Why Our eyes close when we sleep?

First, distracting sensory stimuli can interfere with sleep, and closing your eyes greatly reduces visual input. Second, closing your eyelids protects your eyes from foreign objects and from drying out during sleep. I got this off of yahoo questions and answers. It is a great question

If you did not close you eyes while you were sleeping, they would dry out and it would cause serious eye infections and other eye problems. Even those people who close them halfway, are protecting them enough while sleeping to prevent eye infections. Try not blinking for as long as you can and see how much your eyes dry out in just that short amount of time. Imagine how dry they would get after 6~8 hours of sleep. Shalom~Adoniah

i guess our eyes need to rest too for a certain period of time.mayb thats why

I am not a doctor but as far as I know we need to shut our eyes to stop it from working, allow it to rest and be cleansed. Blinking is done to cleanse our eyes too. There are some people who sleep with their eyes open but i am not sure if it affects their sleep. Also, maybe God designed our eyes wid eyelids as a wiper and a cover from tiny insects and dust. Just imagine how you could get a good sleep when dust would be entering your eyes.

I don't really know. Maybe its because like the first person said they need to be cleansed and rested. Just like the rest of our body needs sleep and relaxation. I would like to know why girls (including me) open our mouth when we put eye make up on? Why is that? Shutting your eyes when your sleeping just seems natural to me.

not all people really shut their eyes while sleeping. My hubby only half shut. they said that people with half-shut eyes while sleeping cares more on their siblings and relatives. don't know if it's true :P our eyes needs refreshments after a day's work. so i guess it's because the nerve system in the eyes would like to relax a while.