I nearly did it once. I was bored in a chemistry lesson and as I'd done before started tipping things from one test tube to another to see what colours things turned. This time round I think tipped some concentrated sulphuric acid (it wasn't usually on the bench but it was in by breif time of A level chemistry before dropping out of school and I think we were doing esters) into something.

It went off with a bang and something splashed in my face. The teacher took some time washing my face and eyes with water and as it turned out, aside from the teacher hoping I'd learned a lesson not to be so stupid in future, I got away with my messing around.

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The most painful eye experience I had came after playing with an arc welder - I looked. Sort of felt like someone's thrown sand in your eyes and is rubbing it in. My mother who was a phisiotherapist who had once done something similar to herself with UV light (IIRC couldn't find her googles and opted to treat someone without her protection) reckoned the time between my exposure and reaction wasn't too bad but even after the initial pain died down, my eyes were sore for a couple of days.