There is a light pollution movement that says lighting at night obstructs melatonin production. They say:
What makes you fall asleep are changes in the level of the hormone melatonin circulating in your body. During the day, light stimulates a part of the brain. This brain part (known as the suprachiasmatic nucleus) tells the pineal gland to decrease the melatonin level when it is light out and to increase it when it is dark. The brighter the light, the bigger the decrease and the darker the dark, the bigger the increase of melatonin. By making your days lighter and your nights darker, you can improve both the quality of your sleep and the amount of time it takes you to fall asleep.
and recommend all kind of protection against the light,
Dark Nights: Make your nights as dark as possible. Draw the curtains, close the shades and keep the lights off. Try a sleep mask if you can’t get eliminate enough light. The darker your night, the quicker you will fall asleep.
Do I sense the light by the whole skin surface or only open eyes? If you sense by eyes, which are closed during the sleep, then what is the problem?
In other words, the question is: is the sleep mask sufficient for melatonin secretion or you need to cover the skin?
update What if I close only one eye? I tend to do this when the blinding sun shines. Does such light eject melatonin?