I have a Lewis N Clark sleep mask with a 3/4" elastic strap around the back. Trouble is it keeps falling off halfway through my sleep. If I tighten the strap then it presses uncomfortably around my eyes. Any suggestions for how to keep it on so it doesn't fall off and cause me to wake up?
I needed to sleep in a lit room without an eye mask on a cycling trip. What I did have with me was a neck tube (a.k.a. neck warmer/Buff). Folded over 3-4 times that was effect and comfortable, and stayed on better lying down than sleep masks. The advantage is that it forms a very wide band, spreading the load.
If I was buying one with that in mind I'd get a black one like this; the one I used was cheaper and only printed with black and a pattern, but 4 layers was sufficiently opaque.
You could also use one of these over an existing sleep mask for a snug fit. They have the added advantage of securing earplugs, which are often needed at the same time.
I've had a big issue with my sleep mask falling off as I sleep, maybe because I might roll around a lot. The most surefire solution I've found is just taping the sleep mask to my face with regular cellophane tape. I use four pieces of tape, each about 3–4 inches long (7.5–10 cm): one on the top-left, one on the top-right, one on the bottom-left, and one on the bottom-right. Make sure the tape isn't over your eyes, in case it stops adhering to the mask and ends up underneath. It's important for the pieces of tape to be reasonably long so they stay on.
Crude, but it works, and I don't think it really hurts to take off the tape.