You may have noticed more than a few "vision tests" popping up on your Facebook news feed. These tests, like the samples in the YouTube video below, are a fun way to pass the time, but do they really tell you anything about your eyesight?

Maybe not. Your vision works like this: Your eye sees an object. That information is sent through your optic nerve to your brain, where your brain interprets what you see. Sometimes your brain can trick your eyes into seeing (or not seeing) something, hence the term "optical illusion," according to Vision Web. 

Have you ever tried the test where you read a box of text with all the letters of a word scrambled, except the first and last letter? LiveScience explains how our brains are actually playing a bigger role than our eyeballs when it comes to interpreting these types of tests:

"We use context to pre-activate areas of our brains that correspond to what we expect next. ... For example, brain scans reveal that if we hear a sound that leads us strongly to suspect another sound is on the way, the brain acts as if we're already hearing the second sound. Similarly, if we see a certain collection of letters or words, our brains jump to conclusions about what comes next,"  said cognitive neuroscientist Marta Kutas, according to LiveScience. 

When you look at an image like the one below, your brain sees the same letter over and over and makes it easy to miss the one that's different. Not only do you have to trick your eyes, you have to trick your brain to find what you are looking for. Try reading each line from left to right slowly. Is it easier to find now? 

While these tests are entertaining, they shouldn't replace regular eye exams. Your eye doctor can better test to see whether you need assistance with your vision and keep track of symptoms of eye disease, according to All About Vision. And, don't just rely on vision screenings, children should get a full exam at least once a year and adults should get an exam at least every other year, according to All About Vision.