Tom:
Thanks for your reply. I remember posting something about the convergence effect I was getting and I thought it was 3 years ago that I came across the Bershak method. Your reply shows it was only 1.5 years ago. I must be having double vision from all this over-convergence and seeing 3 instead of 1.5.
I missed your reply as it came quite a bit later and I visit the forum irregularly.To your point that there must be some effect of the extraocular muscles (EOM) pressing the eyeball against the orbit, there may be something to that, but Bershak's point and this writeup from Merrill Bowan, a behavioral optometrist who specializes in learning disabilities
http://web.archive.org/web/20081119091825/http://www.simplybrainy.com/simplybrainy_034.htm suggest that how the eye focuses may involve EOM and not just the ciliary muscles acting on the lens. I find intriguing Bowan's line of thinking of "accommovergence" where the mechanism for convergence and accommodation work as one system, instead of two systems working in parallel, and this falls into Bershak's approach of using convergence/divergence exercises to get improved accommodation. Additionally, Bowan posits that accommodation is a multifactorial process involving these elements in the eye:
1. The cornea
2. The iris (through the depth of field effect)
3. The anterior chamber
4. The lens
5. The vitreous body
6. The choroid thickens (it's apparently made of "erectile tissue"(!))
So it may not be too outrageous to think that EOMs are also involved in focusing.
It seems the good Dr Bates also had the same thinking that the EOM were involved in accommodation. I don't know whether this puts him more or less into favor with the current eyesight improvement school of thought!
If the EOM are involved in accommodation and eyestrain, my thought then was that the Feldenkrais approach for relieving motor dysfunction may help. Moshe Feldenkrais has built a solid therapeutical approach for relieving muscle tension and also of developing new neuromuscular ways of functioning (his approach is useful for helping stroke patients remap their brains to recover the motor function lost in the stroke, I believe). The key to making the body learn new ways of moving is to go through the desired motion s-l-o-w-l-y for 10-15 repetitions. If EOMs are involved in how the eye function, the prime suspect of astigmatism (the uneven curvature of the cornea) would be uneven tension in the EOM, which distends the surface of the cornea from its original perfect curve by pulling from the back of the eyeball unevenly, or even squeezing the eye through the action of the oblique muscles . So performing slow X patterns with both eyes (slow, meaning about 8-10 seconds to trace each "arm" of the X, say, from the northeast to the south west) may be beneficial. In fact, I am doing this. With the recent if slight improvement in acuity from the three cups exercise and this X-exercise, I seem to be having a better time with my vision this past week (I wear an undercorrected myopia prescription, and with no correction for my astigmatism, which is about 0.50). Of course, I could just be imagining things.
One thing I did not imagine: I am right-handed but had the interesting experience of being left-handed for a day or two after one of the Feldenkrais Awareness through Movement sessions. Sometimes, we can only marvel at how the body works.