-20 D eccentric fixation

Discussion in 'Optometry Archives' started by g.gatti, Jan 8, 2005.

  1. g.gatti

    g.gatti Guest

    I would like the learned men here to explain these things I am going to
    report.

    Now the client who is recovering from -20 D prescription by the use of
    the Original Systemof Self-Treatment by Rest Methods, recorded an
    experience as follows:

    At 2 meters distance from the 200 feet Snellen Chart (the one with the
    big 200 feet C at the top), she says that looking to the right of the C
    2 meters away, so to create an angle of 45 degrees, the big C seems
    MORE BLACK.

    I would like the learned men to explain to me why this happens, if it
    is a fact of physiological optics or just that the retina is damaged
    around the macula and becomes less damaged at the periphery.

    If we think that a -20 D eye is elongated at least by 6 or 7
    millimeters, ad has a bulge at the back, we could say that by looking
    at 45 degrees to the left or to the right, the rays of the big C fall
    an the side of the retina which is LESS DISTANT from the lens, than it
    is when she looks at the big C in the fovea.

    So this may be a good optical explanation: the C in the eccentric field
    falls on a side of the retina which is less myopic than the fovea.

    Now the strange fact is that when she regards the letter B, which is
    half the size of the C, and is read by the normal eye at 100 feet, she
    has no need to push away her gaze at 2 meters lateral, to see it
    blacker, but sensibly less distance.

    How this can be explained with the laws of optics?

    Furthermore,

    The girl says that when she reads microscopic print at 5, 7 or 9 cm,
    she has no "eccentric fixation", that is, she is able to see a little
    bit better where she is looking, the tiny letter she is reading (this
    letters are 1/3 of a millimiter tall).


    I would kindly appreciate any comments from the learned men who are
    here.


    Thanks.
     
    g.gatti, Jan 8, 2005
    #1
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  2. g.gatti

    g.gatti Guest

    Explain why the p.s. seems non existent at close distance regarding the
    eccentric fixation.
     
    g.gatti, Jan 8, 2005
    #2
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  3. g.gatti

    g.gatti Guest

    She has discarded completely her glasses since Jan 1st.

    Please, I do not understand at all the clock example you gave.

    Regarding human perception, this is the only field the medical men
    should investigate, not the optical system, which is totally dependant
    on human perception.

    I will report the progress of the girl in reducing her "eccentric
    fixation" as time goes by and practice is performed.
     
    g.gatti, Jan 9, 2005
    #3
  4. g.gatti

    g.gatti Guest

    Excuse my stupidity, what you said was already explained by myself in
    my first message.

    So we remain with the question:

    Why the trick of the clock does not work by looking at the letter B,
    half the size of the C?
    Perhaps some other learned men or women can answer this question.
     
    g.gatti, Jan 9, 2005
    #4
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