Prevalence of myopia: A large-scale population-based study among children and adolescents in weifang, china

ZEISS Young Investigator Award in myopia research and Josh Wallman Memorial Lecture. Understanding Myopia Development

In this paper, three key questions regarding our understanding of myopia are addressed: predictors of myopia onset, the mechanism underlying its development and potential treatments to slow its progression. To explore these aspects, first, a non-invasive biomarker using the chicken model of myopia was investigated. A strong correlation was found between myopia development and both increased ultraviolet (UV) fundus reflectivity and thinning of the retinal nerve fibre layer (RNFL). Through electron microscopy, it was observed that, within hours of vision deprivation, significant thinning of the myelin sheaths around large axons in the RNFL occurred, accompanied by an increase in UV fundus reflectivity-changes that took place even before eye elongation. These findings suggest that early myelin degradation contributes to myopia development and may serve as a predictive biomarker in the animal model. However, the prediction of myopia onset in humans remains challenging. To investigate the mechanism of myopia development further, visual stimuli affecting emmetropic and myopic eyes differently were examined. The results indicated that myopic eyes have weaker responses to positive defocus and short-term stimulation to simulated chromatic aberrations when compared with emmetropic eyes, suggesting a possible impairment in retinal signalling pathways responsible for detecting blur and defocus. In terms of treatment, it was found that reading large text with inverted contrast (bright letters on a dark background) induced axial length shortening and choroidal thickening in both emmetropic and myopic eyes. Furthermore, repeated exposure to digitally simulated myopic chromatic defocus was shown to reduce axial length and increase choroidal thickness effectively in myopic human subjects. These findings align with results from animal models and indicate that this approach may serve as a potential strategy for myopia control. However, more research is necessary to establish an effective myopia control intervention suitable for children and adolescents.

Design and 3D Printing of Soft Orthokeratology Lenses

The effectiveness of hard orthokeratology (OK) lenses in controlling myopia has been confirmed in clinical practice. However, there exist defects including wear discomfort, limited regulation of mechanical properties and geometry, and effectiveness inconsistency with the expected efficacy. Herein, we analyze the relationship between the mechanical properties of OK lenses and the vertex displacement of the human cornea through the finite element model. It is noted that the expected corneal deformation of 15-20 μm can be achieved by soft OK lenses with an elasticity modulus above 9 MPa, which is far lower than the 2.7 GPa of commercial OK lenses. No obvious displacement difference occurred when the elasticity modulus of the OK lenses exceeded 200 MPa. Thus, we propose the hypothesis of soft OK lenses based on hydrogel materials for controlling myopia. The soft OK lenses are fabricated by a two-step 3D printing technology using a multicomponent bioink containing methyl methacrylate, hydroxyethyl methacrylate, polyethylene glycol diacrylate, and 3-(trimethoxysilyl)propyl methacrylate (KH-570). The printed OK lenses possess comfort wear, high light transmittance, smooth surface, regulated elasticity modulus (from 33 to 535 MPa) and geometry, and excellent biocompatibility. Additionally, the effectiveness of soft OK lenses is confirmed through a porcine corneal model with obvious corneal deformation comparable to that of the commercial ones. This study demonstrates the feasibility of soft OK lenses for controlling myopia and provides support for the design and fabrication of soft OK lenses for comfortable wear.

Exploring the influences of myopia in primary and secondary school students in Xinjiang using propensity score matching

Objective

Due to the high prevalence of myopia among primary and secondary school students in Shihezi City in recent years, this study was conducted to understand the prevalence and the factors influencing it and to provide a scientific basis for future interventions to improve, protect, and promote the visual health of these students.

Methods

The study population consisted of primary and secondary school students in Shihezi City. Stratified random sampling was employed for participant selection. Schools were first randomly chosen from both urban and rural areas of Shihezi City, followed by grade-level stratification within each selected school. Two classes per grade were randomly designated as sample classes. All students underwent vision screening. Students in Grade 4 and above completed questionnaires to investigate myopia-associated factors. To control for confounding effects, four variables-grade level, gender, urban/rural residence, and parental myopia status-were matched and analyzed using propensity score matching.

