Shifting and Swinging - Better Eyesight, December 1919, Editor: W. H.Bates, M.D.

Discussion in 'Optometry Archives' started by Zetsu, Jun 11, 2009.

  1. Zetsu

    Zetsu Guest

    [...]

    When the eye with normal vision regards a letter either at the near-
    point or at the distance, the letter may appear to pulsate, or move in
    various directions, from side to side, up and down, or obliquely. When
    it looks from one letter to another on the Snellen test card, or from
    one side of a letter to another, not only the letters, but the whole
    line of letters and the whole card, may appear to move from side to
    side. This apparent movement is due to the shifting of the eye, and is
    always in a direction contrary to its movement. If one looks at the
    top of a letter, the letter is below the line of vision, and therefore
    appears to move downward. If one looks at the bottom, the letter is
    above the line of vision and appears to move upward. If one looks to
    the left of the letter, it is to the right of the line of vision and
    appears to move to the right. If one looks to the right, it is to the
    left of the line of vision and appears to move to the left.

    Persons with normal vision are rarely conscious of this illusion, and
    may have difficulty in demonstrating it; but in every case that has
    come under my observation they have always become able, in a longer or
    shorter time, to do so. When the sight is imperfect the letters may
    remain stationary, or even move in the same direction as the eye.

    It is impossible for the eye to fix a point longer than a fraction of
    a second. If it tries to do so, it begins to strain and the vision is
    lowered. This can readily be demonstrated by trying to hold one part
    of a letter for an appreciable length of time. No matter how good the
    sight, it will begin to blur, or even disappear, very quickly, and
    sometimes the effort to hold it will produce pain. In the case of a
    few exceptional people a point may appear to be held for a
    considerable length of time; the subjects themselves may think that
    they are holding it; but this is only because the eye shifts
    unconsciously, the movements being so rapid that objects seem to be
    seen all alike simultaneously.

    The shifting of the eye with normal vision is usually not conspicuous,
    but by direct examination with the ophthalmoscope [1] it can always be
    demonstrated. If one eye is examined with this instrument while the
    other is regarding a small area straight ahead, the eye being
    examined, which follows the movements of the other, is seen to move in
    various directions, from side to side, up and down, in an orbit which
    is usually variable. If the vision is normal, these movements are
    extremely rapid and unaccompanied by any appearance of effort. The
    shifting of the eye with imperfect sight, on the contrary, is slower,
    its excursions are wider, and the movements are jerky and made with
    apparent effort.

    It can also be demonstrated that the eye is capable of shifting with a
    rapidity which the ophthalmoscope cannot measure. The normal eye can
    read fourteen letters on the bottom of a Snellen test card, at a
    distance of ten or fifteen feet, in a dim light, so rapidly that they
    seem to be seen all at once. Yet it can be demonstrated that in order
    to recognize the letters under these conditions it is necessary to
    make about four shifts to each letter. At the near-point, even though
    one part of the letter is seen best, the rest may be seen well enough
    to be recognized; but at the distance is it impossible to recognize
    the letters unless one shifts from the top to the bottom and from side
    to side. One must also shift from one letter to another, making about
    seventy shifts in a fraction of a second.

    A line of small letters on the Snellen test card may be less than a
    foot long by a quarter of an inch in height; and if it requires
    seventy shifts to a fraction of a second to see it apparently all at
    once, it must require many thousands to see an area of the size of the
    screen of a moving picture, with all its detail of people, animals,
    houses, or trees, while to see sixteen such areas to a second, as is
    done in viewing moving pictures, must require a rapidity of shifting
    that can scarcely be realized. Yet it is admitted that the present
    rate of taking and projecting moving pictures is too slow. The results
    would be more satisfactory, authorities say, if the rate were raised
    to twenty, twenty-two, or twenty-four a second. The human eye and mind
    are not only capable of this rapidity of action, and that without
    effort or strain, but it is only when the eye is able to shift thus
    rapidly, that eye and mind are at rest, and the efficiency of both at
    their maximum. It is true that every motion of the eye produces an
    error of refraction; but when the movement is short, this is very
    slight, and usually the shifts are so rapid that the error does not
    last long enough to be detected by the retinoscope, its existence
    being demonstrable only by reducing the rapidity of the movements to
    less than four or five a second. The period during which the eye is at
    rest is much longer than that during which an error of refraction is
    produced. Hence, when the eye shifts normally no error of refraction
    is manifest. The more rapid the unconscious shifting of the eye, the
    better the vision; but if one tries to be conscious of a too rapid
    shift, a strain will be produced.

    Perfect sight is impossible without continual shifting, and such
    shifting is a striking illustration of the mental control necessary
    for normal vision. It requires perfect mental control to think of
    thousands of things in a fraction of a second; and each point of
    fixation has to be thought of separately, because it is impossible to
    think of two things, or two parts of one thing, perfectly at the same
    time. The eye with imperfect sight tries to accomplish the impossible
    by looking fixedly at one point for an appreciable length of time;
    that is, by staring. When it looks at a strange letter and does not
    see it, it keeps on looking at it in an effort to see it better. Such
    efforts always fail, and are an important factor in the production of
    imperfect sight.

    One of the best methods of improving the sight, therefore, is to
    imitate consciously the unconscious shifting of normal vision, and to
    realize the apparent motion produced by such shifting. Whether one has
    imperfect or normal sight, conscious shifting and swinging are a great
    help and advantage to the eye; for not only may imperfect sight be
    improved in this way, but normal sight may be improved also.

    Detailed instructions for improving the sight by this method will be
    given in my forthcoming book, The Cure of Imperfect Sight by Treatment
    without Glasses.

    [1] An instrument for viewing the interior of the eye. When the optic
    nerve is observed with the ophthalmoscope, movements can be noted that
    are not apparent when only the exterior of the eye is regarded.

    [...]
     
    Zetsu, Jun 11, 2009
    #1
    1. Advertisements

  2. Zetsu

    Neil Brooks Guest

    Zetsu has long ago reached the level where he/she/it is nothing
    more than the online equivalent of one of those psychotic homeless
    people who stands on the corner, SHOUTING Bible passages, to ...
    nobody.

    What a pathetic little creature.

    Almost SURELY the illegitimate love child of Otis Brown (and ... who
    else?? Desperate people DO do desperate things....).
     
    Neil Brooks, Jun 11, 2009
    #2
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.