2. The refractive system of eyeball is an adjustable "convex lens", so its shape can be changed. When the concave lens is placed in front of the eyes, the eyeball still has the function of self-adjustment, which shows that the eyes can see objects at different distances, and patients with myopia or presbyopia can adapt to wearing glasses.
3. Because ordinary glasses are separated from eyeballs, the images are intuitive and easy to calculate. This section focuses on the influence of glasses on eyeball refraction, and the discussion about glasses is aimed at ordinary glasses. The refractive effect of wearing contact lenses is the same as that of ordinary glasses, and its principle and technology are very mature in the glasses industry, so I won't repeat them here.
4. In refractive optics, only in some special cases can the combination of two lenses with diopters of P 1 and P2 produce the refractive effect of lenses with diopters of P 1+P2. In the optical path composed of eyeball and lens, P 1+P2 can also be found in effect or qualitative calculation, which is not the actual refractive effect after lens combination, but a simplification and approximation, because the eye has the ability to change diopter by itself. Although it is difficult to be verified by experiments, it should be able to offset the diopter of the lens from the perspective of the adjustment function of the eyeball, but this formula can simplify the calculation. For the system composed of eyeball and lens, it is a refractive system composed of two lenses at most, so it can be calculated by refractive optics theory. When wearing a lens, due to the special adjustment function of the eyeball, we can add or subtract the diopter of the lens and the diopter adjusted by the eyeball, or we can get an approximate value. Although there is still a long way to accurately measure the refractive power of the eyeball, the effect is close. In this demonstration, although it is theoretically deduced, it is very difficult to experiment and measure, just like myopia glasses need to be tried on, and experiments need to be carried out in the process of guiding glasses.
5. According to the refractive characteristics of the eyeball, the static refractive power of the eyeball is+58.6 d. Although this is a special case, it basically reflects that the refractive power of the eyeball is very strong, and its adjustment is relatively small. The normal eye is about 0- 10d, and the myopia is about N- 10d(N refers to the myopic refractive power of the eyeball). It can be considered that the distance from the center of the refractive system of the eyeball-the lens to the retina is constant, and in the later calculation, the image distance can be considered as a constant K. For the refraction of the eyeball, if a clear image can be formed on the retina, the refractive system still meets the lens imaging formula.
1/u+ 1/k=P
Where k is a constant, p is the refractive power of the eyeball, which is a variable, meaning that different people look at targets at different distances, and the refractive power of different people's eyeballs is different, and u refers to the distance from the target to the eyeball.
The condition of this formula is that at a certain moment, the eyes look at the target at a certain distance, and the target is between the near point and the far point of the eye.
According to the formula, when looking straight at infinity, 1/u=0, the above formula can be changed to P= 1/K, so that 1/k=P0, that is, P0 is the static diopter of eyeball. When looking at a target with a distance of L from the eyeball, the imaging formula of "lens" becomes 1/L+1/k =1/L+P0, where1/L is the diopter of the eyeball when looking at the target with a distance of L.
For the wearer, under normal circumstances, the distance from the eyeball to the center of the glasses is about 1.2-2.4 cm, which is denoted by H below, but the value at a certain moment is certain for someone. Let the focal length of a lens with a diopter of p' be f, and when looking at a target with a distance of l, the lens imaging formula is as follows:
1/L+ 1/V = P ' = = & gt； 1/V=P'- 1/L ①
At this time, the distance from the lens to the eyeball is |V|+h, and the refractive condition of the eyeball satisfies the formula:1(| v |+h)+1/k = p2.
According to the formula, if |V| is much greater than h, according to formula ①, formula ② can be approximately simplified as:
1/| V |+ 1/K = D = | D '- 1/L |+ 1/K③
Because the eyes see the virtual image through the lens, V.
