What children do to their eyes
We often  see children reading like this -- and nothing is said or done.  Further, the standard medical statement is that long-term reading at -6 diopters has NO EFFECT on the refractive STATE of the eye.  Tragically, the experimenal data demonstrates that reading at this distance has a profound effect on the natural eye's status..  (See the effect of "open" and "canged" environments on the natural eye's refraction as presented below.)

It is indeed very difficult to STOP a child from doing this type of writing.  If a doctor makes the statement that nearsightedness can not be prevented BECAUSE you can not stop a child from reading at 6 inches (-6 diopters) -- then the statement would be correct.  The child must learn to "modify" his reading habits -- as the first step in preventing the development of nearsightedness.  When monkeys are placed in this type of situation, their focal status WILL MOVE in a negative direction.

But the reality is that if you can stop a child from doing this -- and get him to use a proper-strength postive lens, then nearsightedness can be prevented.  Obviously this is not easy, and requires understanding and resolve to make prevention effective -- in the long run.  A great deal of responsibility must rest with you if any optometrist is going to assist you with prevention at the threshold (20/40 to 20/70) level of nearsighedness.

It is easy to discuss prevention -- but  hard to implement.  This is often  because of our resistance to any fundamental change in our personal habits.  Ultimately we must understand the consequence of this bad habit of ours.
We have met the enemy -- and they is us.     -Walt Kelly
Both this type of negative "environment" and a negative lens will result in the eye's refractive STATE moving in a negative direction.  But a reasonable question to ask is whether the refractive STATE of the eye will move in a positive direction from the wearing of a positive lens.
THE EYE'S REFRACTIVE STATE CAN MOVE IN A POSITIVE DIRECTION.
THE EYE'S REFRACTIVE STATE MOVES IN A NEGATIVE DIRECTION -- FROM READING AT 6 INCHES (-6 DIOPTERS) FOR LONG PERIODS OF TIME.
Data from:  "The Distribution of Refractive Errors in Monkeys", by Dr. Francis Young,
Published in:  Experimental Eye Research, Volume 3, Number 3, 1964
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