Tears are usually only noticed in certain situations when people become emotional and cry. Yet they also perform important functions and are always present in a healthy eye.
What are tears?
Tears are a fluid produced in the lacrimal glands. They form a thin layer that covers the cornea. In this process, the so-called tear film has numerous tasks and functions. The tear fluid is evenly distributed in the eye and separates the cornea from the eyelid. People blink every four to six seconds. During the blink, the tear fluid enters the eye as a lubricant. Before dry spots can occur, new tears are formed and these are distributed by another blink. In this way it is possible, for example, to protect the eye from infections and pain due to a dry cornea. In this process, the tear film consists of several layers that are structured differently. Furthermore, it does not measure the same thickness in different regions of the eye. Different diseases affect tear production and lead to differentiated symptoms.
Composition
The various ingredients are produced in differentiated glands. The basic production of an adult human is 1.2 microliters per hour. When the eye is exposed to certain stimuli, more tears are formed. In this process, tears consist of about three components that are present in layers within the eye. First, some glands produce mucus. This is also called mucus. It ensures that the cornea becomes slippery. Only in this way is it possible for the following water layer to adhere to the eye. Otherwise, the tear film would roll off. The mucin layer is followed by the middle layer. This consists of salty water and is responsible for most of the positive effects of the tears. In the event of a stimulus, only this layer is increasingly produced in the large lacrimal glands. The last layer of the tear film consists of lipids. If the thin lipid layer is uneven or other conditions are present, vision is impaired. The lipid layer is produced by the meibomian glands and also forms the outer layer of the tear film. In order to ensure the functions of the tear film, the layers must be optimally coordinated. As soon as unevenness develops in one layer, discomfort of various kinds usually already occurs.
Function and tasks
Tears have different tasks. In emotional situations, people often find crying relieving. In this context, various emotional stimuli can lead to increased tear production. For example, people cry not only out of sadness, but also out of anger, despair, excessive demands or pity. Scientists have not yet been able to reconstruct the exact process. It is therefore not known why people cry. The theory that crying protects against depression has also not been empirically proven. However, the function of tears in the eye is scientifically recognized. The thin tear film protects the cornea from wind blasts and pathogens such as viruses and bacteria. The tears regularly clean the conjunctival sac and the outer cornea. In addition, the tears function as a lubricant between the eye and the skin of the eyelid. This is the only way that smooth blinking is possible. If foreign bodies have entered the eye, more tears are produced to remove them. In the process, the middle layer of the tear film is especially crucial. It also keeps the eye continuously moist and supplies the cornea with important substances. These include oxygen, among other things. The water layer also contains the defense substances that prevent the penetration of bacteria and other pathogens. In addition, tears play an important role in vision. They contribute to the optimal refraction of light. In particular, if the outer layer is not smooth or patchy, even putting on glasses will not help optimize vision.
Diseases and complaints
Tears are usually not noticed in everyday life until the body does not produce enough of them. Different factors, such as heating air or cigarette smoke, can dry out the eye. Fundamental to dry eyes is primarily a change in the composition of the tear film.If the composition or quantity are disturbed, the protective surface is no longer given. The layers build on each other. If one of them is of inferior quality or the quantity does not blend in optimally, the stability and smoothness of the entire tear film are put at risk. Instead, cracks and dry spots occur, which are no longer surrounded by the tears. Dry eyes result in numerous complaints. Causes for a disturbed tear production can be different eyelid diseases and eyelid margin inflammations. This is often triggered by an infection with bacteria. In this case, the sebaceous gland of eyelashes is affected. Eyelid diseases can be tumors, malpositions, inflammations and cosmetic problems, such as eyelid cysts. Correction of the mentioned conditions can be suitable to treat dry eyes. If no disease-related factors could be identified, artificial eye drops, which must be used at regular intervals, are helpful. It is not uncommon for dry eyes to turn into a chronic process. In addition to dry eyes, there may also be an increased production of the water layer. Watery eyes are triggered by different mechanisms. These include, for example, a disturbance in tear drainage. In addition, there may be an overproduction of tears or changes in the tear ducts. Particularly in women, watery eyes occur in the context of hormonal changes, such as during menopause. In cases of temporary overproduction, inflammation of the major lacrimal gland is a possibility.
