Whilst piracy was a violent occupation and eye injuries occurred, a myth supposes that pirates wore a patch over one of their eyes to adjust that eye to darkness in preparation for battle. That way, when they boarded a ship and were ready to go below deck, they could remove their patch and be able to see well in the poorly lit interior of the ship. It takes time for the eye to adjust itself for darkness – had they not prepared their eye ahead of time by using an eyepatch, the boarders would have been at an immediate tactical disadvantage the moment they went below.
