To summarize relevant evidence investigating the association between time spent outdoors and myopia in children and adolescents (up to 20 years).Systematic review and meta-analysis.Results from 7 cross-sectional studies were pooled in a meta-analysis. A further 16 studies (8 cross-sectional not meeting criteria for meta-analysis; 7 prospective cohort studies; 1 randomized, controlled trial [RCT]) were reported in the systematic review.The literature search included 4 databases (Medline, Embase, Web of Science, and Cochrane Central Register of Controlled Trials [CENTRAL]), and reference lists of retrieved studies. Estimates of association were pooled using random effects meta-analysis. We summarized data examining the association between time spent outdoors and prevalent myopia, incident myopia, and myopic progression.Pooled odds ratios (ORs) and 95% confidence intervals (CIs) for myopia for each additional hour spent outdoors per week from a meta-analysis.The pooled OR for myopia indicated a 2% reduced odds of myopia per additional hour of time spent outdoors per week, after adjustment for covariates (OR, 0.981; 95% CI, 0.973-0.990; P<0.001; I(2), 44.3%). This is equivalent to an OR of 0.87 for an additional hour of time spent outdoors each day. Three prospective cohort studies provided estimates of risk of incident myopia according to time spent outdoors, adjusted for possible confounders, although estimates could not be pooled, and the quality of studies and length of follow-up times varied. Three studies (2 prospective cohort and 1 RCT) investigated time spent outdoors and myopic progression and found increasing time spent outdoors significantly reduced myopic progression.The overall findings indicate that increasing time spent outdoors may be a simple strategy by which to reduce the risk of developing myopia and its progression in children and adolescents. Therefore, further RCTs are warranted to investigate the efficacy of increasing time outdoors as a possible intervention to prevent myopia and its progression.Copyright © 2012 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

目的 观察足球、羽毛球和乒乓球三项球类运动对小学1~3年级学生动态视敏度的影响。方法 2019年2月至6月，选择4所小学1~3年级7~9岁学生123名，分为对照组(n = 32)、羽毛球组(n = 33)、乒乓球组(n = 30)和足球组(n = 28)，各实验组参加相应球类训练16周，对照组无相关干预。训练前后进行动态视敏度测量。结果 各实验组的动态视敏度均较训练前提高(t > 2.196, P t = 1.570, P > 0.05)。动态视敏度提高百分比依次为：足球(26.82%)、羽毛球(25.44%)、乒乓球(19.21%)。结论 球类运动对提高小学低年级学生动态视敏度有积极作用；大球类运动效果可能更佳。

The beneficial effects of increasing outdoor physical activity time on children's myopia onset and physical well-being are widely acknowledged. However, in countries with competitive educational systems, such as China, parents and school administrators may be relatively reluctant to increase the extracurricular physical activity time for children due to concerns that this action will compromise children's academic performance.To investigate whether additional extracurricular physical activity time after school compromises the academic performance of schoolchildren.This cluster randomized clinical trial was conducted from October 2020 to June 2021 in Yudu, Jiangxi, China. Eligible children in grades 3 and 4 from 24 elementary schools were randomized to the intervention or control group. Primary analysis was conducted in the full sample using the intention-to-treat principle.The intervention group received 2 hours of after-school physical activity time outdoors on school days. The control group was free to arrange their after-school activity.The primary outcome was the between-group mean difference in mathematics test scores at the end of 1 academic year, with a noninferiority margin of -3.3 points. Standardized mathematics tests, physical fitness assessments (in reference to the 2018 National Physical Fitness Survey Monitoring Programme in China), and cycloplegic autorefraction were performed at baseline and the end of 1 academic year. Myopia was defined as a cycloplegic spherical equivalent refraction of -0.5 diopters or less in either eye.A total of 2032 children (mean [SD] age, 9.22 [0.62] years; 1040 girls [51.2%]) from 24 schools were randomized to the intervention group (12 schools; 1012 children) or control group (12 schools; 1020 children). The mean (SD) mathematics score at the end of 1 academic year was 78.01 (17.56) points in the intervention group and 77.70 (17.29) points in the control group. The adjusted between-group mean difference was 0.65 points (95% CI, -2.85 to 4.15). The adjusted between-group mean difference in physical fitness score was 4.95 points (95% CI, 3.56-6.34; P < .001) and -1.90% (95% CI, -18.72% to 14.91%; P > .99) in myopia incidence.Results of this trial indicate that, compared with the control practice of free play after school, adding 2 hours of extracurricular physical activity outdoors after school was noninferior in academic performance and had superior efficacy in improving physical fitness.ClinicalTrials.gov Identifier: NCT04587765.

