I think it may have to do with the fact that in VR, although your eye divergence to focus is the same as real life, the focal length always stays the same. I guess the strain is your eyes naturally trying to change focal length as you look at different depths.
Conversely I suffer from age-related presbyopia (inability to focus on close objects due to the eye's lens losing its elasticity). This is a real pain to have to deal with in real-life as you either have multiple pairs of glasses for different distances (I have to have special glasses for computer screen use for instance), or use varifocals which cause all sorts of image distortions.
![Frown :( :(](/styles/default/xenforo/vbSmilies/Normal/frown.gif)
![Big Grin :D :D](/styles/default/xenforo/vbSmilies/Normal/biggrin.gif)
That's pretty amazing, though of course it'd be nicer if the VR screens were higher resolution so I could read distant text easier too.
![Roll Eyes :rolleyes: :rolleyes:](/styles/default/xenforo/vbSmilies/Normal/rolleyes.gif)