A patient on CPAP says there was no leak, but he was noticing a “fluttering” of his upper lids as he fell asleep, reports Healio.

Yup, you (and Lenora) guessed it: He has incompetent canalicular valves. Some of his positive pressure flow is going up his tear ducts and flowing across his closed eyes while he sleeps. Great pick-up, huh?!