In the last decade, the market for MC lenses (Myopia Control Progressive lenses for adolescents, initially called MC lenses) has been booming, even more so in the last few years, with major lens manufacturers competing to launch similar products. Suna first launched the “Myopia Control Progressive for teenagers ADD+1.50”, then TAG Heuer launched the “Vision Cola ADD+1.50”, later Essilor launched the “Good Student ADD +2.00”, after the domestic companies in succession to follow suit. A few years ago, when I went to defend my optometrist degree, the seventh question was “What are MC lenses? What is its scope of application?” In order to get a good score, I said yes, and replied as follows: MC lens is a “special” progressive multifocal lens, also known as youth myopia control lens. The reason why it is a special progressive multifocal lens is that its main parameter is the lower additive ADD which is generally +1.50D. MC lenses were first produced and sold by the American company Suna. MC lenses are designed according to the structure of the adolescent eye, the active lifestyle and the reading pattern, providing a wide distance zone, an extra wide and highly positioned near zone, and an extra short transition progressive zone of only 10mm, which can effectively reduce the excessive tension of the ciliary muscle during near vision, thus controlling myopia and preventing pseudomyopia. MC youth myopia control lenses are suitable for adolescents, i.e., ages 9 to 18. It has been reported that MC lenses are also suitable for myopic and hyperopic clients with ADD=+1.50D. However, I think it is not possible to do so because MC lenses are designed for adolescent eyes, the progressive overband is very short, and because of the strong adaptive ability of adolescents, most MC lenses are designed with hardness, so that the peripheral deformation area is deformed, which is not very suitable for older customers with weaker adaptive ability, if the older customers have been fitted and do adapt, but for the future ADD deepening of the lenses will bring difficulties, to re-adapt to the new lens design. The design of the new lenses is difficult to adapt to. Is it really that good to control myopia with progressive lenses? Can they really control the development of myopia effectively? Is every student suitable for wearing myopia control lenses? Is it suitable for those who have astigmatism? Does it have no side effects on the visual method? Can it be used even for exotropia? Can long-term wearers have normal near vision function? What about positive and negative relativity adjustment? Does it have any effect on the normal visual function of the human eye? What kind of people are the most suitable for wearing myopia control progressive lenses for adolescents? Why are they the most suitable and who is least suitable for the Youth Myopia Control Progressive Tablets? Are the research papers on myopia control progressives for adolescents reliable? …… brings so many questions, let me slowly analyze them for you below. In order to better understand the function of myopia control progressive tablets for adolescents, we first need to learn some basic knowledge of the eye. First, the eye’s triplet motion; second, the significance of the AC/A ratio; third, the relationship between eye position and stereopsis; fourth, the magnitude of adjustment and positive and negative relativity adjustment. First, the eye’s triadic movement: that is, the human eye when looking close, the eye brings three kinds of movement, “adjustment → collection → pupil contraction”. In more detail: when the eye looks close, it first adjusts the lens to increase refractive power, both eyes collect to form a binocular monovision function, and the pupil narrows to adjust the depth of focus. In order to better image the focal point on the retina, the degree of depth of focus affects the strength of the adjustment and the size of the pupil reduction. This process is the triplet of near vision in the human eye. The triplet movement ensures good near vision and binocular monocularity, and the human eye performs a series of coordinated movements to ensure that near objects can be seen clearly and quickly. If one of the triplet movements is affected or changed, the near vision function of the human eye will be seriously affected, such as insufficient pooling, no binocular monovision, there is no stereo vision, and can not be sustained to see near; such as insufficient regulation, can not see near objects, will easily produce visual fatigue. Then the youth myopia control progressive film use, the adjustment force will be reduced, but the collection is not reduced, the pupil is not changed, the depth of focus has changed, so that a good triad of movement will be out of balance, long-term use of youth myopia control progressive film, will cause a decrease in the adjustment force, thus reducing the adjustment amplitude, then it will lead to the adjustment of insufficient this visual function problem. (Here also to say a combination of prism, it reduces both regulation and collection, but long-term use will be addictive, the eye regulation function and collection function are changed, the amount of positive and negative relativity regulation also change, here I reserve the prism plus positive mirror to prevent myopia views, later will have a topic to say.) Second, the significance of the AC / A ratio: the concept is that when the human eye to see close to the adjustment force will bring the corresponding size of the collection force, our normal eyes, in general, each use of 1D adjustment force will bring 4 △ collection, so that the human eye in looking at the near to maintain lasting and comfortable. If the adjustment function is found to change, and the collection is unchanged, then it will make the eye move with the internal rectus muscle to make too much force to produce the collection. This will produce an over-assembly of the eye’s near vision in the long term. When there is excessive assembly, the external rectus muscle is stretched and overly compresses the temporal wall of the eye, thus making the eye flatter and longer, so that the eye axis also becomes longer and myopia deepens. After the use of myopia control progressive tablets, those who have normal AC/A ratio, like I mentioned above, do not reduce the development of myopia, but only relax the regulation, not relax the collection force; those who have low AC/A ratio, if they use it, it is more serious, the collection brought by the regulation is very little, and now the regulation is relaxed, the collection completely depends on the eye fusion like the reserve to lead to the internal rectus muscle collection, such people can not last. This kind of people can’t look close for a long time, slowly will make the eyes give up the binocular monocular function, then stereo vision also disappeared, thus triggering