Cover one eye; read the letters aloud. Cover the other eye; read the letters aloud.
Ah, the standard eye exam. A few lines of text and the doctor can tell you whether you have poor vision. But let's be honest, that's boring.
Back in 2007, scientists at MIT developed an optical illusion to determine if you need corrective lenses. It does the same thing as the trusty big 'E' -- but way more fun.
Meet Marilyn Einstein, a creepy hybrid of two icons. If your vision is good you should be able to see the face of Einstein from about a foot away. If, at that distance, you see Marilyn Monroe you probably need glasses because Einstein's never looked that good.
The optical illusion is making the rounds on social media, and you can see why. It's totally mesmerizing.