Axial Length Shortening After Orthokeratology and Its Relationship With Myopic Control

Axial Length Shortening After Orthokeratology and Its Relationship With Myopic Control | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Axial Length Shortening After Orthokeratology and Its Relationship With Myopic Control Anken Wang, Li Shen, Jiaying Wang, Zhehuan Zhang, Weiming Yang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1193988/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Purpose : To determine the pattern of axial variation in subjects with initial shortened axial length during the entire period of orthokeratology and to discuss the possibility of shortened AL after one month of orthokeratology becoming a predictor of myopia control. Method : This study retrospectively included 106 children with myopia aged 8 to 14 wearing OK lenses. eyes with shortened axial length (AL) at the first-month visit were enrolled in the axial length shortening (ALS) group, and 52 eyes without shortened AL were enrolled in the no axial length shortening (NALS) group. Axial length and refractive error at baseline and within the entire period of orthokeratology (20 months), including fitting, washout period and re-wear, were measured. Results : In the ALS group, AL became longer after shortening and slowly exceeded baseline; afterward, AL experienced a rebound during the washout period and shortened again if OK lenses were re-worn. After washout period, significant difference in AL (ALS:0.28±0.19 mm, NALS: 0.52±0.17 mm) and spherical equivalent(ALS:-0.43±0.44D, NALS:-0.91±0.40D) between the two groups were found( P ＜0.05). The changes in AL and SE were both significantly correlated with the changes in AL at the first-month visit ( P ＜0.05). Conclusion : After AL is shortened in the initial stage of orthokeratology, it will experience a rapid rebound during the washout period, and the shortening can reappear when re-wearing OK lenses. Hence, only including the washout period can we make an objective evaluation of orthokeratology. In addition, the existence and degree of axial shortening can be used as a predictor of long-term myopia development. Myopia Orthokeratology Axial length Myopia control Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Currently, myopia affects approximately 90% of teenagers and young adults in China and 28% of the global population, showing a dramatic increase in the past 50 years. Holden et al. predicted that there will be approximately 50% of the global population with myopia by 2050 without any interventions for myopia control [ 1 , 2 ] . Pharmacological and optical methods have been developed to control myopia progression, and among these methods, orthokeratology (OK) has been proven to be an effective method [ 3 – 5 ] . After years of research, the main hypothesis about the mechanism appears to be that orthokeratology increases peripheral myopic defocus to reduce stimuli for axial elongation [ 6 – 8 ] . Interestingly, several studies showed statistically significant axial length (AL) shortening during the study period, especially in the early stage of the trials [ 8 – 15 ] . The occurrences of shortened axial length have been studied by an increasing number of scholars, and it has been proposed that central corneal thinning combined with choroidal thickening contributes to apparent axial length shortening [ 14 – 16 ] . However, few studies have specifically observed people with shortened AL or discussed the relationship between shortened AL and the effect of myopia control. Therefore, we conducted this retrospective study to determine the pattern of axial change in subjects with initially shortened AL during the entire period of wearing OK lenses, including 1 month of discontinuation and 1 month after re-wear, and to compare the change in axial length and refractive error between the subjects with shortened AL and nonshortened AL who both underwent orthokeratology. Additionally, individual variability in the effects of orthokeratology on myopia progression does exist, so it is crucial to predict the effect of orthokeratology on individuals as early as possible. This article will also discuss the possibility that shortened AL after orthokeratology becomes a predictor of myopia control. The authors report no conflicts of interest. Methods subjects In this retrospective study, we reviewed all the patients who started orthokeratology between January 2015 and December 2018 in the Children’s Hospital of Fudan University. Clinical pathway: At the first visit, all the patients underwent comprehensive examinations, including cycloplegic refraction, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), extraocular movements, corneal light reflection test, intraocular pressure, slit-lamp examination, fluorescein staining, corneal endothelial cell density, axial length, fundus photo and corneal topography. Appropriate prescriptions for OK lenses were provided to the participants by different experienced doctors, and the patients were asked to wear OK lenses no fewer than 8 h per night and follow-up one week and one month (the second month after fitting because it usually takes approximately a month from the time the prescription is sent to the manufacturing corporation to the time patients receive their lenses) after wearing. If there were no problems, they were then asked to visit every 3 months afterward. At every subsequent follow-up, they underwent a detailed list of ocular examinations, including corneal light reflection tests, slit-lamp evaluations, fluorescein staining, axial length, UCVA and corneal topography. After 1.5 years of wearing OK lenses (the 19th month after fitting), all patients were required to change the lenses after one month of washout (no OK lens wearing). After the wash-out period (the 20th month after fitting), we repeated all the previous examinations before the first wearing, including cycloplegic refraction. All subjects were treated according to the tenets of the Declaration of Helsinki. When reviewing cases, the inclusion criteria included the following: (1) The spherical refractive error must be less than −5.00 D with regular astigmatism of −1.50 D or less, and the BCVA of logMAR (logarithm of the minimum angle of resolution) must be 0.0 or better before treatment. (2) The subjects were followed up on schedule for at least 6 months, and the data were completed, especially the axial length of each follow-up and the results of two cycloplegic refractions. (3) The UCVA of each eye must be better than 0.1 (LogMar) after removal of lenses at each follow-up. (4) After wearing the lens for one month, the eyes with axial length shortening were assigned to the axial length shortening (ALS) group, and the eyes without axial length shortening were assigned to the no axial length shortening (NALS) group. The exclusion criteria were as follows: (1) The subjects included should not have obvious glare, duplication or any other corneal complications. (2) Subjects with underlying ocular disease, such as obvious tropia, retinopathy, prematurity, neonatal problems, history of genetic disease that might affect refractive development, or other system disorders associated with myopia, were excluded. (3) Decentrations larger than 1 mm was found in at least two consecutive visits. (4) Combined with other treatments, such as low-concentration atropine eye drops. Lenses All patients were fitted with OK lenses (α ORTHO-K®, ALPHA Corp, Nagoya, Japan, with a nominal Dk of 104 × 10 −11 (cm 2 /s) (mL O 2 /mL·mmHg) or LUCID ORTHO‐K® lenses, LUCID Corp, Fenghua County, Korea, with a nominal Dk of 100 × 10 −11 (cm 2 /s) (mL O 2 /mL·mmHg)) according to the manufacturer's fitting instructions. The procedures for fitting, prescription, and replacement of OK lenses were all performed by experienced specialists. Measurements Cycloplegic refraction was measured two times by specialized technicians to ensure exactness. The K value was measured three times routinely with an autorefractor keratometer. (NIDEK, Co; LTD, Japan. Model: ARK-1). Axial length was measured three times routinely with an IOL-Master 500 (Carl Zeiss Meditec, Ag. jena, Germany). The examinations were performed by the same specialized technician, and the average value was recorded. Corneal profiles were measured with a Carl Zeiss ATLAS Corneal Topography System -9000 (Carl Zeiss Meditec, Inc. California, United States of America, Model 9000). Each of the profiles was the best-focus image (accuracy greater than 95%) from the four frames that were captured automatically. Statistical Analysis SPSS Statistics 24.0 (IBM Statistics, Armonk, NY) was used for statistical analysis of the ocular biometric parameters. The Shapiro–Wilk test was used to check the normality. The differences in parameters at baseline and changes in refractive power between the ALS group and NALS group were compared using independent t tests. A repeated measures analysis of variance (ANOVAs) was used to compare the change in AL over time between the two groups. If significant differences were found, post hoc tests with Bonferroni correction were performed to compare the differences between visits in the eyes of the ALS group and NALS group. A P value less than 0.05 was considered statistically significant. Results Subject Demographics A total of 106 subjects were enrolled in this study (54 in the ALS group and 52 in the NALS group). To avoid the influence between two paired eyes, only the right eye was included in this study if the lens was worn with both eyes. After exclusion, there were 54 eyes in the ALS group and 52 eyes in the NALS group. There was no significant difference in sex distribution between the two groups(ALS group: 22 eyes from male and 32 from female, NALS group: 19 eyes from male and 33 from female)according to the Mann–Whitney U test of independent sample༈ P =0.66). There was some difference in age between the two groups (ALS group: 9.63± 1.34, NALS group: 9.12± 1.41) according to the t test of independent samples (P=0.06). Parameter on baseline At baseline (the day of fitting), the axial length, spherical equivalent, spherical and regular astigmatism of the eyes from the ALS group were 24.68±0.90 mm (range 22.06 to 26.71 mm), -2.98±1.25 D (range −0.75 to −5.38 D), -2.68±1.14 D (range −0.75 to −5.00 D) and -0.60±0.58 D (range 0.00 to −1.50 D), respectively. Those in the eyes from the NALS group were 24.50±0.68 mm (range 23.38 to 26.03 mm), -2.60±1.02 D (range −0.75 to −4.88 D), -2.40±0.96 D (range −0.75 to −4.50 D) and -0.38±0.43 D (range 0.00 to −1.50 D), respectively. The difference between the two groups was not statistically significant by t test of independent samples in axial length ( p =0.24), spherical equivalent ( p =0.09) and spherical diopter ( p =0.18), but significant difference between the two groups was found in regular astigmatism ( p <0.05). Before orthokeratology, the difference between the two groups was not significantly different by independent-sample t test t in steep K ( p =0.33), flat K ( p =0.64), equivalent e value ( p =0.97), toric lens ( p =0.73) and diameter of lens ( p =0.25). There was no significant difference in the distribution of lens brand between the two groups by the Mann–Whitney U test of independent samples ( P =0.40). The biological parameters of the eyes and lens data are shown in Table 1 . Table 1 Differences in biological parameters and lenses between the ALS group and NALS group Parameter (Mean ± SD) ALS (n=54) NALS(n=52) p value Axial length(mm) 24.68±0.90 24.50±0.68 0.24 Spherical equivalent refractive error (D) -2.98±1.25 -2.60±1.02 0.09 Spherical refractive error (DS) -2.68±1.14 -2.40±0.96 0.18 Regular astigmatism (DC) -0.60±0.58 -0.38±0.43 <0.05 Equivalent e value 0.62±0.09 0.62±0.07 0.98 Steep K (D) 