Results

A total of 6,732 individuals were surveyed in this study, with 6,092 ultimately included (participation rate: 90.49%), of whom boys represented 51.10%. The overall prevalence of myopia was 59.55%. The prevalence of myopia in urban areas was 68.17%, while in rural areas, it was 42.42%, a difference that was statistically significant. Risk factors for myopia included being female, having myopic parents, engaging in close-distance reading or writing, sleeping less than 8 h per night, and receiving education at an older age. Protective factors against myopia included attending school in a rural area, watching television from a distance of more than 3 m, and having had a vision examination at least once in the past year.

Conclusion

The myopia rates in Shihezi City exceed the national average and show a gradual increase with advancing school age. In addition to inherent factors such as gender, receiving education at an older age, and genetic predisposition, myopia prevention strategies should include proper sitting posture, good eye habits, and health promotion measures.

Case series: Switching myopia management therapies in a real-world academic clinic

SIGNIFICANCE

Slowing myopia progression is quickly becoming the clinical standard of care, but little is known about how changing treatment alters treatment effect. This case series provides insight on how changing treatment modality may affect treatment outcomes in myopia management.

PURPOSE

Aiming to control myopia progression in children is becoming the clinical standard of care. Little is known about the effect of changing treatment on myopic progression. We present a case series of real-world myopia management patients who underwent a change in treatment method and report the observed effect on axial length.

METHODS

Clinical records from the University of Houston Myopia Management Service were reviewed to identify children who underwent a change in treatment. The analyzed dataset consisted of 44 clinic assessments from seven children including two who were switched from peripheral defocus soft contact lenses to orthokeratology, two who were switched from orthokeratology to peripheral defocus soft contact lenses, and three who received combination therapy following an initial period of treatment with either orthokeratology, peripheral defocus soft contact lenses, or atropine alone. Axial length measurements were adjusted by subtracting central corneal thickness from the raw axial length value and then converted to an annualized rate (mm/y) by subtracting the previous corneal thickness-adjusted from the current corneal thickness-adjusted axial length and dividing by elapsed time between the successive clinic visits.

RESULTS

Age at initial assessment ranged from 6.6 to 12.6 years (M = 9.3 ± 2.4) with follow-up times ranging between 26 and 78 months (M = 43 ± 18.5). Each individual had a minimum of two clinical visits per treatment type. The mean (SD) for central corneal thickness-annualized adjusted axial length growth in both the eyes and chronological age at the beginning of each treatment type was calculated. Estimated progression rates are summarized separately for each individual and treatment. Data are grouped by patients who switched treatments for either lack of efficacy or other clinical issues.

CONCLUSIONS

In a real-world setting, there are various reasons that necessitate a change in treatment. In this sample, change in treatment continued to show slowing of myopia progression, regardless of reason for change.

Students' association of poor eye-use behavior with myopia: focus on study phase

BACKGROUND

To investigate the prevalence of poor eye-use behavior and myopia in Chinese students, and examine the associations of poor eye-use behavior with myopia, as well as its study phase differences.

METHODS

From March to July 2023, a total of 67 910 students were selected from 56 schools in 14 cities of China by stratified cluster sampling. The Eye-use Behavior Evaluation Scale for Students (EBESS) was adopted to investigate the eye-use behavior of students. Students underwent an uncorrected visual acuity examination and a non-cycloplegic autorefraction examination. The chi-square test was used to compare the prevalence of myopia between different groups. The binary logistic regression model was conducted to analyze the association of poor eye-use behavior with myopia.

