prism question

Discussion in 'Optometry Archives' started by me, Sep 11, 2010.

  1. me

    me Guest

    Before getting back to that polarization thread....

    Today a friend tested my stereopsis with an old red-button Realist
    slide viewer. In order for me to see the stereo "fusion" and hidden
    stereo image, I had to turn the adjuster lever all the way to one end
    to horizontally superimpose the left and right images. I think it
    uses mirrors inside.

    Would this mean that I should get some "prism" in my eyeglasses

    How much would it cost? Remember I'm a homeless bum who can't simply
    walk into an optometrist's office for an exam and a pair of glasses.
    The fact I've never had "prism" prescribed should indicate
    professional callousness if it would ever have been a major benefit to
    me, Sep 11, 2010
  2. me

    me Guest

    So I should walk around with mirrors on my sunglasses. Or maybe I
    should find an optometrist or opthamologist on the planet Vulcan.
    me, Sep 11, 2010
  3. me

    me Guest

    Here is a private reply I received:

    "The Realist viewer doesn't have prisms in it. - The lever moves the
    lenses closer or further apart. This has a slight prismatic effect.
    Most people with normal eye spacing can view the 3D picture without
    difficulty if the lever is kept in the middle. - Normal eye spacing
    is about 63mm. The slide's film chips are mounted so that objects at
    infinity in a landscape picture are about 63mm apart. So ideally,
    your eyes will be parallel when looking at an object in the viewer
    which is supposed to appear far away. Objects which are supposed to
    appear closer to the viewer are closer together on the film chips but
    the disparity between very near and far objects is no more than 1 to 2

    "Prisms in glasses are often used to to prevent double vision - but
    cross-eyed people sometimes find ways to avoid the confusion of double
    vision on their own (for example by pointing the blind spot of one eye
    parallel to the central vision of the other eye.) - Stereo Sue talks
    about this in her book."
    me, Sep 12, 2010
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