Why do you get "sand" or "crustys" in the corner of your eyes in the morning?

Answer 1

Your eye cleans itself during the night and the dirt goes to the corner of the eye in order to expel it from the eye.

Answer 2

Its that bloody tinker bell and all that fairy dust she sprinkles around I have told her repeatedly to change her shampoo!

It is the natural secretions of the eye that drain into the corners and become dry that makes that gritty sand like substance