Why did pirates wear eye patches?

[James]

Whenever we picture the stereotypical pirate, he’s usually wearing a long coat or striped shirt, is bearing a cutlass, and is sporting an eye patch. While the first two are easily explained as being appropriate for the period, the eye patch is an anomaly that seems more like a modern add-on to give the customary costume a unique touch.
The truth is, however, that the eye patch was part of pirate garb, but that leaves the question as to why. It’s unlikely that so many pirates lost an eye to warrant it becoming synonymous with piracy. While it’s probable that many pirates were covering a damaged eye, there is another plausible reason that may explain why the eye patch was so prevalent out at sea.

The popularity of patches.
Buy any Halloween pirate costume and there is a very good chance an eye patch is going to be included. While it’s a staple of the iconic getup, back in the days of piracy, the eye patch was believed to have had a clear purpose.
Living with a bounty on your head and enemies at every turn, pirates needed to be ready for anything. Whether day or night, if a rival ship came too close or they happened upon a settlement worth sacking, pirates had to be ready. Come nightfall, adjusting to the shift from light to dark was essential to pillaging and plundering. To prevent the night from impeding their vision, pirates allegedly used eye patches so that they would always have one eye well-adjusted to the dark.

The importance of night vision.
According to "Scientific American," it can take the human eye up to 30 minutes to adjust to the darkness. For pirates, those 30 minutes could be the difference between being left on the ocean floor and getting a jump on incoming opposing flags.
Piracy doesn’t follow a set clock, and ships were constantly moving through the night. In the event of a confrontation, it was vital that pirates could see. On starless and moonless nights, the sea could be pitch-black. Pirates who kept one eye in the dark had an advantage over those who didn’t.

Is it plausible?
The issue determining whether or not this reasoning is accurate is that there are no historical records to offer confirmation. There may be no evidence or pirate artifacts that support this theory, but there are real-world applications that at least give reason to believe this theory.
The team behind the "MythBusters" TV show put this idea to the test in their 2007 pirate special. Known for taking the necessary steps to create a controlled environment and mimic the original conditions, the team set up a dark room and sent in light-adjusted eyes. In the dark maze, they stumbled and had a difficult time making it to the exit.
A second dark room served as a maze for eyes that were covered for 30 minutes. This room was completed in significantly less time.

A practice beyond piracy.
To further support the notion that eye patches were used to make navigating the night easier is the fact that even the FAA recommends pilots work on their night vision. Part of the FAA Flying Handbook discusses best practices to train one’s eyes, such as avoiding sunglasses after sunset. According to the FAA, “a pilot should close one eye when using a light to preserve some degree of night vision.”
While there is a relatively long gap between the age of piracy and today, the concept remains the same. With one eye always in the dark, there is a greater chance of being able to see better regardless of how dark it might be. There may not be any solid historical evidence to support this claim, but it’s a plausible answer that gives a reason for one of life’s untold mysteries.

A historical mystery.
As cool as we may think eye patches and pirates are, it’s not enough to assume that any inference of why pirates wore them is true. While the reasoning may make sense, until some historical document or journal clearly states the purpose of eye patches, the answer will forever be an assumption.
Considering how dangerous the life of piracy was, the argument of damaged or missing eyes will always be in the shadows, as if to cast doubt on the idea that it was all about seeing in the dark.