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Thread: Eye Tests

  1. #1
    OptiWizard ksquared's Avatar
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    Eye Tests

    Do any of you perform the following tests. If so, could you shed some light on theory behind the test and how it would effect the RX. THanks!

    Initial MPMVA (Maxium Plus to Maximum VIsual Acuity)
    Initial Duochrome (Bichrome, Red-Green Test)
    Binocular Balance

  2. #2
    OptiWizard OptiBoard Silver Supporter
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    I usually do all three during a refraction

    Initial MPMVA (Maxium Plus to Maximum VIsual Acuity)
    Just means not to over minus on a distance refraction

    Initial Duochrome (Bichrome, Red-Green Test)
    In the green means you over minused the patient. Red means over plus. "In the green" means the black letters on the green side look blacker and more distinct. Theory is that shorter wavelengths refract more, so the green (don't know why they don't use blue) will be in front of the retina at endpoint and the red will be behind.

    This test sometimes helps me make a decision on whether I over minused the patient. Many people are just not senstive to this test.

    Binocular Balance
    Accomodation must be balanced. This can be done by vertical prism and fogging, or alternating between the eyes to see if acuity and image size is the same.


    Hope this helps.

    Harry

  3. #3
    OptiBoard Apprentice
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    If I rememeber correctly the red and green used for the duochrome is supposed to be equidistant either side along the spectrum from the peak sensitivity of the human eye. this is meant to be 555 nanometers = yellowish. If they used blue and red, being clearer on the blue would mean much more overminused than on the green?

    I agree that the duochrome test is not ver realiable and i tend to do a binocular refraction on all Px taht it is possible with.
    Ankur Trivedi

    "It's better to regret something you have done, rather something you haven't done"

  4. #4
    Enjoying the education drk's Avatar
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    The red-green bichrome test, I find, is very useful in determining spherical endpoint, but is best used as a double-check of a binocular blur-balanced endpoint.

    Why red-green and not red-blue has never been explained to me, but I doubt it has to do with retinal sensitivity. It may have more to do with the fact that lenticular opacities reduce blue sensitivity rather disproportionately, rendering the test less useful (however, seniors never need this test)?

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