myopia (Myopia, Nearsightedness) is a condition that is common in about 25% of school-age children. It may occur on one side or both, and both eyes may not be equally short. Patients will be able to see clearly at close distances, but will not be able to see clearly at a distance.
- The disease is often found among many relatives in the same family. and often found in urban people than rural people. (There is a belief that short-sighted people tend to have higher average intelligence than normal people. As can be seen from the university students are more nearsighted than the general population. But this assumption has not been proven.)
- The study found that Females are more nearsighted than males.
- Europeans, such as Australians, are reported to be nearsighted at about 14.5% of the population aged 25 and over, Germans at about 13%, while Russians are found to be nearsighted enough as Europeans. In the UK, it is found about 26%, and for Asians, it is found that Chinese, Japanese, Indians have relatively high myopic populations compared to Thais. (The nations with the least myopia are Eskimos, Americans, and Africans.)
For a person to have normal eyesight, they must consist of organs that help refract light that are proportional to the length of the eye. The part of the eye that is responsible for the refraction of light is cornea and cornea In a normal person, the refractive power of the eye is approximately 63 diopters (from the cornea 43 diopters and from the cornea 20 diopters) and the length of the eyeball is approximately 24 millimeters.
- For example, if light from an object 20 feet or more passes through the cornea and cornea, The light falls on the retina exactly. so that the object can be seen clearly. But if that person has more light refractive power of the cornea than normal (The cornea is more curved than normal, causing too much refractive power. The beams then converge before reaching the retina) to form 46 diopters, of which 3 diopters plus 20 diopters of the cornea become 66 diopters. The eyeball is still 24 mm. The light from the object falls in front of the retina. That is, the person has 3 diopter myopia, but on the other hand, if the person has normal refractive power of the cornea. But having eyes longer than 24 millimeters can also cause myopia.
- However, those who are short-sighted Light from objects that are in close proximity can fall on the retina according to the law and principle of refraction. Therefore, people with nearsightedness can clearly see objects at close distances normally.
Comparison between normal, nearsighted, and farsighted.
Causes of myopia
Myopia may be caused by a corneal curvature than normal. therefore having too much refractive power The beams then converge before reaching the retina. But in some cases, it may be caused by having an abnormally long eyeball that causes the beams of light to converge before reaching the retina.
Myopia is divided into two types:
- Normal myopia It is the most common type. and no serious complications This is caused by the cornea being more curvature than normal. Therefore, it has more power to refract light. Causes the focus of the image of distant objects to fall on the side of the eye. This causes the patient to have blurred vision at a distance. It is believed that this abnormality of the cornea is something that has been inherent in nature of that person. as well as height beauty of the body And it may also be related to heredity and ethnicity.
- severe myopia (Malignant myopia) is a less common type. But it’s serious and it’s from birth. caused by a genetic disorder which is passed on from children to grandchildren causing the patient to be born with an eye socket (distance from the cornea to the retina) is longer than usual, so the focus of light of distant objects falls on the side of the eye.
- Normal type of sight Patients will have blurred vision at a distance (eg looking at a blackboard, watching television), causing them to close their eyes. But looking closely or reading a book is still clearly visible. Symptoms generally begin to show at the beginning of school and gradually increase until the age of 25, thus becoming less short-lived. This type of myopia is not very short. and without any complications
- evil eye Patients are very nearsighted since birth. It will be noticed when the child begins to learn to walk. Which tend to walk into obstacles, often fall, or when looking at something, have to look closely until the eyes are almost close to the object Must wear thick glasses, may need to change glasses often, and can have serious complications, such as retinal bleeding. The retina is torn or detached, etc., which can cause blindness. in young children If your eyesight is very short, it may cause eye strain as well.
How do I know if my eyesight is short-sighted?
For how to determine if your child is nearsighted or not. Let’s start with heredity. By observing whether you or your family members are nearsighted or not, because if there is a chance that your child will also be nearsighted, there will be more. It should also be noted that the various behaviors of children that children who are nearsighted. When looking at something, he likes to take a closer look, squinting his eyes or squinting. Or sometimes they may tilt or tilt their head when looking at a distance, such as when reading a book, having to bend their head until they are close to the book. Or watch TV, have to stand until close to the screen. including having frequent headaches, etc.
how to treat myopia
- If you suspect that your child is nearsighted Parents should always take them for an eye exam at the hospital first. Because the first pair of glasses should be carefully examined. Because it is often difficult to measure eyeglasses in children. because the children did not cooperate Sometimes the doctor may need to instill eye drops or dilate the pupils before measuring the eye. This is because the child has a high focusing power and tends to focus while taking the measurements. Therefore, the value of the eyesight is shorter than the reality. The iris first will help the measurement to be more accurate. The doctor will also take this opportunity to examine the retina in more detail. (Dilating drops will cause the child to dazzle for a while. making it temporarily unclear until the effect of the drug runs out which is normal)
- If nearsighted, the doctor will correct it by insertingConcave lens eyeglasses (In short-sighted people, the beam converges into a single point before reaching the retina. causing a beam of light reaching the retina to become a flare not a single point Therefore, the image is not clear. Concave lens glasses are needed to help diffuse light. (To move the light to gather further and to fall into the middle of the retina until it can see clearly) which at present, the hospital has a tool like a cylinder torch that is used to shine into the patient’s eye Then the doctor will observe the nature of the reflected light and use a lens to help. Thus, it can tell how much myopia, longitudinal, or astigmatism the patient has. Without having to ask the patient like in the past, then the optician will bring the measured glasses to the patient to test and see satisfaction and clarity again. will adjust until the appropriate lens number is obtained. clearly visible and the patient is not numb But recently, computers have been used to help measure the eyesight instead. without having to rely on both the inspector and the examined This will use an instrument to examine images that occur in the patient’s retina. by inserting the program into the tool which the program will be able to read the value out as a number how much the patient has abnormal vision (Accuracy of this instrument is also within acceptable limits. But still have to test the patient to try on the lens of the measured size first until the appropriate number is obtained as well.)
