2023-07-20 12:46:38
When your eyes are exposed to a dry environment around you, or full of smoke or wind, or even when they get tired from using a mobile phone or staring at a computer screen, they will subconsciously use tear fluid to prevent damage and irritation in them. But sometimes you may feel that relying on the eyes to remove this irritation is not enough. And then you may resort to using artificial tears.
artificial tears
Although there are several types of artificial tears available, natural tears are still one of the most important means of protecting the eyes. Until this moment, many aspects related to the components of tears, the layers covering the outer surface of the eyes, and their mechanisms of action are still not completely clear.
Here are 7 facts regarding natural tears, as well as artificial tears:
1. The tears of each eye are produced by a major lacrimal gland, located inside the upper part (fossa of the lacrimal gland) of the bony cavity at the front of the skull, in which the eyeball is located, specifically behind the bone below the outer end of the eyebrow. The lacrimal gland has the shape of an almond, its length is regarding 2 cm, and it consists of several separate glandular lobes. From it emerge regarding 8 to 12 excretory ducts, which drain through the lining of the eyelids, on the outer surface of the eye. Then the excess lacrimal fluid is drained through a lacrimal duct that flows into the nasal cavity.
The American Academy of Ophthalmology (AAO) explains: “Your tears are produced by lacrimal glands located above each eye. When you blink, tears spread across the surface of the eye. The tears then drain through small ducts in the lower eyelid into the lacrimal duct, which empties into the nose. There either the tears evaporate or they are reabsorbed.” In addition to the drainage of these “primary tears,” the academy says: “When many emotional or reflex tears are secreted (as a result of eye exposure to local irritants), they overflow beyond the capacity of the lacrimal drainage system. That is why these tears can leak from your eyes, run down your cheeks, and sometimes drip from your nose.”
2. The cornea of the eye, the conjunctiva of the eye, and the lining of the eyelids (upper and lower) need to be kept moist at all times, to ensure their integrity, preserve their structure, and help them perform their functions. The cornea is the transparent layer that envelops the ring of the iris, which has different colors in humans. The conjunctiva is the transparent layer that covers the white sclera (layer of the sclera) that we see at the front of the eye.
And the process of moisturizing these sensitive parts takes place through the continuous secretion of tear fluid. In addition to moisturizing, these tear secretions work to wash the cornea and conjunctiva of any foreign objects attached to them, such as dust and others.
The tear fluid contains mainly water, a sticky leucine, and a quantity of fat. In addition, there is a percentage of antibodies in the tear fluid, a “lysosome” (a substance capable of resisting bacteria by dissolving the outer covering of certain types of bacteria), glucose sugar, and sodium and potassium elements. It is normal for the lacrimal glands to secrete regarding a quarter of a liter within 24 hours. The amount of these tears decreases with age or if there are some diseases in the body.
Reflexive and emotional tears
3. There are three types of tears produced by the lacrimal glands, in different cases of daily human life. The first of these is “basal tears”, which are the tears that are secreted all the time in order to achieve the task of continuously moisturizing the front parts in the front of the eyes, in addition to lubricating, nourishing and protecting the cornea. That is, the primary tears act as a permanent shield between the eye and the outside world.
As for the “reflexive tears”, which is the second type, they are secreted when the eyes need to get rid of harmful irritants, such as smoke, foreign objects, or onion fumes. The eyes can also be irritated by exposure to intense light, eating hot peppers or very hot foods, or during vomiting or severe coughing. The purpose of these “reflexive tears” is to wash the eye from what has afflicted it. Here, the eyes release larger amounts of essential tears. That is, with the same components as those types of tears, but they may contain more antibodies to help fight bacteria.
4. The third type is “emotional tears,” which are produced and secreted either in response to joy and happy emotional outburst, or during crying, as a result of sadness, fear, or other sad emotional states. Some sources indicate that there are “emotional” people in the world who can easily cry, and others that are “cold”. Likewise, the situation differs between men and women.
The results of a study conducted on a segment of men and women in Britain indicated that the annual average of men’s crying is regarding 17 times, and that the annual average of women’s crying is 64 times. As an American study noted, the most likely time for an adult to cry is between seven in the evening and ten in the evening.
The components of tears produced during crying are different from the components of “primary tears” or “reflexive tears”. This is because the tears of crying contain protein hormones, such as “prolactin” and “para-kidney hormone,” and a natural substance that relieves pain. Regarding this third type of tears, the American Academy of Ophthalmology reports, saying: “Some scientists have suggested that emotional tears contain additional hormones and proteins that are not found in primary or reflex tears.”
Layers of tears
5. Tears form an airtight envelope to protect the parts of the front of the eye, through which the cornea is nourished. But the tear film is not just a watery coating of a saline solution. It has a similar structure to saliva, and contains enzymes, lipids, metabolites, and electrolytes. Not only that, but it is also composed of several layers, which take a complex position when enveloping the parts of the front of the eye, in order to achieve protection for it and to deliver nutrition to it as well.
