I wear contacts, and sometimes, if one of my eyes is irritated, I only wear one. It takes about half an hour for my brain to adjust to using only one eye (my v

I wear contacts, and sometimes, if one of my eyes is irritated, I only wear one. It takes about half an hour for my brain to adjust to using only one eye (my vision is bad enough that I essentially cannot use an eye without a contact). It amazes me that after this happens, I stop noticing the problem. I don't realize that I can't see in 3D up close[1]. Then, I will attempt to do something that requires stereo vision, and I will just fail. I've missed card swipes by about a foot, without being able to tell it was a problem until it happened. I once got a bunch of friends to cover one eye and try to swipe a card, and they had similar experiences, not noticing they were going to fail until the did. [1] Stereo vision only works within a few feet of your eyes. Further out, you use other cues to construct a 3D model of what you are seeing.