44.07±1.59 43.81±1.17 0.33 Flat K (D) 42.92±1.46 42.80±1.02 0.64 Toric Lens (D) -0.06±0.30 -0.04±0.19 0.73 Lens diameter(mm) 10.60±0.19 10.56±0.19 0.25 Grand of lenses* L:46; A:8 L:39; A:11 0.40 *: L=Lucid; A=Alpha Axial Change At first, the AL of the NALS group was slightly lower than that of the ALS group. Then, the AL of the ALS group was shortened after wearing lenses for one month(the 2nd month), while it was not shortened in NALS group at that time which was ascertained by standard of grouping. The axial length of the NALS group continued to increase and finally exceeded that of the ALS group due to the difference in elongation speed. In the end, explosive growth of the AL occurred in both groups after the wash-out period.After 20 monthsin total, the average AL of the ALS group grew from 24.68±0.90 mm to 24.96±0.87 mm(22.59 to 26.71 mm) and that of the NALS group grew from 24.50±0.68 mm to 25.03±0.70 mm(23.63 to 26.35 mm). The time course of axial length is shown in Figure 1. To show the changes in AL more clearly, we subsequently focused on the changes in AL compared with baseline. After wearing OK lenses for one month, the change in AL in the ALS group was -0.08±0.04 mm (-0.03 to -0.18 mm), while it was 0.05±0.03 mm (0.01 to 0.16 mm) in the NALS group. The mean AL of the ALS group did not return to baseline until the 7th month and began to exceed baseline before the 13th month. The mean AL of the NALS group grew as usual and was significantly faster than that of the ALS group at every follow-up visit by further multivariate analysis of variance with Bonferroni correction ( p<0.05 ). After a one- month washout period (without lenses), both the ALS and NALS groups showed an explosive rebound of AL. The rebound was 0.10±0.05 mm (0.00 to 0.24 mm) in the ALS group and 0.06±0.05 mm (-0.02 to 0.27 mm) in the NALS group. The amount of rebound in the two groups was significantly different by t test of independent samples ( p <0.05). There were significant differences in the change in axial length between the ALS group and NALS group over the course of the study (P<0.05, repeated measures ANOVA with Bonferroni correction), as depicted in Figure 2 . The difference in the change in AL between the two groups at every visit was statistically significant, as displayed in Figure 3 . After 20 months, the mean change in AL was 0.28±0.19 mm (-0.04 to -0.75 mm) in the ALS group and 0.52±0.17 mm (0.15 to 0.91 mm). Although the rebound was larger in the ALS group, lower AL growth over the total 20 months was shown in the ALS group. Paired t test was used to compare the amount of axial shortening (absolute value: 0.08±0.04 mm) after the first month of wearing and the axial rebound after a one-month wash-out (0.10±0.05 mm) in the ALS group, and we found that AL rebounded after wash-out even more than the shortening at the beginning( P <0.05). In addition, the difference in elongation of the AL after 1 month of first wearing (0.06±0.41 mm) and rebounding in the NALS group (0.06±0.05 mm) showed no significant difference by paired t test ( P =0.27). The absolute value of the mean change in AL during the shortening period (the 2nd month) and rebounding period (the 20th month) is shown in Figure 4 . The adjusted R 2 of the multiple linear regression model evaluating the predictive performance of the candidate predictors, including baseline age, baseline spherical equivalent (SE), baseline AL and the changes in AL at the first month visit (the 2nd month) for the 20-month AL change was 0.382 (F = 17.239, S=0.167, p < 0.001). The 20-month AL change was significantly correlated with baseline age (standardized β=-0.203, P<0.001) and the changes in AL at the first month visit (standardized β = 0.541, P 0.05). Simple linear regressions can be seen in Figure 5 (A) & (B). Change of refractive error The change in SE, spherical refractive error and regular astigmatism over time can be seen in Figure 6 . The SE of the ALS group decreased from -2.98±1.25 D to -3.41±1.23D (-1.13 to -5.50D) in 20 months, while the SE of the NALS group decreased from -2.60±1.02D to -3.51±1.03D(-1.50 to -5.75D) and the change in SE showed significant difference between the two groups(ALS group:-0.43±0.44D; NALS group:-0.91±0.40D) by independent-sample t test( P <0.05). The spherical refractive error of the ALS group decreased from-2.68±1.14D to -2.98±1.11D(-0.75 to -5.00D) in 20 months, while the spherical refractive error of NALS group decreased from -2.40±0.96D to -3.20±0.99D(-1.25 to -5.25D) and the change in spherical refractive error showed significant difference between the two groups(ALS group:-0.30±0.41D; NALS group:-0.80±0.39D) by independent-sample t test( P <0.05). The regular astigmatism of the ALS group decreased from -0.60±0.58D to -0.82±0.57D (-0.00 to -2.00D) in 20 months, while the regular astigmatism of NALS group decreased from -0.38±0.43D to -0.61±0.47D(-0.00 to -1.75D) and the change in regular astigmatism showed no significant difference between the two groups(ALS: -0.23±0.38D; NALS༚-0.23±0.36D) by independent-sample t test( P =0.99). The difference of those changes can be seen in Figure 7 . The adjusted R 2 of the multiple linear regression model evaluating the predictive performance of the candidate predictors (including the changes in AL at the first month, baseline age, baseline spherical equivalent (SE) and baseline AL) for changes in SE over 20 months was 0.293 (F = 11.903, S=0.4074, p < 0.001). The change in SE over 20 months was only significantly correlated with the changes in AL at the first month (standardized β=-0.500, P<0.001). Simple linear regressions can be seen in Figure 5 (C). Change of AL after re-wearing Among 54 eyes in the ALS group, 46 eyes (85.19%) were replaced with OK lenses and visited routinely after re-wearing for one month, while 29 eyes (55.77%) from the NALS group completed the above process. The change in AL over time in these 75 eyes is displayed in Figure 8 . Axial shortening appeared once again in the eyes from the ALS group after a month of re-wearing, following rebound, while it still did not occur in NALS, although the speed of axial elongation seemed to slow down. A paired t test was used to compare the amount of initial and second axial shortening in the ALS group, which showed a significant difference (initial: -0.08±0.04 mm, second: -0.04±0.05 mm; P<0.05 ). In addition, a significant difference was found between the speed of axial elongation in the NALS group during the same two periods (initial: 0.06±0.04 mm, second: 0.01±0.09 mm; P<0.05) Discussion Owing to the efficacious control of myopia progression in adolescents, there is a gradual incremental application of orthokeratology, which has been chosen by more than 1.5 million adolescents in China [ 17 ] . In recent years, many scholars have noticed the axial shortening of partial subjects at the initial stage of orthokeratology, which may explain why many studies have shown that the axial growth rate in the initial stage is much slower than that in the subsequent stage [ 18 – 21 ] . Some studies have indicated that the average axial length of the eye has a negative growth in the initial stage [ 8 – 15 ] . Therefore, it is necessary to clarify the pattern of axial shortening in the entire period of orthokeratology because neglecting the initial axial shortening and axial rebound after discontinued wear may cause overestimation of the control effect [ 14 ] . According to our study, the AL of the subjects with axial shortening started to grow after one month of wearing OK lenses and then did not return to baseline until the 7th month and began to exceed baseline at nearly the 13th month. With regard to the degree of axial shortening, the data of other studies can be seen in Table 2 [ 8 – 13 , 15 ] . Overall, the amount of axial shortening after one month of wearing in the ALS group of our study (0.08±0.04 mm) was between the results of these studies. As for the quite different results of those studies, on the one hand, is the inconsistent time of exam, and on the other hand is the nonnegligible individual differences, to be more specific, whether the axial length is shortened or not and the degree of shortening depends on the comparison between the causes of shortening and the growth of the axial length. Table 2 Degree of axial shortening according to some studies. Study Axial shortening(mm) Time Number of subjects Country or area Age(y) Inclusion criteria Instrument Gardner. et al. [ 8 ] 0.04 1 M 9 USA 11-15 -1.00~-4.00D Lenstar Ana González-Mesa. et al. [ 9 ] 0.157 1 M 34 Spain 18-30 -0.50~-4.50D IOL-Master António Queirós. et al. [ 10 ] approximately 0.02 1W 62 Asian 5-19 -1.00~-8.00D IOL-Master Lau, Jason K. et al. [ 11 ] approximately 0.25 1W 25 Hong Kong, China 6-10 -0.50~-4.00D Lenstar Lau, Jason K. et al. [ 12 ] 0.26± 0.41 1W 58 Hong Kong, China 6-10 -0.50~-4.00D Lenstar Michael J Lipson. et al. [ 13 ] 0.01±0.53 1Y 97 USA 7-14 -1.00~-6.50D A- scan Helen A. Swarbrick. et al. [ 15 ] 0.04±0.08 3 M 26 Australia 10-17 -1.00~-5.50D IOL-Master Regarding the reasons for the shortening of the AL, the main views by scholars are central corneal thinning combined with choroidal thickening [11,14−16] . Some data about central corneal thinning and choroidal thickening are listed in Table 3 [12,14,22−25] . Central corneal thinning was epithelial in origin, whereas mid-peripheral thickening was primarily stromal. The nature of the epithelial cellular changes underlying central epithelial thinning induced by orthokeratology remains obscure, although some possibilities have been revealed in the literature [ 23 , 25 ] . Axial length collected by A-scan or partial coherence interferometry (e.g., IOL-Master) is likely to be influenced by choroidal thickness because A-scan ultrasonography is an acoustic method in which axial length is defined as the distance between corneal anterior surface and vitreous-retina reflection peak and devices based on partial coherence interferometry, e.g., the IOL-Master, defines the axial length as the distance between anterior cornea and retinal pigment epithelium (RPE) [ 14 ] . Whether the OK lens will cause a tiny transshape of the eyeball needs further study, so strictly speaking, the change in AL mentioned in this study is actually based on the value measured by IOL-Master. Table 3 Data about central corneal thinning and choroidal thickening according to some studies Study central corneal thinning (mm) subfoveal choroid thickening (mm) Time Number of subjects Country or area Age(y) Inclusion criteria Lau, Jason K. et al. [ 12 ] 0.009±0.004 0.009±0.001 1W 58 Hong Kong, China 6-10 -0.50~-4.00D Zhouyue Li. et al. [ 22 ] -0.01±0.01 approximately 0.16 1 M 29 China 8-15 -1.00~-4.00D Alharbi and Swarbrick. [ 23 ] 0.016 ± 0.003 NA 1 M 18 Australia 22-29 -1.25~-4.00D Wan-Qing Jin. et al. [ 24 ] NA 0.006±0.007 3 M 30 China 9-14 -1.00~-6.00D Wook Kyum Kim. et al. [ 25 ] 0.006±0.005 NA 2 M 36 China 7-25 -0.50~-5.00D Zhi Chen. et al. [ 14 ] NA 0.022±0.025 3W 39 China 7-17 -1.00~-5.50D According to the study of Lau [ 11 ] , after the first week of lens wear, central corneal thinning (9 ± 4 µm) and choroid thickening (9 ± 12 µm) contributed to approximately 70% of the axial shortening (26 ± 41 µm). Moreover, the phenomenon of axial shortening is relatively underestimated in our opinion because most previous studies mixed subjects with shortened AL and those without shortened AL. Combined with the obvious axial shortening collected in the ALS group in this study (-0.08±0.04 mm), it can be claimed that central corneal thinning and choroid thickening do not provide entire explanations of axial shortening. Therefore, the mechanism of axial shortening needs further study. There was an obvious rebound in AL after discontinued wear of the lenses (wash-out