A part of photofocus is to allow your eyes to see more of the page. The whole open book is in view so it is unnecessary to move your eyes to look at the page... it's all already in view.
Gentley moving the eyes while in photofocus helps to keep them relaxed and prevents them from watering.
Turn the book upsided down to photoread it makes it easier to keep the divergent gaze since you don't have to focus on the words when its upside down. 
Alex
