Why do some people blink frequently while babies rarely blink?

Audit expert: Liu Dongbao

Chief Physician of Ophthalmology Department, Shenyang Red Cross Hospital

You must have noticed your eyelids: no matter whether you are a man or a woman, young or old, and no matter what activity you are doing, blinking is a natural and subconscious behavior, just like breathing.

When we were young, we may have played this game with our friends: two people looked at each other to see who blinked first, and the one who blinked first was considered to have given up. However, even if we try not to blink, we can usually only last for 1 minute or even less, and it is likely to be accompanied by sore eyes or tears.

But if you observe newborns, you will find an interesting phenomenon: even if you don't deliberately compete, cute babies will often win in the "blinking" competition. They will often stare at you with their innocent big eyes for a long time. Babies blink much less frequently than adults. Why is this strange phenomenon?

Source: hippopx

The mechanism of blinking

Blinking is a rapid opening and closing movement of the eyelids controlled by the facial nerve and oculomotor nerve, also known as the "blink reflex."

Think about it carefully: In our daily lives, under what circumstances do we blink?

When we eat, walk, or read, we all blink unconsciously at a certain frequency; and when someone claps or waves in front of us at a close distance, we often blink uncontrollably. The above are the two classic types of blinking: involuntary blinking and reflexive blinking .

Involuntary blinking is a spontaneous opening and closing movement of the eyelids that does not require deliberate control and is a natural protective movement. In the extremely short interval between blinking, the retinal photoreceptor cells can get a short rest; through blinking, a tear film rich in water, lipids and mucin is formed on the surface of the eyeball, thereby maintaining the moisture of the cornea and conjunctiva ; blinking can also prevent foreign objects from entering the eyes (once foreign objects enter the eyes, a large amount of tears will be secreted and removed through blinking); at the same time, blinking can also promote the normal flow of tears into the tear duct without overflowing .

The normal adult blinks 15-20 times per minute. When reading or using mobile phones, computers and other screen terminals for a long time, the attention is concentrated and the eye muscles are in a state of fatigue, the number of blinks will unconsciously decrease, resulting in insufficient moisture of the cornea and conjunctiva. It is easy to experience symptoms such as dry eyes, foreign body sensation, easy tearing, and even dry eye syndrome.

Reflexive blinking is the eye-closing reflex that occurs when a person is exposed to external stimuli such as foreign objects, strong light, or fright. It can also play a self-protection role to a certain extent.

Causes of Frequent Blinking

We mentioned above that a normal person blinks once every 3-4 seconds on average, but some people blink significantly more frequently than normal. Why is this?

Frequent blinking may be one of the manifestations of dry eye syndrome. This is a seemingly contradictory but logically smooth cycle: staring at the screen for a long time leads to a decrease in blinking frequency, dry cornea and conjunctiva, and then dry eye syndrome; however, patients with dry eye syndrome will involuntarily increase the frequency of blinking to maintain the thickness of the tear film, thereby increasing the moisture of the cornea and conjunctiva and alleviating the symptoms of dry eye.

Source of Dry Eye Syndrome丨Fuhe Health

Tourette syndrome is also manifested as a significant increase in the number of blinks. Tourette syndrome is a chronic neuropsychiatric disorder that often occurs in children. It is manifested by involuntary rapid twitching of multiple muscles, including the face, limbs, and trunk. The specific symptoms are rapid and disordered blinking, mouth, nose, and eyebrow linkage, shrugging, etc., and may also be accompanied by abnormal throat pronunciation and obscene speech.

In addition, eye diseases such as keratitis, conjunctivitis, and trachoma can also lead to an increase in blinking frequency.

Why do babies rarely blink?

Babies blink much less frequently than adults, even less than 4 times per minute; preschoolers' blinking frequency increases to about 8 times per minute, and continues to increase to 15-20 times per minute in adulthood.

The reasons and mechanisms for the developmental increase in blinking frequency with age are still unclear. Some researchers believe that the blinking frequency of infants is mainly determined by the ocular surface conditions such as tear film thickness and ocular surface area, but in recent years, more and more studies have shown that the central dopamine system is involved.

As early as the 1980s, CN Karson conducted research on monkeys: when given dopamine receptor agonists, the monkeys' blinking frequency increased significantly, while dopamine receptor antagonists significantly reduced their blinking. Pediatric studies have shown that blinking frequency is affected in children with pathologies related to the central dopamine system.

Other studies have shown that breastfeeding, visual stimulation of new things, and other factors can significantly increase dopamine secretion in human infants and rats, and their blinking frequency also increases significantly. Studies in multiple fields have shown that there is a consistency between age-related changes in blinking frequency and the development of the central dopamine system, which also provides indirect evidence for the relationship between the two.

Finally, whether you are a school-age child or a hard-working adult, if you read or stare at the screen for a long time, you must get up and move around from time to time, look into the distance, or do eye exercises to protect the windows of our soul.