RESULTS

The prevalence of poor eye-use behavior and myopia of students were 27.6% and 53.0%, respectively. The poorer the eye-use behavior of students, the higher the prevalence of myopia (P < 0.001). After adjusting for age, gender, sibling, parental myopia, parental education level, self-reported learning burden, mode of travel to school, physical education lesson, city, usage distance of mobile phone / iPad / game console, reading and writing distance, weekdays outdoor time, and weekends outdoor time, binary logistic regression model analysis results showed that the poor eye-use behavior was positively correlated with myopia (OR = 1.10, 95% CI: 1.03 ~ 1.19). According to the study phase and further stratified analysis, in primary school (OR = 1.35, 95% CI: 1.20 ~ 1.50) and senior high school students (OR = 1.28, 95% CI: 1.08 ~ 1.51), poor eye-use behavior was positively correlated with myopia. However, in kindergarten and junior high school students, there was no statistically significant difference (P > 0.05).

CONCLUSION

Poor eye-use behavior was a potential risk factor for myopia in students, and this effect was significantly different between study phases. This suggests that future research should establish interventions to protect students from the effects of poor eye-use behavior.

Knowledge, attitude and practice towards myopia among parents of primary school students: a cross-sectional study

BACKGROUND

Myopia is a common visual condition that requires proper management and prevention strategies, especially among children.

OBJECTIVE

To investigate the knowledge, attitude and practice (KAP) towards myopia among parents of primary school-age children.

DESIGN

Cross-sectional study using a self-administered questionnaire.

PARTICIPANTS/SETTING

A total of 552 parents of primary school-age children participated in the study, which was conducted at a primary school in Wuxi City, China, between October and November 2022.

INTERVENTION

No intervention was applied; the study was observational, collecting data through questionnaires.

MAIN OUTCOME MEASURES

KAP scores regarding myopia among parents.

STATISTICAL ANALYSES PERFORMED

Univariable and multivariable logistic regression analyses were performed to identify associations between demographic factors and KAP scores.

RESULTS

Mean scores for KAP were 8.38±2.29 (theoretical minimum-maximum: 0-12), 25.01±2.79 (theoretical minimum-maximum: 6-30) and 26.37±3.96 (theoretical minimum-maximum: 6-33), respectively. Higher education, income, personal and child myopia and having two children were associated with better knowledge. Parental female gender, higher income, myopia and age 33-44 years were associated with positive attitudes. Better attitudes and having a child in the fourth grade were associated with proactive practices.

CONCLUSIONS

Parents of primary school-age children showed positive attitudes and proactive practices but had inadequate knowledge about myopia. Targeted health education programmes for parents with lower education and income levels could be recommended to improve knowledge and maintain positive attitudes towards myopia management.

Machine-learning random forest algorithms predict post-cycloplegic myopic corrections from noncycloplegic clinical data

SIGNIFICANCE

Machine learning random forest algorithms were used to predict objective refractive outcomes after cycloplegic refraction using noncycloplegic clinical data. A classification model predicted post-cycloplegic myopia and could be useful in screening, and a second regression model predicted post-cycloplegic refractive and could provide a useful objective starting point in noncycloplegic subjective refractions.

PURPOSE

A classification model sought to predict post-cycloplegic myopia using noncycloplegic clinical data to enhance myopia screening accuracy, whereas the regression model looked to predict objective refraction outcomes after cycloplegia for use as a starting point for noncycloplegic subjective refraction.

METHODS

A cross-sectional study included data from 2483 eyes. Pre-refraction measurements, such as uncorrected visual acuity, axial length, and corneal curvature radius, were recorded. After cycloplegia, the spherical equivalent was measured. Random forest-based classification and regression models were established with input variables including age, gender, axial length, corneal curvature radius, axial length-to-corneal curvature radius ratio, spherical equivalent, and uncorrected visual acuity. Model performance was assessed using various metrics.

RESULTS

The random forest classification model achieved high out-of-bag validation accuracy (92%), cross-validation accuracy (93%), external validation accuracy (94%), and precision (95%). The external validation sensitivity was 93%, and specificity was 95%. The regression model internal validation showed an out-of-bag validation R2 of 0.86, root mean square error (RMSE) of 0.66, and mean absolute error of 0.49. The 10-fold cross-validation R2 was 0.87, the RMSE was 0.64, and the mean absolute error was 0.48. In the external validation, R2 was 0.88, the RMSE was 0.63, and the mean absolute error was 0.48.

