To Robin MN: I wouldn't be so quick to dismiss the possible role of the external eye muscles (extraocular muscles, or EOM). I am able to get discernible and repeatable, albeit temporary, improvement in clarity by exerting a voluntary muscular tension in my eye. See the thread I started on June 4 on "The Bershak Method." I would be the first to admit that I do not understand how this happens!
Aside from this phenomenon, I am starting to think that the EOM and their role in convergence/divergence is somehow linked to accommodation, the impairment of which results in myopia (and probably hyperopia). I wonder now if there isn't some interesting connection between how the two eyes converge/diverge to measure of the distance of an object, and how (or whether) that information is an input to how the accommodation system works. Are these two separate systems working in parallel or are they on fact two aspects of the same one system? If it's the latter, can be improve accommodation by working on refining the convergence/divergence system?
I have had about a diopter improvement from my starting -5.5 over the past nearly two years, and I think I am continuing to make progress, if slowly. I sense physically that I now have a different kind of seeing, where there is more of a (subtle) muscular action in my eyes, actively doing micro adjustments to get the best clarity. This is not a passive "relax into the distance"; it feels more like there is an active component in the seeing of distant objects, which might or might not be some aspect of the EOM at play.