Eyepatch

Interesting fact: Sailors who were crew members who often went above and below deck, used eye patches to have one eye adjusted for the top deck and the other eye already adjusted for the darkness when suddenly going below deck. The strong sunlight while above deck on an oceangoing vessel could require minutes of adjustment to the dim lighting below deck. With virtually no light sources below deck, sailors would have to rely heavily upon their eyes to adjust. In the critical moments of modifying the rigging, navigating, and especially during battle, those minutes were too precious. A simple switch of the patch from one eye to the other saved time and was more convenient than being temporarily blinded when going between decks. [Link]