The Effect of Light Upon the Eyes - Better Eyesight, November 1919,

Discussion in 'Optometry Archives' started by Zetsu, May 31, 2009.

  1. Zetsu

    Zetsu Guest


    Although the eyes were made to react to the light, a very general fear
    of the effect of this element upon the organs of vision is entertained
    both by the medical profession and by the laity. Extraordinary
    precautions are taken in our homes, offices and schools to temper the
    light, whether natural or artificial, and to insure that it shall not
    shine directly into the eyes; smoked and amber glasses, eye-shades,
    board-brimmed hats and parasols are commonly used to protect the
    organs of vision from what is considered an excess of light; and when
    actual disease is present it is no uncommon thing for patients to be
    kept for weeks, months and years in dark rooms, or with bandages over
    their eyes.

    The evidence on which this universal fear of the light has been based
    is of the slightest. In the voluminous literature of the subject one
    finds such a lack of information that, in 1910, Dr. J. Herbert Parsons
    of the Royal Ophthalmic Hospital of London, addressing a meeting of
    the Ophthalmological Section of the American Medical Association, felt
    justified in saying that ophthalmologists, if they were honest with
    themselves, "must confess to a lamentable ignorance of the conditions
    which render bright light injurious to the eyes." Since then, Verhoeff
    and Bell have reported [1] an exhaustive series of experiments carried
    on at the Pathological Laboratory of the Massachusetts Charitable Eye
    and Ear Infirmary, which indicate that the danger of injury to the eye
    from light radiation as such has been "very greatly exaggerated." That
    brilliant sources of light sometimes produce unpleasant temporary
    symptoms cannot, of course, be denied; but as regards definite
    pathological effects, or permanent impairment of vision from exposure
    to light alone, Drs. Verhoeff and Bell were unable to find, either
    clinically or experimentally, anything of a positive nature.

    The results of these experiments are in complete accord with my own
    observations as to the effect of strong light upon the eyes. In my
    experience such light has never been permanently injurious. Persons
    with normal sight have been able to look at the sun for an indefinite
    length of time, even an hour or longer, without any discomfort or loss
    of vision. Immediately afterward they were able to read the Snellen
    test card with improved vision, their sight having become better than
    what is ordinarily considered normal. Some persons with normal sight
    do suffer discomfort and loss of vision when they look at the sun; but
    in such cases the retinoscope always indicates an error of refraction,
    showing that this condition is due, not to the light, but to strain.
    In exceptional cases persons with defective sight have been able to
    look at the sun, or have thought that they have looked at it, without
    discomfort and without loss of vision; but, as a rule, the strain in
    such eyes is enormously increased and the vision decidedly lowered by
    sun-gazing, as manifested by inability to read the Snellen test card.
    Blind areas (scotomata) may develop in various parts of the field -
    two or three or more. The sun, instead of appearing perfectly white,
    may appear to be slate-colored, yellow, red, blue, or even totally
    black. After looking away from the sun, patches of color of various
    kinds and sizes may be seen, continuing a variable length of time,
    from a few seconds to a few minutes, hours, or even months. In fact,
    one patient was troubled in this way for a year or more after looking
    at the sun for a few seconds. Even total blindness lasting a few hours
    has been produced. Organic changes may also be produced. Inflammation,
    redness of the cojunctiva, cloudiness of the lens and of the aqueous
    and vitreous humours, congestion and cloudiness of the retina, optic
    nerve and choroid, have all resulted from sun-gazing. These effects,
    however, are always temporary. The scotomata, the strange colors, even
    the total blindness, as explained in the preceding chapter, are only
    mental illusions. No matter how much the sight may have been impaired
    by sun-gazing, or how long the impairment may have lasted, a return to
    normal has always occured; while prompt relief of all the symptoms
    mentioned has always followed the relief of eyestrain, showing that
    the conditions are the result, not of the light, but of the strain.
    Some persons who have believed their eyes to have been permanently
    injured by the sun have been promptly cured by central fixation,
    indicating that their blindness had been simply functional.

    By persistence in looking at the sun, a person with normal sight soon
    becomes able to do so without any loss of vision; but persons with
    imperfect sight usually find it impossible to accustom themselves to
    such a strong light until their vision has been improved by other
    means. One has to be very careful in recommending sun-gazing to
    persons with imperfect sight; because, although no permanent harm can
    result from it, great temporary discomfort may be produced, with no
    permanent benefit. In some rare cases, however, complete cures have
    been effected by this means alone.

