For "Frosty Paw" =-- the -1/3 diopter / year at a military college

Discussion in 'Optometry Archives' started by Otis Brown, Apr 10, 2004.

  1. Otis Brown

    Otis Brown Guest

    Dear FrostyPaw --

    Subject: Clarification of the -1/3 diopter per year statement
    about the behavior of the natural eye.

    You asked for background information on the behavior of the
    normal eye at our military colleges.

    I stated specifically, that the "downward" rate for all these
    eyes was approximately -1/3 diopters per year. This is the average
    value for ALL eyes.

    Some eyes went "down" at a faster rate, and some showed a
    rate of zero diopters. But the AVERAGE of all NORMAL EYES was
    -1/3 diopter per year, and obviously -1.333 for four years.

    Since FrostyPaw doubted these statistics, I am posting
    statements by Dr. R. Hayden about various issues concerning this
    basic statistics.

    In general, I simply report objective facts. Others can put
    their own "spin" on them if the like.

    It is often claimed that no one knows how or why the eye
    develops nearsightedness -- and no one can "predict" the
    development of a negative focal status for the eye for a person
    entering college.

    If a pilot enters a four year college with 20/20, but a focal
    status of zero (sometimes called "emmetropia"), it is virtually
    certain that he will not be 20/20 at graduation. The statistics
    show that his vision will be -1.0 to -1.3 diopters with a visual
    acuity of 20/70 to 20/100. No one ever bothers to tell any pilot
    about these statistics. If they only knew they MIGHT be able to
    take effective action for prevention.

    Here are the records and statement about the eyes movement
    from a positive value to a negative value at the Naval Academy.

    When we attempted to institute a "preventive" method at the
    Naval Academy we go nothing but "stone-walling" of the type you
    have seen from

    When I asked you to use the plus for prevention at college, I
    was well-aware of these statistics. It is very hard to miss the
    point -- but it seems everyone manages to do so.



    Dr. Steve Leung
    Dr. Stirling Colgate
    Dr. Dave Guyton
    Dr. Francis Young


    For: discussion

    Dear Bill,

    Re: Dear 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 to establish the student's
    refractive state as having some positive status.


    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

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


    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.


    "...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" was 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 two to four years in the Naval Academy. Experience showed
    that only about one percent of such men had 20/20 on their final
    physical examination."

    [Summary -- if their 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

    [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."


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


    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, including
    +0.25 diopters. At the first year their examination would show
    that they had myopia.

    Occasionally a candidate who showed as much as +0.5 diopters
    "hypermetropia" on preliminary physical examination was found to
    have -0.25 diopters of myopia in the first year.



    "...As is well known, the emmetropic eye is for practical
    purpose an 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 why 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 view 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 diopter 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 to 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
    student have a hyperopic reserve of at least one diopter of
    hypermetropia at the time of admission."

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


    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.



    "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

    "...Any candidate having less than 1/2 diopter 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, Apr 10, 2004
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  2. Otis Brown

    Frostypaw Guest

    That's one doctor from a LONG time before I was born - where's a
    recent study showing this 1/3diopter shift?

    ps. i must clarify that my views are in no way associated with
    teletext, i was simply posting from that address and will shortly
    change to something more suitable.
    Frostypaw, Apr 11, 2004
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  3. Otis Brown

    Otis Brown Guest

    Dear Mike,

    The point you are missing, Mike, is that this is not your

    Your understanding of statistics is poor since you do
    not seem to understand the concept of STATISTICAL
    AVERAGE for an entire population of NATURAL EYES>

    I have greater confidence in engineering students
    (who will review this data) than I do in you.

    Since prevention is indeed hard work, and
    requires a great motivation and insight,
    I doubt that your involvement would
    serve any purpose in this type of work.


    Otis Brown, Apr 11, 2004
  4. Otis Brown

    Dr Judy Guest

    Hayden's 1941 study found about just under 40% of cadets became nearsighted
    by graduation, so 60% did not. Since the average myopia of all students is
    1.33 and 60% are not myopic, the average myopia must be considerably more,
    ie about 3.00D to 3.50D. If, as you propose, the use lof lenses changes
    refractive error, then those who use plus lenses and were destined to be
    myopes will not be myopic, but those who use lenses and were not destined to
    be myopic will then be more hyperopic than they started, presumably by at
    least 3.00D. Should you not be warning those students that they may face
    much earlier than normal need for reading glasses, likely in their late
    twenties to early thirties?

    If the method you proposed looked anything like the proposed "study" you
    have posted here, with its scientific errors and lack of credible
    references, I can imagine that Naval Academy would have politely shown you
    the door and thought you to be a kook. Look up the suggestions that various
    people here made to you about improving the proposal, make the changes and
    try again.

    Dr Judy

    snip balance.
    Dr Judy, Apr 11, 2004
  5. Otis Brown

    Otis Brown Guest

    Dear Judy,

    Again you miss the point -- as a matter of statistics.

    The AVERAGE movement for the entire population of
    natural eyes was -1/4 diopter as reported by
    Dr. Hayder.

    But he was very explicit about the entering midshipman
    who had a refractive status of 0.0, i.e., "squinting 20/20".

    He said that that person has less than a one-percent
    probability of graduating from the Naval Academy
    with 20/20.

    If I were entering a four year college and understood
    THAT statistic correctly, I think I would be interested
    in doing something about it.

    But that would be a matter of intelligent understanding
    of the pilot concerned with keeping his 20/20 vision
    for the four years he would be in an aeronautical

    That is the point, my friend.

    Neither I nor you could ever make that kind of decision
    for the man. Just provide him the facts, and
    allow him to make a choice for a "fighting chance".

    He has nothing to lose -- and it is clear as
    to what will happen if he chooses to do nothing.

    But you put a different "spin" on these obective
    facts concerning the behavior of the natural eye
    at a four year military college.




    If, as you propose, the use lof lenses changes
    Otis Brown, Apr 12, 2004
  6. Otis Brown

    Dr. Leukoma Guest

    (Otis Brown) wrote in
    A refractive status of zero does not imply "squinting 20/20." What it says
    is that the very best visual acuity for this person is achieved with a lens
    of zero power. Your premise is wrong.
    If a person squints, then they are probably already nearsighted.
    Doesn't "fighting chance" imply at least a 50:50 chance of success?
    Dr. Leukoma, Apr 12, 2004
  7. Otis Brown

    Otis Brown Guest

    (Otis Brown) wrote in message

    Dear DrJudy,

    I need a copy of this for my records -- and to
    present to pilots entering a four year college.

    I think they will understand the statistics
    presented by Dr. Hayden. If they do not -- then
    too bad.

    My appreciation that "prevention" with a plus
    lens is not easy or "quick", and the pilot
    (at 20/30 or 20/40) should spend a
    year evaluating your arguments and these
    statistics BEFORE he takes any action.

    Success favors a prepared mind.



    Otis Brown, Apr 12, 2004
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