I got glasses not too long ago: one pair for close-up work, one pair for driving, to help deal with a mild astigmatism. When I first started wearing the close-up glasses, I noticed that windows on my computer started looking like trapezoids, rather than rectangles – the left and right boundaries were parallel, but the top and bottom slanted out. After a bit of wearing the glasses, I stopped noticing the effect. Just took off my glasses, though, after a couple of hours on the computer, and now I’m seeing trapezoids without my glasses. Freaky. . .