Everything about Blink totally explained
Blinking is the rapid closing and opening of the
eyelid. It is an essential function of the
eye that helps spread
tears across and remove irritants from the surface of the
cornea and
conjunctiva. On average, a blink takes approximately 300 to 400 milliseconds. Blink speed can be affected by elements such as fatigue, eye injury, medication, and disease. A person approximately blinks once every two to ten seconds. The blinking rate is determined by the "blinking center", but it can also be affected by external stimulus. When an animal (usually
human) chooses to blink only one eye as a signal to another in a social setting (a form of
body language), it's known as
winking. However, some animals (for example,
tortoises and
hamsters) blink their eyes independently of each other.
Function and anatomy of blinking
Blinking provides moisture to the eye by irrigation using tears and a lubricant the eyes secrete. The eyelid provides suction across the eye from the tear duct to the entire eyeball to keep it from drying out.
Blinking also protects the eye from irritants.
Eyelashes are hairs attached to the upper and lower eyelids that create a line of defense against dust and other elements to the eye. The eyelashes catch most of these irritants before they reach the eyeball.
There are multiple muscles that control the reflex of blinking. The main muscles, in the upper eyelid, that control the opening and closing are the
orbicularis oculi and
levator palpebrae superioris muscle. The orbicularis oculi closes the eye, while the relaxation and contraction of the levator palpebrae muscle opens the eye. The Müller’s muscle, or the
superior palpebral muscle, in the upper eyelid and the
inferior palpebral muscle in the lower eyelid are responsible for widening the eyes. These muscles are not only imperative in blinking, but they're also important in many other functions such as squinting and winking.
Blinking in everyday life
Children
Infants don't blink at the same rate of adults; in fact infants only blink at an average rate of one or two times in a minute. The reason for this difference is unknown, but it's suggested that babies don't require the same amount of eye lubrication that adults do because their eyelid opening is smaller in relation to adults. Additionally, infants don't produce tears during their first month of life. Babies also get a significant amount more sleep than adults do, and, as discussed earlier, fatigued eyes blink more. However, throughout childhood the blink rate increases, and by adolescence, it's usually equivalent to adults.
Adults
Women and men don't differ in their rates of spontaneous blinking, averaging around 10 blinks per minute in a laboratory setting. However, when the eyes are focused on object for an extended period of time, such as when reading, the rate of blinking decreases to about 3-4 times per minute. This is the major reason that eyes dry out and become fatigued when reading.
Eye blinking can be a criterion for diagnosing medical conditions. For example, excessive blinking may help to indicate the onset of
Tourette syndrome,
strokes or disorders of the
nervous system. A reduced rate of blinking is associated with
Parkinson's disease. Parkinson's patients have a distinct, serpentine stare that's very recognizable.
Further Information
Get more info on 'Blink'.
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