There's no evidence that this use was real. Mythbusters tried it and said the trick itself does work (which any of has may already know), but who knows if it was even practical in a pirate boat, vs the loss of stereo vision etc.

The whole idea of pirates wearing eyepatches seems simply the replication of one particularly colorful pirate archetype over centuries of literature and tales.

I feel like the advantages of stereo vision may be oversold in this scenario. At the distances that sailing vessels would engage there's limited need for binocular depth cues - they really only start to come into play at the point where you would begin a boarding action

But the idea of the patches-for-night-vision is precisely to have one eye covered during the boarding, so when you enter the insides of the enemy boat that eye is ready for seeing in the dark.

Have you ever tried to climb a rope ladder on a moving ship?

Stereo vision is helpful on ships (and allmost everywhere else where you need eyes), even when not boarding.

I don't have binocular vision. I lived aboard a sailboat for a few years. I'm quite active with rock climbing etc and I honestly don't think I would be able to do anything better if I had binocular vision...

Just a thought

Good for you!

But I know I am worse doing climbing etc. with one eye.

It is probably something you can train and get used to, that it is not such a big deal, but I cannot imagine doing it on the same level one eyed.

But then again, you did not have enough motivation to spend time learning it. A pirate captain might have enough to actually train this way.

I had assumed it was because, being a pirate, you were more likely to have had one of your eyes poked out during some sort of mêlée.

But that’s much more interesting…

This would explain why only pirates wear them rather than also ordinary seamen.

I've read another theory: It's because of the sun damage to their eye from using a sextant for navigation. Haven't been able to confirm it though.

Such damage is creeping and the brain can just hallucinate the blank patches in the vision away, until only like 10% of the retina is left and it just doesn't work anymore. These days, dumbass laserheads are the most likely to suffer from that problem.

It's amazing how much of our conscious experience is hallucination, and yet a lot of people are disparaging LLMs for doing just the same...

probably because when humans pay full attention and think clearly they can not hallucinate for 99% of things they can sense (disregarfing optical illusion), but there is no 'pay attention and dont hallucinate' switch for LLMs.

People are bullshitting just the same about topics they know nothing about. They often also won't shut about when others tell them and even when they themselves know that they know nothing. To some extent this is necessary for humans to function at all, and the scientific process starts out from uneducated guesses and rigorously refines them and casts away what doesn't hold up to empiric data.

Optical illusions are evidence of the pile of hacks that our senses and our consciousness use to make sense of the world. I think it is really difficult to fully disengage from the biases this induces, and we are sadly best at perceiving such flaws in others. This might be one of the reasons why humans have to socialize with other humans to maintain mental health.