Why You Blink Your Eyes

As children, most of us had staring contests with siblings or friends. How long could you hold a stare without blinking? Your eyes burned and watered and finally you gave up. Why was it so hard to go very long without blinking? In fact, why do you need to blink at all?

Blinking is necessary for two main reasons: clearing away dust particles and lubricating the eyeball. Even though you probably don't notice it, the average person blinks approximately once every 10 seconds. The average blink takes about 400 milliseconds, but the speed can be affected by many things such as fatigue, use of medication, and certain health conditions.

Blinking wipes and renews your tear film, the smooth, moist layer covering our eyeballs. Your tear film and tears are made of water, oil, and mucus (and hundreds of other components such as lysosomes, which function like natural antibiotics). The tear film also contains many nutrients and amino acids to nourish the cells in the cornea, the clear, dome-like structure on the front of the eye. 

Besides keeping your eyes lubricated, tear film also:

• Helps form an almost perfectly smooth optical surface on top of the cornea for light to focus properly
• Transfers oxygen from the atmosphere to the cornea, since there are no blood vessels to deliver it directly.
• Prevents infection due to presence of lysosomes and other antibacterial enzymes
• Washes away debris
• Provides a pathway for white blood cells when there is an injury to the surface

Your eyelids play a significant role here. Aside from protecting your eye and keeping things dark while you sleep, they contain several glands that secrete the components of your tears when you blink.

There is also a slight horizontal movement of the eyelid that pushes debris toward the puncta (tear ducts), small openings in the corners of the eyes through which tears drain. Tears then flush the debris.

While these reasons for blinking are well-established, research also suggests that you may blink for your brain. Scientists speculate that blinks are a way to get a brief mental rest without visual stimuli.

One study found that the precise moments we blink may not be random. We may blink at very predictable times, in fact. For example, when reading, most people blink at the end of a sentence. When people listen to a speech, they tend to blink when the speaker pauses between statements. And when people watch a video, they tend to blink when the action on the video lags for a moment. 

Researchers also found that when people blinked, mental activity spiked in certain areas of the brain that function when the mind is in a state of wakeful rest. They felt that activation of this part of the brain serves as a short mental break that allows for better attention when the eyes open again.

Additional research is needed.