Xu Yuan, Zhao Wei CCTS: R778.1+1 Literature ID: A Article ID: 7237 Cai Yan, Department of Ophthalmology, PLA 474 Hospital Abstract: This article presents a literature review on the topics of myopia occurrence and development, epidemiologic study of myopia, regression of the theory of accommodation, early-onset myopia versus late-onset myopia, sustained near work versus myopia and experimental study of defocus, suggesting that myopia occurrence , development may be related to a variety of factors. We also talked about various attempts to intervene in the development of myopia based on the theory of accommodation in the context of clinical practice. Attempts have been made to use prisms to change the direction of gaze in conjunction with orthokeratology to control patients with myopic progression. Here, our theoretical research and ideas are provided in the hope that more optometrists will participate. Keywords: Myopia; Control; Orthokeratology; Prism Development of Myopia and Its Optical Intervention Xu Yuan, Zhao Wei From the Department of Ophthalmology, Xijing Hospital, Fourth Military Medical University 710032 Xi’an, China. Military Medical University 710032 Xi’an, Shaanxi Province, China Abstract: This review summarized literature about the development of myopia, epidemiologic study of myopia, recurrence of accommodation theory, early onset myopia (EOM) and late onset myopia (LOM), persistent near work with myopia, and experiment about myopia. It was proposed that development of myopia might be related with many factors. Some opinions were discussed considering clinical practice basing attempts on the development of myopia. It was proposed that development of myopia might be related with many factors. Some opinions were discussed considering clinical practice basing attempts to intervene development of myopia by accommodation theory. A method to control the development of myopia was attempted, which applied a prism to change the direction of visual fixation combined spherical lens. Key words: myopia, control, spherical lens, prism Myopia, a phenomenon that has kept pace with human civilization, has caused many inconveniences to people. Myopia is a product of human’s adaptation to nature, and low myopia is not inferior to orthopia in some aspects, such as the adaptation to long-time close work and the convenience of near eye use after presbyopia. When myopia is stable, wearing a pair of glasses is not a big problem. However, the continued increase in myopia causes many people to develop complications without realizing it. The number of people with low vision and blindness due to these complications is second only to cataracts and glaucoma in China. As the incidence of myopia continues to grow in China and as this group of myopic people ages, the number of people with permanent visual impairment due to their complications is likely to increase dramatically, potentially surpassing cataract and glaucoma as the number one killer of vision. 1 Studies related to the onset and development of myopia In the 1960s, according to the hypothesis of accommodation tension, it was believed that excessive near-eye work during myopia can cause accommodation fatigue, loss of flexibility of the ciliary muscles, and inability to relax sufficiently during distance vision, hence the development of pseudomyopia; and it was noted that myopia is accompanied by a temporary far-distance shift, i.e., an aggravation of myopia, after sustained near-eye use[1]. Ciuffreda et al.[1] (1998) found that myopia induced -0.35 D of myopia after 10 min of sustained near eye use (equivalent to a 5D accommodation load), which gradually disappeared after 1-2 min, and was not present in orthokeratology.Vera-Diaz et al.[2] (2002) reported that temporary myopia induced by 10 min of 4D accommodation exceeded static myopia in progressive myopia and even exceeded orthokeratology. myopia and even more than orthopia.Ciuffreda et al[3] (2002) found that reading continuously for 4 h induced a tendency for temporary refractive conversion to myopia also in myopia, but not in hyperopia.Wolffsohn et al[4] (2003) found that this phenomenon was more pronounced in the yellow race, in which myopia is prevalent. This phenomenon was more pronounced in eyes with progressive myopia and late onset myopia (LOM) than in eyes with stationary myopia and early onset myopia (where genetic factors may be more important). This study is direct evidence that conditioning factors can induce myopia in humans and suggests that some individuals may be more sensitive to conditioning loads, i.e., prone