According to this formula, the size of |V| depends on the object distance L and the focal length of the lens. Considering the actual situation, the diopter of myopia glasses is mostly greater than -6D, and the reading and writing distance of students is mostly greater than 0.25m. Moreover, according to the lens imaging formula, the refractive power of concave lens is P' (Note D'
In other words, for thin lenses, if the distance from the eyeball to the lens is ignored, it can be considered that the added accommodation of wearing myopia glasses is equal to the refractive power of the lens. In the optical system composed of eyeball and glasses, the diopter produced by each part can be approximately increased or decreased. This analysis can simplify the calculation and simplify the problem. In the following discussion, we will use this result for qualitative analysis and approximate calculation.
6. Error analysis. If the formula is taken as the standard, there are many reasons for the error, which are analyzed now.
(1) Because the adjustment and deformation of the eyeball are carried out at the same time, if there is adjustment, there will be deformation, and if there is deformation, there will be changes in the anterior and posterior diameter of the eyeball, as well as changes in the cornea, aqueous humor and the optical center of the lens caused by the deformation of the lens and cornea itself. Although myopia or presbyopia itself can't explain the change of the anterior-posterior diameter (myopia is that the eyeball images in front of the retina, but it can be achieved through too strong close adjustment or the ciliary muscle can't relax, which can't fully explain the elongation of the anterior-posterior diameter of the eyeball), it can't explain its invariance. The existence of these factors determines that k in the formula is only an approximation, and the larger the tuning range, the greater the change of k value, which is also one of the reasons for the error. However, considering that the diopter adjustment of the lens is far from the diopter of the eyeball (about 60 diopters), and the adjustment range of the eyeball is generally less than 10 diopter, the change of corneal diopter is smaller, so it can be considered that the distance from the optical center of the "lens" to the retina is almost unchanged.
(2) Because the anterior-posterior diameter of eyeball varies from person to person, K is not a constant, so it is difficult to measure it accurately. For a certain stage of a person, the anterior and posterior diameter of the eyeball remains the same, so K can be considered as a constant.
(3) For different people, the distance between the lens and the optical center of the "convex lens" is a difficult variable to measure, which also affects the accuracy of calculation. It can be seen from the calculation that when h increases, the error increases, and vice versa.
7. When the lens is placed in front of the eyes, if the eyes can still see the target clearly compared with the normal eyes, from the regulatory role of the eyeball, the glasses first offset the lack of regulation of the eyeball. So in the future calculation, as long as the effect of the offset lens is within the normal adjustment range of the eyeball, it can be established in theory, and we don't need to pay attention to the change of the actual diopter of the eyeball. For the eyeball, no matter how many diopters of glasses you wear, you must reduce the role of glasses and increase the diopter adjustment to see the target in front.
8. Because of the error and adaptation of glasses, even if all factors are taken into account, theory is only an approximation to practice. When the range of eyeball accommodation is large, this simplified and idealized theory will increase the error due to its own deformation. Moreover, the distance from the lens to the optical center of the eyeball varies from person to person, which cannot be expressed by physical formula. The specific problems are to be analyzed in detail.
9. For the refractive system composed of eyeball and lens, the refractive power of lens is certain, but the refractive power of eyeball is a variable. Therefore, the eyeball is regarded as an adjustable convex lens, which means that the refractive power of the eyeball is determined when the eye can see a certain target clearly through glasses, so it can be calculated by refractive theory, but when the distance between the eyeball and the target changes, its refractive power also changes.
10. For the refractive system composed of eyeballs and glasses, there are only two "lenses", which can be regarded as an equivalent lens group, and the degrees of the lenses can be increased or decreased. For example, the +5D lens can be regarded as a (+2D)+(+3D) lens group. Although it is not true in most cases, it provides convenience for us to solve the problem in theory.
Myopia correction includes refractive correction and pathological treatment of myopia. At present, the effect of treatment is uncertain, or only optical correction, or ineffective. Children with low vision cannot be treated blindly, and the effectiveness and practicability of some prevention and treatment commodities currently implemented need further practice to confirm. Don't blindly deny and easily affirm the creation of various methods.
