When auto stereograms were all the rage in the late 80's I had a program on my Mac Plus that let me make/edit them and I used to edit for hours WHILE looking at them in 3D. Then one time I was walking down a hallway with a repetitive wallpaper pattern, my eyes did the thing, the entire hallway appeared to shift in front of me, and I stumbled and fell. Still to this day my eyes will sometimes automatically snap into 'alternate' focus when viewing a repetitive pattern.