Answer: Plausible or not, and why...?

OUR CHALLENGE  this week was pretty straightforward, but perhaps not simple... 

Here they are:  Can you determine if these stories make sense or not? 

From: The Pirates Own Book, Or Authentic Narratives of the Lives, Exploits,
and Executions of the Most Celebrated Sea Robbers (1837)

1.  Pirate eyepatches:  In a lecture this week I heard the speaker say that "...the reason pirates are often depicted wearing an eyepatch over one eye is that they'd keep that eye dark-adapted in case they were going to jump aboard a ship they'd captured and needed to instantly be able to see in the depths of a dark ship interior.  Remember, in those days there was no on-ship interior lighting, so you needed to be able to flip up the eyepatch and have one dark adapted eye ready-to-see."   Really?  

2.  Rocker sunglasses:  Recently, the rock star Bono announced that he's been wearing sunglasses constantly for the past twenty years to help with his glaucoma.  I immediately wondered--does that make sense, is it plausible story?  How can sunglasses help with glaucoma? Is it really a treatment?  (Or is it a ruse to give him plausible reason to be cool.)  

Are these stories plausible?  If so, why? If not, why not?  


Pirate eyepatches:  I have to admit to being initially skeptical.  Sure, we know that pirates wore eyepatches.  But is this the reason why?  And... wait a second... how do we know pirates wore eyepatches? 

The fundamental skill of critical thinking is to ask the fundamental question:  How do you know?  What is the source of your knowledge?   

That's partly why I included the illustration from "The Pirates Own Book" of 1837 (above).  

First, note that when I asked the question about "pirates," I didn't specify pirates of a particular era.  Still, if you show a picture from the Golden Age of piracy (roughly the 100 years from the mid-17th century to the mid-18th century) I did a quick browse of illustrations of pirates from that era, poking through several books I found on Google Books.  (Such as Piracy: The Complete History by Angus Konstam, or Pirates of colonial Virginia, by Lloyd Haynes Williams.)  

In none of these books could I find a contemporary illustration of a pirate with an eye patch.  That strikes me as odd, but maybe I just missed something.    

As Ramón pointed out in his search, 

     [Pirate eye patches origin]

leads to a nice episode of Mythbusters (the television show that specializes in testing out various legends and myths) on commonly held beliefs about pirates.  In this episode, they report on their test (to become dark-adapted and try to do some tasks in the dark, then repeat the tasks with light-adapted eyes--no question, the dark adaptation was useful).  

I was inspired by this, so I repeated the experiment myself in the dark of the early morning.  

At 4AM I put on my eye patch (see below), and let my left eye become dark adapted for 30 minutes.  

The eye patch is an adapted eye mask that was piratically appropriated from
a commercial airline.  Arrgh!  

I then entered a small, hold-like room in my house (okay.. a bathroom with a very dim skylight, but no windows), switched off the light at 4:30AM and took off the eyepatch.  

I was amazed at how well I could see with my left eye.  I could count fingers held up at arm's length, and even read large printed text (1 cm high on white paper at arm's length).  

What really surprised me was that my right eye (the non-dark-adapated one) was completely blind.  It was as though I'd suddenly changed the eyepatch from one eye to the other.  It was SO striking that I reached up to touch my eyelid to be sure it was open.  Yes, it was... but it was also completely black--my right eye was terrifyingly blind.  

This brings up a good point that Marian raised in the comments:  When you wear an eyepatch, you've compromised your depth perception AND taken away all vision over half your visual field.  It's a HUGE disadvantage in a fight.  Likewise in the dark of the hold--if there's any threat there (including things you might walk into, like cannons or other crewmen defending their ship), you're literally missing half the picture.  

It took about 20 minutes for my right eye vision to accomodate to the changes in lighting.  

What really surprised me (but in retrospect should not have) was that my right eye vision returned in the periphery first, slowly progressing towards the center.  It's really odd and interesting to be able to see perfectly on the left (with my left eye), and all the way on the right (in the periphery of my right eye), but not in the middle of the right.  To get the effect, hold your right hand over your right eye with the edge of your hand touching your nose.  You can see on the left, and a bit on the far right... but nowhere else.  

In any case, based on my personal experience with an eye patch, it seems unlikely that you'd wear this thing constantly for a 20 minute advantage whenever you boarded a ship.  If you were going in and out of holds all the time, maybe... otherwise, it would be a hassle.  

Ramon's discovered that Howard Pyle (the 19th century illustrator) apparently created the common image of the pirate in his images (large gold earring, head scarves, broad sashes and belts, etc.) by adapting Spanish peasant dress of that time (late 1800s) in his pictures.  (As documented in the book Pirates: The Golden Age, by David Rickham and Angus Kostam.) 

In any case, given the lack of contemporary evidence, and the dysfunction of wearing an eyepatch most of the time, I'm going to say that this seems implausible to me.  Possible, but unlikely.  

 

Bono's sunglasses:  It's not hard to find that Bono has glaucoma, but it's a bit more difficult to find any support for wearing sunglasses as a therapy for glaucoma.  The obvious search in Google Scholar: 

     [ glaucoma sunglasses ] 

yields rather little of use.  There are lots of hits, but when you read the documents, you'll see that glaucoma is usually referred to separately, as another condition, and not in conjunction with sunglasses as a therapy.  

This is when  you want to use the AROUND operator.  

     [ glaucoma AROUND(5) sunglasses ] 

This gives you somewhat better results (on Google Web search) because it's looking for near adjacency of the terms (as opposed to a term like "glaucoma" being mentioned in a distant article somewhere on the page).    

But after reading through the top ten results, it becomes clear that sunglasses help with glare and being sensitive to light, but they don't actually act as a treatment or therapy for glaucoma.  

Just to check on this, I also did a search on Pubmed (the National Library of Medicine's scholarly medical collection).  My search was: 

     [ glaucoma sunglasses ] 

If you use Pubmed's Advanced Search tool, you'll see they have 57K hits for glaucoma alone, but only 2  (not 2K, just two) hits for glaucoma and sunglasses.  

I found that pretty interesting.  There are 28K results for [ glaucoma treatment ] but only 2 for [ glaucoma sunglasses ] 

Don't get me wrong--wearing sunglasses is a great idea, and if you're sensitive to bright lights and often exposed to flashes when indoors (as Bono is), then it's a good idea.  But the sunglasses aren't therapeutic, but tonic.  

Search Lessons:  

1. Sometimes it's good to do the experiment yourself.  My eyepatch experiment was really interesting.  I had no idea that my dark vision would return from the periphery to the center, nor that it would work as well as it did.  That experience also pointed out the difficulties of wearing an eye patch for any length of time when you didn't need to.  (My right shoulder now has a bruise where I hit the door jamb because I couldn't see it...)  

2. The LACK of information is often a signal in-and-of itself.  After looking at dozens and dozens of contemporary illustrations of pirates--and not finding a single eyepatch--I'm dubious that this was a standard practice.  To be sure, this isn't conclusive, but it's pretty interesting...  especially when.... 

3.  Very authoritative resources sometimes have (nearly) no results when they have nothing to say.  If you can't find more than 2 articles on Pubmed for a treatment mode (e.g., sunglasses), you can be pretty sure that the silence is telling you something.  

Great work this week--as always.  

Search on!