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Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. [1] A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portion of the orbicularis oculi , not the full open and close.
The corneal reflex, also known as the blink reflex or eyelid reflex, [1] is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though it could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response (response of the opposite eye).
Blepharospasm usually begins with occasional twitches of both eyelids, which progress over time to forceful and frequent spasms and contractions of the eyelids. In severe episodes, the patient cannot open their eyelids (apraxia), which severely limits their daily activities. Prolonged closure of the eyelids may result in functional blindness. [4]
The eyelids close or blink voluntarily and involuntarily to protect the eye from foreign bodies, and keep the surface of the cornea moist. The upper and lower human eyelids feature a set of eyelashes which grow in up to 6 rows along each eyelid margin, and serve to heighten the protection of the eye from dust and foreign debris, as well as from ...
The eyelid margin from which lashes grow is among the most sensitive parts of the human body, with many nerve endings enveloping the roots of the lashes, giving it sensitivity to very light tactile input even at the tips of the lashes, [2] enabling it to trigger the blink reflex when touched. [3]
It is, however, present behind forcibly closed eyelids in most healthy people and should not be regarded as a pathognomonic sign. Also, traumatic abrasions are generally located in the central or inferior cornea due to Bell's phenomenon. [citation needed] Bell's phenomenon does not occur during short blinks. [3] [4]
Electromyogram (EMG) activity of the orbicularis oculi muscle, which controls eyelid closure, is considered to be the most prominent and sensitive component of blinking (Lavond et al., 1990) and is, thus, the most common behaviorally-derived dependent variable in studies of EBC.
The menace response is one of three forms of blink reflex. It includes the reflexive blinking that occurs specifically in response to the rapid approach of an object. [ 1 ] The menace response comprises blinking of the eyelids , in order to protect the eyes from potential damage, but may also include turning of the head, neck, or even the trunk ...