AlexWP.txt

Re: The West Point (Gmelin) Study and results.

Subject: The refractive behavior of the young eye.

A large number of studies of school children show
that when their eyes "go negative", they will continue
to go down at -1/2 diotper per year. In college
this rate slows down to about -1/3 diopter per year,
till graduation.

These statistics are reviewed below:

Otis Brown quoted Gmelin quoting McKinney's "Study of
Refractive Trends at West Point", saying:

Otis> The AVERAGE increase in myopia was -1.37 diopters (the range
being -1.12 diopters through -1.62 diopters).

Alex> What I think Gmelin and McKenny were saying was that for those
myopic cadets (or perhaps non-myopic as well) whose myopia
increased, the increase was an average of -1.37 diopters
over four years, or about a third of a diopter per year.
Those cadets, myopic or not, who did not experience a myopic
shift were not included in the figure.

Otis> Tragically, we would need ALL of the original data to settle
this dispute. We would have to know EXACTLY what was
considered a negative change. Would it be 1/8 diopter? 1/4
diopter? 1 diopter? The report does not say. It would
make a huge difference. For example, all went down, but
only 5 were greater that 1 diopter.

Otis> So that would be your -1.1 to -1.6 diopters (for the five)
All others (250) stayed where they were, or went postive.
Maybe, but that is the issue.

Alex> This figure cannot be compared, unadjusted, to the results of
animal experiments where the refractive trend of all
subjects is included in the average.

Otis> As always, a matter of human judgment.

Alex> Francis Young speaks about this discrepancy of convention in his
1981 paper, "Primate Myopia". I quote:

Young> <<When fully adult monkeys (one even gave birth in the chair)
were
enclosed in the hooded situation, 7 of 10 developed myopia
or changes toward myopia which averaged 0.75 D in the period
of 1 year. While this amount is not spectacular, it does
exceed the usual amount of myopia of approximately 0.5D
developed in children over the same period. The
calculations of the amount of myopia developed included
those subjects who did not change into myopia whereas in
most human situations we exclude the subjects not changing
and deal only with subjects who are changing into myopia.
If the nonchanging subjects are excluded, the amount of
myopia developed is approximately 1.25 D of myopia in 1
year. Human subjects of a comparable age (18 to 23 years),
such as submariners, cadets at Virginia Military Institute,
or at the U.S. Naval academy tend to change at a rate of
approximately 0.25 D a year into myopia.>>

Otis> Excellent! I read the paper. The amount of accommodation
change was very small, about -0.8 diopters. The resultant
refractive STATE change was also very small.

Otis> In order to make a judgment of the behavior of all natural
eyes, you must take the AVERAGE of the refractive STATES of
all natural eyes. You can not just take, selectively, one
eye. The "noise" or randomness of these measurements is
such that it will effectively hide the deeper meaning of the
behavior of the population of natural eyes.

Otis> What is truly required is a much greater change in the value
of accommodation. When a -3 diopter lens is applied to a
population of natural eyes, the refractive STATE will change
by -2 diopters (average) in six months.

Otis> This is truly the inherent behavior characteristic of all
normal and fundamental eyes.

Otis> In some aspects of science, you must realize that you can
not perform this experiment on the primate-human eye. And
you must exagerate the conditions of the test -- to get
meaningful results.

Otis> How you think about his -- is up to you.

Alex> When the entire population of cadets is included in the numbers,
there still is a "negative" refractive trend, but it is much
smaller.

Otis> But the critical issues is to note that a Cadet with a
refractive STATE of zero and 20/20 has about a 1 in 100
chance staying at zero through four years of college. If
you are a cadet at zero, you should know this fact, and the
supporting information as per above. It might inspire you
to do something wise to prevent entry into myopia.

Alex> From the National Research Council book "Myopia: Prevalence and
Progression":

http://books.nap.edu/openbook/0309040817/html/31.html

Study> <<At entry 362 (43.7 percent) were myopic, while at graduation
443
(53.5 percent) were myopic.

Alex> Using Gmelin's frequency distributions for calculation, the mean
refractive error at entry was -0.873 D., while at graduation
it was -1.251 D. This is a mean change of -0.378 D., which
would be a rate change of -0.0945 D./yr, if the interval
between exams was four years.>>

OTis> Again, a matter of judgment. The Annapolis report showed a
"down" rate of -1 diopter in four years. If the person has
a refractive STATE of +1 diopter -- then he is safe. If
zero diopters, he is a serious risk of going negative. That
is the true issue -- and he should know about it.

Otis> If you wish to make the argument that nothing should be done
-- I accept your argument.

Otis> Indeed, most people truly do not care for or about
preserving or keeping their distant vision clear for life.
That is always a personal choice or decision.

On a good day.

Otis> Clearly I belive that the =1/3 diopter/per year figure is
very, very accurate, and that any person, enterning a four
year college witha refractive STATE of -1/4 diopter (20/30)
should understand these statistics. Again, this is a
personal choice.

Otis> If the person UNDERSTANDS them and these issues, it might
encourage him to clear his Snellen by assidious use of a
strong plus for all close work.

Otis> If he does this, he can avoid picking up that -1.1 to -1.6
diopters of myopia for the four years in college.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.

Liar.