Can you predict your developing myopia in college?

Discussion in 'Optometry Archives' started by Otis Brown, Oct 22, 2003.

  1. Otis Brown

    Otis Brown Guest

    Dear Bill,


    Re: Otis -- If a person is not myopic by the time they reach
    college (USAF Academy) what are the chances of becoming
    myopic from the required reading load? Has the USAF run any
    experiments to find out what causes myopia in their
    personnel? Bill


    If you know the refractive state of an "entering" student can
    you predict the resultant refractive state after four years?

    If you check the person's focal status, and find it to be
    "zero" or "plano", then the probability the person will retain
    his 20/20 is about one percent -- as stated by Dr. Hayden.


    Note: Refractive state is determined by using a trial-lens kit.
    It is first established that the pilot (or entering
    student) has 20/20. The next step it to use a sequence of
    stronger plus lenses that establish the students
    refractive state as some positive degree.


    REFERENCES

    1. Reynolds Hayden, M.D., "Development and Prevention of Myopia at
    the United States Naval Academy", Volume 25, (old series
    Volume 82), Number 4., Copyright, 1941, The American
    Medical Association.

    2. Gmelin, Maj. Robert T., MSC, USA, "Myopia at West Point: Past
    and Present." Military Medicine, 141 (8) 542-3, August
    1976.


    Here is the information I have on your question concerning
    "base-line data concerning the behavior of the normal
    healthy eye at that Naval Academy.


    SYNOPSIS

    For years, since 1879 in fact, studies of military cadets in
    the United States have shown that their vision changes over the
    years of their academic work. Records reveal that a large
    percentage of the cadets (39% of those at the U.S. Military
    Academy in 1956) [2] became nearsighted and needed negative lenses
    by graduation.

    Further, of those who developed 20/25 vision, only one
    percent recovered to 20/20 over the four years, [1]. (They were
    not provided with plus-lenses, and for this reason had no chance
    to recover.)

    In early years their degraded vision was blamed on the fumes
    of gas lighting, and later, on any number of factors, but the
    upshot of the studies was that none of these circumstance were
    really behind the cadet's loss of visual acuity. The myopia
    (change of focal state) was a result of the fact that the natural
    eye controls its focal state to its average visual environment.
    Roughly, that is looking close, studying, reading, looking at
    books, for long periods of time -- rather than at distant objects.


    SELECTED STATEMENTS FROM DR. HAYDEN

    "...For many years the high incidence of myopia which
    apparently developed among midshipmen after admission to the
    United States Naval Academy with supposedly normal vision was a
    cause of serious concern to all those interested.

    (Extended "rest" offered, as stated by Dr. Hayden)

    "... and by retaining may of them (who became nearsighted) in
    the Naval Academy for one to three years in the hope that their
    vision would improve. "

    "...In the vast majority of cases their vision did not
    improve, and the midshipmen was forced to leave the naval service
    after tow or two to four years in the Naval Academy. Experience
    showed that only about 1 percent of such men had 20/20 on their
    final physical examination.

    [Summary -- if there focal status became even SLIGHTLY
    negative (20/25) they had virtually no chance of clearing their
    distant vision to 20/20. OSB]

    "...Furthermore, an excessive number of junior line officers
    were being retired because of defective vision, and the records
    showed that the vision of 3/4 of these had become defection
    defective (vision less than 20/20 for each eye) at the Naval
    Academy."

    [Dr. Hayden then reviews the statistics on a class by class
    basis -- to long to type up.]

    "...Any candidate, however, who if found to have any degree
    of myopia following the use of a cycloplegic, even -0.12 or -0.25
    diopters is rejected."


    NECESSITY OF HYPEROPIC RESERVE

    (For young health men with 20/20 -- A
    Positive focal state of the eye. OSB)


    PARAPHRASE

    Review of the refraction of the eye of candidates at the time
    of preliminary physical examination showed that the great majority
    of candidates whose refraction was of the plano-type, or +0.25
    diopters, at the time of later examination showed that they had
    slight myopia.

    Occasionally a candidate who showed as much as 0.5 diopters
    "hypermetropia" on initial physical examination was found to have
    -0.25 diotpers of myopia.