to myopia. So, what exactly are those characteristics that these individuals would exhibit? The focus of research has been on the normal vision population, especially those who have maintained normal vision through advanced education. In the past 30 years, myopia research has emphasized animal experimental research, clinical research has not been given due attention, and to a certain extent, the differences between experimental animals and human beings have been ignored, and the results obtained from animal experiments used in the clinic have not received the expected results. Functional studies (e.g., temporary myopia caused by persistent myopia, etc.), optical index analysis, biochemical testing, and pathological studies (including ultrastructure, immunohistochemistry, molecular pathology, and other means) have gradually become the main direction of myopia research [5]. 2 Epidemiologic studies of myopia Epidemiologic investigations have confirmed that the occurrence of myopia is related to near eye work. Higher prevalence of myopia is associated with higher near eye workloads, and this phenomenon persists after adjusting for family history [6,7]. In cohort surveys, higher prevalence of myopia was found in those with higher education, which may be related to higher near eye workload, and higher prevalence of myopia in those with higher income may be due to their income being related to their education [8,9]. The difference in the prevalence of myopia between urban and rural children may also be related to higher near eye workload in urban areas [10]]. The United Nations Health Organization arranged for a population-based census to be conducted in China, Chile, and Nepal, and found that the prevalence of myopia among residents of a district in Beijing increased annually from 5 to 15 years of age, with an increase that exceeded that of Chile and far exceeded that of Nepal [11]. A 2-year follow-up confirmed that this trend still exists [12]. The prevalence of myopia in Asian yellow populations (China, Japan, and Singapore, among others) has been increasing in recent years, and the prevalence of myopia in adult populations in both Japan and Singapore exceeds that in European and American populations [8,9]. In contrast, the prevalence of myopia in Europe and the United States has remained relatively stable [13]. The vast majority of scholars now accept that the development of myopia is related to both genetics and the environment. The mode of inheritance is also mostly considered to be polygenic, i.e., each group of genes acts minimally and cumulatively. In recent years, higher genetic indices of myopia have been calculated in Western countries based on twin studies or family aggregation analysis, but the role of environmental factors is also still recognized, especially in Eastern countries [14]. 21st-century work in this field has mainly verified phenomena observed in the 20th century, with little exploration of new and unknown environmental factors [5]. 3 The Return of the Regulation Theory Experimental animal studies in the 20th century confirmed that environmental factors play a role in the development of myopia, emphasized myopia-causing changes dominated by retinal signals, and discovered many biochemical substances that influence the development of myopia, which gave a strong impetus to the study of the pathogenesis of myopia. However, when applying the results to clinical practice, researchers have not sufficiently recognized the species differences between humans and experimental animals (especially the differences between chickens and mammals) and the age differences (most experimental animals are juveniles, while the age of high incidence of myopia in humans is adolescence); they have not sufficiently understood the differences between the two intrinsically different types of myopia (formative deprivation myopia is extremely rare in humans, and is only occasionally seen in individual cases of high blepharoplasty in young children and in those with refractive media turbidity; the vast majority of human myopia is closer to defocus myopia), has also led to some misperceptions. In the past, in the study of the mechanism of myopia, it was observed that visual deprivation myopia could still occur in chickens after severing the optic nerve, destroying the Edinger-Westphal nucleus, and severing the ciliary and choroidal nerves, thus denying the role of modulation in the development of myopia. However, in fact: ① most human myopia is defocus myopia. Cutting the optic nerve of experimental animals has an