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

====================

Calculation:

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
effect.

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.

Best,

Otis