The blink of the eye occurs several times in a minute. Although it is usually rarely consciously perceived, its function is relevant to the overall health of the eye. Disruptions can cause unpleasant discomfort.
What is the blink?
The blink is the unconscious closing and opening of the eyelid. The blink is the unconscious closing and opening of the eyelid. The opening occurs immediately after the closing, so that the action is normally not perceived. It is mostly involuntary, but can also be controlled. The blinking of the eyelid ensures an even distribution of tear fluid and the removal of dirt particles via the tear duct. The movement of the blink involves the upper and lower eyelids, but the upper part does most of the work in humans. The closing phase can be differentiated into three sections: Acceleration, constant velocity, acceleration. A blink has different temporal lengths. Normally, it varies between 50 and 125 milliseconds. If there is severe fatigue, the blink usually slows down as well. Different muscles are decisive for the general mobility of the eyelids and the action itself. Overall, people blink approximately every four to six seconds. Under different environmental conditions, the frequency of eyelid blinking also varies.
Function and task
The blink exhibits elementary tasks. For example, it ensures the distribution of the tear film. Tears are usually only perceived when they emerge from the eye in a very sad or sometimes happy moment. In this case, the fluid is constantly produced by tear glands and serves the health of the eye. The film provides separation between the cornea and the eyelid. Without the even distribution through the blinking of the eyelid, the opening and closing of the eyes could not proceed smoothly, and instead, unpleasant discomfort such as dryness and pain would occur. While sufficient fluid is available through the tear glands, the blinking of the eyelids is responsible for ensuring that no dry spots occur. The tear film protects the eye from wind blows, bacteria and viruses. As soon as foreign bodies have entered the eye, more tear fluid is produced and distributed by vigorous blinking. This is to flush the intruders out of the eye. The cornea can also be supplied with all important nutrients via blinking and tear fluid. Because the tissue has no connections to blood vessels, nutrition via the tear film is important. Gaps in the tear film due to suboptimal distribution are responsible for poor vision. The transparent tear film on the cornea is also important for refraction of light. Vision, in turn, is based on light waves and their refractions. If gaps can be observed, even putting on glasses usually does not help because no optimal refraction of light can take place. The blinking of the eyelids is thus primarily intended to distribute the tear film. This is irreplaceable for the proper functioning of the visual process. If threats such as strong wind or flying sand are imminent, a direct protective function of the blink takes place. Closing the eye can thus protect the sensitive cornea from injury or intruders. Disturbances of the blink result in different manifestations. If a disorder could be diagnosed, the appropriate therapy should follow.
Diseases and complaints
If the function of the eyelid blink is restricted, unpleasant consequences threaten. Thus, a doctor should be consulted as soon as the first symptoms become apparent. Infrequent blinking causes the tear film to dry out. Although new tear fluid is formed, it is not distributed due to the lack of blinking. Affected persons experience burning eyes and itching. Blinking can be uncomfortable at such a time because the protective lubricant is missing and irritation occurs instead. Working on the computer or cell phone often results in relatively infrequent blinking. The eye is less protected from intruders and is usually perceived as dry. Furthermore, disorders of eyelid blinking can result in excessively frequent blinking. For example, they are part of a tic disorder. Thereby, such habits occur mainly in children.Doctors estimate that about 30 percent of 8 to 14 year olds suffer from tic disorders. However, these often disappear with age. In the case of frequent blinking, it is a motor tic. The rapid movement occurs without a broader sense. Patients usually fail to suppress the action. A tic can be primary or secondary. In a primary tic, the cause is a physical component; secondary tics reveal themselves after another illness. Examples here include trauma, brain inflammation, or carbon monoxide poisoning. If multiple motor tics occur, as well as at least one vocal tic, it is referred to as Tourette’s syndrome. There is no cure for such a disorder. Very frequent or even permanent blinking also occurs in some patients suffering from dystonia. Dystonia is manifested by involuntary muscle contractions that persist over a long period of time and cannot be relieved independently. The trigger lies in the central nervous system. The disorder does not take place in the muscle itself, but is controlled by the responsible brain areas. The frequent blinking of the eyelids in dystonia is thus a neurological disorder. Regular contractions occur, causing the eyelid to close and open without the affected person being able to control the process.