inhibitory effect on defocus myopia, which indicates the importance of the center in myopia. The fact that myopia still occurs in experimental animals after destroying the Edinger-Westphal nucleus only suggests that accommodation is not the only mechanism of myopia, but it does not mean that accommodation does not play a role in myopia under normal conditions. After severing the ciliary and choroidal nerves, myopia could still occur in chickens, but myopic refraction was significantly reduced, suggesting that the efferent nerves still play a role in myopia [14]. The recent findings in experimental animals that accommodation plays a role in the refractive changes induced by the dual visual planes [15] and the finding of transient myopia induced by persistent myopia in clinical studies [2,3] have reawakened the attention of researchers to the mechanisms of accommodation. 4 Early-onset myopia and LOM A recent myopia classification system is based on age-related myopia incidence and age of onset. Early-onset myopia is the most common type of myopia, with onset between the ages of 6 and 15 years, and once it occurs, myopia continues to increase until it stabilizes closer to the age of 20 years.The onset of myopia after the age of 17 years is referred to as LOM, and most of this type of myopia does not progress as rapidly, and changes in the average myopia are not as pronounced as those in early-onset myopia.4 The most common type of myopia is early-onset myopia. The distinction between early-onset myopia and LOM is based on the fact that myopia in children tends to stop at age 16 or 17 years, when overall body development has essentially stopped. 5 Constant near work and myopia There are two types of myopia caused by constant near work: temporary myopia and permanent myopia. Temporary myopia is when the far point is temporarily moved closer resulting in a refractive state that resembles myopia, whereas examination for ciliary muscle paralysis will reveal that the true refractive state is hyperopia or hyperopia. Many studies of permanent myopia have demonstrated a strong association with near work, and Zadnik et al [16] concluded that the best model for predicting refractive error should take into account not only the parents’ history of refractive error, but also the child’s own near work. And it is also of great interest to study the myopia of college students and those who work in near work, as such studies reveal that a great deal of near work is directly related to the development of myopia in adults. Because myopia development in the LOM is closely related to the near-visual environment, studies of people with myopia caused by near work may offer the possibility of investigating the ocular components and oculomotor mechanisms that contribute to the development of myopia. Because near work includes enhanced amounts of accommodation and vergence, it is important to investigate the role of accommodation and vergence and the entire oculomotor system in the development of myopia. Accommodation and vergence are fundamental elements in the oculomotor system’s mechanism of near work, and they both combine to produce a monocularly clear image in the binocular state. Based on Westheimer’s pioneering research, feedback control theory has been used to produce models that describe the static and dynamic responses of the accommodation and vergence systems. The essential feature of all models is that modulation initiated by fuzzy imaging and convergence initiated by lavish opening are controlled by two negative feedback loops, and the interaction between the two is represented by two feedback crossings of the control output. In this way, modulation control can trigger a convergence response (modulated convergence or AC) and, conversely, convergence control can trigger a modulation response (convergent adjustment or CA). The acquisition of AC or CA is represented by AC/A or CA/C, respectively. Either the modulation system or the vergence system can be separated by opening the feedback loop, e.g., covering a glance opens the vergence feedback loop, or using a pinhole pupil opens the modulation feedback loop. Control of the regulatory convergence (ACG) can be estimated from the magnitude of the stimulus/response function of regulation in the open-loop convergence state, and control of the convergence system (VCG) from the gaze lavage curve in the open-loop regulatory state; whereas regulation and convergence measured in the dark is the physiologic resting state. Temporary myopia due to near work is considered to be a temporary shift of