period) in both groups, which corresponds with the recent discovery by Swarbrick [ 15 ] and Zhouyue Li [ 21 ] . This means that the data about AL after orthokeratology becomes relatively true only after the washout period. In other words, if we use the AL data measured without wash-out period as the cutoff point of the experiment about axial elongation after orthokeratology, we will likely overestimate the control effect of the OK-lens especially in the research between orthokeratology group and group without orthokeratology(e.g., blank control group, glasses, atropine, etc.). Other researchers have not observed that if OK lenses were re-worn after the washout period, the phenomenon of axial shortening would reappear, similar to the initial phenomenon. This means that axial shortening does repeat in some subjects; in addition, the observation of this phenomenon can now close the loop in the timeline. The differenrent size of the sample regarding re-wear between the two groups in this study may be because subjects with better control effect are more likely to continue, but the reduced sample size did not affect the repeating axial shortening. In the ALS group, the amount of axial shortening after re-wear for one month (20-22 M) was less than that of the first time (0-2 M). In this regard, we think it is caused by the remaining influence of the OK lens even after a one-month washout period In other words, the longer washout period required in clinical research needs further study. It has been suggested that myopia control with OK lenses is influenced by a number of factors, including patient age and sex, age at onset, degree of myopia, and various anatomic features, including corneal power and shape, anterior chamber depth, iris color, pupil diameter, corneal relative peripheral power change and choroidal thickness [21,26−29] . Although the effect of OK lenses is worth affirming, all these factors remind us that the mechanism by which orthokeratology might control myopia is complex and influenced by individual differences. Therefore, it is very important to predict the development of myopia as soon as possible and to filter OK-lens wearers who may still undergo rapid myopia progression. The comparative study of the ALS group and NALS group showed significantly slower growth in AL, SE and spherical refractive error in subjects with axial shortening. Because the final data are measured after the washout period, the accuracy of the results can be certain. Under such circumstances, we can conclude that axial shortening after one month of wearing as the indicator of the ideal control effect of myopia and subsequently predict myopia progression. Through a multiple linear regression model, our study showed a significant correlation between axial change after one month of wearing OK lenses and changes in both AL and SE. In other words, the more axial shortening at the beginning, the slower the progression of myopia; the more the AL increases after one month of wearing OK lenses, the faster myopia will progress. Although the degree of shortening itself is related to the speed of axial growth, it does not affect the correlation. In the clinic, if we encounter patients with axial shortening after the first month of orthokeratology, we can confidently instruct them to continue wearing OK lenses. In another situation, if we encounter patients with rapid growth of AL after the first month of orthokeratology, whether to combine AL with other methods, such as low-concentration atropine, is worth further study [ 30 , 31 ] . In addition, compared with several other prediction methods, AL is a routine examination, which means obvious operability and feasibility. We also found that older age at baseline was correlated with a lower increase in AL, which matches previous studies [ 26 , 29 ] . Regarding the relationship between SE and the progression of myopia, some studies reported slow progression with higher baseline myopia [ 19 , 32 ], and some reported lower baseline myopia [ 33 ] , whereas more studies showed that the rate of progression was not significantly associated with baseline myopia [20,34−36] . In our study, we did not find a significant correlation between them. Although this paper is the first to study axial shortening and propose the relationship between axial shortening and myopia control, including AL and SE, there are still some deficiencies in this study. Although the samples were selected continuously, this study still cannot answer the question about the proportion of patients with shortened AL due to the exclusion of some of the subjects with shortened AL and the heavy workload. However, in line with the research of Swarbricks and Zhi Chen [ 14 , 15 , 23 ] , 19%-50% of the patients with OK lenses showed axial shortening, which means that this phenomenon should not be ignored. In addition, this study cannot exclude influencing factors such as parents' situation and pupil size, which are difficult to avoid completely in retrospective studies. Finally, we still cannot completely reveal the reason for axial shortening, which is worthy of further study. Conclusion In conclusion, after AL is shortened in the initial stage after orthokeratology in some subjects, it will experience a rapid rebound during the wash-out period, and this process can be recovered when re-wearing OK lenses. There was a significant correlation between axial shortening after one month of wearing OK lenses and the effect on myopia control. The existence and degree of axial shortening can be used as a predictor of long-term myopia development. Our results suggest that short-term axial change can serve as a practical and valuable measurement to identify some aspects of rapid myopia progression and thereby improve outcomes in children with myopia. Abbreviations AL: Axial length SE: Spherical equivalent UCVA: Uncorrected visual acuity BCVA: Best-corrected visual acuity Declarations Acknowledgements: Not applicable. Funding/Support: This study was supported by Shanghai Hospital Development Center with Project: SHDC2020CR1043B-002 Ethics approval and consent to participate: This study was approved by the Ethics Committee of Children's Hospital of Fudan University. Informed written consent was obtained from all patients. For the patients under 18 years old, informed consents were sighed with their parents before the study. We confirm that all methods were performed in accordance with the relevant guidelines and regulations. Financial Disclosures: The authors have no proprietary or commercial interest in any materials discussed in the article. Competing interests: The authors declare no competing financial interests. Consent for publication: not applicable. Availability of data and material: Raw data has been uploaded as a supplementary file and all data generated or analysed during this study are included in this article. About material of patients please correspond with Chenhao yang. 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Optometry and Vision Science. 2010; 87:323-329 Kang P & Swarbrick HA.New perspective on myopia control with orthokeratology. Optom Vis Sci. 2016; 93:497-503 Gardner DJ, Walline JJ & Mutti DO. Choroidal Thickness and Peripheral Myopic Defocus during Orthokeratology. Optometry and Vision Science.2015; 92:579-588 GM Ana, VC César & LV Amalia. Anterior Segment Changes Produced in Response to Long-Term Overnight Orthokeratology. Current Eye Research. 2013; 38:862–870 Q António, LF Daniela, Y Brigitte, I Stan, ADS Ana, VC César & GM José. Refractive, biometric and corneal topographic parameter changes during 12 months of orthokeratology. Clinical and Experimental Optometry.2020; 103:454–462 Lau JK, Cheung SW, Collins MJ & Cho P. Short-term changes in choroidal thickness and axial length in children fitted with orthokeratology lenses of different compression factors. Investigative Ophthalmology & Visual Science.2018; 59:1786 Lau JK, Wan K, Cheung SW, Vincent SJ & Cho P. Weekly Changes in Axial Length and Choroidal Thickness in Children During and Following Orthokeratology Treatment With Different Compression Factors. Translational Vision Science & Technology.2019; 8 Lipson MJ, Harris JK, Lather HD, Niziol LM & Musch DC. Axial Length in Orthokeratology Patients: Large Case Series. Advances in Ophthalmology & Visual System.2016; 5: 00154 Chen Z, Xue F, Zhou JQ, Qu XM & Zhou XT . Effects of Orthokeratology on Choroidal Thickness and Axial Length. Optometry and Vision Science.2016; 93:1064-1071 Swarbrick HA, Alharbi A, Watt K, Lum E & Kang P. Myopia Control during Orthokeratology Lens Wear in Children Using a Novel Study design," American Academy of Ophthalmology.2015; 122:620-630 Cho P & Cheung SW. Protective Role of Orthokeratology in Reducing Risk of Rapid Axial Elongation: A Reanalysis of Data From the ROMIO and TO-SEE Studies. Clinical and Epidemiologic Research.2017; 58:1411-1416 Xie P & Guo X . Chinese Experiences on Orthokeratology. Eye Contact Lens.2016; 42:43–47 Zhao YY, Hu PK, Chen DY & Ni HL. Is It Possible to Predict Progression of Childhood Myopia Using Short-Term Axial Change After Orthokeratology? Eye & Contact Lens.2020; 46:136-140 Cho P, Cheung SW & Edwards M. The Longitudinal Orthokeratology Research in Children (LORIC) in Hong Kong: A Pilot Study on Refractive Changes and Myopic Control. Current Eye Research.2005; 30:71–80 Hiraoka T, Kakita T, Okamoto F, Takahashi H & Oshika T. Long-Term Effect of Overnight Orthokeratology on Axial Length Elongation in Childhood Myopia: A 5-Year Follow-Up Study. Investigative Ophthalmology & Visual Science.2012; 53:3913-3919 Li ZY, Hu Y, Cui DM, Long W, He MG & Yang X. Change in subfoveal choroidal thickness secondary to orthokeratology and its cessation: a predictor for the change in axial length. Acta Ophthalmol.2019; 97:454–459 Li ZY, Cui DM, Hu Y, Ao SC, Zeng JW & Yang X. Choroidal thickness and axial length changes in myopic children treated with orthokeratology. Contact Lens & Anterior Eye.2017; 40 Alharbi A & Swarbrick HA. The Effects of Overnight Orthokeratology Lens Wear on Corneal Thickness. Investigative Ophthalmology & Visual Science.2003; 44:2518-2523 Jin WQ, Huang SH, Jiang J, Mao XJ, Shen XM & Lian Y. Short term effect of choroid thickness in the horizontal meridian detected by spectral domain optical coherence tomography in myopic children after orthokeratology. Int J Ophthalmol.2018;11:991–996 Kim WK, Kim BJ, Ryu IH, Kim JK & Kim SW. Corneal epithelial and stromal thickness changes in myopic orthokeratology and their relationship with refractive change.2018; PLOS ONE 25 Santodomingo-Rubido J, Villa-Collar C, Gilmartin B & Gutie ́rrez-Ortega R. Factors Preventing Myopia Progression with Orthokeratology Correction. Optometry and Vision Science.2013; 90:1225-1236 Yang X, Li ZY & Zeng JW. A Review of the Potential Factors Influencing Myopia Progression in Children Using Orthokeratology," Asia-Pacific Journal of Ophthalmology.2016; 5:429-433 Chen Z, Niu LL, Xue F, Qu XM, Zhou ZM, Zhou XT & Chu RY. Impact of pupil diameter on axial growth in orthokeratology. Optom Vis Sci.2012; 89:1636-1640 Zhong YY, Chen Z, Xue F, Zhou JQ, Niu LL & Zhou XT. Corneal power change is predictive of myopia progression in orthokeratology. Optom Vis Sci.2014; 9:404-411 Tan Q, Alex LK, Choy B, Cheng G, Woo V & Cho P. One-year results of 0.01% atropine with orthokeratology (AOK) study: a randomised clinical trial. Ophthalmic & Physiological Optics.2020; 40:557-566 Sánchez-González JM, De-Hita-Cantalejo C, Baustita-Llamas MJ, Sánchez-González MC & Capote-Puente R. The Combined Effect of Low-dose Atropine with Orthokeratology in Pediatric Myopia Control: Review of the Current Treatment Status for Myopia. Journal of Clinical Medicine.2020; 9:2371 Fu AC, Chen XL, Lv Y, Wang SL, Shang LN, Li XH & Zhu