Why do you get Boogers in your Eyes?

Why do you get Boogers in your Eyes?

Rheum is made up of mucus, skin cells, oils and dust. The rheum that comes from the eyes and forms eye boogers is called gound, which you may know as eye sand, eye gunk, sleep dust, sleep sand, sleep in your eyes. When you're awake, gound doesn't cause any problems.
Your eyes produce mucus throughout the day, but a continuous thin film of tears bathes your eyes when you blink, flushing out the rheum before it hardens in your eyes.
When you're asleep  and not blinking, eye discharge collects and crusts in the corners of your eyes and sometimes along the lash line, hence the term "sleep in your eyes."