Nocturnal lagophthalmos is a condition in which people sleep with their eyes open, and it is estimated that about 20% of people do sleep with their eyes at least partially open. It is thought to be hereditary, though kids who have it tend to outgrow it. The condition causes the person to be unable to fully close their eyelids. It is not always an indication that something more serious is wrong, but it could signal that a person has had a stroke, has a thyroid condition, or has sustained potential nerve damaged to their face. It may be coupled with other signs of a potential problem. Enlarged or bulging eyes caused by these diseases does make it difficult to fully close the eyes.
An inability to fully close the eyes during sleep could also be a problem caused by damage to a person’s eyelids. A person with obstructive sleep apnea, which causes the narrowing of the airways, can cause floppy eyelid syndrome. This is easier to see at night when the sufferer is trying to sleep. It is best to have this checked out as obstructive sleep apnea can cause a person to stop breathing while sleeping, as well as making them at a higher risk of heart problems and stroke.
Less risky but still potentially harmful, having your eyelid partly open can disrupt your sleep, cause dry eyes, infection to the eyes, blurred vision, and other vision issues. Eye masks can help to fix the problems, as well as using goggles that keep your eyes from getting dry. There are also specially made eyelid weights to force eyes closed. Another solution is optional surgery if a person suffers from a severe case of nocturnal lagophthalmos.
Since you are unable to see that you have this problem, having a partner or member of the family check can help you to know if you keep your eyes open when you sleep.
For more details, check out Do You Sleep with Your Eyes Open? (You’ll Be Surprised How Many of Us Do) for details and other potential solutions.