Why Does the Human Eye Blink?
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How the Eye Works
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The human eye, like that of many other living organisms, has "camera-type eyes," where what the eye sees is filtered through a lens in the eye and focuses on the membrane at the back of the inner eye called the retina.
The human eye is covered with a thin film called the cornea which must remain moist in order to protect itself and the eyeball from damage such as that caused by friction. Friction could result in small tears to the corneal coating, providing openings for invading microorganisms.
Purpose of Blinking
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Blinking of the human eye serves a twofold purpose: The movement of the upper lid over the surface of the eye disperses moisture evenly across the surface of the eyeball. This same movement also clears the eye surface of any debris that may be present.
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In-depth Information on Blinking
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On average, the eyes blink every 5 seconds, but unless you are concentrating on noticing the blink, you will not notice this regular activity throughout your waking hours. Scientists at University College London have determined that the human brain suppresses the part which responds to visual input for the microsecond a blink requires.
Blinking is an automatic action, much like breathing and the heart beating. When eyes become dry due to atmospheric, environmental or physical conditions of the body, the rate of blinking will increase in an effort to maintain adequate moisture on the outer eyeball lining. Irritants such as dust, infection or a foreign body on the eye will also result in faster blinking.
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References
- Photo Credit Martin Kingsley, http://www.flickr.com/creativecommons
