I just realized upon rereading Pete's response is that he is assuming that binocular vision is working perfectly in the reader. And for people with good distance vision that is usually the case. However for nearsighted myopics like myself, our eyes are hardly ever the same in clarity. So it would follow that binocular vision would be not very functional. If there's no binocular vision, there is no eyestrain, as the eyes cannot cross as only one is focused on the page at a time. Usually the stronger one, of course. Or in other words the brain takes the better of the two images presented to it by the two eyes.
