Question about color vision

Discussion in 'Eye-Care' started by caveat, Oct 19, 2008.

  1. caveat

    caveat Guest

    Hi all,

    I'm not sure if this is the group to ask but I hope that you will point me
    in the correct direction if it is not.

    Years ago I noticed that while wearing my 2.75 reading glasses I can see the
    world clearly but could not focus on the numbers of my blue led alarm clock.
    I have no problems with focus on my wife's red led alarm clock.
    When I take off my glasses I can see the numbers on my blue led alarm clock
    clearly (after a little focus) but can not see the rest of the world
    clearly.
    I tested my self on some of the online color vision tests and it seems like
    I do NOT have any color blindness.
    I have used both dime store reading glasses and the high quality ones from
    my local eye doctor with expensive coatings with the same issue.
    My doctor didn't know what would cause this issue. Time to find a new
    doctor?

    This is not a major issue to me but I was simply wondering why this is so.
    I have some theories but I would like to know if anyone has any real world
    explanation as to why this happens.

    If it helps, I'm almost 40 and can no longer read small print clearly at
    night without a 60-75 watt light bulb (bummer, I remember reading small
    print in the dark with no light bulb or glasses) and have a slight
    stigmatism.

    Thanks,

    Chris
     
    caveat, Oct 19, 2008
    #1
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  2. caveat

    caveat Guest

    P.S. I just remembered this, I am nearly blind in one eye (lazy muscle is
    what I was told, eye is good but the optic nerve is defective) and can only
    make out faint shapes in that eye. If you are born like this then you grow
    used to it and don't think about it much.

    Chris
     
    caveat, Oct 19, 2008
    #2
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  3. caveat

    Salmon Egg Guest

    I think that you are seeing the effects of chromatic aberration. The
    natural eye also has chromatic aberration, but your brain has
    accommodated to this by suitable processing of the color receptors
    (cones). Wearing glasses introduces new aberration which the brain has
    not been trained to process correctly.

    Use of this effect was made during the heyday of psychedelics. Posters
    in red and blue appeared to not be flat but in relief.

    I am not a vision professional. My comments are based upon some
    biological knowledge and fairly good understanding of optical physics.
    If you think that you do have a physical problem with your eyes, see an
    ophthalmologist.

    Bill
     
    Salmon Egg, Oct 19, 2008
    #3
  4. caveat

    Mike Ruskai Guest

    It's the correct group, and as you've been told already, it's chromatic
    aberration that's at the core of what you're experiencing. In theory, you
    could create an incredibly expensive, and incredibly heavy pair of glasses
    that minimized the problem by using several different types of lens material
    with different levels of dispersion (it'd look like a couple of miniature
    telescopes mounted in front of your eyes), but the best you can do in practice
    is use an extra-low dispersion material for the one lens.

    I don't know off hand what's available for eyeglass use (likely not fluorite,
    which would require coatings just to stay intact in the air), but aside from
    forcing your OD to look up the best materials for a new pair, the more
    practical solution would be to avoid alarm clocks with blue digits.
     
    Mike Ruskai, Oct 19, 2008
    #4
  5. caveat

    Dan Abel Guest

    I was wondering about this. Camera lenses can be heavy and expensive,
    but that's because you want perfect sharpness from edge to edge of the
    film, and those lenses that are expensive usually are capable of very
    low light use. Camera lenses that are small are really quite cheap.
    Since only the macula requires sharpness, I don't see why glasses with
    multiple elements would be that expensive and stick out a long ways.
    Perhaps I just haven't thought it through or maybe I don't understand
    the issues.

    I agree that you have the practical solution for that small problem. I
    bought an LED clock with 2" red digits when I couldn't see at night. It
    still works well even though I can see OK now.

    However, there are a whole lot of blue things in this world, and
    sometimes they include numbers and letters, and not always very big.
     
    Dan Abel, Oct 19, 2008
    #5
  6. caveat

    Salmon Egg Guest

    In no way are camera lenses "perfect." The design is always a compromise
    among conflicting desires. Optical performance of an eye can be
    relatively lax because you turn your eye toward the object being used to
    obtain best acuity. Off-axis performance is relatively poor. As you turn
    your eye but not your head, you look through a different region of the
    spectacle lens. This increases aberration.
    There never was a guarantee that optometry would get you back to where
    you were before glasses. In principle, lasik should be able to give you
    close to theoretical performance considering the fundamental limitation
    of eye anatomy. That performance, however, will be on-axis only. With
    glass lenses, the process akin to lasik is called figuring.

    I am not a vision or health professional. I know little about the nuts
    and bolts of lasik.

    Bill
     
    Salmon Egg, Oct 20, 2008
    #6
  7. caveat

    caveat Guest

    Thank you all!!!

    I will now set forth upon a great adventure and learn all I can about
    chromatic aberration.

    This leads to another question, would actual glass be better at minimizing
    this characteristic than a poly lens?

    Thanks

    Chris
     
    caveat, Oct 22, 2008
    #7
  8. caveat

    Salmon Egg Guest

    Glass comes in a large number of varieties. Look, for example, at the
    Schott catalog. Color correction usually uses two different kinds of
    glass. That makes color correction for spectacles difficult and
    expensive.

    Bill
     
    Salmon Egg, Oct 22, 2008
    #8
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