First, myopia correction
Objective: To improve hyperopia, reduce diopter, prevent development and prevent complications.
Requirements: effective, reasonable, practical and harmless.
Methods: Including optical correction and myopia treatment (optics, medicine, surgery, etc. ).
Means: symptomatic-↓ diopter, ↑ vision (surgery, conservative).
Cause-pathological process such as myopia degeneration.
Efficacy indicators: hyperopia, refraction, axial length and other visual functions.
Do you need glasses? Should you wear it often?
Objective: To add special glasses for myopia, such as visual glasses, therapeutic glasses, protective glasses and cosmetic glasses. Myopia can generally be matched with glasses. You can also get ready first.
Glasses should always be worn in the following situations: high diopter, obvious astigmatism, amblyopia or amblyopia tendency, abnormal eye position or eye movement, and others such as visual fatigue or other eye diseases. Contact lenses (such as RGP) can be recommended.
What happened to RGP?
RGP is a kind of gas permeable rigid contact lens (contact lens), which can make myopia get better optical correction effect, especially for those with obvious astigmatism and rapid development of myopia. Existing data show that it may help to alleviate the progress of myopia. Those who have the ability to take care of themselves can try as appropriate. However, it is necessary to go to a qualified optometry service unit for a comprehensive examination, accurate optometry and reasonable glasses. Require correct use and ensure timely follow-up.
What are therapeutic glasses?
After accurate examination (diagnostic optometry) and reasonable design and manufacture, appropriate glasses (including contact lenses and auxiliary glasses) are selected as the main or auxiliary measures to correct vision abnormalities and other eye diseases caused by amblyopia, strabismus, asthenopia and ametropia.
Children and teenagers are mostly therapeutic glasses except for augmentation glasses.
Glasses review:
Because of the characteristics of glasses (selectivity, adaptability, variability, and with the continuous emergence of high-tech products, they can better meet the needs of different objects), it can be predicted that glasses will remain an irreplaceable practical optical correction method for myopia for a long time.
Progressive multifocal lenses, breathable rigid contact lenses (RGP) and orthokeratology lenses (OK) have their own characteristics, but the effect of "controlling myopia" needs to be confirmed.
Why should myopia surgery think twice?
There are many kinds of myopia surgery, and the existing refractive surgery, such as excimer laser corneal surgery, can obviously reduce myopia diopter, and the effect is positive. It is suitable for some abnormal refraction (such as anisometropia). ) and people with some special needs. Like wearing glasses, it belongs to optical correction (symptomatic, non-causal).
Once the human eye is operated, it will enter a persistent pathological state, and the long-term effect is still unknown.
Judging from the functional requirements, myopia surgery is an elective surgery, which requires a lot: it can only be opened well, not broken.
For most people, whether near vision efficiency and other visual functions ("functional vision") will be affected or not, just seeking to improve far vision may be gain and loss in the long run. What's more, people have different physiological requirements for hyperopia and eye refraction in different periods of life. From the point of view of ophthalmology, it is one-sided to improve hyperopia once and for all. "Cure myopia" and "farewell glasses" are all exaggerated. In short, any treatment for myopia (including surgery) should know the truth, weigh the pros and cons, compare the gains and losses, and think twice before you act.
★ Think twice before myopia surgery.
At present, myopia laser surgery belongs to refractive keratoplasty, which can obviously reduce myopia diopter and improve hyperopia. In addition, it has the advantages of quick operation, quick effect, no obvious pain and easy acceptance by patients. For modern ophthalmology, as a treatment, it does have some merits. For example, it can be used to correct anisometropia (binocular anisometropia), pathological hyperopia and astigmatism. In China, people are willing to give it a try at a high price because of attractive publicity and guidance such as "passing the physical examination", "curing myopia" and "farewell glasses". Various places compete to introduce equipment, and many small hospitals treat tens of thousands of patients. The huge economic benefits make myopia surgery far ahead of medical activities and academic research in China. Foreign manufacturers have seen hundreds of millions of objects, thus China has become a supermarket and experimental base for myopia surgery in the world.
