Have you ever woken up in the morning with the corners of your eyes filled with crud? Sleepy sand? Eye goblins? Dozy dust? Bed boogers? Why do our eyes make this stuff, anyway? And why does it build up when we’re asleep? We asked Yale eye doctor Soshian Sarrafpour to help us get to the bottom of this issue.

Got a question that you can’t keep a lid on? Send it to us atBrainsOn.org/contact, and we’ll find someone who can answer it in the blink of an eye.