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Thread: Anisometropia and PALs

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    Anisometropia and PALs

    Hi Everyone,

    I understand that some people can have convergence issues in the near with anisometropia, but what about in the distance with PALs? I have a patient who's one eye is +025 and the other -450. There's no prism thinning so at the cross (4mm drop) there's almost 4 diopters of prism in the left eye and barely any in the right. Is this ok for a patient to wear?

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    Master OptiBoarder optical24/7's Avatar
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    What’s the patient’s history? Have they been this way for long or is this a recent event like cat-x surgery? Is this their 1st multifocal? If they’ve been like this for long and particularly in multifocals they’ve most probably developed a monocular vision habit. If recent event, best to treat the high minus eye with cl’s or IOL prior to attempting any multifocal.

    ( For curious minds, slab-off won’t fix the issues the patient will have if a recent, visual changing event.)

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    Interesting. What about a bifocal (Flat Top 28) with Slab-off?
    Would it work?

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    Quote Originally Posted by Oscar View Post
    Hi Everyone,

    I understand that some people can have convergence issues in the near with anisometropia, but what about in the distance with PALs? I have a patient who's one eye is +025 and the other -450. There's no prism thinning so at the cross (4mm drop) there's almost 4 diopters of prism in the left eye and barely any in the right. Is this ok for a patient to wear?
    Hi Oscar. Not convergence, but Vertical prism Imbalance.

    The VI in the distance with the parameters you've posted is roughly 2∆ BU left, enough to cause asthenopia for some, diplopia for others, and no symptoms for the rest, assuming some degree of binocularity. We could introduce a cancelling prism, but then the VI at near would increase to about 6∆.

    Quote Originally Posted by optical24/7 View Post
    What’s the patient’s history? Have they been this way for long or is this a recent event like cat-x surgery? Is this their 1st multifocal? If they’ve been like this for long and particularly in multifocals they’ve most probably developed a monocular vision habit. If recent event, best to treat the high minus eye with cl’s or IOL prior to attempting any multifocal.
    Yup, insufficient data for even an educated guess. If it was from cataract surgery, the problem is solved when the fellow eye is operated on. If it was unilateral, pray for the surgeons soul.

    ( For curious minds, slab-off won’t fix the issues the patient will have if a recent, visual changing event.)
    From my experience, it's the sudden onset events that present the most symptoms, with the others adapted/suppressed. Am I misreading this?

    Quote Originally Posted by MIOPE View Post
    Interesting. What about a bifocal (Flat Top 28) with Slab-off?
    Would it work?
    It would minimize the VI at near.

    Best regards,

    Robert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

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    Master OptiBoarder optical24/7's Avatar
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    Quote Originally Posted by Robert Martellaro View Post



    From my experience, it's the sudden onset events that present the most symptoms, with the others adapted/suppressed. Am I misreading this?

    It would minimize the VI at near.

    Best regards,

    Robert Martellaro
    Absolutely agree it's sudden onset that will be the most problematic. As far as slab not addressing all issues; The patient, if sudden onset and hasn't been suppressing ignoring one eye, will have image size issues that a slab alone won't address and as far as minimizing the VI at near; only in a 3-4mm vertical area of the seg will it do that, creating an extremely small area of non-diplopic vision.

    As you mentioned, more info/history on this particular patient is needed to give any kind of practical advise.

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