In actuality, it was simply a result of navel combat. Splinters caused by the wood of the ship be hit with cannon fire and gun fire could get in the eye, gun powder itself can be damaging, not to mention, the chance of bullets and knives landing in them.
So to sum it up for you, pirates wore patches because they damaged or lost their eyes. Nothing else.
Pirates wore a patch so that they could go into a the pitch black hull of the ship in brightest day and have instant night vision w/ the previously patched eye.
(There's actually no historical evidence to support the notion of wearing an eye patch for light adaptation. Mythbusters proved it would work, but that doesn't mean that's the historic reason they wore them. And if it were the reason, why wouldn't EVERY pirate or sailor wear an eye patch.)