Nearly all people in the world have myopia, and the number of myopic eyes in China is about 400 million. The prevalence of myopia in our population is 33%, which is 1.5 times higher than the world average of 22%. Among them, our students have the second highest prevalence of myopia in the world and the highest number in the world.
I. How does myopia occur?
Myopia is a type of refractive error in which light from distant objects converges on the retina before it can form a clear image on the retina, resulting in blurred vision. Simply put, it means that objects in the distance are not visible, while objects in the near distance can be seen clearly.
The cause of myopia is still not well understood, and the accepted view is that myopia is caused by a variety of factors. Recent evidence suggests that a combination of genetic and environmental factors are involved in the development of myopia. Eye scientists have found that if both parents are highly myopic, the next generation has a higher incidence of myopia. However, the genetic predisposition to low to moderate myopia is generally less pronounced.
The onset and development of myopia is very closely related to close eye use. The eyeballs of adolescents are in the growth and development stage, the adjustment ability is very strong, the stretching of the eyeball wall is also relatively large, reading, writing and other close work, not only need to play the role of eye regulation, both eyeballs also need to internalize, so that the extraocular muscles exert a certain pressure on the eyeballs, over time, the front and back axis of the eye may become longer. The axis of the eye increases by about 300 degrees for every 1 mm of myopia.
What is pseudomyopia?
In school-age children or adolescents who do not read or write properly for a long time or do not have enough lighting, the ciliary muscle is often contracted, and the lens becomes convex and does not relax easily, so that when parallel light from a distance enters the eye, after the strong refraction of the lens becomes convex, its focus no longer falls on the retina, but falls in front of the retina, making things blurry, which is medically called pseudomyopia. If the ciliary muscle is relaxed with proper rest or atropine drops, the vision can be restored. True myopia is when the eye axis becomes longer and cannot be restored, while pseudomyopia is when the lens becomes more convex and can be restored.
Pseudomyopia is a state of fatigue that precedes true myopia. If this state is not relieved in time, organic changes in the eye can lead to true myopia. To determine true and false myopia, a dilated eye exam is required. Some parents worry that dilated pupils are harmful to their children’s eyes, but in fact, the purpose of dilated pupils is to relieve eye fatigue and relax tense muscles so that the refractive error is accurate. If the naked eye vision can reach 1.0 after pupil dilatation, it is “pseudomyopia”, and vision can be restored if the paralyzed and spastic ciliary muscle is relaxed with proper rest or atropine drops.
True myopia, once formed, is irreversible and is an organic change in the eye. The anterior and posterior axes of the eye become longer and external objects are imaged in front of the retina through the refractive system of the eye, so that there is no clear image on the retina and, of course, no good vision. This organic change can not make the eye shorten and change the refractive power by any method except surgery, which is the reason why myopia is difficult to be cured.
How to prevent myopia?
Myopia develops faster in adolescence, so in order to prevent myopia, we should pay attention to the following points.
1. Develop the correct posture of writing and reading for teenagers, do not lie on the table or twist your body. Books and eyes should be kept at a distance of 25 to 30 cm.
2. The time spent using eyes at close range should not be too long, and rest for 10-15 minutes every 45-60 minutes. When resting, you should look out of the window or do outdoor activities so that the eye adjustment muscles can be fully relaxed.
3, the light should be moderate when using the eyes at close range. Too much light or too little light when using eyes at close range are important factors that cause myopia. Therefore, at night or in a dark environment, lighting is best used 40 to 60W incandescent lamp, placed in the upper left corner of the desk. This is because the incandescent light is softer, good color rendering performance, the eye can easily adapt to prevent the light is too strong or too dark brought about by eye fatigue.
4.When writing, hold the pen in the correct posture, fingers should not cover the pen tip.
5.Do eye exercises carefully.
6, actively participate in physical exercise to enhance physical fitness. The quality of the body is also closely related to the occurrence of myopia in adolescents. For example, malnutrition, acute and chronic infectious diseases, weakness, partiality or craving for sweets are common in children with myopia. 7. You should eat more foods rich in various vitamins and have balanced nutrition.