Y. Higher spherical equivalent refractive errors is associated with slower axial elongation wearing orthokeratology. Cont Lens Anterior Eye.2016; 39:62–66 Santodomingo-Rubido J, Villa-Collar C, Gilmartin B & Gutie ́rrez-Ortega R. Factors Preventing Myopia Progression with Orthokeratology Correction. Optometry and Vision Science.2013; 90:1225-1236 Zhu MJ, Feng HY, He XG, Zou HD & Zhu JF. The control effect of orthokeratology on axial length elongation in Chinese children with myopia. BMC Ophthalmol.2014; 14:141 Cho P & Cheung S. Retardation of myopia in orthokeratology (ROMIO) study: A 2-year randomized clinical trial. Invest Opthalmol Vis Sci.2012; 53:70-77 Santodomingo-Rubido J, Villa-Collar C, Gilmartin B & Gutiérrez-Ortega R. Myopia control with orthokeratology contact lenses in Spain: refractive and biometric changes. Invest Ophthalmol Vis Sci.2012; 53:5060–5065 Additional Declarations No competing interests reported. Supplementary Files rawdata.xlsx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revision 01 Apr, 2022 Reviews received at journal 21 Mar, 2022 Reviews received at journal 15 Mar, 2022 Reviewers agreed at journal 04 Mar, 2022 Reviewers agreed at journal 04 Mar, 2022 Reviewers invited by journal 04 Mar, 2022 Editor assigned by journal 03 Mar, 2022 Editor invited by journal 19 Jan, 2022 Submission checks completed at journal 18 Jan, 2022 First submitted to journal 21 Dec, 2021 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-1193988","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":77413709,"identity":"f287944b-232b-4e5c-93b7-9afecdd5522c","order_by":0,"name":"Anken Wang","email":"","orcid":"","institution":"Children's Hospital of Fudan University","correspondingAuthor":false,"prefix":"","firstName":"Anken","middleName":"","lastName":"Wang","suffix":""},{"id":77413711,"identity":"63277088-dd4b-4ce6-98bc-37e708e971a8","order_by":1,"name":"Li Shen","email":"","orcid":"","institution":"Children's Hospital of Fudan University","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Shen","suffix":""},{"id":77413713,"identity":"c43d0e3f-745f-4c32-b0c2-695db435c619","order_by":2,"name":"Jiaying Wang","email":"","orcid":"","institution":"Children's Hospital of Fudan University","correspondingAuthor":false,"prefix":"","firstName":"Jiaying","middleName":"","lastName":"Wang","suffix":""},{"id":77413714,"identity":"8e9f8677-6b08-41a9-8add-fb21ef6029c2","order_by":3,"name":"Zhehuan Zhang","email":"","orcid":"","institution":"Children's Hospital of Fudan University","correspondingAuthor":false,"prefix":"","firstName":"Zhehuan","middleName":"","lastName":"Zhang","suffix":""},{"id":77413715,"identity":"e5de81aa-49ea-44ab-83c4-10f2bb4b1ad2","order_by":4,"name":"Weiming Yang","email":"","orcid":"","institution":"Children's Hospital of Fudan University","correspondingAuthor":false,"prefix":"","firstName":"Weiming","middleName":"","lastName":"Yang","suffix":""},{"id":77413716,"identity":"4b3ec36a-e363-40ad-9243-8618df4eb359","order_by":5,"name":"Chenhao Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwUlEQVRIiWNgGAWjYFACHjYgYZMAZicUEK8lLYEBRCUYEK/lMEQLAzFaDI6fPfbg447zefzy3YkfHhgwyPOLHSCg5UxeuuHMM7eLJdt4N0sAHWY4c3YCAS03eMykedtuJ244xrsBpCXB4DYxWv62nQNp2fyDeC2MbQdAWrYRZ4vkmRxzw9625MSZbbnbLBIMJAj7he/4GbMHP9vsEvuZz26++aPCRp5fmoAWhQOofAn8ykFAvoGwmlEwCkbBKBjpAAAFt0SdxaA3eQAAAABJRU5ErkJggg==","orcid":"","institution":"Children's Hospital of Fudan University","correspondingAuthor":true,"prefix":"","firstName":"Chenhao","middleName":"","lastName":"Yang","suffix":""}],"badges":[],"createdAt":"2021-12-22 02:29:01","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1193988/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1193988/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":17509174,"identity":"7f473503-4858-4f99-9a26-3f3aabec49ae","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":32424,"visible":true,"origin":"","legend":"\u003cp\u003eAxial length over time in the ALS group and NALS group.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/045f2a13504db62c232eaa83.jpg"},{"id":17509175,"identity":"d8e391a5-d99d-42b0-b57d-9960de4290a3","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":33644,"visible":true,"origin":"","legend":"\u003cp\u003eChange in axial length in the ALS group and NALS group over time. After a one-month washout period (without lenses), both groups showed explosive AL growth.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/3d7a6aadedb8b7c62a890673.jpg"},{"id":17509180,"identity":"abaef689-c874-4cf4-9033-13cbdb882d89","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":35262,"visible":true,"origin":"","legend":"\u003cp\u003eThe difference in the change in AL between the two groups at every visit. ***:P＜0.001\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/800bcedd068385e450f2db47.jpg"},{"id":17509179,"identity":"6b973dce-e90f-40c5-8369-d2cd5f037ab1","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":32944,"visible":true,"origin":"","legend":"\u003cp\u003eAbsolute value of the mean change in AL during the shortening period (the 2nd month) and rebounding period (the 20th month). ***:P＜0.001\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/799cf667f7fd96d0609f0d0e.jpg"},{"id":17509181,"identity":"bb5151db-7675-4dea-9e77-4166fcda8a21","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":206902,"visible":true,"origin":"","legend":"\u003cp\u003eSimple linear regressions between 20-month AL change and baseline age (A) and the changes in AL at the first month visit (B). Simple linear regressions between 20-month SE change and the changes in AL at the first month visit (C).\u003c/p\u003e","description":"","filename":"Figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/9a5e742e906c8f0d524f27a2.jpg"},{"id":17509176,"identity":"f116bbc6-c7c0-4ffa-810c-8064a37d7f97","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":29024,"visible":true,"origin":"","legend":"\u003cp\u003eMean change in SE, spherical refractive error and regular astigmatism between the two groups over time.\u003c/p\u003e","description":"","filename":"Figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/5231d0e23b9080a06146b9e1.jpg"},{"id":17509177,"identity":"4736b9f8-26d2-4115-b78d-4f12d518ac94","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":32788,"visible":true,"origin":"","legend":"\u003cp\u003eThe difference in the change in refractive error between the ALS group and NALS group. ***:p＜0.001\u003c/p\u003e","description":"","filename":"Figure7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/32ddea49cc16c9e21f7be0dc.jpg"},{"id":17509216,"identity":"7445e718-7ae1-4826-a3fd-f4edeaeaedee","added_by":"auto","created_at":"2022-01-20 19:20:02","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":38191,"visible":true,"origin":"","legend":"\u003cp\u003eMean change in AL over 22 months in the two groups. Axial shortening appeared once again in the eyes from the ALS group after one month of re-wearing, following rebound, while it still did not occur in the NALS group, although the speed of axial elongation seemed to slow down.\u003c/p\u003e","description":"","filename":"Figure8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/715317188a110b3339d9b979.jpg"},{"id":17509217,"identity":"ccccc61e-9059-490f-891c-f3864eb5c762","added_by":"auto","created_at":"2022-01-20 19:20:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":539930,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/de6ce202-fad7-4e7f-996b-dd837f125aa8.pdf"},{"id":17509178,"identity":"f44cd9a1-244c-4950-9061-fe9ead3b7f5e","added_by":"auto","created_at":"2022-01-20 19:17:02","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":94154,"visible":true,"origin":"","legend":"","description":"","filename":"rawdata.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-1193988/v1/f8015616ea011571d9d88281.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eAxial Length Shortening After Orthokeratology and Its Relationship With Myopic Control\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCurrently, myopia affects approximately 90% of teenagers and young adults in China and 28% of the global population, showing a dramatic increase in the past 50 years. Holden et al. predicted that there will be approximately 50% of the global population with myopia by 2050 without any interventions for myopia control \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Pharmacological and optical methods have been developed to control myopia progression, and among these methods, orthokeratology (OK) has been proven to be an effective method \u003csup\u003e[\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. After years of research, the main hypothesis about the mechanism appears to be that orthokeratology increases peripheral myopic defocus to reduce stimuli for axial elongation \u003csup\u003e[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eInterestingly, several studies showed statistically significant axial length (AL) shortening during the study period, especially in the early stage of the trials \u003csup\u003e[\u003cspan additionalcitationids=\"CR9 CR10 CR11 CR12 CR13 CR14\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. The occurrences of shortened axial length have been studied by an increasing number of scholars, and it has been proposed that central corneal thinning combined with choroidal thickening contributes to apparent axial length shortening \u003csup\u003e[\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. However, few studies have specifically observed people with shortened AL or discussed the relationship between shortened AL and the effect of myopia control. Therefore, we conducted this retrospective study to determine the pattern of axial change in subjects with initially shortened AL during the entire period of wearing OK lenses, including 1 month of discontinuation and 1 month after re-wear, and to compare the change in axial length and refractive error between the subjects with shortened AL and nonshortened AL who both underwent orthokeratology.\u003c/p\u003e \u003cp\u003eAdditionally, individual variability in the effects of orthokeratology on myopia progression does exist, so it is crucial to predict the effect of orthokeratology on individuals as early as possible. This article will also discuss the possibility that shortened AL after orthokeratology becomes a predictor of myopia control.\u003c/p\u003e \u003cp\u003eThe authors report no conflicts of interest.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003esubjects\u003c/h2\u003e \u003cp\u003e In this retrospective study, we reviewed all the patients who started orthokeratology between January 2015 and December 2018 in the Children\u0026rsquo;s Hospital of Fudan University.\u003c/p\u003e \u003cp\u003eClinical pathway: At the first visit, all the patients underwent comprehensive examinations, including cycloplegic refraction, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), extraocular movements, corneal light reflection test, intraocular pressure, slit-lamp examination, fluorescein staining, corneal endothelial cell density, axial length, fundus photo and corneal topography. Appropriate prescriptions for OK lenses were provided to the participants by different experienced doctors, and the patients were asked to wear OK lenses no fewer than 8 h per night and follow-up one week and one month (the second month after fitting because it usually takes approximately a month from the time the prescription is sent to the manufacturing corporation to the time patients receive their lenses) after wearing. If there were no problems, they were then asked to visit every 3 months afterward. At every subsequent follow-up, they underwent a detailed list of ocular examinations, including corneal light reflection tests, slit-lamp evaluations, fluorescein staining, axial length, UCVA and corneal topography. After 1.5 years of wearing OK lenses (the 19th month after fitting), all patients were required to change the lenses after one month of washout (no OK lens wearing). After the wash-out period (the 20th month after fitting), we repeated all the previous examinations before the first wearing, including cycloplegic refraction. All subjects were treated according to the tenets of the Declaration of Helsinki.