You’re probably familiar with the iconic image of a pirate:
Three corner hat, earring, and of course AN EYEPATCH.
You probably assumed, as I assumed, that the eye patch was there to cover up a missing eye.
Pirates lived dangerous lives! Makes sense they might’ve lost an eye or two. You know, sword fights, hungry parrots, etc.
But! It turns out that pirates wore eyepatches to keep one eye adapted to the dark so when they went under deck they could switch the patch to the other eye and be able to see right away.
This was especially helpful during battles, where they might find themselves fighting in the dimly lit belly of the ship.
Imagine asking for a time out during a pirate fight so your eyes could adjust?
So there you have it! Pirates wore eye patches for dark-adjustment. Not because they only had one eye.
H/T: Frank Stags