Expert answer: The BabyCenter Editorial Team
Yes, it's normal, but it certainly looks odd. As Concord, California, naturopathic doctor Tara Levy puts it: "Zombie kid! Watch out!"
Open-eyed sleeping – called nocturnal lagophthalmos in medical speak – is harmless and doesn't indicate that your child has a sleep problem. It's fairly common in infants, though most outgrow it by about 12 to 18 months.
No one knows exactly why some babies sleep with their eyes open – "No one's funding that research," Levy says. But it may have something to do with spending more time in REM sleep.
"Sleeping with the eyes open happens during REM, which is a more active sleep cycle," Levy explains. "Babies spend much more time in REM sleep than adults, about 50 percent of their total sleep time.”
If your baby's "zombie sleep" bothers you, gently stroke his or her eyelids closed. "That's what I used to do, because it looked creepy," Levy says.
Consult your pediatrician if your child sleeps with his or her eyes open for many hours at a time or does it regularly after 18 months old. In very rare cases, malformation of the eyelids can prevent them from closing normally. But otherwise, don't fear the zombie kid.
Incidentally, there's some evidence that nocturnal lagophthalmos is hereditary. If you notice your child sleeping with a glassy stare, ask your partner if you ever sleep wide-eyed yourself. (Note: In rare cases, this can be a sign of health problems in adults – facial nerve damage, thyroid problems, even certain kinds of tumors. Talk to your healthcare provider if you're concerned.)