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Thread: Persistent strand of light in polarized lens

  1. #1
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    Persistent strand of light in polarized lens

    I'm stumped. I made a pair of poly polarized lenses for a customer and the left lens has a persistent strand of light down the center. I chalked it up to a defect and ordered a redo on a different base curve just to be safe, but the new lens has the exact same problem. Two lenses, dif bases, same problem. Has anybody ever seen this before? What causes it? Is it some byproduct of birefringence between polarization coat and the lens itself? I don't want to waste a third redo, and make the customer have to wait longer, so any info is def helpful.

    Btw, the rx for this lens is -7.25 +1.25 @10, the axis doesn't matter because the strand moves with the axis...or maybe it's moving with the polarization. It appears to be gone once it is off 90 degrees. Anyways, take a look at the pic and let me know.

    The right eye RX, which has no issues, is -6.50 +2.00 @170. Just in case you guys want to know.

    Thanks so much.
    Attached Thumbnails Attached Thumbnails photo.jpg   line two.jpg  

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    Master OptiBoarder CCGREEN's Avatar
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    Is that line visiable with the lens out of the frame? If not I say that light colored spot on the frame has something to do with it. Has this frame had polorized lenses in it before? If so was it a issue at that time?

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    Actually, yes, it is visible without the frame. And the original lenses were polarized and had no issue.

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    Actually, yes, it is visible without the frame. And the original lenses were polarized and had no issue.

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    Is this strand of light apparent after surfacing? if not then apparent after edging? if not did this appear after mounting? I am wondering if the strand is not apparent until after mounting that the lens is being overly stressed in the frame (the exact same way twice would bring that to mind). If the lenses showed no strand prior to mounting check the center thickness of the bad lenses; if you find the CT a tad thin try bumping it up a couple of tenths or try you could a different polar lens manufacturer and run a new pair.

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    Quote Originally Posted by Plausible View Post
    Is this strand of light apparent after surfacing? if not then apparent after edging? if not did this appear after mounting? I am wondering if the strand is not apparent until after mounting that the lens is being overly stressed in the frame (the exact same way twice would bring that to mind). If the lenses showed no strand prior to mounting check the center thickness of the bad lenses; if you find the CT a tad thin try bumping it up a couple of tenths or try you could a different polar lens manufacturer and run a new pair.
    The lenses have the strand both in and out of the frame. As for surfacing, we receive the lenses surfaced from the lab, so I do not know. Also, would the CT be a factor? since the lens becomes thicker away as you move away from the CT? hmmmmmm...... you might be onto something though.

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    Independent Problem Optiholic edKENdance's Avatar
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    Had a similar problem recently. There was a small crack in the lens.

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    Quote Originally Posted by Jaketull View Post
    The lenses have the strand both in and out of the frame. As for surfacing, we receive the lenses surfaced from the lab, so I do not know. Also, would the CT be a factor? since the lens becomes thicker away as you move away from the CT? hmmmmmm...... you might be onto something though.
    Understood, both in and out of the frame as the lens is now. What I would be looking for is the strand after edging and BEFORE mounting. If the strand appears after mounting there is likely too much stress across the A. Now increasing the CT may help eliminate the strand but if stress is truly causing the issue I would fix the shape as well as bump the CT. Just my 2cents.

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    Who puts a -7.00 in Poly?

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    ABOM Wes's Avatar
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    Quote Originally Posted by chip anderson View Post
    Who puts a -7.00 in Poly?
    In some retail stores, that's the only option available for sale.
    Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA

    “As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein

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    lens was broken while edging

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    IF the strand was in the same location, it could be a bad batch of polar blanks. I have seen more poor polar blanks lately, includng one that had effective polarization on only one half of the blank. Weird. If its in a different locations, edging or surfacing stress would we one culprit.

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