I've always been one of those weirdos who kind of enjoys a trip to the optician, but now I've seen ASAPScience's super creative eye test, I've seen how much more fun those little tests can be!
All you have to do is take a look at this image. Who do you see?
If you see Albert Einstein, you have good eyesight. If you see Marilyn Monroe, you may need to have your eyes tested. I can personally attest to the veracity of this test as I wear glasses all the time for shortsightedness. With my glasses on, I see Einstein. When I take my glasses off, I see Marilyn Monroe!
The principle is nicely explained in this video from ASAPScience.
Basically, the image was created by blending an image with low spatial frequency with one with high spatial frequency; that is, a blurry picture and one with finer details.
If you've got really good eyesight, the only way you'll catch a glimpse of Marilyn is to start with a really small image. Take a look at this GIF of the pic zooming towards you and try to pinpoint the moment that Marilyn Monroe becomes Albert Einstein.
The question that remains to you all is... do you need to get your eyes tested?