What medical reason could there be for pirates wearing eye patches?

Moleman

Presumably, their 'job' involved a lot of flintlock shooting, much of which was done a close quarters. If these weapons are not maintained (and sometimes if they were) there was a tendency to explode, back fire and/or shower the user with sparks, hot metal or gunpowder. Jan 18 01, 2:28 PM

l3i7l

To supplement Moleman's good answer, the leather eye patch was worn to protect one eye from injury. Blacksmiths, also, often wore patches for the same reason. You could not make a living, if totally blinded. Some patches were also made with small slits, this acted somewhat like polarized sunglasses. Jan 19 01, 4:57 AM

Mr. B.

Pirates used a sextant (series of lenses inside, much like a telescope) to help them navigate the ocean. The sextant was aimed at the sun. Gradually they burned the retina of their eye and became partially or totally blind. They had no idea this was happening. Jan 23 01, 12:42 PM

Yaarbiriah

Another theory is that the eye covered is adapted to the dark below decks and the eye uncovered is adapted to the sunlight above. When the pirate goes down below he simply switches the eye patch and can see comfortably in the dimmer light without waiting for adaptation. This works! (see 'mythbuster' archives) Apr 25 07, 3:37 PM

salami_swami

The eye patch was worn to keep one eye constantly adjusted to the dark. This made it much easier to navigate much faster when they went below the deck. Here is a link. http://en.wikipedia.org/wiki/Eye_patch#Sailors Feb 27 09, 10:01 AM