We blink our eyes every six seconds. Although blinking eyes ins an involuntary action, we can raise or lower the number of blinks voluntarily. The reason for blinking eyes can be easily understood by a very simple and common example- windscreen wipers of cars. The wiper of a car, when switched on, moves to and fro on the windscreen and wipes away dust, water or any other undesirable item. The same is the case with our eyelids. Our eyelids are made up of folds of skin and certain muscles of our eyes move them up and down the eyes. The eyelids have fingers of hairs edging them, known as eyelashes, that, with each movement, prevent dust, water or perspiration from entering the eyes by trapping it in the eyelashes. The result is a clean eye, free from unwanted foreign bodies.
But one more function is also carried our while blinking. There are around thirty tiny sebaceous glands at the edge of each eyelids and they have their openings between the eyelashes. Every time we close our eyelids, these glands secrete a secretion that lubricates the edges of the eyelids and eyelashes and prevent them from becoming dry. And in order to keep the eyes moist, the eyelids draw a liquid from the tear glands (here the liquid that makes tears is stored) and wets the eye. This prevents the eye from drying out.