At the end of 2004, the news that myopia laser surgery was stopped came from Britain, which undoubtedly brought a lot of shock to our myopic country with very prosperous surgery and triggered deeper thinking. How should this be treated and how should it be treated?
Myopia surgery in Britain has not been carried out for a long time, but equipment has been introduced in a controlled way, special research has been organized in a planned way, and a relatively sound management system has been established. The competent authorities not only actively pay attention to finding problems in time, but also make decisive decisions and take corresponding measures that are conducive to normal medical activities and effectively protect patients' interests. This is a scientific and responsible attitude. For enthusiasts, some information is at least a useful reminder. The main reason for stopping laser surgery for myopia is to worry about safety (especially the long-term safety of surgery). After a year's evaluation, the National Institute of Standardization of Diagnosis and Treatment pointed out that the existing evidence is not enough to support the promotion of such operations in the national medical service system. In fact, the same situation also exists in Europe, America and Asian countries. There are many reservations about whether it can be routinely used in clinic. For some time, people have been repeatedly warned in various ways not to act rashly despite the positive effects of surgery. Not long ago, some data in the United States pointed out that the failure rate of surgery is not11000 as mentioned in some reports, but110 (and it only refers to the immediate effect, excluding other adverse consequences).
Everyone in the industry knows that myopia corneal surgery is performed on a normal eye. Therefore, we can only succeed, not fail. Moreover, once the human eye operates, it enters a continuous pathological state. Improving or improving far vision does not mean curing myopia. There are two purposes of myopia correction: optical correction of myopia refraction and treatment of myopia lesions. Now the function of corneal surgery is the same as wearing glasses, which belongs to refractive correction. But glasses can be changed and adjusted, and surgery is irreversible. The only function of surgery is to improve hyperopia, but hyperopia is only a part of human visual function. For a normal person, good near vision is more important than far vision in most cases. Moreover, many people may unconsciously affect myopia function after improving hyperopia. In this regard, patients should be psychologically prepared. And you can't "say goodbye to glasses" after surgery. With a person's life, the refraction of eyes is a dynamic process. Due to the special variability of human eyes and the complementarity of visual functions, in order to meet the temporary needs of hyperopia, irreversible methods are used to change refraction, ignoring the different physiological requirements of people at different ages for hyperopia and refraction and the influence on other visual functions, which is gain and loss, or even loss for most myopia.
Myopia is a major medical problem, and it is still in the cognitive stage. When using any therapy, we should objectively and reasonably measure the ratio of benefit to risk. Although some methods are effective, their effectiveness is not equal to their practicality. Moreover, due to the short time, it is too late to make a final comment on the medium and long-term effects and existing problems (including refractive stability after intervention, practicality of functional changes, possible complications and sequelae, etc.). As a selective operation, we should be alert to the double danger of correcting myopia. One depends on myopia itself and the other depends on the attitude of the performer. When the person subjected to execution shows strong interest, the harm is even greater. Some lessons in the history of myopia surgery are still fresh in people's memory. In foreign countries, medical units and operators should be responsible for any adverse consequences or injuries caused by incorrect guidance.
Myopia correction is an important event to meet the needs of medicine and society. Recently, China's Chinese Journal of Ophthalmology (No.9, 2004) also appealed to Dai Wen that myopia should be corrected reasonably. Ophthalmologists have the obligation to guide correctly, and some situations should be explained clearly so that patients can truly understand the advantages and disadvantages of surgery. We can't violate the principles of medical ethics and create economic benefits in order to meet the special needs of some people (for example, just passing the medical examination) (some countries have stipulated that those who have medical examination requirements are also unqualified). Facing medical problems, we need to dare to think and do, and seek truth from facts. Don't be far-fetched and impetuous, be eager for quick success and instant benefit. The relevant administrative departments should take the initiative to intervene and manage scientifically (for example, they can review and summarize the work in the current period) in order to find and solve problems and earnestly safeguard the interests of the broad masses. Hope to Correct Myopia Reasonably Because of one-sided orientation and blind requirements, "fear of myopia" is widely popular in China, and people are eager to seek treatment. China has become a supermarket and experimental base for myopia treatment in the world.