目的 探究闭锁性技能身体活动结合动态视觉任务对小学四年级近视儿童动态视敏度和静态视敏度的影响。方法 2019年9月,选取苏州市带城实验小学四年级近视学生37例作为受试者。根据屈光系统调节工作原理,设计结合视觉切换任务的闭锁性技能身体活动干预方案,干预16周。干预前、干预8周后和干预16周后测量动态视敏度和静态视敏度。结果 干预16周后,所有近视学生动态视敏度和静态视敏度均显著提高(F > 15.933, P t| > 3.353, P t = -2.830, P 结论 闭锁性技能身体活动结合动态视觉任务可改善四年级近视学生的视力水平。

Myopia has reached epidemic levels in parts of East and Southeast Asia. However, there is no effective intervention to prevent the development of myopia.To assess the efficacy of increasing time spent outdoors at school in preventing incident myopia.Cluster randomized trial of children in grade 1 from 12 primary schools in Guangzhou, China, conducted between October 2010 and October 2013.For 6 intervention schools (n = 952 students), 1 additional 40-minute class of outdoor activities was added to each school day, and parents were encouraged to engage their children in outdoor activities after school hours, especially during weekends and holidays. Children and parents in the 6 control schools (n = 951 students) continued their usual pattern of activity.The primary outcome measure was the 3-year cumulative incidence rate of myopia (defined using the Refractive Error Study in Children spherical equivalent refractive error standard of ≤-0.5 diopters [D]) among the students without established myopia at baseline. Secondary outcome measures were changes in spherical equivalent refraction and axial length among all students, analyzed using mixed linear models and intention-to-treat principles. Data from the right eyes were used for the analysis.There were 952 children in the intervention group and 951 in the control group with a mean (SD) age of 6.6 (0.34) years. The cumulative incidence rate of myopia was 30.4% in the intervention group (259 incident cases among 853 eligible participants) and 39.5% (287 incident cases among 726 eligible participants) in the control group (difference of -9.1% [95% CI, -14.1% to -4.1%]; P < .001). There was also a significant difference in the 3-year change in spherical equivalent refraction for the intervention group (-1.42 D) compared with the control group (-1.59 D) (difference of 0.17 D [95% CI, 0.01 to 0.33 D]; P = .04). Elongation of axial length was not significantly different between the intervention group (0.95 mm) and the control group (0.98 mm) (difference of -0.03 mm [95% CI, -0.07 to 0.003 mm]; P = .07).Among 6-year-old children in Guangzhou, China, the addition of 40 minutes of outdoor activity at school compared with usual activity resulted in a reduced incidence rate of myopia over the next 3 years. Further studies are needed to assess long-term follow-up of these children and the generalizability of these findings.clinicaltrials.gov Identifier: NCT00848900.

目的 研究追加视觉识别任务的体育活动对儿童动态视敏度和静态视敏度的影响。方法 基于ICF视功能及看的活动分析,设计4种追加视觉任务的体育活动。2018年6至8月,选取38名6~9岁视觉功能正常的业余体校学生,训练8周。训练前、训练4周和训练8周时,测量动态视敏度和静态视敏度。结果 训练后,被试动态视敏度和静态视敏度均有显著提高(F &#x0003E; 24.368, P &#x0003C; 0.001)。男生双眼静态视敏度改善程度大于女生(t &#x0003E; 2.161, P &#x0003C; 0.05)。动态视敏度与静态视敏度正相关(r &#x0003E; 0.424, P &#x0003C; 0.01)。结论 追加视觉任务的体育活动对改善6~9岁儿童动态视敏度和静态视敏度有积极作用,可以作为提高儿童视力健康的干预手段。

Our meta-analyses assess the benefit of outdoor activities on myopia onset and myopic shift among school-aged children reported in prospective intervention studies.The purpose of this study was to investigate the reduced risk of myopia development, myopic shift, and axial elongation with more outdoor activity time among school-aged children.A literature search was conducted using PubMed, MEDLINE, Scopus, EMBASE, VisionCite, and Cochrane Library. Five clinical trials met our selection criteria. Three outcome variables were used to assess the benefit of intervention: relative risk (RR), difference in myopic shift rate, and difference in axial elongation rate. Meta-analyses were applied to each outcome variable under the random-effects model. Children were grouped according to their initial refractive status: initial myopes, initial nonmyopes, or mixed.The pooled RR indicates that there is a reduced risk of developing myopia with more hours of outdoor activities per week (RR, 0.66; 95% confidence interval [CI], 0.49 to 0.89). The overall rate of myopic shift rate was slower in the intervention group compared with the control group (0.13 diopter/y; 95% CI, 0.08 to 0.18). The axial elongation was also slower (-0.03 mm/y; 95% CI, -0.05 to -0.00). The benefit of slowing myopic shift was observed in all initially nonmyopic cohorts (three of three) and most of the initially myopic cohorts (two of three).The meta-analysis results suggest that there is a slightly lower risk of myopia onset and myopic shift with more hours of outdoor activities. Future clinical trials are needed to assess its long-term effect and whether the effect varies by initial myopic status.

