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Thread: Stumped !!

  1. #1
    Master OptiBoarder Clive Noble's Avatar
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    Stumped !!

    I know we get some difficult problems, but that's why we're better than the others (and more modest too!!!)

    This Pt has been wearing similar Rx over the last 10 years

    ou (approx) -3.00 / -2.00 with a +3.00 add and 6^out each eye

    The last couple of pairs have been dispensed as Glass PGX 1.6 Natural, the last pair she's had for just over a month.

    Long Distance Vision and Near Vision are great, but from 8-10 meters (25 - 30 feet) everything is blurred and there's no part of the lenses that give her clear vision.

    The Rx is great, we've added and minussed to no avail.
    As I said at the top, we're stumped!!

    Any ideas???

  2. #2
    What's up? drk's Avatar
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    My thinking is this: you have to isolate the cause.

    Incorrect distance RX:
    Put the distance Rx in a trial frame without prism. Theoretically, 6M IS DISTANCE, so I can't reconcile why she says she can see far away, but not at 8-10M. That does not compute. See what she can do on a Snellen chart monocularly. She possibly has cataracts? Is she overminused? Is only one eye out of whack?

    Binocular problem:
    Assuming that the refraction is good at distance, put her in the trial frame again with the distance Rx and prism and see what her fusional status is @6M with a Worth-dot type test. She possibly has intermittent esotropia, and she suppresses at 6M, but has diplopia ("blur" to her?) at intermediate distances (but that would still be a closer distance than what she reported). She may be fusing at near, hence the good vision. If you can, try moving the Worth dot target to different distances to confirm the theory. If that is it, a different prism amount may help. She even may be currently overcorrected in prism, and can suppress the diplopia at distance, but not at intermediate distances.

    I can't think of any possible dispensing errors that could cause this symptom. I don't think that this is a progressive problem, either, with symptoms at that far a distance.

  3. #3
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    As I was painfully reminded last week, don't use aspheric (even when just the add is apheric ) lenses with prism.

    Chip

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    Master OptiBoarder keithbenjamin's Avatar
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    Has she been having the problem all along or is this new?

    How much has the prescription changed?

    Any cyl?

    Any change in prism/prism split?

  5. #5
    Master OptiBoarder Clive Noble's Avatar
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    Hi guys, thanks for the input.... just one question...

    Is the Natural 1.6 PGX an aspheric design lens?

  6. #6
    What's up? drk's Avatar
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    I don't think that matters, since the problem being referred to is when aspheric lenses are decentered to achieve prismatic effect, as opposed to prismatic grinding of the back surface. There's no way that you can decenter a progressive, and even if you tried, it'd be very tough to achieve that 6 pd BO by decentration!

    Have you been able to reproduce the distance at which she is "blurry"? That is important, IMHO.

  7. #7
    Master OptiBoarder Clive Noble's Avatar
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    No way can we get prism by decentration, it's not a S/V lens!

    The Pt (says) she sees ok from 3m on in the trial frame...(ou)

    Still stumped!

  8. #8
    What's up? drk's Avatar
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    Blue Jumper

    Now we may be getting somewhere. 3M is not very far out (10ft), so we're talking about her distance vision. Put her in a trial frame without prism and see if she's blurry with either eye, tested independently. What's her acuity level, anyway? I'll bet she has nuclear cataracts. Sometimes they notice that more at distance than near, because they get a type of double focus effect, somewhat like an aspheric multifocal contact.

    But you still need to check for diplopia. If she can't tell what distance she's blurry at, she probably can't tell the difference between mild diplopia and blur, either!

    Keep us posted.

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