The purpose of myopia correction includes improving distant vision, reducing diopter, preventing development and preventing complications. Means include myopia correction (symptomatic) and myopia treatment (causal). The former refers to optical correction, including glasses and all refractive surgery. The latter is mainly conservative treatment such as drugs (treatment of degeneration and myopia complications). Therapeutic indicators should include vision, refraction, axial length, other visual functions and satisfaction with the chief complaint. The treatment of myopia is very difficult. At present, it should be mainly aimed at degenerative myopia (comprehensive therapy), and optical correction with glasses is the first choice for simple myopia. Long-term practice shows that it is difficult to solve the problem only by adjustment. According to the various therapies designed by it, it is difficult to have an effect. The continuous improvement of surgery is a big leap in ophthalmology. However, its effectiveness is not equal to its practicality, so we should be cautious about classifying it as routine and popularization prematurely. Refractive surgery is an optical correction method, which is only symptomatic treatment and cannot stop the pathological process of myopia. Once the cornea is operated, it will enter a persistent pathological state. When measuring the benefit-risk ratio, we should not only consider no or few side effects, reliable predictability and short-term and long-term effects, but also pay attention to the visual quality. The possible consequences should be described in detail in a realistic way. The human eye is an extremely precise and complex organism with special variability, elasticity and complementarity of visual functions. Therefore, people's different physiological needs for refraction and vision at different ages can not be ignored. Especially in order to improve temporary hyperopia and affect other visual functions (such as myopia efficiency), in the long run, there are gains and losses, and the gains are not worth the loss. In the treatment of myopia, we should also be alert to the double dangers: first, it depends on myopia itself, and second, it depends on the attitude of the performer. When the performer shows strong interest, the harm is even greater. The treatment of myopia is an important subject to meet the needs of medicine and society. We can neither easily affirm nor blindly deny any exploration. Professionals should be reasonably oriented, and should not violate the principles of medical ethics in order to meet the special needs of some patients (for example, just to pass the physical examination) and create economic benefits. As an elective operation, the scope of indications cannot be expanded at will at present.
In short, myopia needs to be corrected, but it should be corrected reasonably according to the existing conditions and levels.
★ Looking forward to reasonable correction of myopia
Myopia is a major medical problem. Although the research has been carried out one after another, due to the complexity of myopia itself, it is still in the cognitive stage. Looking back on the history of myopia treatment, it is not difficult to find that from early relief and adjustment drugs to various physical therapies; From the initial optical correction to modern refractive surgery, there are many methods that keep pace with the times. With the support of modern high technology, significant progress has been made in myopia correction methods, especially refractive surgery. According to statistics in recent years, three of the top ten ophthalmology projects are related to myopia (excimer laser technology, corneal ring implantation in stroma and intraocular lens implantation in phakic eyes). It is even called "the great pioneering work of ophthalmic surgery" and "the great revolution of taking off glasses". Myopia correction in China is more distinctive. Because of the blind demand for hyperopia and the theory that myopia is reversible, preventable and treatable, people are eager to seek treatment and have various correction methods. Its variety and high curative effect rank first in the world. But there are many lessons and fresh memories. The blind implementation of some early methods not only caused a huge waste of manpower and material resources, but also caused medical complications, which is difficult to estimate. What's more, because of the attractive publicity and guidance such as "passing the physical examination" and "radically curing myopia", surgical treatment has unlimited scenery in China. Many hospitals treat thousands of patients. And whenever there is a physical examination or a holiday, it is even more crowded. Huge benefits have become the "new economic growth point" with the most strength and potential. As we all know, RGP is about to start, and progressive multifocal lenses will be put into use again ... More methods not only arouse great interest of professionals, but also famous figures and scientists in special cultures are actively involved. And frequently innovate. The input is wide, the number of participants is large, and the three religions and nine streams show their magical powers. For a long time, myopia patients, including ophthalmologists, have been at a loss. Nowadays, new terms such as refractive surgery have become a hot topic. The commercial activities of myopia correction are far ahead of academic research. In the commodity war of myopia prevention and treatment, domestic and foreign manufacturers have seen hundreds of millions of objects, making China a supermarket and experimental base for myopia correction in the world.
