in ictu oculi
Blinking is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrea superioris and the activation of the orbicularis oculi, not the full open and close. It is an essential function of the eye that helps spread tears across and remove irritants from the surface of the cornea and conjunctiva. Blink speed can be affected by elements such as fatigue, eye injury, medication, and disease. 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 is known as winking. Some animals (for example, tortoises and hamsters) blink their eyes independently of each other.
Central nervous system control
Though one may think that the stimulus triggering blinking is dry or irritated eyes, it is most likely that it is controlled by a "blinking center" of the globus pallidus of the lenticular nucleus—a body of nerve cells between the base and outer surface of the brain. Nevertheless, external stimuli can contribute. The orbicularis oculi is a facial muscle; therefore its actions are translated by the facial nerve root. The levator palpebrae superioris’ action is sent through the oculomotor nerve. The duration of a blink is on average 100-150 milliseconds according to UCL researcher and between 100-400ms according to the Harvard Database of Useful Biological Numbers. Closures in excess of 1000 ms were defined as microsleeps.
Greater activation of dopaminergic pathways dopamine production in the striatum is associated with a higher rate of spontaneous eye blinking. Conditions in which there is reduced dopamine availability such as Parkinson's disease have reduced eye blink rate, while conditions in which it is raised such as schizophrenia have an increased rate.
Types of Blinks
There are two types of blinking. The first being spontaneous blinking which is done without external stimuli and internal effort. This type of blinking is conducted in the pre-motor brain stem and happens without conscious effort, like breathing and digestion. The second type of blinking is reflex. This blink is the response of an external stimulus like contact with the cornea or objects that appear rapidly in front of the eye. A reflex blink is not necessarily a conscious blink either; however it does happen faster than a spontaneous blink.
Adults
There have been mixed results when studying gender-dependent differences in blinking rates, with results varying from the female rate nearly doubling the male to no significant difference between them. In addition, women using oral contraceptives blink 32% more often than other women on average for unknown reasons. Generally, between each blink is an interval of 2–10 seconds; actual rates vary by individual averaging around 10 blinks per minute in a laboratory setting. However, when the eyes are focused on an object for an extended period of time, such as when reading, the rate of blinking decreases to about 3 to 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 stare that is very recognizable.
Blinking is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrea superioris and the activation of the orbicularis oculi, not the full open and close. It is an essential function of the eye that helps spread tears across and remove irritants from the surface of the cornea and conjunctiva. Blink speed can be affected by elements such as fatigue, eye injury, medication, and disease. 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 is known as winking. Some animals (for example, tortoises and hamsters) blink their eyes independently of each other.
Central nervous system control
Though one may think that the stimulus triggering blinking is dry or irritated eyes, it is most likely that it is controlled by a "blinking center" of the globus pallidus of the lenticular nucleus—a body of nerve cells between the base and outer surface of the brain. Nevertheless, external stimuli can contribute. The orbicularis oculi is a facial muscle; therefore its actions are translated by the facial nerve root. The levator palpebrae superioris’ action is sent through the oculomotor nerve. The duration of a blink is on average 100-150 milliseconds according to UCL researcher and between 100-400ms according to the Harvard Database of Useful Biological Numbers. Closures in excess of 1000 ms were defined as microsleeps.
Greater activation of dopaminergic pathways dopamine production in the striatum is associated with a higher rate of spontaneous eye blinking. Conditions in which there is reduced dopamine availability such as Parkinson's disease have reduced eye blink rate, while conditions in which it is raised such as schizophrenia have an increased rate.
Types of Blinks
There are two types of blinking. The first being spontaneous blinking which is done without external stimuli and internal effort. This type of blinking is conducted in the pre-motor brain stem and happens without conscious effort, like breathing and digestion. The second type of blinking is reflex. This blink is the response of an external stimulus like contact with the cornea or objects that appear rapidly in front of the eye. A reflex blink is not necessarily a conscious blink either; however it does happen faster than a spontaneous blink.
Adults
There have been mixed results when studying gender-dependent differences in blinking rates, with results varying from the female rate nearly doubling the male to no significant difference between them. In addition, women using oral contraceptives blink 32% more often than other women on average for unknown reasons. Generally, between each blink is an interval of 2–10 seconds; actual rates vary by individual averaging around 10 blinks per minute in a laboratory setting. However, when the eyes are focused on an object for an extended period of time, such as when reading, the rate of blinking decreases to about 3 to 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 stare that is very recognizable.