In our lives, some people seem to have tears that are always so abundant that they can tear up their eyes when they touch it; And some people, even if they move forward in the wind and rain, it is rare to see them shed a tear. The mystery of this is actually hidden in tears. Tears, which act like guardians of the eyes, are secreted by the lacrimal glands above our eyes. It is not only a transparent liquid, but also an eaux-de-vie with rich connotations.
Today, let's walk into the world of tears and explore the story behind it. In this world of mysteries, we will find that tears are not only the guardians of our eyes, but also the witnesses of our emotions.
Physiological composition of tears
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Tears, moisturized like spring rain, are mainly made up of water, but it is not just water. It also contains small amounts of inorganic salts and proteosomes, which together make up the weakly alkaline properties of tears. It is this weak alkaline nature that makes tears play an irreplaceable role in protecting our eyes from external aggression.
Tears are a transparent and milky white watery fluid secreted by lacrimal glands and conjunctival goblet cells, and the main organic components of tears are proteins, including albumin, globulin, lysozyme, immunoglobulin IgA, IgG, IgE, etc. Gamma globulin and lysozyme are the main components of antimicrobial effect in tears, and gamma globulin is mainly IgA, IgG and IgE, of which the content of IgA is particularly high. Lysozyme may play a synergistic role with IgA in the process of dissolving bacteria.
Physiological function of tears
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The presence of tears is not only to keep the eyes moist, but also a physiological self-protection mechanism. When we feel sad, joyful, or excited, tears flow out of our inner world like an outlet for our emotions. And when we face external stimuli, tears can quickly clean the eyeballs, carry away dust and bacteria, and provide a solid barrier for our eyes.
Protects the eye from germs or other harmful substances, including gamma globulin and lysozyme, which dissolve pathogenic bacteria that invade the eye. This reduces the potential risk of eye infections. In addition, when the eye area is stimulated by foreign harmful substances, tears are secreted in large quantities to cleanse or dilute the harmful substances and protect the eye tissue from harmful substances.
It makes the surface of the eye silky smooth and protects the physiology of the cornea and conjunctiva. In a calm life, every time you blink, tears are like a delicate painter, drawing a moist picture on the surface of the eyeball with its brushstrokes, so that the corneal conjunctiva is always bathed in a tear film 7 10nm thick, as if gently covered by soft morning dew.
Composition and function of the tear film
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The ions in the tears contain K+, Na+, Cl-, and the concentration is higher than that in the serum, and there are also a small amount of glucose and urea, and the pH value is 520～8.35, an average of 735. Under normal circumstances, tears are isotonic, and tears form a thin membrane of about 7 10 m, that is, tear film.
Covers and fills the corneal surface to create a smooth optical interface.
Moistens and protects the corneal and conjunctival epithelium.
Inhibits the growth of microorganisms by mechanical flushing and antimicrobial action.
Provides essential nutrients for the cornea.
Stratification and function of the tear film
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The tear film is made up of three different layers of film. The outermost layer is the lipidoid layer, which is in direct contact with the air, the middle layer is the aqueous layer, and the inner layer is the mucin layer tightly attached to the corneal epithelium.
The lipid-like layer can prevent excessive tear evaporation, mucin has hydrophilic properties and helps to retain water, the middle layer is the serous layer secreted by the lacrimal gland and accessory lacrimal glands, and the inner layer is the mucus layer secreted by goblet cells and other cells. The normal ratio of the three components gives the tear film a normal surface tension and can remain on the surface of the corneal conjunctiva for a longer time.
Studies have shown that human tear films have amazing staying power, being able to survive for up to 15 seconds. This number is much larger than the interval between our blinks, so the surface of the corneal conjunctiva is always gently covered with a thin film of tears, avoiding direct contact with the air. This subtle protective mechanism is essential for maintaining the physiological and optical properties of the cornea, which silently guards our vision like a patron saint.
The tear film not only guards our vision, but also plays a key role in the process of topical application of the eye. Changes in its quality and quantity, as well as a decrease in blinking movements, can pose a threat to the integrity and persistence of the tear film. The effects of certain medications can also disrupt the balance of the tear film, and in severe cases, it may even trigger dry eyes, which can deprive the eyes of their proper moisture and comfort.
Therefore, we should cherish this miraculous tear film and keep it healthy and stable, so that the eyes are always bathed in moisture and comfort.
