One of the side effects from PhotoReading is that a few people have noticed it improved their eyesight. When exercising the muscle we benefit when we hold the muscle in a certain position too long we tend to harm them.
Photoreading requires the divergant gaze for about 5 minutes to a book, after that we do a short postview with our focused vision. So in effect we are exercising our eye muscles.
I agree if you hold your eyes in a peripheral focus all the time you would have blurred vision, that's why the print is often blurred when in photofocus 
Alex
