The Natural Eye "adapts" its refractive STATE to a "near" environment.

Discussion in 'Eye-Care' started by otisbrown, Oct 21, 2006.

  1. otisbrown

    otisbrown Guest

    Dear Prevention minded friends,

    Subject: Analysis of refractive STATE change in
    a school environment -- after 8 years, from
    plus to minus as natural process.

    I am convinced that Jake Raphaelson was correct -- and convinced
    that ONLY you can protect your own children with the plus.

    As far as I am concerned, a child with a refractive STATE of
    from zero to +1/2 diopter should receive a written notification
    of the potential for plus prevention.

    At that stage the child would have 20/30 vision or better,
    and could wear a +1.0 diopter all the time.

    The lens would create 20/60 to 20/70, for a period of time,
    but -- with understanding -- the child could wear it all
    the time.

    [Yes, I KNOW the difficulties.]

    But from the primate studies, the refractive STATE will
    slowly move positive. And after three or four months
    the refractive state would move towards +3/4 to +1 diopters.

    [As previously discussed, a +1.5 diopter has been prescribed
    for a child. The only issue is to get the parent to
    understand the reason and need for the preventive-plus
    at that point.]

    This type of result is predictable from the primate studies.

    But it would take a wise parent the understand this issue.

    The other alternative is to BEGIN the use of a plus
    for all close work, and adjusted for the child's
    habitual reading distance.

    It is easy to say the above, but difficult to implement -- indeed.


    I have Fancis Young's records and reports.

    The most critical item was to measure 600 some wild monkeys
    and establish that they had an average value of +0.7 diopters
    with a standard deviation of 0.7 diopters. (Slight round off.)

    For all practical purposes that indicates that
    positive refractive STATES should never be called "errors"
    which can not be the case -- since all normal eye's
    have them.

    So man, and Eskimos with have positive refractive states
    and good distant vision -- provided they live as "hunters".
    The gaussian distribution would be the same.

    With statistics, there
    are always a few exceptions -- but they amount
    to maybe 2 percent of the population.

    Here is the data on children at age 9 and age 17
    from, "Ocular Biometry of Eskimo Families"

    Francis Young, George Leary

    Reprinted from:

    Massin, J. and Poujol, J. (Eds.))
    Diagonstica Ultrasonica
    in Ophthalmologia,
    Paris, Centre National d'Ophthalmologie des
    Quinze-vingts, 1973

    Here are the numbers:

    At Age 9

    N = 109

    Mean +1.43

    SD = 1.40


    At Age 17

    N = 97

    Mean = -0.94

    SD = 1.97



    Z = X(c) - X(t) / Sqrt [ X(c) ^2 / N(c) + X(t) / N(t)

    Z = 2.37 / Sqrt [ 1.4 ^2 / 109 + 1.97 ^2 / 97 ]

    Z = 9.84


    This compares with 95 percent (significant) and
    99 percent (highly significant). These values are
    1.64 and 2.33.

    Virtually certain is anything above 3.9, and this
    value is far above that number.

    No single study, no one assessment can be

    But over 30 years you would expect that
    we could get "smarter" about the need
    for plus-prevention at the threshold.

    Or at the very minimum, understand the
    long-term consequences of rejecting
    the preventive plus at the zero to + 1/2 diopter phase.

    Perhaps these statistics will help a parent ACCEPT
    the need for the preventive plus -- even when
    their child as 20/20 and +1/4 diopter.

    Below are some commentary by the
    majority-opinion ODs for your interest.


    otisbrown, Oct 21, 2006
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