the occurrence of exotropia; AC/A ratio high people use youth myopia control progressive film, this kind of people are more suitable to wear, because the AC/A ratio is high, the regulation draws too much collection, relax the regulation so that can reduce the amount of collection, thus making the eyes more comfortable. However, people with a high AC/A ratio account for a very small percentage of the youth myopia population, less than 10%. Third, the relationship between eye position and stereopsis: most of our normal people’s far-sighted eye position in the external oblique position, the current normal eye position is: BO 1 △; BI 3 △ within, so that is considered the positive eye position. When viewing near, the eye position is usually in BI 4△±2△. In order to ensure normal distance and near vision in stereo, and to be durable and comfortable, the eye position should preferably be within these expected values. The use of juvenile myopic control progressives with normal eye position does not produce adverse consequences; however, for people with high amounts of ectopic myopia, the consequences of using juvenile myopic control progressives without a prism prescription are very serious. If a person with exotropia myopia requires full correction or overcorrection, but if a progressive piece is dispensed, after the adjustment is relaxed, the collection of visual near is completely inadequate and it is simply impossible to perform binocular monovision function, which will cause the eye to form exotropia which is a fatal problem. As for people with internal oblique myopia, such people are suitable for wearing youth myopia control progressive lenses. IV. Adjustment magnitude and positive and negative relativity adjustment. General formula: 180.33 x age = adjustment amplitude. Adjustment amplitude is related to age, when 10 years old, the adjustment amplitude is as high as 14D, and then slowly decreases. When the eyes are nearsighted, wearing glasses or not wearing glasses, the regulation used is lower than the regulation used by normal eyes, more obvious without glasses, long time not wearing myopic glasses to see close, regulation used little or almost no, only use the collection. Then, such people, the normal adjustment power will be reduced, the adjustment range is much lower than the same age. When we correct their look far and near vision luminosity, we will find that they wear nearsighted glasses to see close very difficult, which is the visual problem of under-regulation. Positive and negative relative regulation, refers to a certain distance to see near, the eyes relaxed regulation and the degree of tension, these two degrees are preferably the same, so that the eyes will be comfortable and lasting, such as one side is greater than the other, then the regulation of the problem appears, such as a decline in the flexibility of the regulation, near vision or far vision of the moment appear blurred time band. After the use of youth myopia control progressive tablets, the long-term relaxation of the adjustment, so that the magnitude of the adjustment decreases, and finally part of the loss of a healthy vision of the adjustment force used by the near vision. In the long run, MC wearers will rely more on relaxed adjustment, which will eventually produce the visual problem of under-adjustment and then trigger the inability to sustain the adjustment power. To use an unprofessional analogy, a young person with presbyopia; a person with normal positive and negative relative regulation, using a youth myopia control progressive tablet, because it is artificially relaxed regulation, changing the middle position of the positive and negative relative regulation when the eye sees near. In summary, not every child can wear myopia control progressive lenses for teenagers, and most teenagers are not suitable for progressive lenses in terms of normal visual function. However, due to the manufacturers and stores to pursue higher profits, they ignore or do not understand the problem of visual function, thus allowing more teenagers’ visual function to be affected. Some manufacturers have made some papers in order to get better sales of myopia control progressives for adolescents, but these papers do not specify what type of adolescents to do the clinical work, for example, I found some adolescents with high AC/A ratio and internal strabismus to do the clinical work of “myopia control progressives for adolescents”, and I am sure I can get good results. This is because adolescents with high AC/A ratio and internal strabismus need these lenses to improve their visual function. Except for adolescents with “high AC/A with internal strabismus” who are most suitable for this type of progressive lenses, almost all other adolescents are not suitable. Currently, many optometrists are blindly pushing myopia control progressives for young people for the sake of sales profit. If you want to fit them, please systematically check their AC/A ratio, eye position, adjustment magnitude and positive and negative relative adjustments. In other words, at most two out of ten teenagers are suitable for these lenses. I can say that most of the customers who wear myopia control progressive lenses for teenagers will have increased myopia, because the lenses do not change the habits and posture of the customer, and the relaxation of the adjustment that the lenses say will bring new visual problems and will cause visual fatigue, which are side effects. Due to the design of the progressive lenses, customers with astigmatism have more problems, and the deformation zone between the left and right will be more obvious, which will bring more visual fatigue and thus make the eyes more likely to deepen. If a teenager is exotropia (most myopic customers are exotropia), the visual problem will be amplified by the use of myopia control progressive lenses for teenagers, because the exotropia also relaxes the adjustment and reduces the force of the internal set, so that the eye slowly changes from occult to dominant strabismus, which destroys the stereo vision function of the eye. Without stereo vision, there is no sense of space and distance, which destroys the fusion function of the eye. The majority of our staff engaged in optometry should understand the need to be careful with “youth myopia control progressive lenses”. For the sake of better eyes of the next generation and less visual problems, please do more examinations, more tests, more professional contents when you give the youth optometry and dispensing, so that you can give the most correct prescription and advice to each customer within your ability, the eyeglass industry is a conscience industry, please be honest with your conscience when you make each decision, not to hurt people for the sake of sales, please be careful with the prescription! “Youth myopia control progressive tablets”!