The American Ophthalmological Association reports, “Tears have layers. Tears aren’t just saline. Each tear has three layers. She explains that first there is an inner mucus layer, which is directly attached to the parts of the front of the eye, and its task is to maintain that all tears are attached to the eye. Then there is a thick middle layer, made mostly of water and so it is a watery layer, whose main task is to maintain eye hydration, repel bacteria and protect the cornea. Then there is an outer oily tear layer whose main task is to keep the tear surface transparent and smooth, so that the eye can see through it clearly, as well as to prevent the other inner layers of the tear envelope from evaporating.
artificial tears
6. Artificial tears are drops or gels that moisturize dry eyes. Unlike medicated eye drops, artificial tear solutions can be purchased without a prescription.
Artificial tears can be used to treat dehydration by adding more moisture to the tear film, or to reduce friction on the cornea by adding lubrication. It is also useful for calming irritation, and for reducing redness and swelling. Therefore, one may need to use artificial tears from time to time if they are in windy, smoky, or dry places. Or when eye strain from fatigue or using the computer for long periods of time. Or when you take certain medications, such as allergy medications and some antidepressants, that may increase dry eyes, or when you get older, because this can affect moisture levels in the eyes.
But it’s worth noting, Cleveland Clinic doctors say: “If your eyes seem like they’re always dry and irritated, you should contact your eye health care provider, so they can help you figure out what’s going on and what kind of treatment you might need.”
7. Basically, artificial tear products work in one of two ways: they either add water or they add lipids to the tear film. Therefore, not all artificial tear products are created equal. Some artificial tears products may also contain preservatives, which allow for a longer shelf life. However, the disadvantage of this type of product is that the preservative can irritate the eyes. It may be best not to use certain types of artificial tears with preservatives if you wear contact lenses. There are special products for contact lens wearers. Preservative-free products often come in small, single-use containers. They are small packages that must be disposed of within 24 hours of opening. You should consult your eye care professional regarding the type and brand of artificial tears. Also check with him regarding how often artificial tears can be used and how long they can be used continuously. Cleveland Clinic doctors explain: “If you need to use it a lot, you may need your provider’s help to see if you have a more serious condition. If you use artificial tears that contain preservatives, limit their use to four to six times a day. And if you need to use products more than that, you should use products that do not contain preservatives.
Emotional tears contain a natural pain-relieving substance, and reflex tears occur when the eyes are exposed to topical irritants.
Tear secretion disorders… expected and strange cases
There are several pathological conditions in which the tear secretion process is disturbed, and thus the response to exposure of the eyes to environmental irritants or to the crying process is affected. Among them is what is “expected”, as happens to the infant who has not yet developed important parts of the nervous system, as it is expected that he will cry without this being accompanied by the secretion of tears. There are cases of Familial Dysautonomia, a genetic condition in which members of certain families suffer from the inability to shed tears during crying spells.
On the other hand, there are cases in which the secretion of tears may be disturbed in a way that some may see as strange. To clarify, the fifth cerebral nerve (the trigeminal nerve), which exits directly from the brain, works to receive the sensation of the reaction shown by the parts of the eye when exposed to what irritates the secretion of tears in it. And when this nerve is cut, the secretion of the type of “reflexive tears” (reaction) stops when the eye is exposed to the entry of a hair between the eyelids or irritating gases. However, at that time the eye still has the ability to secrete tears when crying.
A British study indicated that the annual rate of men crying is 17 times, and women 64 times
And when the seventh brain nerve, (facial nerve) is damaged, some patients have bouts of tear production during operations that are not usually related to tear production, such as eating. The facial nerve is damaged in cases of Bell’s Palsy and mid-facial paralysis. In cases of “dry eye syndrome” DES, and cases of Keratoconjunctivitis Sicca, the patient suffers from dry eyes as a result of the low secretion of “primary tears” that moisturize it. That is, the natural moisturizing tears that are secreted all the time. But following a period of infection with this condition, and with the continued lack of secretion of moisturizing tears, it is noted that these patients increase the secretion of tears as a result of the reaction shown by the eye towards its dryness, that is, the increased secretion of “reflexive tears”.
There are cases called PLC, or Pseudobulbar Affect, described by neurologists at the Mayo Clinic by saying: “It is characterized by bouts of sudden, inappropriate, uncontrollable laughing or crying. Pseudobulbar affect occurs more commonly in people with neurological diseases or certain injuries, and can affect the way the brain controls emotion. The main sign is the occurrence of recurrent, involuntary, uncontrollable bouts of crying or laughing, exaggerated or not related to the patient’s emotional state. Laughter often turns into tears.
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