Pirate garb is known for a few signature items: bandannas, tri-corner hats, overcoats, and of course, eye patches. But were eye injuries that common? Pirate history is understandably lacking, with ships logs rarely kept and communications to land impossible. So while injured eyes may explain the need, there are other potential reasons. One theory — similarly with little if any historical support for it — suggests that the patches served a practical purpose, allowing a pirate to retain effective night vision. And while the history behind the theory is lacking, the science actually works.
Pirates, of course, spent a great deal of time on ships. Above deck, during the day, that meant a lot of time out in the sunlight. But going below deck, in a pre-lightbulb era on a ship made of wood (so no open flames!) often meant entering rooms with very little light. To compensate, the theory goes, pirates wore an eye patch to train one eye to work well in the dark. When duty required the pirate to go below deck, the pirate would flip the patch to the “outside” eye and rely on the darkness-trained eye as his guide.
While history is silent as to the likelihood of this use, it’s definitely possible. Mythbustersdedicated an episode to investigating pirate-related assertions, and called this one “plausible:”
The Mythbusters entered dark room with light-accustomed eyes and aimed to complete certain objectives. Their movements were hampered by the darkness and it took them five minutes to finish. When they went into a rearranged but equally dark room with an eye that was covered for thirty minutes, the Mythbusters were able to complete the test in a fraction of the time. As a control test, the Mythbusters then went back into the same exact room with light-accustomed eyes and ran into the same difficulty as the first test.
Does this have practical, modern day uses? Maybe. Next time you wake up in the middle of the night and need to turn the light on (e.g. to use the bathroom), try covering one eye until you turn the light back off — it may prevent the otherwise inevitable stubbed toe.
Bonus fact: Bats, nocturnal animals not known for their vision (you’ve probably heard the saying “blind as a bat”), nevertheless tend to navigate their way in the dark quite well. They use echolocation, a form of sonar, to “see” their surroundings. The noises they emit in this process are mostly outside the audible range for us humans. (And, while bats have poor vision, no species of bats, actually, blind.)
From the Archives: Bat Man: A blind man who uses echolocation, like bats, to “see.”
Related: Pirate costumes. For grown ups.