By wearing glasses, the hyperopia of millions of myopia patients has been corrected. Moreover, for a period of time, some people who adapt to surgery do benefit from meeting their current needs and special requirements. However, people (especially the majority of myopia students) are more eager to cure myopia and get rid of glasses forever. However, the reality is far from the requirements. In this regard, it is necessary to analyze many problems in the understanding and methods of myopia correction according to modern medical concepts, and put forward some discussion opinions and suggestions for reference.
First, the purpose and characteristics of myopia correction
(1) The human eye is a precise organ, and refraction is its main function. The ideal refractive state is not emmetropia. Refraction is a dynamic process with people's life. Moreover, the human eye, as an extremely complex organism, has special variability, elasticity and complementarity in its visual function. Therefore, in order to meet the needs of temporary hyperopia, it is not worth the loss to take irreversible measures to change refraction and ignore the different physiological needs of people at different ages for refraction and vision and their influence on other visual functions. What is the ideal refractive state of human eyes? The answer is non-hyperopia, non-myopia, and non-emmetropia (emmetropia is a point with zero static diopter, which is actually gone, and the number is very small). So far, people have not found an effective measure to stop eye development at this point. Normal diopter is the physiological refractive value of normal distribution at different ages (the specific figure is the average refractive value within 2 standard deviations). In other words, during the whole growth period, the eyeball is constantly developing and the refraction is constantly changing (myopia). In the meantime, whether we can find a "braking" mechanism that can stop different individuals from looking directly at their eyes may be one of the goals that people should pursue when studying myopia.
(2) Correcting myopia effectively and reasonably is the ultimate goal of studying myopia. However, the basis and key to overcome myopia is to clarify the essence and pathogenesis of myopia. In-depth discussion on prevention and control methods will help to understand and explore its mechanism.
(3) The purpose of myopia correction includes: improving far vision, reducing diopter, and curing myopia diseases and complications. The specific methods belong to refractive correction and pathological treatment. That is to say, it includes optical correction of myopia refractive abnormality and treatment of myopia lesions. The former is symptomatic, the latter is causal, and the ideal result is to have both. However, due to the current medical level and technical conditions, except for a few cases, the principle of action is basically symptomatic.
(4) Optical correction of myopia includes indirect method and direct method. The former refers to wearing glasses or contact lenses, and the latter refers to temporarily or permanently reducing myopia diopter (including all refractive corneal surgery and refractive lens surgery, etc.). ).
Second, there are many designs of myopia correction methods, and the confirmed ones are mainly glasses and surgery.
(1) With the development of modern high technology, myopia surgery has been continuously improved, with more improvements and innovations, such as the application of wavefront aberration technology. In the process of operation, many units seek truth from facts, guide correctly, take overall responsibility, choose rationally, emphasize personalized treatment and pay attention to visual quality. But refractive surgery is optional. According to the new concept, the choice of objects is not only to strictly limit indications, but also to vary from person to person and from time to time according to different characteristics and requirements. Effectively be effective, reasonable, practical and harmless. Generally speaking, the following factors can be considered in evaluating myopia surgery: equipment conditions (advanced and mature methods, continuous innovation and perfection), professionals (technical level and service attitude), patient conditions (treatment purpose, indications, compliance, age, occupation, habits, education level and psychological state, etc. ).
