Eye Patches and Pirates
Did pirates wear eye patches?
Those that needed them probably did. A patch was cheaper than an glass eye and more comfortable. It isn't just cosmetic. The patch keeps crap out of the eye socket. If the eye isn't completely missing a damaged or diseased eye will suffer atrophy that is wither and shrink. Either way you are left with space where contaminants can get in and cause further pain and suffering. Once the eye is gone or withered, the eyelid may not close properly over the open hole. This means things can get in and cause irritation. Even smoke or wind could cause irritation if the eyelid is not closing properly. The cheapest remedy: wear a patch to cover the hole.
The glass eye used in the 17th and 18th centuries were not like today's glass eyes. The first prosthetic eye was invented in Venice in 1579. It was a thin curved piece of glass (shells) worn behind the eyelids. These shells did not restore the lost volume left by dried up or missing eyeball. The edges were sharp and uncomfortable and the wearer had to remove the shell at night in order to get relief from discomfort. They shells were also prone to breakage.
This was the artificial eye used until the nineteenth century. That's right no wooden eyes or round glass balls. The eye shells were not popular and most people continued to use eye patches. The first "modern" glass eye was made the German glassblower, Ludwig Muller-Uri. He had been making life-like eyes for dolls, however when his son lost an eye, Muller-Uri took a stab at making a glass eye for his him. After about 20 years he perfected his design, and then devoted the remaining days of his life to making artificial eyes for people full-time.
It is hard to say how often a pirate lost an eye but it is safe to assume that even small flying splinters could take an eye out during battle. Other dangers to eyesight would be explosive gases from cannons and even the flash from the frizzen of musket. The eyes were vulnerable during sea battles but it is doubtful that you would have a crew full of one eyed pirates. The loss of an eye was a liability. A one eyed pirate was fighting at a disadvantage and could prove worthless when it came to the watch. Two eyes are needed for depth perception and a lack of depth perception could prove fatal when judging distances.
Eye Patches and Pirates and Night Vision
Did pirates wear eye patches to improve, preserve night vision?
The short answer is probably not, it is just a myth but as the Myth Busters showed, it is plausible. But plausible does not mean probable or even practical. So here is a long answer.
The problem is there are not a lot of books written by pirates about how they fought and the tricks they employed. The few that were written mention nothing about eye patches as a fighting strategy. Considering the details provided by Exquemelin you'd think he would have mentioned this tidbit if it were true.
For the most part, pirates used the same tactics and strategies used by the navies of the time. We also have no mention of this occurring within any of the navies of the time.
Now with that said; there are current and not so current military doctrines discussing night vision but guess what? None of them trace their roots to pirates nor do these tactics involve the use of eye patches. (There is anecdotal evidence but then again there is anecdotal evidence that suggests a woman bought a rat that she thought was dog!)
A person hiding in a dark area, such as below decks will have an advantage over a person entering the deck from bright light of battle on the top deck. Pirates had to be aware of this, having spent quite a bit of time on ships. With this common knowledge in mind, some speculate pirates would see some usefulness in keeping an eye covered during the boarding a ship if they were were expecting to go below decks during the attack. Having knowledge night vision problems however doesn't translate into using eye patches.
The plan is to keep an eye covered to more quickly gain night vision for the dark decks below. Remove a patch and one eye which should be more accustomed to the dark and then sally forth below deck with terrific night vision. Unfortunately reasons not cover a good eye out weigh this plan of attack:
When it comes to the initial fight, it would be more logical to have a group secure the top deck then bring over a second party with eyes adjusted for action below deck. (Boarding party worked in waves when possible.) You would want to secure the open deck before going below. After all you don't want bad guys behind you. This first group would secure an area where a second group, acclimated to the dark could then begin clearing the lower decks. Of course it would be even more logical to smoke out your foe using stink pots rather than duke it out down below. This would be the pirate's first option. no use getting killed chasing down the merchant crew. Stink 'em out and drop hand grenades.
If they needed to go down below they probably covered their eyes for a minute or two (if the situation permitted it) and then headed below. They would not wear eye patches. This is the same method soldiers use today (if they lack night vision equipment). Maybe the guys on Myth Busters could give that method a go and see if it works and see if it is effective.