I sleep only on my back so it stays on without anything to seal it. It fits flush against the skin into my eye sockets. The eye drops and my open eyes evaporate water into the cavity created by the cups against my skin. Now most people of course move around when sleeping. It comes with a strap that keeps it on and you can buy extra straps that are not expensive should the original strap fail. In winter being bald I put on a night hat that also goes down enough to lay on top of the goggles which keeps them snug as well. I keep them clean by using this stuff: https://smile.amazon.com/CleanSmart-Antimicrobial-Cleanser-Bottle-Alcohol-Free/dp/B00GX25ZK4/ref=sr_1_15?dchild=1&keywords=clean+smart&qid=1627840544&sr=8-15 I spritz a bit on the inside of the cups while getting ready for bed letting it set there and then before hopping into bed I dry them off, put the drops in my eyes, and put them on. Works well for me.