- Those who are short-sighted can see far away clearly. If you want to see clearly, wear glasses. But if myopia is not much and everyday life does not need to look far You don’t even need to wear glasses. But if a child in a student age who has to read a lot or in the classroom who has to look at the blackboard from a distance it is necessary to put (Usually an ophthalmologist will recommend that When making myopia glasses, they should be worn at all times, whether looking at close or far. so that the eyes can see normally like normal people In general, short-sighted people can see clearly already without focusing. Therefore, often do not wear glasses when looking closely. causing the eyes to not exercise focus (Accommodation), which focusing is an automatic mechanism when we want to look at close range. Therefore, as you get older and don’t practice focusing your eyesight, it may cause problems when looking at close distances.)
- Usually, eyeglass lenses need to be replaced. (Including contact lenses) at least 1-2 years at a time until at the age of about 20-25 years old, the eyesight begins to stabilize and do not need to change lenses often until over 40 years of age that often begins to have problems in close up Therefore, the lens must be replaced again.
- Using contact lenses or contact lenses (Contact lenses) another option that is becoming popular. which there are many types to choose from However, the use of contact lenses has more precautions and special care than wearing eyeglasses. because if used incorrectly It can cause eye infections and corneal ulcers. Before use, seek professional advice and follow directions. If used and found that there are abnormal symptoms such as feeling irritated to the eyes More tears than usual, blurred vision, red eyes, etc., contact lenses should be removed and consult a doctor urgently.
- in patients with malignant myopia You should go for eye exams and change your glasses periodically.
- Today, there are many methods of treating myopia through surgery, including:
- Radial keratotomy to reduce the curvature of the cornea. so that the focus of light falls on the retina
- Using laser light to destroy the surface in the center of the cornea to flatten. (Photorefractive keratectomy)
- Using a laser to adjust the curvature of the cornea so that the focus of light falls on the retina. also known as “LASIK” (LASIK – Laser assisted in situ keratomileusis)
Complications of myopia
- uncorrected myopia children They tend to stye more often than normal-sighted children. (The exact cause of the relationship is unknown.)
How to prevent myopia
- Schools should have an eye test sheet. (Snellen chart) for all students’ eyesight If it is found that myopia is abnormal will send the child to the hospital for examination and wear glasses
- Myopia is not caused by eye behavior or from oversight as the general public understands. (e.g. reading a lot, sleeping in a book playing computer games watching television up close), but because of the nature of the person born with the structure of the eye that causes myopia Especially the cornea, cornea, and eye cylinder, as well as some people who are born tall or short, so there are no effective prevention and treatment methods. In addition to when it is, then come to fix later by various methods such as wearing eyeglasses, surgery (reading in the light is not enough. It is not a cause for myopia as well. It will only make it not visible clearly. have to focus more on the eyes that cause eye fatigue easily)
- Parents who warn their children not to look too close to their eyes will cause nearsightedness. Please understand again that what your child has to look closely until they are close to their eyes may be because they can’t see clearly. have eye problems just can’t explain Therefore, it is the duty of parents to take them to an ophthalmologist for treatment before they cause permanent damage to the eyesight.
- Do people with nearsightedness wear eyeglasses regularly? It did not affect the change in eyesight. That is, it does not increase myopia, nor does it prevent further nearsightedness. The belief that wearing eyeglasses regularly or changing eyeglasses frequently will increase myopia is therefore not true. If the eyesight becomes more short, it is because of the nature of that person. In general, by the age of 25 years, eyesight tends to be stable and does not require frequent replacement of glasses. Wearing more myopia glasses for an extended period of time can cause a temporary increase in myopia. This is often seen in children who did not instill eye focusing drops before the eye exam.
- Textbook of general medical examination 2. “Myopia (Myopia)”. (Dr. Surakiat power Pages 944-945.
- Find a doctor. com.”Nearsighted (Nearsighted)” [ออนไลน์]. Accessed from: haamor.com. [07 เม.ย. 2016].
- Village Doctor Foundation. “What is myopia caused by?”. (Dr. Noppawut Tripornchaisak). [ออนไลน์]. Can be accessed from : www.doctor.or.th. [07 เม.ย. 2016].
illustration : www.clarksoneyecare.com, www.sciencenews.org, www.laservision.co.uk, www.imo.es
Compiled by the Maid Thai website (Medthai)