Eye Exercises for Myopia Prevention and Control: A Systemic Review and Meta-Analysis

BackgroundMyopia is increasing in prevalence and developing at a younger age, a trend exacerbated by the COVID-19 pandemic. To combat the epidemic of myopia, eye exercises have been promoted in recent national efforts in mainland China, continuing a compulsory national school policy for over 50 years. We aimed to evaluate the efficacy of eye exercises in preventing and controlling myopia. MethodsIn this systemic review and meta-analysis, we searched nine major Chinese and English databases from their inception to December 15, 2022. We included studies that compared the effects of eye-exercise interventions with controls (no eye exercises) on at least one myopia-related indicator. Studies could be either randomized or non-randomized controlled trials. Two coders independently screened records for eligibility; extracted study-level data (study information, sample sizes, interventions, and myopia indicators); and assessed the risk of bias (Cochrane Risk of Bias Tool 2.0) and study heterogeneity (I2). Using random-effect models and sensitivity analysis, we estimated the effects of eye exercises compared to control on changes in visual acuity, diopter, and curative effects (axial length was not reported). We used standardized mean differences (SMDs) to evaluate visual acuity and diopter outcomes, and risk ratios (RRs) to assess curative effects. This study is registered on the Open Science Framework (https://osf.io/dr5jk). FindingsOf the 1765 records identified, 1754 were excluded: 423 were duplicates, 1223 did not have a control group, 16 did not have full-text, and 92 did not fulfill other inclusion criteria. In total, 11 studies were included in the meta-analysis, with 921 participants (399 in eye-exercise interventions and 522 in control groups). Nine studies had some concerns of bias in at least two domains, and two studies had a high risk of bias in two domains. Seven studies used visual acuity to measure myopia; visual acuity declined after eye-exercise interventions (SMD=-0{middle dot}67, 95% CI -1{middle dot}28 to -0{middle dot}07, Z=2{middle dot}17, p=0{middle dot}03) and the effect was not better than control (SMD=-0{middle dot}50, 95% CI -1{middle dot}16 to 0{middle dot}16, Z=1{middle dot}49, p=0{middle dot}14). Two studies used diopter to measure myopia; the effect of eye-exercise interventions did not differ from control (SMD=-1{middle dot}74, 95% CI -6{middle dot}27 to 2{middle dot}79, Z=0{middle dot}75, p=0{middle dot}45). Seven studies reported curative effects; eye exercises had a higher curative effect than control (RR=0{middle dot}40, 95% CI 0{middle dot}23-0{middle dot}71, Z=3{middle dot}13, p<0{middle dot}01). InterpretationEye exercises are not effective in preventing or controlling the progression of myopia, as measured by changes in visual acuity and diopter. A small positive effect is observed in curative effects, but the studies have high heterogeneity and potential publication bias, with major weaknesses in design (inadequate measures, small sample sizes, biases, failure to consider side effects, and failure to include established effective interventions as control). There is little evidence to support the continued use of eye exercises to manage myopia in schoolchildren. FundingGuangdong Basic and Applied Basic Research Foundation (2019A1515110574) and Shenzhen Fundamental Research Program (JCYJ20210324134603010). Research in contextO_ST_ABSEvidence before this studyC_ST_ABSMyopia is a growing global public health challenge and has reached epidemic proportions in East and Southeast Asia. Given the large population of schoolchildren in these regions and the societal burden and personal costs of myopia, myopia control has become a top public health priority, particularly in mainland China. Schoolchildren in mainland China have been required to perform eye exercises twice a day for over 50 years; this compulsory policy has also been emphasized in recent national efforts to combat the myopia epidemic. We searched PubMed for meta-analyses of controlled trials that assessed the efficacy of eye exercises against myopia onset or its progression, using search terms related to "myopia" and "eye exercises", but did not retrieve any from database inception until January 23, 2023. Added value of this studyThis study is the first meta-analysis of controlled trials examining the efficacy of eye exercises in preventing and controlling myopia. By including trials published in Chinese and English from database inception to December 15, 2022, the meta-analysis found that visual acuity declined after eye-exercise interventions (SMD=-0{middle dot}67, 95% CI -1{middle dot}28 to -0{middle dot}07, Z=2{middle dot}17, p=0{middle dot}03) and the effect was not better than control (SMD=-0{middle dot}50, 95% CI -1{middle dot}16 to 0{middle dot}16, Z=1{middle dot}49, p=0{middle dot}14), with a similar pattern in diopter measures (SMD=-1{middle dot}74, 95% CI -6{middle dot}27 to 2{middle dot}79, Z=0{middle dot}75, p=0{middle dot}45). Additionally, the curative effect of eye-exercise interventions was higher than control (RR=0{middle dot}40, 95% CI 0{middle dot}23-0{middle dot}71, Z=3{middle dot}13, p<0{middle dot}01). The meta-analysis also highlighted five major weaknesses in extant studies: inadequate measures, small sample sizes, biases, failure to consider side effects, and failure to include established effective interventions as control. Implications of all the available evidenceThe findings of this study, along with previous observational evidence, suggest that there is little support for using eye exercises to prevent myopia or control its progression. These results challenge the continued use of eye exercises as a policy to control myopia in schoolchildren and emphasize the need for rigorous research to establish their efficacy.