If you're one in five people who sleep with your eyes open, you may want to call your doctor. According to the National Sleep Foundation, sleeping with your eyes open could be hereditary and a sign of an underlying health condition. Experts say that sleeping with your eyes open—a condition known as nocturnal lagophthalmos—may also be a sign of a stroke, thyroid disease, or facial nerve damage, according to CNN. The inability to fully close your eyes may also be a result of Graves' disease—an autoimmune disorder that causes an overactive thyroid—or floppy eyelid syndrome.
A symptom of floppy eyelid syndrome is obstructive sleep apnea, in which the soft tissue in your throat temporarily relaxes, which narrows your airway and momentarily cuts off your breathing. Sleeping with your eyes open can also be disruptive, as it allows light to pour through, which stimulates the brain. Additionally, it can also be very drying to your eyes, so consider using eye drops before you go to sleep to increase moisture.
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In some cases, you may not even realize that you are sleeping with your eyes open unless a partner or family member notices. Ask a loved one to take a picture if they see this happening, which you can then show your optometrist during your next visit.
Fortunately, experts say sleeping with your eyes open is a treatable condition. Try wearing an eye mask while sleeping, which can prevent light from coming through, or taping your eyelids shut with medically-safe tape. If an eye mask doesn't work, doctors can provide eye weights, which you wear on the outside of your upper eyelids and can prevent them from fully opening when you sleep. If not treated, the National Sleep Foundation says that nocturnal lagophthalmos can lead "to dry eyes, blurred vision, infection, and even permanent vision problems."