the far point after sustained near eye use. This type of myopia is considered the first stage of refractive error. Unlike true myopia, pseudomyopia is a temporary form of myopia in which the far point continues to move closer, and when examined without ciliary muscle paralysis pseudomyopia is a myopic refractive error. However, pseudomyopia is reversible because the refraction in pseudomyopia is orthoptic when examined after ciliary muscle paralysis, suggesting that the temporary myopia is due to either accommodation spasm or ciliary muscle spasm. Transient myopia due to near work has been extensively studied in the laboratory. Since the confirmation of the dark focus as a sign of accommodation rest since 1960-1970, a preliminary approach to speculate on the oculomotor/ocular component was proposed: a person with a dark focus that is too far away (low refractive error) will exert more oculomotor force to focus on a myopic target during near work than a person with a dark focus that is close. However, similar studies have had varying results, with some finding that the dark focus of the LOM is significantly farther away than that of the orthokeratology eye, while others have concluded that there is no significant difference between the two [17].The diversity of findings is emphasized by Gilinartin and Bullimore’s single study. In their study, the dark focus values were the same for the orthoptic and LOM groups, and the result seems to be as follows: although the dark focus of a given individual is relatively stable, inward proximity work induces an inward shift of the dark focus, which continues for a period of time up to the point when the proximity work stops for a period of time, and such a shift is referred to as accommodative adaptation or accommodative lag. Since accommodation hysteresis refers to a sustained increase in ciliary muscle tone over a long period of time, it is conceivable that this hysteresis is associated with myopia induced by near work [17,18]. However, studies of accommodative adaptation between refractive groups have yielded different results. It has been reported that the LOM group showed greater accommodative adaptation than other types of refractive groups, but other studies did not find differences between the orthokeratology group and the LOM group. Although all of these studies were designed to identify differences in dark focus across refractive groups, because they were cross-sectional or retrospective, it is not possible to determine whether the differences in dark focus observed in these subjects were the cause of myopia occurrence or a consequence of myopia [19-21]. The same problem described above exists for the comparison of differences in oculomotor parameters between refractive groups cited in the following paragraphs, where Jiang conducted a longitudinal study and found that dark focus values were lower in LOM than in orthokeratology. However, this low dark focus was altered when a person’s myopia progressed to permanent myopia. Instead, orthopneic people with high dark focus values were at risk of developing myopia. It is clear that a far dark focus is evidence of accommodation spasm or hysteresis and can lead to the development of myopia [22]. McBrien and Millodot recorded the regression process of dark focus after sustained near work in the orthokeratology and LOM groups, and they were unable to determine the rate of regression in the orthokeratology group because there was almost no change in the dark focus of these subjects after near work, whereas in the LOM group there was a significant shift of the dark focus closer to the dark focus after near work, and there was no significant regression process of the dark focus for 15 min after the end of the near work [ 19,20].Rosenfield and Gilmartin found no significant difference between the orthokeratology group and the LOM group after relatively short periods (15, 30, and 45 s) of fixation on a proximal reticle (3D) [23,24], however, Gilmartin and Bullimore reported that the dark focus regression rate of the LOM group after 20 min of fixation on the same proximal reticle was was significantly lower than that of the orthoptic group, and this difference was even more pronounced if the near visual standard was increased to 5 D. Strang et al. also showed that dark focus regression was slower in the LOM group after adaptation [26]. In conclusion, all these studies indicate that the time constant for dark focus regression after accommodation adaptation is longer in the LOM group than in the orthoptic group when sustained proximity work is performed or when high accommodation is required. It is possible that the vagal inhibition of the ciliary muscle is weaker in the LOM group than in the orthoptic group. If this phenomenon existed before the onset of myopia, it would be a precursor to the triggering of adjustment lag under near working conditions [27]. 