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 really knows why children do it.
My niece does this, and still does and she is 3 yrs old...she don't have any muscles to hold her eye lids open or closed..she will soon have surgery to fix it...she had surgery once before but got infected....but in newborns, it is common, their muscles have to get built up..
So they can see what is going on around them
To look for who ever comes after them I guess