Factors affecting the tear film
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The tear film, which is like a tulle, is the guardian of the stability and function of the epithelium on the ocular surface. Its existence, like a guardian, guards our visual world. However, once the integrity and function of this tear film is compromised, it will be like a calm lake being broken, bringing all kinds of discomfort.
In this era of information, the popularization of electronic products has undoubtedly brought convenience to our lives, however, staring at the screen for a long time, our tear film is silently under pressure. In addition, wearing soft contact lenses and the inadvertent reduction in the frequency of blinking are all inadvertently threatening the health of the tear film.
Studies have shown a strong correlation between gender, time spent on electronic devices, wearing soft contact lenses, and blinking frequency and tear production. Female sex, prolonged use of electronic devices, wearing soft contact lenses, and low blinking frequency are all risk factors for abnormal tear production in college students.
Among them, the role of sex hormones cannot be ignored. Androgens, the "behind-the-scenes", play a key role in regulating the morphology, physiology and immunity of the lacrimal glands. It is like a skillful artist, regulating the meibomian glands to secrete oil into the tear film and maintain the stability of the tear film. When androgen levels are low, women's tear secretion is prone to abnormalities, like dancers who lack vital support, and their dance steps become messy.
Therefore, we should cherish this thin tear film like a cicada's wings, care for it, and let it continue to protect the clear world for us.
I strongly recommend that we consciously reduce the amount of time we spend on electronic devices, not only for our eye health, but also for our overall health. Ensuring that there is an appropriate distance between the eyes and the screen when using electronic devices is very critical to prevent eye strain and myopia. In addition, it is essential to give your eyes a regular rest, after all, the eyes also need to "breathe" fresh air.
We need to be more cautious when wearing glasses. Prolonged continuous wear of soft contact lenses may lead to decreased tear film function and damage to the corneal epithelium, which worsens with the duration of wear. Therefore, we must pay attention to controlling the wearing time, and have regular eye check-ups and rest to ensure our eye health.
Eyes are the windows of the soul, protecting eye health and making our lives clearer and better. Let's start from now on, take practical actions to care for our eyes, and jointly protect this precious vision.
Tear secretion is measured
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In clinical practice, the measurement of tear secretion is generally not very accurate, and the Schir-Mer method is commonly used. Take a piece of filter paper with a length of 35mm and a width of 5mm, fold one end of the filter paper 5mm into a hook, hang it in the conjunctival sac near the small punctum at the lower eyelid margin, and measure the length of the filter paper moistened by tears after 5 minutes without the influence of drugs or external stimuli, between 5 and 15mm for normal people.
The relationship between tears and eye health
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The amount of tears also reflects the health of the eyes, mainly including: suspected blockage of tears and suspected dry eyes without tears.
Tearful suspicion blockage:
The lacrimal duct is a thin tube that is not too long, it is the only passage for tears to pass through the nasal cavity, the lacrimal duct includes the upper and lower lacrimal dots, the upper and lower lacrimal tubules, the common lacrimal duct, the lacrimal sac and the nasolacrimal duct, as long as any of them are blocked, the lacrimal duct is blocked. Tears cannot enter the nasal cavity, so they flow out of the eyes, manifesting as tears.
Suspicious dry eyes without tears
If tears are missing, the effect of the tear film on moisturizing the eyeball is greatly reduced, and the surface of the eye becomes dry. Therefore, the eyes have symptoms such as dryness, foreign body sensation, burning sensation, photophobia, blurred vision, easy eye fatigue, and inability to see for a long time.
Write to the end
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Tears, this trickle, are not only an emotional catharsis, but also a guardian of eye health. It gently falls on the surface of the eyeball like a drizzle, bringing moisture and vitality to this paradise of bright eyes. The magic of tears lies in their unique composition, which keeps the surface of the eyeball moist, like spring rain moistening the earth, allowing the cells on the surface of the eye to thrive in a moist environment.
Not only that, tears are also the guardians of the cornea, providing a steady stream of oxygen and nutrients to this transparent window, keeping the cornea crystal clear, bringing clarity and brightness to our vision. When our eyes encounter foreign bodies or metabolites, tears become brave cleaners, rinsing and cleaning the ocular surface and tear ducts, removing these uninvited guests one by one, and protecting the purity and health of the eyeballs.
What's even more amazing is that tears can also fill in the subtle unsmooth surfaces on the surface of the eyeball, like a mirror carefully polished by craftsmen, making our vision clearer and sharper. Therefore, when we feel eye discomfort, we should seek a diagnosis as soon as possible, so that the silent guardian of tears can continue to protect our eye health.