It is thought that the reason pirates would wear an eyepatch even if they did not have an eye injury was to help their eyes adjust to going back and forth between light and dark. It typically takes the eyes 25 minutes to adjust to seeing in the dark because they must regenerate photopigments, which send visual signals to the brain. Pirates would often have to go quickly from being in the dark below the decks of their ships to being on the sunlit ship decks. Wearing an eyepatch would allow a pirate to switch the eye patch to the other side when moving between locations and bypass the 25-minute adjustment period.

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