Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portion of the orbicularis oculi, not the full open and close.

What causes us to blink?

The eyes need a smooth surface for light to properly focus on, so vision doesn't become blurry. Blinking releases a tear film — which mostly consists of water, oil and mucus — to keep the surface of the eyeball smooth. It also prevents the eye from drying out, which can be uncomfortable.

Do you fully close your eyes when you blink?

You should not feel any movement under your fingers if you used your eye muscles. After closing your eyes, pause. This step is important because if a blink is to be effective, the eyes must fully close. You can quickly check this by placing a finger under your eye, right above the cheekbone.