Well, dear one, I think it was sometime in my late 20's, that I could fall asleep with just a little night light on.
TV is my sleeping pill, usually I try to set the timer, but I always have to see when I wake up.
I would be terrified as you say, if I could not see. Try some night lights in the outlets around the house for a dimmer set of lights. I have them all over.
I have to, have to, have to, see all around me, or I will not sleep a wink.
Also when I come in, I check every nook and cranny to make sure I am alone.
Not as often, but most of the time.
Hey, it keeps me saner, and all I'm doing is preventing a mental fear, or a real fear, either way, it keeps me secure.
Hope this helps, its normal to me, and then some...
Donna-Lynne