CONCLUSIONS

By analyzing noncycloplegic clinical data, the classification model enables earlier detection of myopia, supporting timely intervention and management. The regression model aims to accurately predict post-cycloplegia myopic corrections, providing reliable initial data for subjective refraction. This could help optometrists perform noncycloplegic subjective refraction more efficiently and is particularly relevant in China, where retinoscopy is not yet fully popularized and many school students decline cycloplegic refraction due to academic pressures and limited free time, primarily because it requires a follow-up the next day.

Prevalence of myopia and refractive parameters among children and adolescents in Hi-tech District of Chengdu City

Objective

To analyze the prevalence of myopia among children and adolescents in Chengdu from 2021 to 2023, providing insights for myopia prevention and control.

Methods

This study was a school-based cross-sectional study in children and adolescents aged 3-18 years in Hi-tech District of Chengdu City. All the students underwent comprehensive ocular measurement, including uncorrected binocular visual acuity (VA), spherical equivalent error (SER) with noncycloplegic autorefraction, corneal radius (CR), and axial length (AL).

Results

Over the three-year study period from 2021 to 2023, the overall prevalence of myopia was 38.15%, with annual rates of 38.74% in 2021, 38.67% in 2022, and 37.03% in 2023. The prevalence and severity of myopia increased significantly with age (P < 0.001). The prevalence was consistently higher among girls (P < 0.001) with 40.17% in 2021, 39.43% in 2022, and 38.33% in 2023 compared to 37.03%, 38.05% and 35.85% among boys in the years, respectively. The myopia prevalence increased with school level (P < 0.001). Mild myopia was the most common (24.47%), followed by moderate (10.77%) and severe myopia (2.91%). The mean SER were -1.72 ± 1.57 D in 2021, -1.32 ± 1.51 D in 2022, and -1.42 ± 1.36 D in 2023 (P < 0.001). AL was stable across most age groups, with mean AL across the overall sample of 23.80 ± 1.02 mm in 2021, 23.79 ± 1.04 mm in 2022, and 23.81 ± 1.04 mm in 2023.

Conclusion

Myopic prevalence among children and adolescents in Hi-tech District of Chengdu City decreased from 2021 to 2023. The prevalence increased with age and school level, indicating a need for targeted interventions. Significant changes in spherical equivalent refraction and AL emphasize the importance of early intervention and regular monitoring of myopia for an effective management.

Electroacupuncture alleviates damage to myopic RGCs probably through lncRNA-XR_002789763.1-mediated mitophagy

BACKGROUND

Mitophagy is closely related to the regulation of retinal ganglion cell (RGC) structure and function. Our previous study suggested that long noncoding RNAs (lncRNAs) can cause damage to myopic RGCs. However, whether electroacupuncture (EA) treatment can delay myopia progression through lncRNA-mediated mitophagy in RGCs is currently unknown. This study aimed to investigate the effect of EA on lncRNA-mediated mitophagy in myopic RGCs.

METHODS

Our study investigated the modulatory effect of EA on mitophagy in RGCs of guinea pigs with form-deprived myopia (FDM). RNA sequencing was performed to further analyze the expression profiles of lncRNAs and mRNAs in RGCs of guinea pigs with FDM after EA treatment, and the related competing endogenous RNA (ceRNA) network was constructed. Importantly, PINK1, a mitophagy-related gene, was included in the core ceRNA network to explore the relationship between lncRNAs and mitophagy in myopic RGCs regulated by EA. We also collected eyeballs from myopic and highly myopic adults to further verify the mechanistic results.

