I bet that with your eyes closed, the difference between "black out blind dark" and "no light" isn't much. I bought black out blind about 5 years ago and they're amazing. If I'm in my parents house or staying in a hotel during summer, I get crappy sleep and I'm wide awake at 5am.
I might mention that, believe it or don't - a living skull is translucent, and our brains can detect light all by themselves. So a mask is good, but not nec a whole solution.
In old experiments, just the light coming in under a door diminished melatonin in mice.