6 Experimental studies on defocus McFadden et al. gave guinea pigs to wear concave lenses for 6 weeks then they were able to make a relatively significant change in their eye axis length [28]. Ouyang Zhaohu et al. also observed that guinea pigs showed different axial changes and refractive changes over time using convex and concave lenses of different power [29,30]. 7 Attempts to Intervene in the Development of Myopia Based on the Theory of Adjustment Based on the theory of adjustment, many scholars both at home and abroad have made a lot of attempts in addressing the effects of adjustment on myopia. 7.1 Progressive multifocal lenses (PAL) Leung JT, Brown B (reported in 1999) conducted a 2-year study in Hong Kong with a small sample (N = 168) with progressive multifocal lenses in an attempt to improve the clarity of the imaging on the retina, (because progressive multifocal lenses provide clear vision in the distance, intermediate, and near regions in a continuous manner). Chinese children in the study were fitted with progressive lenses for 2 years, resulting in significantly less myopic progression and ocular axis increase than children fitted with monofocal lenses. Children aged 9 to 12 years were selected for the experiment, randomized into groups, and followed up every 6 months. It was concluded that progressive lenses could alleviate myopia progression [31]. In 1998, led by the U.S. National Eye Institute, in conjunction with the New England College of Optometry, the University of Houston College of Optometry and four other institutions of higher education, a randomized, double-blind method was used to conduct a study of progressive lenses to control myopia in nearly 400 U.S. children with myopia, which was controlled by single-optical lenses [32,33]. During the same period, Wenzhou Medical College and Beijing Tongren Hospital and Shanghai Wugong Hospital in China also used a similar experimental design to study 300 Chinese myopic children with progressive lenses to control myopia. The same conclusion was obtained that progressive lenses could alleviate the progression of myopia. For PAL used for myopia control in adolescents, various manufacturers in the current market have used fixed down-added diopters (ADD), mostly +1.50 D. Overseas studies have used different ADDs, but the results have mostly used 1.50-2.00 D, which is considered to be more scientific. The control of myopia progression by PAL is still controversial because there are still conflicting results in different countries and regional populations, and in some regions researchers have found that the use of PAL in myopia progressors with internal oblique myopia can delay some myopia progression [34]; and for most of the general adolescent myopia, it does not have a great effect. PAL mainly optically alters accommodation and changes eye movement parameters such as vergence, so its use is limited, and some scholars’ have even suggested that PAL may negatively affect visual development such as stereopsis in children. 7.2 Myopic regression lenses A type of myopic regression lenses tried in China at the same time as the student’s progressive multifocal lenses, taking into account the effect of convergence on accommodation, has obtained a recent improvement in visual acuity by adding prisms facing inward in the base direction to the near-fog vision therapy [35,36]. Seduced by this effect, a variety of myopic regression products were developed in an attempt to get patients to remove their glasses, but it was not to be, and these recent improvements in visual acuity were quickly overwhelmed by the subsequent development of myopia, which prevented the realization of myopic regression. It has been proven that without clear distance vision, myopia cannot be controlled. Would such regression lenses for myopia control make a difference? Since it is not possible to provide clear gaze without taking into account the astigmatism of each pair of spectacles, and since the causes of myopia progression vary, whether abandoning the use of a myopic patient with external occultation will aggravate the effect of the external occultation and make the progression of myopia even faster after a long period of time of use of a prism with the base facing inward has not yet been reported in long term observation. 