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I Alternative to bifocal and varifocal spectacle lenses?

  1. Mar 19, 2016 #1
    Hi Everyone

    I am not sure but I seem to remember that about ten years ago, I either read something or saw something on TV about a revolutionary new type of lens which could potentially replace bifocal and varifocal spectacle lenses. The main drawback of bifocal and varifocal lenses is that you have to look through different parts of the lens to benefit from the different focal lengths. (Basically, you look through the upper part of the lens in order to look into the distance and the lower part in order to read up close.) I think this would be a pain in the neck (quite literally) and I am not sure I could get used to it.

    If I remember correctly, the lenses I saw mentioned about ten years ago work like as if two lenses of different focal lengths co-exist in exactly the same place (like a ghost passing through a wall co-exists in exactly the same place as the wall) so that you don't have to look through different parts of the lens to benefit from the different focal lengths. If I remember correctly, they do this by borrowing some aspects of lenticular technology or something similar.

    EDIT:
    I think the idea is that the lenses present to your eye both the focused image and the blurry image together and your brain learns to filter out the blurry image.
    END OF EDIT
    EDIT2:
    I think what I saw about ten years ago involved concentric interleaving and did not involve lenticular technology directly.
    END OF EDIT2

    I am now just starting to get to the point with my eyesight whereby reading small text up close is starting to get a bit difficult. I have therefore just searched Google for any mention of the lenses that I think I remember from ten years ago but I have not managed to find anything about them. Does anyone know anything about these lenses? If yes, I would be very grateful if you could point me in the right direction.

    Thank you very much.

    Kind regards

    Tim
     
    Last edited: Mar 19, 2016
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  3. Mar 19, 2016 #2

    phinds

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    I've never heard of such a thing and given what a nifty thing it sounds like, it seems very unlikely that it works in practice. After all, how would the lens "know" which image, a near-focused or a far-focused, to present to your eye? Just seems impossible. Be very cool if it does exist though.

    As for bifocals, most everyone who gets them gets used to them pretty quickly. I had no trouble at all. I DID find trifocals impossible, and I do recommend that if you get bifocals you get the kind with the obvious line between the two sections of each lens. The "no-line" type my look nicer but I think they are just confusing as all get-out when you're looking near the upper part of the lower lens or the lower part of the upper lens. Having a clear demarcation between the two works much better for me.
     
  4. Mar 19, 2016 #3
    Hi phinds

    Thank you very much for your reply.

    I think the idea is that the lenses present to your eye both the focused image and the blurry image together and your brain learns to filter out the blurry image.

    Kind regards

    Tim
     
  5. Mar 19, 2016 #4

    phinds

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    OK, that does make some sense. Be a bit tricky though in cases where the difference is pretty small but large enough to require bifocals.
     
  6. Mar 19, 2016 #5

    Simon Bridge

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    I wear varifocals and they are easy to get used to. The only difference is I have to sit up more to watch TV in bed.
    What you are describing would look like two "puddles" of in-focus vision - with blurry between. It sounds like something that cannot be done with a single lens.
    May be possible to interleave two lenses ... I'd expect the boundary between the leaves to make the lenses hard to see through.

    Lenticular images do not occupy the same place - they are "next to" each other, but at different angles.
     
  7. Mar 19, 2016 #6

    Andy Resnick

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  8. Mar 19, 2016 #7
    Hi Simon and Andy

    Thank you very much for your replies.

    This rings a bell. I think what I saw about ten years ago involved concentric interleaving.

    Yes, I know about what you have said about lenticular images. To be honest, I think that my faded memories from ten years ago were confusing the interleaving with the shape of lenticular lenses.

    I don't think so but it sounds like a good idea.

    Kind regards

    Tim
     
  9. Mar 19, 2016 #8

    Simon Bridge

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    ... that's what I was thinking too: the brute force approach would look like a fresnel lens but alternating bands are lenses with different focal length.
    A quick hunt suggests the approach for eyeglasses did not yield fruit.
     
  10. Mar 19, 2016 #9
    Hi Simon

    Thank you for your reply.

    I think that what you have described might exactly what I saw. Do you think that it might work if the bands are extremely fine? Or do you think this would cause too much diffraction or some other similar phenomenon which would mess it up?

    Kind regards

    Tim
     
  11. Mar 20, 2016 #10

    Andy Resnick

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  12. Mar 20, 2016 #11

    mfb

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    If the blurry image comes from one eye and the sharp one from the other, it is quite easy to filter out the blurry one. Source: tested it. Don't know how that would work if you have the blurry image around all the time, and I cannot test it within a single eye.
     
  13. Mar 20, 2016 #12

    phinds

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    I agree.
    I had a severe case of Graves Disease fairly recently and I was surprised at how resilient the brain is in being able to filter out bad information and keep the good. It got so bad for me that my left eye would be looking straight ahead at the road when I was driving and my right eye was looking squarely at the speedometer down on the dashboard, but after a while I was able to completely ignore the right-eye input (except at night, which became a serious problem because the left eye was looking at a dark road and the right at a brightly lit dashboard and could not be ignored. Had to drive w/ one eye closed at night until the operation (so didn't drive much at night)
     
  14. Mar 20, 2016 #13
    Someone I knew had glasses where one lens was for near vision and the other for distance vision. Maybe they were contacts, I don't remember. Anyhow, I couldn't imagine how that would work but he apparently had no problem with them.
     
  15. Mar 20, 2016 #14
  16. Mar 20, 2016 #15
    I am wondering now whether at some point in the future one could use eye tracking, or specifically, lens tracking, to adapt the glasses in real-time.
     
  17. Mar 20, 2016 #16

    mfb

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    Needs at least one camera (better two to also measure distance of the viewing target), a CPU to do eye tracking and a power source. Making all that small enough to not disturb is probably not so easy. A few years?
     
  18. Mar 20, 2016 #17
    I was actually thinking the other way around, I.e. instead of looking outward to analyze the scenery, all you do is measure the stretch of the eye lens. The lens will still do its normal job (just not enough anymore), so you can piggyback on that detection, and the glass lens would just serve as an "amplifier" so to speak.
     
  19. Mar 20, 2016 #18

    mfb

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    That sounds interesting as well.
     
  20. Mar 20, 2016 #19
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