    HAYDEN STATES THAT "EMMETROPIA" IS "NOT NORMAL"

    "...As is well known, and emmetropic eye is for practical
    purpose and abnormal eye, the great majority of persons with
    so-called normal vision being actually hypermetropic. Those
    candidates, then, whose refraction was of the plano (emmetropic --
    focal status exactly zero) had borderline conditions definitely on
    the way to myopia. For all practical purposes, experience here
    has shown that patients with +0.25 diopters of hypermetropia are
    in the same class."

    [This is I use the word "focal state" to define what we
    measure, rather than implying "defect" for what is in fact natural
    an normal. OSB]

    "In vies of the experience at the Naval Academy during the
    past three years as described, it is evident that a reserve of
    preferably 1 diopter and at least 1/2 dipoter is necessary at the
    time of preliminary refraction to be reasonably sure that the
    candidate will pass his physical examination for admission.

    "Furthermore, in order o be reasonably sure of being visually
    qualified for a commission in the line of the Navy after four
    years at the Naval Academy it is necessary that the a hyperopic
    reserve of at least 1 diopter of hypermetropia at the time of
    admission.

    "Of course, an occasional candidate will 0.25 to 0.5 diotper
    of hypermetropia at the time of admission admission will survive
    visually and receive a commission, but this is exceptional.


    DR. HAYDEN THEN DISCUSSES ATROPINE A CYCLOPLEGIC

    He details the loss of people in various classes who were
    "emmetropic" (focal state zero) on entry, using various drugs and
    percentage mixtures. It was hoped that using different drugs
    would produce better results and these emmetropic eyes could be
    "saved". However:

    In one case (c, d) the loss was 70 percent after three years,

    In another case (c, d) the loss was 85 percent at 2 years.


    THERE IS ADDITIONAL DISCUSSION OF ILLUMINATION LEVELS AND EFFORTS
    TO IMPROVE THESE LEVELS


    CONCLUSIONS

    "It is considered that during the past three years the Naval
    Academy has definitely proved the necessity of midshipmen having a
    "hyperopic reserve" of at least 1 diopter at the time of admission
    to the Naval Academy, and of their meeting the present visual
    requirements if the visual standards of the Naval are to be
    maintained."

    "...Any candidate having less than 1/2 dipoter of
    hypermetropia at the time of a preliminary ocular refraction
    should be informed that, while visually qualified at the time, he
    has a borderline condition which may progress to a low degree of
    myopia by the time he takes his physical examination for admission
    to the Naval Academy, and may therefore be rejected.

    Any candidate having from 0.5 to 1.0 diopters of hypermetropia
    at the time of a preliminary ocular refraction should be informed
    that, while he should pass the physical examination for entrance
    to the Naval Academy, he stands no better than an even chance of
    visually obtaining a commission in the line of the Navy on
    graduation."

    ____________________________________


    Note 1: All these men had healthy retinas. All retinas had the
    capability of resolving 5 minute-of-angle targets at 20
    feet. Their natural eye's behaved as expected. The
    controlled their focal state to the visual environment.
    For this reason an "undesired" focal state does no
    indicate an "organic defect" or words to that effect.
    For that reason I use the term focal state so their is no
    confusion in your mind about that point.


    Note 2: The words emmetropia and ametropia were introduced by
    Donders. Donders took the focal states of the normal eye
    to be DEFECTS of the eye. Any non-zero focal state of
    the eye was, by definition, a defect (ametropia). A
    focal state of EXACTLY zero was defined as "normal".
    Under this definition, very few, if any, animals or
    humans have eyes that are normal!
     
    Otis Brown, Oct 22, 2003
    #1
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  2. Otis Brown

    Otis Brown Guest

    Mike, this is NOT what I stated.

    This is by the way the statement of a Medical Doctor -- not me.

    The entry requirements were 20/20 -- for all entering.

    If a man had 20/20, and a measured forcal status of zero,
    the good doctor stated that he had about a 1 percent
    probability of retaining 20/20.

    If you do not believe this -- that is fine with me,
    since you only believe what YOU want to believe.

    Of the entire population, a man with a focal state
    of +1.0 diopter had an EXCELLENT chance of getting
    out with 20/20.

    Of the entire population, on entry, the spread
    was between zero to +1.5 diopters.

    Of this population, about 30 percent became myopic.

    But of course do not believe any of this -- and you
    fail to learn anything you do not like.

    Best,

    Otis

    cc:

    Dr. Steve Leung
    Rex
    Keith
    Alfred
    Don
    Dr. Stirling Colgate
     
    Otis Brown, Oct 23, 2003
    #2
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