In nature, it seems nothing uncommon when you find some animals sleep with their eyes open. Snakes and fishes sleep this way because they have no eyelids; marine mammals like dolphins can even keep one eye open to stay alert. But what if you find that your friend, partner or family sleep with their eyes open?
Quirk or condition?
You may feel it kind of weird, thinking that it may be some sort of sleep quirk. But it’s not the case. It's a condition known as nocturnal lagophthalmos, which means their eyelids cannot close enough to cover the eyeballs even though they have been snoring.
The National Sleep Foundation estimates that up to 1/5 of the population has this condition. Although it is usually believed to be a harmless habit, it can cause serious eye problems and influence sleep quality.
What you may suffer
Evolution has developed a way that helps human beings protect the eyes. Eyelids can keep foreign bodies out of your eyes and the blinking reflex gives your eyes a moist environment. As you stop blinking during sleep, eyelids are like shields that keep your eyes clean and hydrated.
When your eyelids fully shut, tears and moisture can clean and repair your cornea, getting your eyes refreshed after the overuse in the daytime. This process is critical to the lubrication and health of your eyes, without which you may suffer dry eyes, blurry vision, infection, and even permanent eye injuries.
Sleeping with your eyes open can also compromise your sleep quality. Your eyelids shut at night to block light from your eyes and help switch yourself into the ‘low-power mode.’ Otherwise, the light will be an existing stimulator to your brain part which controls the circadian rhythms, making it hard to sleep soundly.
Sign of other conditions or injuries
Sleeping with your eyes open is possibly due to many reasons, and sometimes it may signal an underlying condition or injury.
· Autoimmune diseases and infections such as Lyme disease
· Bell's palsy, a condition that causes sudden and temporary weakness in the facial muscles
· Moebius syndrome, which affects cranial nerves
· Damage to the eyelid, including floppy eyelid syndrome that makes eyelids too loose and rubbery to shut, associated with obstructive sleep apnea, a dangerous sleep disorder that may cause the onset of coronary artery disease, heart attack, heart failure, and stroke.
· Thyroid-related eye problems, including bulging eyes due to Graves’ disease, a form of hyperthyroidism or overactive thyroid.
Hereditary but Treatable
The condition has been proved hereditary (most children grow out of it). But if one day you are told you sleep with eyes open too (since you can hardly find it by yourself), there are always silver linings!
· Wear eye masks or a specially made goggle to trap moisture at night
· Use artificial tears in the daytime
· Put a humidifier in your room
· Wear eyelid weights (if your doctor recommends)
· Tape your eyelids shut with surgical tape
· Get a surgery (only in the most severe cases)
“Sleeping with one eye open” is a metaphor that suggests you stay alert while sleeping with both your eyes open is a health concern. If you often suffer tired, dry, or itchy eyes after you wake up, you’d better try to find out whether you sleep with your eye open and go to a doctor as soon as possible. Sweet dreams!