(2) Because glasses have the characteristics of selectivity, adaptability and variability (they can be adjusted and replaced at any time), and with the continuous emergence of high-tech products, they have been able to better adapt to the needs of different objects. It can be predicted that it will remain an irreplaceable practical optical correction method for myopia for a long time.
In addition to obvious astigmatism, anisometropia, amblyopia, strabismus, abnormal eye muscle function and high diopter, myopia should be worn early and often. Generally, glasses can be used as backup. Don't blindly refuse glasses.
In order to correct myopia accurately, reasonably, economically and practically, ensure the quality and improve the efficiency, it is necessary to distinguish between the types of optometry (diagnostic optometry, light-corrected optometry and epidemiological optometry) and the purpose of glasses (glasses for adding vision, therapeutic glasses, protective glasses and cosmetic glasses). Different purposes, different methods and different division of labor; The method caters to the purpose, not the purpose obeys the method.
Diagnostic optometry and therapeutic optometry are mainly the tasks of ophthalmologists, with static optometry and objective examination as the main indicators. Optical correction optometry and glasses are mainly the tasks of optometrists, mainly dynamic optometry, combining subjective and objective examination. As an art, the latter is very professional. This is a reluctant thing for most ophthalmologists. But in our country, at present, we have to act accordingly. It is unrealistic and unnecessary to invest a lot of energy and time in this area. But as a normal business, we should actively participate in diagnostic optometry (mainly qualitative) and therapeutic optician.
There is great room for the development of contact lenses, which can be gradually popularized. The biggest problem is that there is a great shortage of fitting technicians. This problem may require the national authorities (including commerce, health and education) to know, understand, attach importance to and take active actions to gradually solve it. Rigid permeable contact lens (RGP) and orthokeratology lens (OK) have their own characteristics, but the function of "controlling myopia" needs further verification. Therapeutic glasses refer to choosing appropriate glasses (including contact lenses, goggles, etc.). After accurate examination and diagnosis and reasonable design and manufacture, it is the main or auxiliary measure to correct vision abnormality and other eye diseases caused by amblyopia, strabismus, asthenopia and ametropia. In order to adapt to the development of ophthalmology (especially pediatric ophthalmology), it should be strengthened in the future.
The application of progressive multifocal lenses is expanding, including the control of myopia in adolescents. However, due to the complexity of human eye function and structure, the uncertainty of accommodation theory in the occurrence and development of myopia, and the limitation of optical characteristics of progressive multifocal lenses, the existing achievements are still in the exploration stage. In China, recently, due to the one-sided introduction of commercial speculation, there have been some calls and guidance for promotional activities in some places. People are worried about this, and think that the current statement from "possible" to "sure" and "progressive multifocal lens is the best choice for students to control myopia" are inappropriate. It is understood that the three-year progressive lens research plan has been jointly launched by Beijing, Shanghai and Wenzhou, and a correct conclusion will be drawn in a few days. It remains to be seen whether it will eventually become an ideal choice for teenagers to prevent and control myopia.
(3) Drugs have always been one of the main methods to treat myopia, and are usually used to improve the function of eyes, prevent the development of diseases and treat complications. Usually, drug selection requires a positive result. Is it clear whether drug treatment is symptomatic or causal? Especially according to the principle of evidence-based medicine, we should give consideration to both effectiveness and safety. It should also be considered that due to the characteristics and laws of drug therapy, there are bound to be certain limitations in specific applications (compliance, timeliness, dominant and recessive side effects, etc.). ). Because primary myopia is axial elongation and progressive irreversibility, drugs generally have no direct effect on improving myopia's far vision and changing myopia diopter. So far, the selected drugs (including some drugs introduced at that time) have various modes of action, the mechanism is not fully clarified, the curative effect is different, and opinions are different. With the in-depth exploration of the pathogenesis of myopia, it is expected that drug therapy will also have new development. People have great interest and great hope in this regard.