7.3 READING ADDITIONAL LENSES Guided by the above theory of accommodation, it was envisioned that common characteristics might be found in a population of people with more than a bachelor’s degree education who still maintain normal vision. After investigating various refractive parameters in more than 100 such normal vision populations and comparing them with a large number of myopic patients [37], no significant differences were found other than the known differences in refractive error and degree of external occult obliquity, and data from larger samples may be needed. It has been seen in a large number of myopic investigations that many progressive myopes, exhibit varying degrees of fatigue symptoms, most of these fatigue symptoms appear after prolonged periods of reading, and for each fatigue symptom some obvious triggers may be found. So, can addressing these triggers play a role in limiting the progression of myopia? By chance, we added bottom-facing 5Δ prisms to the original +1.50DS reading glasses for a patient who could not find a specific cause of visual fatigue, and the symptoms of visual fatigue were relieved. Inspired by this phenomenon, a reading add-on mirror was designed for improving reading fatigue symptoms, and satisfactory results were obtained. In the observation, it was found [38] that this reading add-on lens also provided some relief for some patients with progressive myopia. As early as in the 1960s, there were studies suggesting that reducing myopia degree or increasing hyperopia degree during close reading can effectively prevent myopia from occurring or slow down the progression of myopia, but the past research data have some design flaws, such as reasonable design of the control group, adequate longitudinal observations, standardization and uniformity of testing instruments or standardization of testing instruments, and so on. There is no conclusive information to prove that this method can prevent the onset of myopia or slow down the progression of myopia. However, as it can relax the adjustment of close reading, based on the “adjustment theory” of myopia occurrence and development, it has the value of further research. After searching, we have not yet seen any attempts to control myopia progression with a downward-facing prism. Under normal conditions, binocular accommodation increases as the gaze point moves from far to near and both eyes turn inward. Proper convergence is a prerequisite for maintaining normal visual function in both eyes. People with excessive convergence often experience eye discomfort and headaches after short periods of reading, and occasional blurred or double vision in near work. Excessive convergence is essentially occultation-free at distance gaze, but internal occultation occurs at near gaze with an increased AC/A ratio (usually greater than 6Δ). Reading Plus (+1.50Ds) can drastically alter convergence and alleviate the symptoms caused by convergence hypermetropia. In this case, it has been found that myopic progression is significantly reduced with this add-on, i.e., it is most effective in internal esotropia. For most of the myopic eyes with external occultation, the use of a base-facing nasal prism with a +1.50 DS add-on lens not only improved the fatigue symptoms that many myopic eyes are prone to after reading for a long period of time, but also alleviated the progression of myopia, and the naked-eye visual acuity of some patients was also improved. However, this measure did not show desirable results after prolonged use. On the contrary, some patients even showed accelerated progression of myopia after abandoning its use. As for the patients who were clinically found to have no obvious eye position abnormality and still showed a sharp progression of myopia, the observation of their reading habits revealed that the gazing habits of some patients were not excessively lowered, but rather, they were sitting in a straight posture at the request of their parents and teachers, but with their eyes excessively turned downward. As shown in Fig. 1: Fig. 1 Downward turning of the eyeballs while reading The chance of visual fatigue increases when reading for a long time in this posture. The following factors were analyzed: first, the role of the lower eyelid. When gazing downward, the lower cornea is deformed due to the pressure of the lower lid on the cornea, which increases the refractive power in this area. In aberration, this may be manifested as a higher-order aberration that is concave above and convex