It should be because of long-term lack of sleep. This happens when you don't get enough sleep for a long time. You know, you want to sleep, but you have to keep your eyes open. Of course, the eyes will be tired.

It's not the eyes. It's okay. It's been more than a year since a single eyelid became a double eyelid. Later, I slept a lot after the college entrance examination, and this phenomenon disappeared immediately, or my double eyelids were restored ~