Pirate Eye-Patches

Last night, while playing poker, one of the players almost got a delay of game penalty becuase he was explaining why pirates used to wear eye-patches.

It wasn't because they all had injured eyes.
It wasn't a special sign of authority.
It wasn't because they kept a treasure map on the inside of the eye patch.
It wasn't because it made it easier to use a one-eyed telescope.

According to my friend who got it from a reliable television source (Mythbusters), it was because often going below deck was a dangerous endeavor. In order to be prepared for a violent doublecross or some other attempt on said pirate's life, the pirate would wear an eye-patch so that he would have INSTANT NIGHTVISION. Going into a dark hole of a bilge? Switch the eyepatch to the other eye and the one that had been covered is able to see in the darkness and ready to fight.

We thought that it was cool enough to spare the guy the delay of game penalty.