Most of my work came from my question, "did I do (myopia) to myself" (meaning my "habits") did it to me. The medical mind, wishing to "not offend me", claimed that my "habits" did not create negative status, for my totally normal eyes. I consider this now a proven lie.
I would prefer to be told the truth (before that first minus) and given encouragement to "wear the plus", and "sit up" while wearing the plus, even with 20/20 (but a refractive state of zero.) This is what I mean by "total empowerment for true-prevention". It is necessary to be technically honest with yourself - if you child is going to do this. I do not consider this type of prevention to be medicine, nor can it be medical-directed - at this time. (I had your younger child's problem - that was resolved - but I do not want to cover that subject now.)
The ophthalmologists love to do "plus astigmatism". The optometrists love to do "minus astigmatism". They are not equivalent. If you said -4 with -2 diopters astigmatism, your sphere equivalent would have been -5 diopters. That is a big difference.
Yes, for distant visual acuity, you probably do need some astigmatism at this time. But our "near vision" simply does not have to be that sharp. Since I calculate your "refraction" at -2 diopters, that means you can probably work at 20 inches with no lens on your face. (You can experiment with that concept.) But if you can, that would be a great help and a step forward. (You obviously will need your self-selected minus (probably about -2.75 for distant objects.
I realized when I talked to the honest OD who called the minus, (poison) that he was telling the truth about all natural eyes. I realized that my vision had been totally screwed up with that minus (always increased). But I simply did not "blame" him, or anyone.
I just did not want my nephew to do what I did - and suffer the consequences. That means understanding that NO OD is prepared to deal with us. (Who can accept plus-prevention as an absolute requirement.)
That means that plus-prevention must be self-taught. That means teaching yourself how to "prescribe for yourself". This is part of your "learning process". Your adult children might learn from your "engineering approach" even if you are not successful.
I consider this to be very difficult - but not totally impossible. By making this sacrifice to work on plus prevention, you might be helping them, more than you help your self.
I think that a truly honest preventive study (at a four year college) could succeed, if each person (at 20/40) had the resolve to do what you are doing. But I always get "blocked" from publication - by the ODs who "assume they know everything". I regret the "friction" this causes me.
Thank you for your quick input. I have tried looking at a chart with no glasses, and I can get letter recognition with some squinting at 20/80 or 20/100. This is the problem with using equivalent spherical number with alot of astigmatism. The astigmatism creates a general blur, which I thinks requires me to "wean" myself slowly off of the cylinder correction.
As far as children, I have three kids, all adults now. My oldest has had perfect vision his whole life, but is now beginning to get some eye strain (slight blur) at the end of a day after staring at computer screens. He was thinking he was going to have to start with glasses. But thanks to people like you and others in this forum, I was able to share this "new" knowledge about plus lens protection with him. He has trying out reading glasses when computer viewing and he says it has stopped the clarity degradation at the end of day. He buys into this technique and I feel now this vision has been protected for the rest of his life (I wish I had this info when I was his age). My youngest (19 yrs old) does have glasses (-1.50 D, and -.50 D). I am working on her to start with plus lenses. My third kid does not wear glasses (yet) but has had a unique optical history. When he was very young he had strabismus (crossed eyes). He went through two surgeries where they reattached muscles around eyes so that would point in the same direction. The end result of this is that he cannot see in 3D. His brain does not fuse two images. Despite this, this brain has adapted to this and it uses both eyes somehow back and forth when it comes to spatial perception like hand/eye coordination. I do not know if there is any therapy that can be done to re-teach his brain to join the two images. Before finding this forum, I did not have any hope or expectation that this would be possible. Now that my eyes have been "opened" up regarding Myopia, maybe there is way to help post-surgery strabismus.
Regarding the plus astigmatism, as you know this sign convention is arbritrary. I like the plus cyl. value as it shows the spherical value as its worst or maximum value. I have kept most of my old glasses, but did not have all the prescriptions. So I came up with a homemade measurement setup that uses sunlight and aperatures(circular holes cut into paper) to project an oval shaped image. The long direction of the oval is the maximum spherical divergence plane represented by the spherical correction component (with plus astigmatism notation).