Do you see Albert Einstein or Marilyn Monroe? If you see Einstein, that means your vision is good! If you see Marilyn Monroe, your eyes need some help. In the GIF above, you should see both as it zooms in. When the image is further away and smaller, you'll see Marilyn. As it comes closer, you'll see Einstein. The quicker you see him, the better your eyesight.
ASAP Science's latest video delves into vision and gives the test of Monroe/Einstein to illustrate their points. The photo is basically a hybrid image of low and high spatial frequency to test our eyeballs. Watch the video below to learn.