\u003c/p\u003e \u003cp\u003eWhen reviewing cases, the inclusion criteria included the following: (1) The spherical refractive error must be less than \u0026minus;5.00 D with regular astigmatism of \u0026minus;1.50 D or less, and the BCVA of logMAR (logarithm of the minimum angle of resolution) must be 0.0 or better before treatment. (2) The subjects were followed up on schedule for at least 6 months, and the data were completed, especially the axial length of each follow-up and the results of two cycloplegic refractions. (3) The UCVA of each eye must be better than 0.1 (LogMar) after removal of lenses at each follow-up. (4) After wearing the lens for one month, the eyes with axial length shortening were assigned to the axial length shortening (ALS) group, and the eyes without axial length shortening were assigned to the no axial length shortening (NALS) group. The exclusion criteria were as follows: (1) The subjects included should not have obvious glare, duplication or any other corneal complications. (2) Subjects with underlying ocular disease, such as obvious tropia, retinopathy, prematurity, neonatal problems, history of genetic disease that might affect refractive development, or other system disorders associated with myopia, were excluded. (3) Decentrations larger than 1 mm was found in at least two consecutive visits. (4) Combined with other treatments, such as low-concentration atropine eye drops.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eLenses\u003c/h2\u003e \u003cp\u003eAll patients were fitted with OK lenses (α ORTHO-K\u0026reg;, ALPHA Corp, Nagoya, Japan, with a nominal Dk of 104 \u0026times; 10\u003csup\u003e\u0026minus;11\u003c/sup\u003e (cm\u003csup\u003e2\u003c/sup\u003e/s) (mL O\u003csub\u003e2\u003c/sub\u003e/mL\u0026middot;mmHg) or LUCID ORTHO‐K\u0026reg; lenses, LUCID Corp, Fenghua County, Korea, with a nominal Dk of 100 \u0026times; 10\u003csup\u003e\u0026minus;11\u003c/sup\u003e (cm\u003csup\u003e2\u003c/sup\u003e/s) (mL O\u003csub\u003e2\u003c/sub\u003e/mL\u0026middot;mmHg)) according to the manufacturer's fitting instructions. The procedures for fitting, prescription, and replacement of OK lenses were all performed by experienced specialists.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eMeasurements\u003c/h2\u003e \u003cp\u003eCycloplegic refraction was measured two times by specialized technicians to ensure exactness. The K value was measured three times routinely with an autorefractor keratometer. (NIDEK, Co; LTD, Japan. Model: ARK-1). Axial length was measured three times routinely with an IOL-Master 500 (Carl Zeiss Meditec, Ag. jena, Germany). The examinations were performed by the same specialized technician, and the average value was recorded.\u003c/p\u003e \u003cp\u003eCorneal profiles were measured with a Carl Zeiss ATLAS Corneal Topography System -9000 (Carl Zeiss Meditec, Inc. California, United States of America, Model 9000). Each of the profiles was the best-focus image (accuracy greater than 95%) from the four frames that were captured automatically.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eSPSS Statistics 24.0 (IBM Statistics, Armonk, NY) was used for statistical analysis of the ocular biometric parameters. The Shapiro\u0026ndash;Wilk test was used to check the normality. The differences in parameters at baseline and changes in refractive power between the ALS group and NALS group were compared using independent \u003cem\u003et\u003c/em\u003e tests. A repeated measures analysis of variance (ANOVAs) was used to compare the change in AL over time between the two groups. If significant differences were found, post hoc tests with Bonferroni correction were performed to compare the differences between visits in the eyes of the ALS group and NALS group. A \u003cem\u003eP\u003c/em\u003e value less than 0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003eSubject Demographics\u003c/h2\u003e\n\u003cp\u003eA total of 106 subjects were enrolled in this study (54 in the ALS group and 52 in the NALS group). To avoid the influence between two paired eyes, only the right eye was included in this study if the lens was worn with both eyes. After exclusion, there were 54 eyes in the ALS group and 52 eyes in the NALS group. There was no significant difference in sex distribution between the two groups(ALS group: 22 eyes from male and 32 from female, NALS group: 19 eyes from male and 33 from female)according to the Mann\u0026ndash;Whitney \u003cem\u003eU\u003c/em\u003e test of independent sample༈\u003cem\u003eP\u003c/em\u003e=0.66). There was some difference in age between the two groups (ALS group: 9.63\u0026plusmn; 1.34, NALS group: 9.12\u0026plusmn; 1.41) according to the \u003cem\u003et\u003c/em\u003e test of independent samples (P=0.06).\u003c/p\u003e\n\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n\u003ch2\u003eParameter on baseline\u003c/h2\u003e\n\u003cp\u003eAt baseline (the day of fitting), the axial length, spherical equivalent, spherical and regular astigmatism of the eyes from the ALS group were 24.68\u0026plusmn;0.90 mm (range 22.06 to 26.71 mm), -2.98\u0026plusmn;1.25 D (range \u0026minus;0.75 to \u0026minus;5.38 D), -2.68\u0026plusmn;1.14 D (range \u0026minus;0.75 to \u0026minus;5.00 D) and -0.60\u0026plusmn;0.58 D (range 0.00 to \u0026minus;1.50 D), respectively. Those in the eyes from the NALS group were 24.50\u0026plusmn;0.68 mm (range 23.38 to 26.03 mm), -2.60\u0026plusmn;1.02 D (range \u0026minus;0.75 to \u0026minus;4.88 D), -2.40\u0026plusmn;0.96 D (range \u0026minus;0.75 to \u0026minus;4.50 D) and -0.38\u0026plusmn;0.43 D (range 0.00 to \u0026minus;1.50 D), respectively. The difference between the two groups was not statistically significant by \u003cem\u003et\u003c/em\u003e test of independent samples in axial length (\u003cem\u003ep\u003c/em\u003e=0.24), spherical equivalent (\u003cem\u003ep\u003c/em\u003e=0.09) and spherical diopter (\u003cem\u003ep\u003c/em\u003e=0.18), but significant difference between the two groups was found in regular astigmatism (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05).\u003c/p\u003e\n\u003cp\u003eBefore orthokeratology, the difference between the two groups was not significantly different by independent-sample t test t in steep K (\u003cem\u003ep\u003c/em\u003e=0.33), flat K (\u003cem\u003ep\u003c/em\u003e=0.64), equivalent e value (\u003cem\u003ep\u003c/em\u003e=0.97), toric lens (\u003cem\u003ep\u003c/em\u003e=0.73) and diameter of lens (\u003cem\u003ep\u003c/em\u003e=0.25). There was no significant difference in the distribution of lens brand between the two groups by the Mann\u0026ndash;Whitney \u003cem\u003eU\u003c/em\u003e test of independent samples (\u003cem\u003eP\u003c/em\u003e=0.40). The biological parameters of the eyes and lens data are shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eDifferences in biological parameters and lenses between the ALS group and NALS group\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eParameter (Mean \u0026plusmn; SD)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eALS (n=54)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNALS(n=52)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ep value\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAxial length(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24.68\u0026plusmn;0.90\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24.50\u0026plusmn;0.68\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.24\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSpherical equivalent refractive error (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-2.98\u0026plusmn;1.25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-2.60\u0026plusmn;1.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.09\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSpherical refractive error (DS)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-2.68\u0026plusmn;1.14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-2.40\u0026plusmn;0.96\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.18\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eRegular astigmatism (DC)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.60\u0026plusmn;0.58\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.38\u0026plusmn;0.43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eEquivalent e value\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.62\u0026plusmn;0.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.62\u0026plusmn;0.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.98\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSteep K (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e44.07\u0026plusmn;1.59\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e43.81\u0026plusmn;1.17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.33\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eFlat K (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42.92\u0026plusmn;1.46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42.80\u0026plusmn;1.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.64\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eToric Lens (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.06\u0026plusmn;0.30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.04\u0026plusmn;0.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.73\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLens diameter(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.60\u0026plusmn;0.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.56\u0026plusmn;0.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.25\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGrand of lenses*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eL:46; A:8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eL:39; A:11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.40\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e*: L=Lucid; A=Alpha\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n\u003ch2\u003eAxial Change\u003c/h2\u003e\n\u003cp\u003eAt first, the AL of the NALS group was slightly lower than that of the ALS group. Then, the AL of the ALS group was shortened after wearing lenses for one month(the 2nd month), while it was not shortened in NALS group at that time which was ascertained by standard of grouping. The axial length of the NALS group continued to increase and finally exceeded that of the ALS group due to the difference in elongation speed. In the end, explosive growth of the AL occurred in both groups after the wash-out period.After 20 monthsin total, the average AL of the ALS group grew from 24.68\u0026plusmn;0.90 mm to 24.96\u0026plusmn;0.87 mm(22.59 to 26.71 mm) and that of the NALS group grew from 24.50\u0026plusmn;0.68 mm to 25.03\u0026plusmn;0.70 mm(23.63 to 26.35 mm). The time course of axial length is shown in Figure 1.