Why Do We Blink?

You blink your eyes around 20,000 times a day, even though you're completely unaware of it. When you're intently focused on something like gazing at a computer screen, the number of times you blink drops from around eighteen times a minute down to twelve. What purpose does eye blinking serve? Why do we blink our eyes at all?

Why Do We Blink: The Function of Blinking Eyes

Eyes blink to keep their surfaces moist and free of debris - and to protect themselves from damage. Blinking is a natural reflex that occurs when a foreign body threatens to fly into the eyes, or when a person is startled or exposed to a bright light. Even a loud sound can activate the blink response - also known as the corneal reflex.

Doctors sometimes test the blink reflex during a neurological exam by touching the corner of the eye with sterile cotton. Normally both eyes blink or shut even when only one cornea is touched, which is called a consensual response. If there's damage to the fifth or seventh cranial nerves, the corneal reflex may be absent, or the response may not be consensual.

You Blink Your Eyes to Keep Them Moist

Another reason you blink your eyes is to keep them from drying out. Eyes produce three types of lubricating fluids: tears, mucous and lubricating oil. Blinking the eyes helps distribute these fluids over the surface of the eyes - to keep them from becoming uncomfortably dry.

Dry eyes are a common problem as people age, and the lack of adequate tear production can cause uncomfortable eye symptoms such as redness, tearing, light sensitivity, burning, stinging, blurred vision, and eye pain. Severe dry eyes lead to erosions on the surface of the cornea, which can threaten vision.

Dry eyes can be a problem even for normal people who focus too long on a computer monitor and forget to blink their eyes. Dry, irritated eyes are a symptom of computer vision syndrome, a condition which comes from staring at a computer screen all day without blinking frequently enough. People who develop computer vision syndrome blink as little six times a minute, which isn't enough to keep their eye surfaces moist and lubricated.

Why Do We Blink: The Bottom Line?

Blinking is something most people aren't conscious of, but not doing it enough causes a host of unpleasant, dry eye symptoms. When you're sitting in front of a computer screen, be more conscious of keeping your eyelids moving. Blinking your eyes really does serve an important purpose.

References:

Merck Manual. Eighteen edition. 2006.