below. Second, accommodation may be enhanced due to the influence of the inferior rectus as well as the internal rectus muscles in both eyes. When both eyes gaze downward, accommodation is increased due to the constant impulses of the bilateral inferior rectus muscles, which habitually increase the action of the internal rectus muscles, whose impulses match the impulses of accommodation. Third, coma arises after the direction of gaze has deviated from the optical axis. Again, this affects visual quality as a higher order aberration and produces fatigue. Under normal circumstances optometry only measures the refractive state under direct horizontal vision, whereas underneath gaze may have an effect on the refractive power of the human eye for the above reasons. In order to allow these patients to read without having to lower their heads excessively (a lowering motion, although conducive to improving the direction of gaze, tends to reduce the reading distance), and without altering the refractive state by raising the head to gaze downward, we tried a prism with a downward facing base for this purpose. As shown in Figure 2: Figure 2 Role of prisms The excessive downward rotation of the eyeball is reduced by attaching a prism to the reading mirror to assist downward gaze. This type of reading add-on lens made of an orthoglobe lens with a bottom-facing downward-facing prism provides some relief from reading fatigue symptoms and thus serves to control the progression of these patients who do not have significant ocular positional abnormalities and who have progressed in myopia. Can some attempts be made with this method for the majority of myopia progressors who present with occult external strabismus? Theoretically, this method does not alter binocular accommodation and dispersion with continued use, and certainly does not rebound after abandonment, so it should be worth a try. 8 Summary The optical mechanism of myopia is well understood, but its etiology, natural history, and best methods of prevention are not yet fully understood. Moderating factors are once again being recognized, and the involvement of factors such as eye movement parameters and occult strabismus complicate the mechanism of myopia development. Due to the complexity of the causes of myopia and the many factors that trigger the progression of myopia, it is impossible to solve all the problems with one method, and the indications for each method need to be confirmed by a large number of practices. In our clinical practice, we have tried different methods for myopic progression in patients with different conditions, and we have obtained preliminary results, but we still need a lot of controlled observations and longitudinal studies. Here, our theoretical studies and ideas are provided in the hope that more optometrists will be involved to find the best myopia control program in a large number of practices. References [1] Ciuffreda KJ, Wallis DM. Myopes show increased susceptibility to nearwork aftereffects[J]. Invest Ophthalmol Vis Sci 1998;39(10):1797-1803. [2] Vera-Diaz FA, Strang NC, Winn B. Nearwork induced transient myopia during myopia progression[J]. . Curr Eye Res 2002;24(4):289-295. [3] Ciuffreda KJ, Lee M. Differential refractive susceptibility to sustained nearwork[J]. Ophthalmic Physiol Opt 2002;22(5):372-379. [4] Wolffsohn JS, Gilmartin B, Li RW, et al. Nearwork-induced transient myopia in preadolescent Hong Kong Chinese[J]. Invest Ophthalmol Vis Sci 2003;44(5):2284-2289. [5] Hu Xuan-Ning. Progress in the etiology and pathogenesis of myopia, 2004. [6] Saw SM, Zhang MZ, Hong RZ, Fu ZF, Pang MH, Tan DT. Near-work activity, night-lights, and myopia in the Singapore-China study[J]. . Arch Ophthalmol 2002;120(5):620-627. [7] Mutti DO, Mitchell GL, Moeschberger ML, Jones LA, Zadnik K. Parental myopia, near work, school achievement, and children “s refractive error and children “s refractive error[J]. Invest Ophthalmol Vis Sci 2002;43(12):3633-3640. [8] Wong TY, Foster PJ, Hee J, et al. Prevalence and risk factors for refractive errors in adult Chinese in Singapore[J]. Invest Ophthalmol Vis Sci 2000;41(9):2486-2494. [9] Shimizu N, Nomura H, Ando F, Niino N, Miyake Y, Shimokata H. Refractive errors and factors associated with myopia in an adult Japanese population[J]. Jpn J Ophthalmol 2003;47(1):6-12. [10] Zhang MZ Fu ZF et al. Relationship between near eye use and myopia in urban and rural children in Xiamen[J]. Journal of Ophthalmology 2002:4. [11] Zhao J, Pan X, Sui R, Munoz SR, Sperduto RD, Ellwein LB. Refractive Error Study in Children: results