Myopia, especially high myopia, would cause damage in the choroid, retina and sclera, thereby leading to vision loss. Although refractive error correction can help improve visual acuity, the pathology of myopia, a global issue, remains unclear and myopia progression, as well as concomitant fundus progression, remains uncontrolled. Under such circumstances, prevention of myopia is of great significance and thus should be prioritized.To explore whether outdoor time has positive significance for myopia prevention.Databases of Pubmed, Science Direct, the Cochrane Library, the Chinese National Knowledge Infrastructure and the Wanfang Database were searched. The following terms or their combinations were used: myopia, prevention, control, random, randomized, randomization, intervention, outdoor. The full search strategy was shown in the Appendix below. The databases were last searched on -October 24, 2018.Randomized controlled trials (RCTs) that participants accepted outdoor activity as an intervention measure for myopia prevention were included.Two review authors independently extracted data and assessed the risk of bias for included studies. A fixed-effects model was applied, given that the heterogeneity among included studies was small.Five RCTs with 3,014 subjects were included. Subjects' age ranged from 6 to 12 years, and the follow-up duration ranged from 9 to 36 months. Spherical equivalent error (SER) of the outdoor group was larger than that of the control group, and the pooled mean difference (MD) was 0.15 (95% CI 0.06-0.23) diopter (D). The change in SER of the outdoor group was smaller than that of the control group, with a pooled MD of 0.17 (95% CI 0.16-0.18) D. New myopia cases in the outdoor group were fewer than that of the control group, and the pooled risk ratio was 0.76 (95% CI 0.67-0.87). The change in axial length of the outdoor group was smaller than that of the control group, and the pooled MD was -0.03 (95% CI -0.03 to -0.03) mm. For all analyzed outcomes, there was no heterogeneity across included studies (I2 = 0%) and there was no publication bias either.Outdoor time helps slow down the change of axial length and reduce the risk of myopia.© 2019 S. Karger AG, Basel.

Sport has been known to be one of the most important factors in preventing cardiovascular disorders; some studies suggest its role in preventing neurodegenerative diseases. This review discusses the results of various studies regarding the effects of physical exercises on intraocular pressure (IOP), myopia, certain physical parameters of the eye, ocular blood flow, and retinal electrical function. Although dynamic exercises are known to reduce IOP from 1.2 to 5.9 mm Hg only for a short period of time, uncertainty persists about whether isometric exercises or activities such as yoga can increase IOP up to 16.7 mm Hg. There has been an established connection between the time being spent outdoor and reduction in the odds of myopia-2% less odds for every hour spent outdoor. Physical activity and the level of physical fitness have an impact on the changes of b-wave electroretinogram and P100. Physical exercises increase perfusion pressure up to 190% baseline and also increase choroidal blood flow up to 140%, thus providing more blood to retina. Sport-induced change on visual field is a subject of controversy. Majority of patients show a better ocular physiological function due to sports and sports are thus considered essential for preventing common ocular diseases. Further research should focus more on long-term effects of sport-induced changes in ocular physiology and newly discovered techniques may be utilized for such purposes.

There is an epidemic of myopia in East and Southeast Asia, with the prevalence of myopia in young adults around 80-90%, and an accompanying high prevalence of high myopia in young adults (10-20%). This may foreshadow an increase in low vision and blindness due to pathological myopia. These two epidemics are linked, since the increasingly early onset of myopia, combined with high progression rates, naturally generates an epidemic of high myopia, with high prevalences of "acquired" high myopia appearing around the age of 11-13. The major risk factors identified are intensive education, and limited time outdoors. The localization of the epidemic appears to be due to the high educational pressures and limited time outdoors in the region, rather than to genetically elevated sensitivity to these factors. Causality has been demonstrated in the case of time outdoors through randomized clinical trials in which increased time outdoors in schools has prevented the onset of myopia. In the case of educational pressures, evidence of causality comes from the high prevalence of myopia and high myopia in Jewish boys attending Orthodox schools in Israel compared to their sisters attending religious schools, and boys and girls attending secular schools. Combining increased time outdoors in schools, to slow the onset of myopia, with clinical methods for slowing myopic progression, should lead to the control of this epidemic, which would otherwise pose a major health challenge. Reforms to the organization of school systems to reduce intense early competition for accelerated learning pathways may also be important.Copyright © 2017 Elsevier Ltd. All rights reserved.

The prevalence of myopia in developed countries in East and Southeast Asia has increased to more than 80% in children completing schooling, whereas that of high myopia has increased to 10%-20%. This poses significant challenges for correction of refractive errors and the management of pathological high myopia. Prevention is therefore an important priority. Myopia is etiologically heterogeneous, with a low level of myopia of clearly genetic origins that appears without exposure to risk factors. The big increases have occurred in school myopia, driven by increasing educational pressures in combination with limited amounts of time spent outdoors. The rise in prevalence of high myopia has an unusual pattern of development, with increases in prevalence first appearing at approximately age 11. This pattern suggests that the increasing prevalence of high myopia is because of progression of myopia in children who became myopic at approximately age 6 or 7 because age-specific progression rates typical of East Asia will take these children to the threshold for high myopia in 5 to 6 years. This high myopia seems to be acquired, having an association with educational parameters, whereas high myopia in previous generations tended to be genetic in origin. Increased time outdoors can counter the effects of increased nearwork and reduce the impact of parental myopia, reducing the onset of myopia, and this approach has been validated in 3 randomized controlled trials. Other proposed risk factors need further work to demonstrate that they are independent and can be modified to reduce the onset of myopia.