The high myopia vision is low, difficult to correct, wear fully corrected glasses and often can not tolerate) so the prescription should be low correction, strive for some improvement in visual acuity and can remain comfortable as appropriate, without the pursuit of the best corrected vision. Highly myopic eyes with corneal contact lenses (i.e. contact lenses) to correct vision better than ordinary glasses, and can reduce the trigeminal effect of ordinary glasses, visual field limitations and other discomforts.
Another characteristic of high myopia is that the disease progresses, with significant progression during development and does not stop in adulthood. This is mainly determined by genetic solid elements, but the acquired visual environment, nature of work, lifestyle habits, general health and nutritional status also play a role, so more attention should be paid to visual hygiene, strengthening physical fitness and preventing vitamin A and calcium deficiency and malnutrition than others.
High myopia is accompanied by a series of ocular degenerative pathologies and is prone to serious complications that can jeopardize vision. Highly myopic eyes become longer, the posterior sclera is weak, the retina and choroid are atrophied, and the vitreous humor is degenerated. Under the action of external force or vitreous traction, the degenerated retina is prone to form fissures and then develop into retinal detachment. Therefore, highly myopic eyes should pay special attention to avoid violent head shocks and impacts to reduce the possibility of retinal detachment, and once the flash sensation and other aura occur, timely examination is required. In addition, macular degeneration also seriously endangers central vision, and retinal hemorrhage, glaucoma and cataract may occur in highly myopic eyes, all of which should be examined and treated in time.
How to prevent myopia in childhood?
Measures to prevent myopia should begin in the early childhood of every child. The focus of vision protection is to develop good visual habits from an early age. Children should maintain proper posture when reading, writing and drawing. Children should not read or write for too long in a row (usually no more than half an hour). The child should be placed on the right side of the light source when reading, so that the light comes from the upper left front, and the light bulb (tube) should be covered with a suitable lampshade to avoid glare. Light intensity should be moderate. Do not read books while walking, riding in the car and lying down. The table and chairs used for children should be of appropriate height and coordination, and should be constantly adjusted as the child grows. It is best to keep a light on in the room while the child is watching TV.
The distance between the child and the TV screen should be 5 times the size of the TV (generally more than 3 meters), and attention should be paid to the moderate brightness and contrast of the TV screen, and do not continuously watch TV for a long time to the child. In addition, to ensure the right amount of outdoor activities every day, carefully do eye exercises, and regularly check your child’s vision are important measures to prevent myopia. Only when these comprehensive measures are implemented in the child’s daily life can myopia be effectively prevented. Children with high myopia should be instructed to avoid strenuous activities to prevent retinal detachment, and may be treated with surgery.
As mentioned above, since the above-mentioned reactions are normal physiological phenomena, and most of the local and systemic reactions to the vaccination preparations currently used in China are mild and short-lived, no special treatment is required. At that time, children should pay attention to rest, drink more water, and give them a light and easy-to-digest diet. Localized skin redness and swelling usually do not require treatment. If there are swollen lymph nodes, hot compresses can be applied. For fever of moderate degree or above, physical cooling and antipyretic sedatives can be administered at the same time, and the fever can generally be reduced within 1 or 2 days. After the child receives the vaccination, if there is no special abnormality other than fever and mild local reaction, the child may not go to the hospital for treatment.
Try not to apply antibiotics and other drugs to the child to avoid reducing the effect of vaccination. If the child has persistent high fever, headache, vomiting, depression, etc., or if the local reaction is serious and lasts too long, the child should be taken to the hospital in time. In addition, fainting may occur if the child is hungry or highly stressed when receiving the vaccination. Therefore, before the vaccination, you should arrange the child’s diet reasonably and comfort or encourage him/her to eliminate his/her nervousness as much as possible. If fainting occurs, the child should be laid down immediately and given sweetened water, and will generally return to normal after a short time.
What eye diseases can be caused by myopia?
Myopia can cause many eye complications, most of which are blinding, and the higher the degree of myopia, the greater the likelihood of complications. These complications are.
1. Retinal detachment is the most common complication of myopia. Due to myopic eye axis elongation and intraocular nutritional disorders, cystic degeneration and lattice-like degeneration often occur in the peripheral part of the retina. The retina in the degeneration area is very thin and is very prone to perforation, and some have already perforated to form Über-cleft, coupled with vitreous liquefaction and increased mobility, pulling the retina to detach. In retinal detachment, 70% of them are myopic eyes.