from Shunyi District, China[J]. Am J Ophthalmol 2000;129(4):427-435. [12] Zhao J, Mao J, Luo R, Li F, Munoz SR, Ellwein LB. The progression of refractive error in school-age children. Shunyi district, China[J]. Am J Ophthalmol 2002;134(5):735-743. [13] Mutti DO, Zadnik K. Age-related decreases in the prevalence of myopia: longitudinal change or cohort effect? [J]. Invest Ophthalmol Vis Sci 2000;41(8):2103-2107. [14] Hammond CJ, Snieder H, Gilbert CE, Spector TD. Genes and environment in refractive error: the twin eye study[J]. Invest Ophthalmol Vis Sci 2001;42(6):1232-1236. [15] Wildsoet CF, Schmid KL. Emmetropization in chicks uses optical vergence and relative distance cues to decode defocus[J]. Vision Res 2001;41(24):3197-3204. [16] Rah MJ, Mitchell GL, Mutti DO, Zadnik K. Levels of agreement between parents” and children “s reports of near work [J]. Ophthalmic Epidemiol 2002;9(3):191-203. [17] Gilmartin B. Myopia: precedents for research in the twenty-first century [J]. Clin Experiment Ophthalmol 2004;32(3):305-324. [18] Bullimore MA, Reuter KS, Jones LA, Mitchell GL, Zoz J, Rah MJ. The Study of Progression of Adult Nearsightedness (SPAN): design and baseline characteristics[J]. Optom Vis Sci 2006;83(8):594-604. [19] McBrien NA, Gentle A, Cottriall C. Optical correction of induced axial myopia in the tree shrew: implications for emmetropization[J]. Optom Vis Sci 1999;76(6):419-427. [20] Adler D, Millodot M. The possible effect of undercorrection on myopic progression in children[J]. Clin Exp Optom 2006;89(5):315-321. [21] Woung LC, Lue YF, Shih YF. Accommodation and pupillary response in early-onset myopia among schoolchildren[J]. . Optom Vis Sci 1998;75(8):611-616. [22] Jiang BC, White JM. Effect of accommodative adaptation on static and dynamic accommodation in emmetropia and late-onset myopia[J]. Optom Vis Sci 1999;76(5):295-302. [23] Rosenfield M, Carrel MF. Effect of near-vision addition lenses on the accuracy of the accommodative response[J]. . Optometry 2001;72(1):19-24. [24] Gilmartin B. Myopia: pathways to therapy[J]. Optom Vis Sci 2004;81(1):1-3. [25] Bullimore MA, Zadnik K. Consistency between visual acuity scores obtained at different test distances[J]. Arch Ophthalmol 2004;122(11):1729-1731; author reply 1731-1722. [26] Strang NC, Winn B, Bradley A. The role of neural and optical factors in limiting visual resolution in myopia[J]. Vision Res 1998;38(11):1713-1721. [27] Jiang BC. Oculomotor parameters in temporary and permanent myopia induced by near work (Part I)[J]. Journal of Ophthalmology 1999:2. [28] McFadden SA, Howlett MH, Mertz JR. Retinoic acid signals the direction of ocular elongation in the guinea pig eye[J]. Vision Res 2004;44(7):643-653. [29] Ouyang Chaohu Hu WZ et al. Effects of concave lenses on the growth and refractive development of the guinea pig eye[J]. Ophthalmology Research 2002:3. [30] Cui Dongmei Gao Yan Wu Kaili Huang Qiang Zeng. Effects of lenses on the refractive error and axial development of guinea pig eyes[J]. Journal of Shandong University: Medical Edition 2006:3. [31] Leung JT, Brown B. Progression of myopia in Hong Kong Chinese schoolchildren is slowed by wearing progressive lenses[J]. Optom Vis Sci 1999;76(6):346-354. [32] Hung GK, Ciuffreda KJ. Quantitative analysis of the effect of near lens addition on accommodation and myopigenesis[J]. Curr Eye Res 2000;20(4):293-312. [33] Gwiazda JE, Hyman L, Norton TT, et al. Accommodation and related risk factors associated with myopia progression and their interaction with treatment in COMET children[J]. Invest Ophthalmol Vis Sci 2004;45(7):2143-2151. [34] Zhang H Gong. Effects of progressive multifocal lenses on the development of myopia in adolescents[J]. Chinese Journal of Practical Ophthalmology 2005:2. [35] Li Xujuan Zhang Jinsong Zhang. Can the onset and development of myopia be prevented? –A report on the clinical application of myopic regression lenses[J]. Journal of Ocular Trauma and Occupational Ophthalmology 2008:4. [36] Yang QX Zhang XH Li J. Tang Y. Chang Q. Zhu. Clinical observation of myopic regression lenses in controlling myopia development in adolescents[J]. International Journal of Ophthalmology 2008:2. [37] Xu Yuan, Zhao Wei, Hui Yannian, Tian Yanming, Zhou Fanghong, Gao. Corneal eccentricity and related parameters in 393 cases of myopia[J]. Journal of the Fourth Military Medical University 2003:2. [38] Xu Yuan. A method and device for controlling the increase of longitudinal modulus in near-use add-on lenses. Patent Notice of the State Intellectual Property Office of the People’s Republic of China, 2006.