Know why a pirate wore a patch over his eye? I do.
It wasn't because he poked his eye out. Well, maybe there were a few pirates who wore one for that reason. After all, they did run with sharp objects in their hands.
But the most likely reason according to the Mythbusters is that it maintained night vision in one eye.
So when me has to go below decks for a fresh jug o' rum, I move me eye patch to me other eye and aye! I can see me rum!
Also, if I want to ambush some scallywags in the middle of the night I use me night eye and the advantage is mine! Arg.
Pretty clever, them pirates.