating binocular vision issues or perception issues, then you should get an anisekonia consult or simply do what the other ODs here recommend: reduce the power magnification factor.
    http://books.google.com/books?id=yq5...um=1&ct=result


    Since I'm not Harry, I can't post a nice-looking formula for spectacle magnification, but I think this link will show it.
    Last edited by drk; 10-10-2008 at 01:44 PM.

  13. #13
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    Quote Originally Posted by drk View Post
    My take: What would be needed is eisekonic lens design if the patient is experiencing symptoms of anisekonia, which hasn't exactly been established, and is difficut to establish in the average clinic.
    Since we have so many newbies reading this formum let's get the spelling right... 'aniseikonia' and 'iseikonic'

    as in a 'seiko' watch in the middle of the word.;)

  14. #14
    OptiBoard Apprentice Trevor D's Avatar
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    Stop reviving old threads you guys! I'd actually forgotten completely about this patient as she never returned for me to try out the iseikonic SV option.... Thanks for the ideas :)

  15. #15
    What's up? drk's Avatar
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    Quote Originally Posted by tmorse View Post
    Since we have so many newbies reading this formum let's get the spelling right... 'aniseikonia' and 'iseikonic'

    as in a 'seiko' watch in the middle of the word.;)
    Hey, you're right. Thanks.

  16. #16
    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    Tell you one thing - you can't adjust to 13 diopters of imbalance.:hammer::D
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