2. Cataracts are caused by abnormal nutrient metabolism in myopic eyes, resulting in changes in the lens capsule membrane permeability, gradual clouding of the lens due to nutrient disorders and metabolic malfunction, and gradual vision loss resulting in concurrent cataracts. This kind of cataract develops slowly, and core clouding and posterior capsule clouding are the main causes.
Macular hemorrhage and macular degeneration have poor blood supply and retinal ischemia, and the retina produces a kind of neovascular growth factor, which causes the growth of neovascularization under the retina, and the wall of these neovascularization is extremely thin, so it is easy to rupture and bleed, and macular hemorrhage is formed after bleeding. After the absorption of the bleeding, the new blood vessels can rupture and bleed again, and after repeated bleeding, a short scar is formed locally, resulting in macular degeneration, and macular degeneration permanently damages vision.
4, vitreous liquefaction degeneration vitreous is colorless and transparent jelly-like. When the myopic eye enlarges, the vitreous does not increase again, so the vitreous cannot fill all the space in the eye, appearing liquefaction, increased mobility, clouding, causing black shadows in front of the eyes, inducing retinal detachment.
5, glaucoma myopic eye atrial corner of the filter curtain structure is not normal, so the atrial water flow resistance in the eye, easy to cause an increase in intraocular pressure. According to statistics, 30% of highly myopic eyes have glaucoma, and this glaucoma will cause gradual loss of vision.
6, strabismus, amblyopia myopia can cause exotropia or exotropia, such as binocular myopia difference of more than 300 degrees, easy to cause the degree of deep eye exotropia and amblyopia.
Do myopic people not have presbyopia?
Many people think that myopic people do not have presbyopia. In fact, this is not true. Myopic people, like others, experience a series of aging and degenerative changes in their eyes as they age. First, the nucleus of the crystal body gradually increases and hardens, and the elasticity of the crystal becomes less and less, and second, the force of the ciliary muscle gradually becomes weaker, so that when looking at the near target, the necessary adjustment force is lacking, and the phenomenon of difficulty in reading and writing occurs, which is presbyopia, commonly known as presbyopia.
However, the performance of myopic people after the occurrence of presbyopia is different from the general orthokeratology people, so the number of glasses needed is also different. People with normal vision start to have presbyopia after the age of 40, about +1.00-+1.50D at the age of 45, +2.00D at the age of 50, +2.50D, +3.00DS and +4.00D at the age of 55, 60 and 70, respectively, but the number of glasses needed for myopic people after presbyopia occurs However, the number of glasses a myopic person needs after the onset of presbyopia depends on their original myopia, as well as their specific age.
For example, a person with myopia-3.00D, no matter how old he is, as long as his myopia remains unchanged, he will always wear his original myopic glasses for distance viewing. However, as he gets older, the number of glasses he needs to read and write or do fine work at close range changes after age 40. For example, when he reaches age 50, his eyes also undergo +2.00 presbyopia. For example, when he reaches 50 years old, his eyes become presbyopic with a +2.00 presbyopia, so the degree of glasses he wears when looking close should be -1.00 ((-3.00D) + (+2.00) = -1.00D), i.e. myopia -1.00D. Similarly, when he reaches 60 and 70 years old, the degree of glasses he wears when looking close should be zero degrees (native light) and +1.00D respectively.
So we often see in real life: the elderly who wear the original myopic glasses, when reading and writing, often need to take off the myopic glasses. Others, even if they take off their glasses, still do not look close enough and need to move the target closer or farther away. All of these are actually caused by the occurrence of different degrees of presbyopia on top of myopia.
In this way, we come to a conclusion that the number of glasses worn by a myopic person after the occurrence of presbyopia should be the algebraic sum of his original myopia and the number of presbyopia at that age, and the number of degrees after the offset of the two is the number of glasses he should wear for near vision. However, when we fit presbyopia glasses for myopic people, we can’t simply do that. We must also take into account the wearer’s personal constitution, nutrition, work environment, occupational requirements and personal habits, and then after a full trial and error, we will finally fix a pair of presbyopia glasses for myopic people.
What is the classification of myopia?
