Subject: There has been no "pure plus" study -- because that would be "not medical".
The primate data, that shows that the totally normal eye can be made myopic with the forced wearing of a minus lens -- is the real scientific truth of this difficult situation. But that is pure engineering/science, not medical.
But how do you run a pure-plus study -- with children? The answer is that you can not, because the child is not old enough to take and follow instructions. This is why a "plus -- or bifocal" is used. You can FORCE the child to wear the "plus" by putting a minus 'on top'. Even here the child can defeat the purpose of the plus, if he "leans forward" and cancels out the desired effect of the plus. Thus if a person can be taught HOW to use the plus, (i.e., sit up, and read at the just-blur point), then the plus can be effective. But that assumes that the person is going to monitor his Snellen and use the plus for all close work. This puts all responsibility on the person himself --to learn these issues, and make the commitment to wear the plus for the six to nine months to clear his Snellen from 20/40 to 20/25 or better.
But the only "plus" study is the one conducted by Francis Young on children. The child would be given no "minus" on top, if the child was at 20/40, and requested to wear a "plus" on bottom. Where the child could not read the 20/40 line, he would get a minus lens with a plus on bottom. (If these were pilots, and understood this issue -- I think they could make the required commitment to wear the plus, and get out of it in about one year.)
So what were the results of Frank Young's study? First the results were highly significant (0.01 level). These results showed that the plus could stop entry into serious myopia. The plus group did not go down, and the pure-minus went down at a rate of -1/2 diopter EACH YEAR.
This is the reason I accept a "limit" on getting out-of-it. This is why I suggest avoiding the minus, consistent with passing the 20/40 to 20/50 line (for starters). What truly "comes through" on this, and so many other studies, is the fact that we induce this situation in our natural eyes because of our 'reading habit'. In other bi-focal studies, the control-group ALWAYS WENT DOWN AT AN AVERAGE OF -1/2 DIOPTER PER YEAR -- through high school and into college. Any SERIOUS REVIEW with an intelligent person entering a four year college, would know the implication of that fact -- and should be understood that way. Otis