But sleeping with eyes open is more than a metaphor. It’s an actual sleep condition—known as nocturnal lagophthalmos —and it is more common than you might think.

ANSWER These two cases are similar, but they represent two very different sleep conditions. The first - being asleep at night with the eyes open - is probably an example of parasomnia.

As to how common it might be, that study suggested about 5 percent of adults are affected, but estimates do vary, with some suggesting up to 20 percent of people may sleep with their eyes open.

Covering their eyes with their paws, according to Harrison, is the feline equivalent of sending a "do not disturb" sign to others. You can read more about cats' sleeping positions here.

How Much Sleep Is Normal for Cats? Adult humans need between 7 to 8 hours of sleep every day. However, you cannot use this criterion to judge your cat’s sleeping habits. Your furry friend needs ...

A file photo of a cat covering its eyes. A kitten's unusual sleeping position has left internet users in stitches. getty images The video quickly went viral on social media and it has so far ...