Okay that might sound weird but I think my eyes have just lost a ability

To make it short, I have a 3DS for one day thanks to a friend who lend it to me and well, I always could see the 3D effect perfectly, when I looked at the demo units in stores and I could also see it on my friends 3DS.
Then after playing about 40 minutes of Zelda with 3D I took a break of about half an hour and guess what, I couldn't see 3D anymore when I played on, all I see is either blurry vision or double vision

Not that I mind much since I will give the 3DS back tomorrow and I can always play without 3D but is there such a thing as temporary loss of stereo vision? o.o I will see how it is tomorrow after I slept^^