Casa Bonita: Skeleton pirate at the entrance to Black Bart's Cave

Why Did Pirates Wear Eye Patches?

This Wall Street Journal article from back in 2013 answers some important questions about whether reading in dimly lit conditions or reading on a device like an iPad or phone can actually cause damage to your eyes. It turns out there is no evidence of long-term damage or change in the physiology to the eyes but it may cause discomfort or fatigue.

However, the lead is buried in the last paragraph of the article and explains why pirates wore eye patches:

“Ever wonder why a pirate wears patches? It’s not because he was wounded in a sword fight,” says Dr. Sheedy. Seamen must constantly move between the pitch black of below decks and the bright sunshine above.

Smart pirates “wore a patch over one eye to keep it dark-adapted outside.” Should a battle break out and the pirate had to shimmy below, he would simply switch the patch to the outdoor eye and he could see in the dark right away—saving him 25 minutes of flailing his cutlass about in near blindness

Am I Shortsighted?

Test For Shortsightedness

If you want to check if you need glasses while sitting at your computer, the above image will help you test whether or not you are shortsighted. At normal screen viewing distance you should see the face of the great scientist Albert Einstein. This would indicate you have normal vision. Shortsighted people will see Marilyn Monroe. If you squint, or move a few meters away from your screen (replicating having short-sighted vision) you will see Marilyn Monroe.

The Marylin Einstein hybrid image was created by Dr. Aude Oliva for the March 31st 2007 issue of New Scientist magazine. Other examples of hybrid images can be found in the links below:
Cat/Dog
Cheetah/Tiger
Leopard/Elephant
Dolphin/Car
Astronaut/Scuba Diver (my favorite)