When you close your eyes, it doesn’t get really pitch black dark. More of a darkish grey mush. Try it yourself, there is a huge difference in darkness when you just close the eyelids and then you close them hard.

Well, I had forgotten about that so when I earlier today closed the eyes hard I got a bit of a panic. “I broke something! In my eyes!” were my first thoughts, then I opened them and everything was as normal. Soon that even applied to my heart rate.