\u003c/p\u003e\n\u003cp\u003eTo show the changes in AL more clearly, we subsequently focused on the changes in AL compared with baseline. After wearing OK lenses for one month, the change in AL in the ALS group was -0.08\u0026plusmn;0.04 mm (-0.03 to -0.18 mm), while it was 0.05\u0026plusmn;0.03 mm (0.01 to 0.16 mm) in the NALS group. The mean AL of the ALS group did not return to baseline until the 7th month and began to exceed baseline before the 13th month. The mean AL of the NALS group grew as usual and was significantly faster than that of the ALS group at every follow-up visit by further multivariate analysis of variance with Bonferroni correction (\u003cem\u003ep\u0026lt;0.05\u003c/em\u003e). After a one- month washout period (without lenses), both the ALS and NALS groups showed an explosive rebound of AL. The rebound was 0.10\u0026plusmn;0.05 mm (0.00 to 0.24 mm) in the ALS group and 0.06\u0026plusmn;0.05 mm (-0.02 to 0.27 mm) in the NALS group. The amount of rebound in the two groups was significantly different by \u003cem\u003et\u003c/em\u003e test of independent samples (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05).\u003c/p\u003e\n\u003cp\u003eThere were significant differences in the change in axial length between the ALS group and NALS group over the course of the study (P\u0026lt;0.05, repeated measures ANOVA with Bonferroni correction), as depicted in Figure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eThe difference in the change in AL between the two groups at every visit was statistically significant, as displayed in Figure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. After 20 months, the mean change in AL was 0.28\u0026plusmn;0.19 mm (-0.04 to -0.75 mm) in the ALS group and 0.52\u0026plusmn;0.17 mm (0.15 to 0.91 mm). Although the rebound was larger in the ALS group, lower AL growth over the total 20 months was shown in the ALS group.\u003c/p\u003e\n\u003cp\u003ePaired \u003cem\u003et\u003c/em\u003e test was used to compare the amount of axial shortening (absolute value: 0.08\u0026plusmn;0.04 mm) after the first month of wearing and the axial rebound after a one-month wash-out (0.10\u0026plusmn;0.05 mm) in the ALS group, and we found that AL rebounded after wash-out even more than the shortening at the beginning(\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). In addition, the difference in elongation of the AL after 1 month of first wearing (0.06\u0026plusmn;0.41 mm) and rebounding in the NALS group (0.06\u0026plusmn;0.05 mm) showed no significant difference by paired \u003cem\u003et\u003c/em\u003e test (\u003cem\u003eP\u003c/em\u003e=0.27). The absolute value of the mean change in AL during the shortening period (the 2nd month) and rebounding period (the 20th month) is shown in Figure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eThe adjusted R\u003csup\u003e2\u003c/sup\u003e of the multiple linear regression model evaluating the predictive performance of the candidate predictors, including baseline age, baseline spherical equivalent (SE), baseline AL and the changes in AL at the first month visit (the 2nd month) for the 20-month AL change was 0.382 (F = 17.239, S=0.167, p \u0026lt; 0.001). The 20-month AL change was significantly correlated with baseline age (standardized \u0026beta;=-0.203, P\u0026lt;0.001) and the changes in AL at the first month visit (standardized \u0026beta;\u0026thinsp;=\u0026thinsp;0.541, P\u0026lt;0.001), whereas the other factors did not affect axial elongation (all p \u0026gt; 0.05). Simple linear regressions can be seen in Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (A) \u0026amp; (B).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n\u003ch2\u003eChange of refractive error\u003c/h2\u003e\n\u003cp\u003eThe change in SE, spherical refractive error and regular astigmatism over time can be seen in Figure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. The SE of the ALS group decreased from -2.98\u0026plusmn;1.25 D to -3.41\u0026plusmn;1.23D (-1.13 to -5.50D) in 20 months, while the SE of the NALS group decreased from -2.60\u0026plusmn;1.02D to -3.51\u0026plusmn;1.03D(-1.50 to -5.75D) and the change in SE showed significant difference between the two groups(ALS group:-0.43\u0026plusmn;0.44D; NALS group:-0.91\u0026plusmn;0.40D) by independent-sample \u003cem\u003et\u003c/em\u003e test(\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). The spherical refractive error of the ALS group decreased from-2.68\u0026plusmn;1.14D to -2.98\u0026plusmn;1.11D(-0.75 to -5.00D) in 20 months, while the spherical refractive error of NALS group decreased from -2.40\u0026plusmn;0.96D to -3.20\u0026plusmn;0.99D(-1.25 to -5.25D) and the change in spherical refractive error showed significant difference between the two groups(ALS group:-0.30\u0026plusmn;0.41D; NALS group:-0.80\u0026plusmn;0.39D) by independent-sample \u003cem\u003et\u003c/em\u003e test(\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). The regular astigmatism of the ALS group decreased from -0.60\u0026plusmn;0.58D to -0.82\u0026plusmn;0.57D (-0.00 to -2.00D) in 20 months, while the regular astigmatism of NALS group decreased from -0.38\u0026plusmn;0.43D to -0.61\u0026plusmn;0.47D(-0.00 to -1.75D) and the change in regular astigmatism showed no significant difference between the two groups(ALS: -0.23\u0026plusmn;0.38D; NALS༚-0.23\u0026plusmn;0.36D) by independent-sample t test(\u003cem\u003eP\u003c/em\u003e=0.99). The difference of those changes can be seen in Figure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eThe adjusted R\u003csup\u003e2\u003c/sup\u003e of the multiple linear regression model evaluating the predictive performance of the candidate predictors (including the changes in AL at the first month, baseline age, baseline spherical equivalent (SE) and baseline AL) for changes in SE over 20 months was 0.293 (F = 11.903, S=0.4074, p \u0026lt; 0.001). The change in SE over 20 months was only significantly correlated with the changes in AL at the first month (standardized \u0026beta;=-0.500, P\u0026lt;0.001). Simple linear regressions can be seen in Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (C).\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n\u003ch2\u003eChange of AL after re-wearing\u003c/h2\u003e\n\u003cp\u003eAmong 54 eyes in the ALS group, 46 eyes (85.19%) were replaced with OK lenses and visited routinely after re-wearing for one month, while 29 eyes (55.77%) from the NALS group completed the above process. The change in AL over time in these 75 eyes is displayed in Figure \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e. Axial shortening appeared once again in the eyes from the ALS group after a month of re-wearing, following rebound, while it still did not occur in NALS, although the speed of axial elongation seemed to slow down. A paired t test was used to compare the amount of initial and second axial shortening in the ALS group, which showed a significant difference (initial: -0.08\u0026plusmn;0.04 mm, second: -0.04\u0026plusmn;0.05 mm; \u003cem\u003eP\u0026lt;0.05\u003c/em\u003e). In addition, a significant difference was found between the speed of axial elongation in the NALS group during the same two periods (initial: 0.06\u0026plusmn;0.04 mm, second: 0.01\u0026plusmn;0.09 mm; P\u0026lt;0.05)\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eOwing to the efficacious control of myopia progression in adolescents, there is a gradual incremental application of orthokeratology, which has been chosen by more than 1.5 million adolescents in China \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. In recent years, many scholars have noticed the axial shortening of partial subjects at the initial stage of orthokeratology, which may explain why many studies have shown that the axial growth rate in the initial stage is much slower than that in the subsequent stage \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. Some studies have indicated that the average axial length of the eye has a negative growth in the initial stage \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Therefore, it is necessary to clarify the pattern of axial shortening in the entire period of orthokeratology because neglecting the initial axial shortening and axial rebound after discontinued wear may cause overestimation of the control effect \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eAccording to our study, the AL of the subjects with axial shortening started to grow after one month of wearing OK lenses and then did not return to baseline until the 7th month and began to exceed baseline at nearly the 13th month. With regard to the degree of axial shortening, the data of other studies can be seen in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Overall, the amount of axial shortening after one month of wearing in the ALS group of our study (0.08\u0026plusmn;0.04 mm) was between the results of these studies. As for the quite different results of those studies, on the one hand, is the inconsistent time of exam, and on the other hand is the nonnegligible individual differences, to be more specific, whether the axial length is shortened or not and the degree of shortening depends on the comparison between the causes of shortening and the growth of the axial length.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eDegree of axial shortening according to some studies.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eStudy\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAxial shortening(mm)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTime\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNumber of subjects\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eCountry or area\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAge(y)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eInclusion criteria\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eInstrument\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGardner. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.04\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUSA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e11-15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-4.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLenstar\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAna Gonz\u0026aacute;lez-Mesa. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.157\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSpain\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e18-30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.50~-4.50D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eIOL-Master\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAnt\u0026oacute;nio Queir\u0026oacute;s. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eapproximately 0.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1W\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e62\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAsian\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e5-19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-8.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eIOL-Master\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLau, Jason K. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eapproximately 0.25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1W\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eHong Kong, China\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e6-10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.50~-4.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLenstar\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLau, Jason K. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.26\u0026plusmn; 0.41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1W\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e58\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eHong Kong, China\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e6-10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.50~-4.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLenstar\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMichael J Lipson. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.01\u0026plusmn;0.53\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1Y\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e97\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUSA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e7-14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-6.50D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eA- scan\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eHelen A. Swarbrick. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.04\u0026plusmn;0.08\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e26\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAustralia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e10-17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-5.50D\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eIOL-Master\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eRegarding the reasons for the shortening of the AL, the main views by scholars are central corneal thinning combined with choroidal thickening \u003csup\u003e[11,14\u0026minus;16]\u003c/sup\u003e. Some data about central corneal thinning and choroidal thickening are listed in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e\u003csup\u003e[12,14,22\u0026minus;25]\u003c/sup\u003e. Central corneal thinning was epithelial in origin, whereas mid-peripheral thickening was primarily stromal. The nature of the epithelial cellular changes underlying central epithelial thinning induced by orthokeratology remains obscure, although some possibilities have been revealed in the literature \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. Axial length collected by A-scan or partial coherence interferometry (e.g., IOL-Master) is likely to be influenced by choroidal thickness because A-scan ultrasonography is an acoustic method in which axial length is defined as the distance between corneal anterior surface and vitreous-retina reflection peak and devices based on partial coherence interferometry, e.g., the IOL-Master, defines the axial length as the distance between anterior cornea and retinal pigment epithelium (RPE) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. Whether the OK lens will cause a tiny transshape of the eyeball needs further study, so strictly speaking, the change in AL mentioned in this study is actually based on the value measured by IOL-Master.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eData about central corneal thinning and choroidal thickening according to some studies\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eStudy\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ecentral corneal thinning (mm)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003esubfoveal choroid thickening (mm)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTime\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNumber of subjects\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eCountry or area\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAge(y)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eInclusion criteria\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLau, Jason K.\u0026nbsp;et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.009\u0026plusmn;0.004\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.009\u0026plusmn;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1W\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e58\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eHong Kong, China\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e6-10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.50~-4.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eZhouyue Li. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.01\u0026plusmn;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eapproximately 0.16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eChina\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e8-15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-4.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAlharbi and Swarbrick. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.016 \u0026plusmn; 0.003\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAustralia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e22-29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.25~-4.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eWan-Qing Jin.\u0026nbsp;et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.006\u0026plusmn;0.007\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eChina\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e9-14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-6.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eWook Kyum Kim. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.006\u0026plusmn;0.005\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2 M\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e36\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eChina\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e7-25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.50~-5.00D\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eZhi Chen. et al. \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.022\u0026plusmn;0.025\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3W\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eChina\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e7-17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-1.00~-5.50D\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to the study of Lau \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e, after the first week of lens wear, central corneal thinning (9 \u0026plusmn; 4 \u0026micro;m) and choroid thickening (9 \u0026plusmn; 12 \u0026micro;m) contributed to approximately 70% of the axial shortening (26 \u0026plusmn; 41 \u0026micro;m). Moreover, the phenomenon of axial shortening is relatively underestimated in our opinion because most previous studies mixed subjects with shortened AL and those without shortened AL. Combined with the obvious axial shortening collected in the ALS group in this study (-0.08\u0026plusmn;0.04 mm), it can be claimed that central corneal thinning and choroid thickening do not provide entire explanations of axial shortening. Therefore, the mechanism of axial shortening needs further study.\u003c/p\u003e\n\u003cp\u003eThere was an obvious rebound in AL after discontinued wear of the lenses (wash-out period) in both groups, which corresponds with the recent discovery by Swarbrick \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e and Zhouyue Li \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. This means that the data about AL after orthokeratology becomes relatively true only after the washout period. In other words, if we use the AL data measured without wash-out period as the cutoff point of the experiment about axial elongation after orthokeratology, we will likely overestimate the control effect of the OK-lens especially in the research between orthokeratology group and group without orthokeratology(e.g., blank control group, glasses, atropine, etc.).\u003c/p\u003e\n\u003cp\u003eOther researchers have not observed that if OK lenses were re-worn after the washout period, the phenomenon of axial shortening would reappear, similar to the initial phenomenon. This means that axial shortening does repeat in some subjects; in addition, the observation of this phenomenon can now close the loop in the timeline. The differenrent size of the sample regarding re-wear between the two groups in this study may be because subjects with better control effect are more likely to continue, but the reduced sample size did not affect the repeating axial shortening. In the ALS group, the amount of axial shortening after re-wear for one month (20-22 M) was less than that of the first time (0-2 M). In this regard, we think it is caused by the remaining influence of the OK lens even after a one-month washout period In other words, the longer washout period required in clinical research needs further study.\u003c/p\u003e\n\u003cp\u003eIt has been suggested that myopia control with OK lenses is influenced by a number of factors, including patient age and sex, age at onset, degree of myopia, and various anatomic features, including corneal power and shape, anterior chamber depth, iris color, pupil diameter, corneal relative peripheral power change and choroidal thickness \u003csup\u003e[21,26\u0026minus;29]\u003c/sup\u003e. Although the effect of OK lenses is worth affirming, all these factors remind us that the mechanism by which orthokeratology might control myopia is complex and influenced by individual differences. Therefore, it is very important to predict the development of myopia as soon as possible and to filter OK-lens wearers who may still undergo rapid myopia progression.\u003c/p\u003e\n\u003cp\u003eThe comparative study of the ALS group and NALS group showed significantly slower growth in AL, SE and spherical refractive error in subjects with axial shortening. Because the final data are measured after the washout period, the accuracy of the results can be certain. Under such circumstances, we can conclude that axial shortening after one month of wearing as the indicator of the ideal control effect of myopia and subsequently predict myopia progression.\u003c/p\u003e\n\u003cp\u003eThrough a multiple linear regression model, our study showed a significant correlation between axial change after one month of wearing OK lenses and changes in both AL and SE. In other words, the more axial shortening at the beginning, the slower the progression of myopia; the more the AL increases after one month of wearing OK lenses, the faster myopia will progress. Although the degree of shortening itself is related to the speed of axial growth, it does not affect the correlation. In the clinic, if we encounter patients with axial shortening after the first month of orthokeratology, we can confidently instruct them to continue wearing OK lenses. In another situation, if we encounter patients with rapid growth of AL after the first month of orthokeratology, whether to combine AL with other methods, such as low-concentration atropine, is worth further study \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e. In addition, compared with several other prediction methods, AL is a routine examination, which means obvious operability and feasibility.\u003c/p\u003e\n\u003cp\u003eWe also found that older age at baseline was correlated with a lower increase in AL, which matches previous studies \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e. Regarding the relationship between SE and the progression of myopia, some studies reported slow progression with higher baseline myopia \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e],\u003c/sup\u003e and some reported lower baseline myopia \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e, whereas more studies showed that the rate of progression was not significantly associated with baseline myopia \u003csup\u003e[20,34\u0026minus;36]\u003c/sup\u003e. In our study, we did not find a significant correlation between them.\u003c/p\u003e\n\u003cp\u003eAlthough this paper is the first to study axial shortening and propose the relationship between axial shortening and myopia control, including AL and SE, there are still some deficiencies in this study. Although the samples were selected continuously, this study still cannot answer the question about the proportion of patients with shortened AL due to the exclusion of some of the subjects with shortened AL and the heavy workload. However, in line with the research of Swarbricks and Zhi Chen \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e, 19%-50% of the patients with OK lenses showed axial shortening, which means that this phenomenon should not be ignored. In addition, this study cannot exclude influencing factors such as parents' situation and pupil size, which are difficult to avoid completely in retrospective studies. Finally, we still cannot completely reveal the reason for axial shortening, which is worthy of further study.