Practice looking at 3D images it's not unusual to have the blip page disappear quickly. The tiredness can be because you were crossed eyed or it can simply be because you are not used to using the eyes in this way.
This site shows the difference between parallel view and cross viewing... useful for some tricks for learning and also has some explaination of how this can cause some eye fatigue (muscles haven't been exercised 
)
http://www.vision3d.com/3views.html
It's parallel vision that you want for photoreading. Have fun with it.
Alex
