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Thread: plaese explain phenomenon

  1. #1
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    Arrow plaese explain phenomenon

    i've observed interesting phenomenonin with high myopic people, whn they remove their spectacles,eyes take exo deviation and put back eyes normal & in orthophoric position.one of patient i checked had no prism incorporated in hisd specs.Why mypoes take exophric position when they remove specs????please explain.

  2. #2
    OptiWizard
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    Deepak,
    Is the exo at near or distance. If at near it may be because an uncorrected high myope will not be accommodating when view at near and therefore not have any accommodative convergence and will have an exo position relative to a corrected myope who will have accommodative convergence with near viewing tasks. Also high myopes don't need as much convergence for near viewing because of the base in prism they get when they view near objects.:cheers:

    Life is too short to drink cheap beer

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    Stopper-Exo is when looking at distanc,i hav'nt marked for near.When they put on their specs exo deviatin disappears and there is ni prism indorporated in their specs!-Deepak

  4. #4
    sub specie aeternitatis Pete Hanlin's Avatar
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    Okay, I'm going to take a crack- not because I really understand phorias or anything, but just as a guess based on the optics involved.

    When a high myope (let's say, a -10.00) is wearing his/her eyewear, the lenses have a virtual focal point 10cm in front of the eyes. In addition, if the patient is overcorrected (which- at near- is probably the case), s/he is probably accommodating away some of the extra minus- and accommodation usually triggers convergence.

    Perhaps the A/CA ratio of the patient becomes "reset" due to the high minus power in front of their eyes all day. Once the glasses are removed, the "need" to accommodate (and therefore, to converge) is gone, and the eyes become exophoric in response.

    Again, I may be completely out of my depth here- just a wild guess.

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    Hello Deepak,

    When your high myopic customer removes his spectacle he looks exophoric and when he puts them on his exophoria disappears and his eyes looks normal aligned (orthophoric) and you did not find any prism in his spectacle.

    Did you check his PD against Centration Distance of his spectacle to see if they match?

    I guess your customer had been wearing high power off-centered minus lenses for quite a long time that induced unnecessary base-in prismatic effect in his spectacle. It made his eyes look temporarily exophoric on removal of his spectacle. Watch him for 10 minutes without spectacles and see if eyes start to align up to look normal. Do you educate young myopic patients on benefits of wearing RGP contact lenses?

    Regards,
    Optom

  6. #6
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    Shamir-i did not check his pd & cd.ity was mistake:hammer:
    yes,i do educate on rgp contact when n w her neccessary.
    Thanx guays!

  7. #7
    Master OptiBoarder Darryl Meister's Avatar
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    I, too, would be guessing, but it could be, given how high his refractive error is, that his eyes are just assuming their natural positions of rest without the lenses -- at least until he looks at something close enough to be nearly in focus. The physiological positions of rest for the eyes are generally a little divergent, and he might have a natural exo deviation, as well, which would disappear once he wore his lenses.

    Also, because of the high minus powers of his lenses, his face will appear distorted (smaller and more narrow, for instance) through his lenses, and your eyes might just be playing tricks on you when you see him take his glasses off. ;)

    Best regards,
    Darryl

  8. #8
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    that's how his eyes are

    i believe Darryl assumption to be true coz that how his eyes rest physiological;ly i got to see him 2day when he came to pick uop his duplicate pair.
    Some deatils from his record-R-475/-0.75x90,
    -L-5.25,
    Pd 74mm.
    No other dtails available.
    Thanxxx!
    Deepak

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    Exclamation I hope you are not confusing

    Deepak,

    You may be confusing wide PD with exo deviation Some people with wide pupillary distance, like 74 mm you mentioned in case of your patient, can look in appearance like exophoria. What is his ethnicity? Wide pupillary distance is more common in some ethnic group e.g. blacks, orientals, middle easterner.

    Regards,
    Optom

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