that is what eyelids are designed for.... to block light while you sleep.... it's not because your eyelids are thicker than others... it's because you are probably a heavy/deep/quick sleeper who are simply not bothered by light.
some people are just light sleeper (how unfortunate) and they can be disturbed by any little thing such as light coming from doorframe, slightest vibration from people walking by, etc.
if I recall correctly... you are under medications. that probably explains why you are not bothered by light while sleeping.
for me - I'm a heavy sleeper and I sleep like a log. I've slept thru earthquake that struck east coast, heavy thunderstorm that shook earth, etc.