In reality, the proverbial "blink of an eye" lasts only a tenth of a second, but that's all the time needed to clear away dust particles and spread lubricating fluids across the eyeball. Every time you blink, your eyelids spread a cocktail of oils and mucous secretions across the surface of the eye to keep your globes from drying out. Blinking also keeps eyes safe from potentially damaging stimuli, such as bright lights and foreign bodies like dust.
So why don't you notice the world plunging into darkness every two to ten seconds? Scientists have found that the human brain has a talent for ignoring the momentary blackout. The very act of blinking suppresses activity in several areas of the brain responsible for detecting environmental changes, so that you experience the world as continuous.