I really don't think that has anything to with how thick your eyelids are. I bet it has to do with how heavy a sleeper you're. Some people can sleep through anything . I can fall asleep with the light on too and my eyelids are normal.
Bingo. When one of my disabilities is bothering me and I struggle to sleep, any light on is a bitch to sleep through. When things aren't so bad and I sleep as I normally do, I can easily sleep through lights. It's why light flashing alarm clocks were useless for me.
My daughter and I were comparing how much light and shadows we see when our eyes are closed. I see a lot less than she does. I am glad I found this thread. I could not find any other information ... besides medical conditions. Thank you