1, simple myopia: refers to congenital myopia, and is currently divided into true, pseudophakic, mixed myopia. True myopia is axial myopia, caused by the elongation of the eye axis, and cannot be reduced by conservative treatment. Pseudomyopia is not myopia, but low farsightedness or orthopia, due to excessive force of the regulating muscle and myopia, once the treatment to relax the regulation of vision can be restored, this myopia is rare, treatment is eliminated, not treated, then relapse, and finally can also lead to true myopia.
Mixed myopia refers to both true and false myopia, mostly seen in myopic eyes below 200 degrees, after relaxing the regulating muscle treatment can reduce the number of degrees, but can not eliminate all degrees, adolescents at the beginning to pseudomyopia is common, but over time can lead to revitalization of myopia.
2, pathological myopia: refers to the family hereditary high myopia, family members have high myopia or with high myopia gene, their children are born with high myopia gene or high myopia, very young myopia is higher, with the age of myopia reading also deepen, after 20 years old still have development trend, usually called progressive myopia, pathological myopia, myopia reading up to 1200 degrees The super high myopia above, corrected vision often does not reach normal.
Classification according to the degree of myopia.
1, mild myopia: below -3.00D;
2, moderate myopia: -3.00D — 6.00D;
3. High myopia: higher than -6.00D.
Etiology.
① Axial myopia: It refers to a long eye axis with normal refractive power of the eye, which is the most common kind of myopia. This is the most common type of myopia. It is commonly associated with development and genetics, and is accelerated by poor health habits, such as unreasonable lighting when reading, improper sitting posture, being too close to books and work targets, and excessive eye use.
Refractive myopia: Refractive power of the eye is increased despite normal eye axis. It is common to have bulging cornea and circle robe cornea. Lens abnormalities, spherical hanging crystals, and tilted crystal position. Ciliary muscle spasm, causing over-regulation of the lens.
Nutritional imbalances increase the likelihood of myopia in adolescents. Calcium, chromium, zinc and other trace elements as well as vitamins A, B, C, D, and E are essential components in the growth and development of a healthy eye. Children who are partial eaters, picky eaters and long-term consumers of refined foods are bound to suffer from eye dysplasia due to a lack of these substances, resulting in a decrease in the elasticity of the eye wall and an elongation of the eye axis, leading to myopia or a deepening of myopia.
Treatment of myopia
To date, there is no drug that can effectively treat myopia. The most commonly used methods of myopia correction include glasses, contact lenses and refractive surgery.
Wearing frame glasses is currently the most common treatment method, the use of safe, inexpensive is its advantage. However, it also has a major weakness, which is that it is less convenient to use. While contact lenses overcome many of the disadvantages of frames, they also have their own unavoidable drawbacks. First, contact lenses have a relatively short lifespan and need to be replaced frequently, making them more expensive to use in the long term. Secondly, the process of contact lens removal and daily care is rather tedious. Moreover, since contact lenses are contact lenses that are attached to the cornea, they can easily cause conjunctivitis, keratitis, or even more serious eye diseases if hygiene is not taken care of.
Refractive surgery in ophthalmology contains a variety of surgical methods, and currently the most important method is excimer laser corneal surgery. Excimer laser technology was introduced in China in the early 1990s and has been rapidly expanding in recent years. Since excimer laser treatment allows myopic patients to remove their glasses and have good vision like normal people, more and more people are embracing this method. The three main methods of myopia treatment by excimer laser currently include LASIK, LASEK and PRK.
LASIK is the most commonly used mainstream method and is suitable for most myopic patients; LASEK is mainly for patients with low to moderate myopia who are unable to perform LASIK due to thin corneas; PRK is the first excimer laser myopia treatment, but is rarely used due to post-operative pain and other disadvantages. LASIK with wavefront phase contrast guidance plus iris localization, also known as individualized cutting, developed on the basis of LASIK, can achieve better visual results than regular LASIK.
In addition, IOL implantation and lens replacement surgery for crystalline eyes are excellent complements to excimer laser corneal surgery. For young patients with moderate to high myopia whose corneas are too thin to undergo LASIK treatment, they can be corrected by intraocular IOL implantation, which is equivalent to putting glasses into the eye. For elderly myopic patients or middle-aged myopic patients who cannot receive LASIK treatment due to thin corneas, they can be treated with lens removal combined with IOL implantation.