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, after AL is shortened in the initial stage after orthokeratology in some subjects, it will experience a rapid rebound during the wash-out period, and this process can be recovered when re-wearing OK lenses. There was a significant correlation between axial shortening after one month of wearing OK lenses and the effect on myopia control. The existence and degree of axial shortening can be used as a predictor of long-term myopia development. Our results suggest that short-term axial change can serve as a practical and valuable measurement to identify some aspects of rapid myopia progression and thereby improve outcomes in children with myopia.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAL: Axial length\u003c/p\u003e\n\u003cp\u003eSE: Spherical equivalent\u003c/p\u003e\n\u003cp\u003eUCVA: Uncorrected visual acuity\u003c/p\u003e\n\u003cp\u003eBCVA: Best-corrected visual acuity\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding/Support:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by Shanghai Hospital Development Center with Project: SHDC2020CR1043B-002\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Children\u0026apos;s Hospital of Fudan University. Informed written consent was obtained from all patients. For the patients under 18\u0026thinsp;years old, informed consents were sighed with their parents before the study. We confirm that all methods were performed in accordance with the relevant guidelines and regulations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFinancial Disclosures:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no proprietary or commercial interest in any materials discussed in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003enot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRaw data has been uploaded as a supplementary file and all data generated or analysed during this study are included in this article. About material of patients please correspond with Chenhao yang.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eHolden BA, Fricke TR, Wilson DA, Jong M, Naidoo KS, Sankaridurg P, Wong TY, Naduvilath TJ \u0026amp; Resnikoff S. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050.Ophthalmology.2016; 123:1036\u0026ndash;1042\u003c/li\u003e\n \u003cli\u003eDolgin E. The myopia boom. Nature.2015; 519: 276\u0026ndash;278\u003c/li\u003e\n \u003cli\u003eKakita T, Hiraoka T \u0026amp; Oshika T. Influence of overnight Orthokeratology on axial elongation in childhood myopia. 2011; Invest Ophthalmol Vis Sci 52:2170\u0026ndash;2174\u003c/li\u003e\n \u003cli\u003eTarutta EP \u0026amp; Verzhanskaya TY. Stabilizing effect of orthokeratology lenses (ten-year follow-up results). Vestn Oftalmol.2017; 133: 49-54\u003c/li\u003e\n \u003cli\u003eLi X, Friedman IB, Medow NB \u0026amp; Zhang C. 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Translational Vision Science \u0026amp; Technology.2019; 8\u003c/li\u003e\n \u003cli\u003eLipson MJ, Harris JK, Lather HD, Niziol LM \u0026amp; Musch DC. Axial Length in Orthokeratology Patients: Large Case Series. Advances in Ophthalmology \u0026amp; Visual System.2016; 5: 00154\u003c/li\u003e\n \u003cli\u003eChen Z, Xue F, Zhou JQ, Qu XM \u0026amp; Zhou XT . Effects of Orthokeratology on Choroidal Thickness and Axial Length. Optometry and Vision Science.2016; 93:1064-1071\u003c/li\u003e\n \u003cli\u003eSwarbrick HA, Alharbi A, Watt K, Lum E \u0026amp; Kang P. Myopia Control during Orthokeratology Lens Wear in Children Using a Novel Study design,\u0026quot; American Academy of Ophthalmology.2015; 122:620-630\u003c/li\u003e\n \u003cli\u003eCho P \u0026amp; Cheung SW. Protective Role of Orthokeratology in Reducing Risk of Rapid Axial Elongation: A Reanalysis of Data From the ROMIO and TO-SEE Studies. Clinical and Epidemiologic Research.2017; 58:1411-1416\u003c/li\u003e\n \u003cli\u003eXie P \u0026amp; Guo X . Chinese Experiences on Orthokeratology. Eye Contact Lens.2016; 42:43\u0026ndash;47\u003c/li\u003e\n \u003cli\u003eZhao YY, Hu PK, Chen DY \u0026amp; Ni HL. Is It Possible to Predict Progression of Childhood Myopia Using Short-Term Axial Change After Orthokeratology? Eye \u0026amp; Contact Lens.2020; 46:136-140\u003c/li\u003e\n \u003cli\u003eCho P, Cheung SW \u0026amp; Edwards M. The Longitudinal Orthokeratology Research in Children (LORIC) in Hong Kong: A Pilot Study on Refractive Changes and Myopic Control. Current Eye Research.2005; 30:71\u0026ndash;80\u003c/li\u003e\n \u003cli\u003eHiraoka T, Kakita T, Okamoto F, Takahashi H \u0026amp; Oshika T. Long-Term Effect of Overnight Orthokeratology on Axial Length Elongation in Childhood Myopia: A 5-Year Follow-Up Study. Investigative Ophthalmology \u0026amp; Visual Science.2012; 53:3913-3919\u003c/li\u003e\n \u003cli\u003eLi ZY, Hu Y, Cui DM, Long W, He MG \u0026amp; Yang X. Change in subfoveal choroidal thickness secondary to orthokeratology and its cessation: a predictor for the change in axial length. Acta Ophthalmol.2019; 97:454\u0026ndash;459\u003c/li\u003e\n \u003cli\u003eLi ZY, Cui DM, Hu Y, Ao SC, Zeng JW \u0026amp; Yang X. Choroidal thickness and axial length changes in myopic children treated with orthokeratology. Contact Lens \u0026amp; Anterior Eye.2017; 40\u003c/li\u003e\n \u003cli\u003eAlharbi A \u0026amp; Swarbrick HA. The Effects of Overnight Orthokeratology Lens Wear on Corneal Thickness. Investigative Ophthalmology \u0026amp; Visual Science.2003; 44:2518-2523\u003c/li\u003e\n \u003cli\u003eJin WQ, Huang SH, Jiang J, Mao XJ, Shen XM \u0026amp; Lian Y. 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Impact of pupil diameter on axial growth in orthokeratology. Optom Vis Sci.2012; 89:1636-1640\u003c/li\u003e\n \u003cli\u003eZhong YY, Chen Z, Xue F, Zhou JQ, Niu LL \u0026amp; Zhou XT. Corneal power change is predictive of myopia progression in orthokeratology. Optom Vis Sci.2014; 9:404-411\u003c/li\u003e\n \u003cli\u003eTan Q, Alex LK, Choy B, Cheng G, Woo V \u0026amp; Cho P. One-year results of 0.01% atropine with orthokeratology (AOK) study: a randomised clinical trial. Ophthalmic \u0026amp; Physiological Optics.2020; 40:557-566\u003c/li\u003e\n \u003cli\u003eSánchez-González JM, De-Hita-Cantalejo C, Baustita-Llamas MJ, Sánchez-González MC \u0026amp; Capote-Puente R. The Combined Effect of Low-dose Atropine with Orthokeratology in Pediatric Myopia Control: Review of the Current Treatment Status for Myopia. Journal of Clinical Medicine.2020; 9:2371\u003c/li\u003e\n \u003cli\u003eFu AC, Chen XL, Lv Y, Wang SL, Shang LN, Li XH \u0026amp; Zhu Y. Higher spherical equivalent refractive errors is associated with slower axial elongation wearing orthokeratology. Cont Lens Anterior Eye.2016; 39:62\u0026ndash;66\u003c/li\u003e\n \u003cli\u003eSantodomingo-Rubido J, Villa-Collar C, Gilmartin B \u0026amp; Gutie ́rrez-Ortega R. Factors Preventing Myopia Progression with Orthokeratology Correction. Optometry and Vision Science.2013; 90:1225-1236\u003c/li\u003e\n \u003cli\u003eZhu MJ, Feng HY, He XG, Zou HD \u0026amp; Zhu JF. The control effect of orthokeratology on axial length elongation in Chinese children with myopia. BMC Ophthalmol.2014; 14:141\u003c/li\u003e\n \u003cli\u003eCho P \u0026amp; Cheung S. Retardation of myopia in orthokeratology (ROMIO) study: A 2-year randomized clinical trial. Invest Opthalmol Vis Sci.2012; 53:70-77\u003c/li\u003e\n \u003cli\u003eSantodomingo-Rubido J, Villa-Collar C, Gilmartin B \u0026amp; Guti\u0026eacute;rrez-Ortega R. Myopia control with orthokeratology contact lenses in Spain: refractive and biometric changes. Invest Ophthalmol Vis Sci.2012; 53:5060\u0026ndash;5065\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Myopia, Orthokeratology, Axial length, Myopia control","lastPublishedDoi":"10.21203/rs.3.rs-1193988/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1193988/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePurpose\u003c/em\u003e: \u003c/strong\u003eTo determine the pattern of axial variation in subjects with initial shortened axial length during the entire period of orthokeratology and to discuss the possibility of shortened AL after one month of orthokeratology becoming a predictor of myopia control.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cem\u003eMethod\u003c/em\u003e: \u003c/strong\u003eThis study retrospectively included 106 children with myopia aged 8 to 14 wearing OK lenses.\u0026nbsp;eyes with shortened axial length (AL) at the first-month visit were enrolled in the axial length shortening (ALS) group, and 52 eyes without shortened AL were enrolled in the no axial length shortening (NALS) group. Axial length and refractive error at baseline and within the entire period of orthokeratology (20 months), including fitting, washout period and re-wear, were measured.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cem\u003eResults\u003c/em\u003e: \u003c/strong\u003eIn the ALS group, AL became longer after shortening and slowly exceeded baseline; afterward, AL experienced a rebound during the washout period and shortened again if OK lenses were re-worn. After washout period, significant difference in AL (ALS:0.28±0.19 mm, NALS: 0.52±0.17 mm) and spherical equivalent(ALS:-0.43±0.44D, NALS:-0.91±0.40D) between the two groups were found(\u003cem\u003eP\u003c/em\u003e＜0.05). The changes in AL and SE were both significantly correlated with the changes in AL at the first-month visit (\u003cem\u003eP\u003c/em\u003e＜0.05).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cem\u003eConclusion\u003c/em\u003e:\u003c/strong\u003e After AL is shortened in the initial stage of orthokeratology, it will experience a rapid rebound during the washout period, and the shortening can reappear when re-wearing OK lenses. Hence, only including the washout period can we make an objective evaluation of orthokeratology. In addition, the existence and degree of axial shortening can be used as a predictor of long-term myopia development.\u003c/p\u003e","manuscriptTitle":"Axial Length Shortening After Orthokeratology and Its Relationship With Myopic Control","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-01-20 19:17:00","doi":"10.21203/rs.3.rs-1193988/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2022-04-01T10:14:02+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2022-03-21T18:38:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2022-03-15T20:48:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"12584ec2-ac7e-4c32-8722-6f65e60aaed4","date":"2022-03-04T19:52:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"53df0ace-6842-4984-a89d-0739fa9c67be","date":"2022-03-04T16:50:33+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-03-04T05:02:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-03-04T04:50:55+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2022-01-19T22:32:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2022-01-18T12:52:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Ophthalmology","date":"2021-12-22T02:24:31+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7f5e68a6-be3b-4e63-8467-6257edb37c0e","owner":[],"postedDate":"January 20th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2022-05-18T16:14:11+00:00","versionOfRecord":[],"versionCreatedAt":"2022-01-20 19:17:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1193988","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1193988","identity":"rs-1193988","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}