Why does sleep appear in your eyes? What causes it?

Question

Why does sleep appear in your eyes? What causes it?

Answer 1

Your eyes are very special.

They can self adjust from things up close to far away and many other things I cannot remember off the top of my head.

They also clean them selves.

When you go to sleep all the junk you got in your eye is pushed out and left to harded where you find it in the morning.

Unless you just want to believe the sandman story. I thought it was weird when my grandma told me it.

Answer 2

Your eyes clean themselves from all the dust and pollution that gets in them during the day.