    In one of these cases the sensitiveness of the patient, even to
    ordinary daylight, was so great that an eminent specialist had felt
    justified in putting a black bandage over one eye and covering the
    other with a smoked glass so dark as to be nearly opaque. She was kept
    in this condition of almost total blindness for two years without any
    improvement. Other treatment extending over some months also failed to
    produce satisfactory results. She was then advised to look directly at
    the sun. The immediate result was total blindness, which lasted
    several hours; but next day the vision was not only restored to its
    former condition, but was improved. The sun-gazing was repeated, and
    each time the blindness lasted for a shorter period. At the end of a
    week the patient was able to look directly at the sun without
    discomfort, and her vision, which had been 20/200 without glasses and
    20/70 with them, had improved to 20/10, twice the accepted standard
    for normal vision.

    Like the sun, a strong electric light may also lower the vision
    temporarily, but never does any permanent harm. In those exceptional
    cases in which the patient can become accustomed to the light, it is
    beneficial. After looking at a strong electric light some patients
    have been able to read the Snellen test card better.

    It is not light but darkness that is dangerous to the eye. Prolonged
    exclusion from the light always lowers the vision, and may produce
    serious inflammatory conditions. Among young children living in
    tenements this is a somewhat frequent cause of ulcers upon the cornea,
    which ultimately destroy the sight. The children, finding their eyes
    sensitive to light, bury them in the pillows and shut out the light
    entirely. The universal fear of reading or doing fine work in a dim
    light is, however, unfounded. So long as the light is sufficient so
    that one can see without discomfort, this practice is not only
    harmless, but may be beneficial.

    Sudden contrasts of light are supposed to be particularly harmful to
    the eye. The theory on which this idea is based is summed up as
    follows by Fletcher B. Dresslar, specialist in school-hygiene and
    sanitation of the United States Bureau of Education:
    "The muscles of the iris are automatic in their movements, but
    rather slow. Sudden strong light and weak illumination are painful and
    likewise harmful to the retina. For example, if the eye adjusted to a
    dim light is suddenly turned toward a brilliantly lighted object, the
    retina will receive too much light, and will be shocked before the
    muscles controlling the iris can react to shut out the superabundance
    of light. If contrasts are not strong, but are frequently made, that
    is, if the eye is called upon to function where frequent adjustments
    in this way are necessary, the muscles controlling the iris become
    fatigued, respond more slowly and less perfectly. As a result,
    eyestrain in the ciliary muscles is produced and the retina is
    overstimulated. This is one cause of headaches and tired eyes." [2]

    There is no evidence whatever to support these statements. Sudden
    fluctuations of light undoubtedly cause discomfort to many persons,
    but far from being injurious, I have found them, in all cases
    observed, to be actually beneficial. The pupil of the normal eye, when
    it has normal sight, does not change appreciably under the influence
    of changes of illumination; and persons with normal vision are not
    inconvenienced by such changes. I have seen a patient look directly at
    the sun after coming from an imperfectly lighted room, and then,
    returning to the room, immediately pick up a newspaper and read it.
    When the eye has imperfect sight, the pupil usually contracts in the
    light and expands in the dark, but it has been observed to contract to
    the size of a pinhole in the dark. Whether the contraction takes place
    under the influence of light or of darkness, the cause is the same,
    namely, strain. Persons with imperfect sight suffer great
    inconvenience, resulting in lowered vision, from changes in the
    intensity of the light; but the lowered vision is always temporary,
    and if the eye is persistently exposed to these conditions, the sight
    is benefited. Such practices as reading alternately in a bright and a
    dim light, or going from a dark room to a well-lighted one, and vice
    versa, are to be recommended. Even such rapid and violent fluctuations
    of light as those involved in the production of the moving picture
    are, in the long run, beneficial to all eyes. I always advise patients
    under treatment for the cure of defective vision to go to the movies
    frequently and practice central fixation. They soon become accustomed
    to the flickering light, and afterward other lights and reflections
    cause less annoyance.

    [1] Proc. Am. Acad. Arts and Sciences, July, 1916, vol. 51, No. 13.

    [2] School Hygiene, Brief Course Series in Education, edited by Paul
    Monroe, Ph.D., 1916, pp. 235-236.

    Zetsu, May 31, 2009
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  2. Zetsu

    Don W Guest


    You should be shot for this type of posting.

    Don w.
    Don W, May 31, 2009
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  3. 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 ...

    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 1, 2009
  4. Zetsu

    Don W Guest

    If only that...
    Don W, Jun 1, 2009
  5. Zetsu

    otisbrown Guest

    Dear Don,

    Don> You should be shot for this type of posting.
    I may not "like" what Zetzu posts, but I believe that we should not

    Perhaps we should BURN all Bates books also?

    Perhaps we should destroy people who develop the second-opinion -- in
    any profession?

    I don't know who said it, but:

    It begins with the burning of books -- and ends with the burning of

    No, I defend Bates and other second-opinion medical and scientific
    people -- whether I agree with them or not.

    otisbrown, Jun 1, 2009
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