RESULTS

This study demonstrated that EA treatment delayed the reduction in refraction and increase in axial length and alleviated RGC damage in guinea pigs with FDM. We further found that EA could induce mitophagy in guinea pig RGCs with FDM by promoting the mitophagy-related PINK1/Parkin signaling pathway. Moreover, mitophagy is inhibited in the retina of highly myopic adults. RNA sequencing revealed that 599 lncRNAs and 455 mRNAs were differentially expressed in guinea pig RGCs with FDM after EA treatment. A core ceRNA network was constructed by incorporating PINK1 and verified by related molecular experiments, and we found that EA treatment may induce mitophagy and attenuated RGC injury in guinea pigs with FDM by sponging miR-342-5p through lncRNA-XR_002789763.1 to activate the PINK1/Parkin signaling pathway and promote Mfn2 ubiquitination.

CONCLUSION

EA treatment might regulate lncRNA-XR_002789763.1/miR-342-5p axis and activate the mitophagy-related PINK1/Parkin signaling pathway, and promote Mfn2 ubiquitination, thereby alleviating RGC damage and delaying myopia progression.

Myopia in Children: Epidemiology, Genetics, and Emerging Therapies for Treatment and Prevention

Refractive errors, particularly myopia, are among the most prevalent visual impairments globally, with rising incidence in children and adolescents. This review explores the epidemiology and risk factors associated with the development of refractive errors, focusing on the environmental and lifestyle factors contributing to the current surge in myopia. We provide an overview of key genetic factors and molecular pathways driving the pathogenesis of myopia and other refractive errors, emphasizing the complex interplay between genetic predisposition and environmental triggers. Understanding the underlying mechanisms is crucial for identifying new strategies for intervention. We discuss current approaches to slow myopia progression in pediatric populations, including pharmacological treatment regimens (low-dose atropine), optical interventions, and lifestyle modifications. In addition to established therapies, we highlight emerging innovations, including new pharmacological agents and advanced optical devices, and insights into potential future treatments. Cutting-edge research into gene therapy, molecular inhibitors, and neuroprotective strategies may yield novel therapeutic targets that address the root causes of refractive errors. This comprehensive review underscores the importance of early intervention and highlights promising avenues for future research, aiming to provide pediatricians with guidance to ultimately improve clinical outcomes in managing and preventing myopia progression in children and young adults.

Research Hotspots of Acupuncture Treatment for Myopia Over the Past Decade: A Bibliometric Analysis (2014-2023)

Objective

To explore the research hotspots in acupuncture treatment for myopia from 2014 to 2023.

Methods

A comprehensive search was conducted in the Science Citation Index-Expanded (SCI-E) within the Web of Science Core Collection (WOSCC). We used CiteSpace 6.2.R6 to perform an in-depth analysis of the annual publication trends, prolific authors, institutions, keyword co-occurrences, and citation bursts. The study followed the PICO framework: the population (P) includes studies on patients with myopia, the intervention (I) is acupuncture treatment, no direct comparison (C) is applied, and the primary outcome (O) focuses on the identification of research trends and hotspots. Major outcome assessments included the analysis of publication trends over time, author productivity, influential journals, and the detection of emerging research topics through citation burst analysis. This bibliometric analysis was conducted on November 15, 2023.

Results

A total of 281 articles were included in the analysis. The trend line of annual publications over the past decade showed a modest increase, with a significant decline in 2019 and a surge in 2021. China and its affiliated academic institutions led globally in publication volume, with Ma Xiaopeng being the most prolific author and Fudan University the most influential institution. Ophthalmology emerged as the journal with the highest citation frequency. The most frequently occurring keywords were related to adolescent myopia and its complications. The developmental trajectory of the field is distinct, characterized by the integration of a single discipline.

Conclusion

Acupuncture shows promise as a complementary and alternative therapy for treating myopia, with growing interest in its clinical efficacy and mechanisms of action. Future research is likely to focus on optimizing treatment protocols and understanding the underlying biological mechanisms of acupuncture in myopia management.

Incidence of myopia in Swedish schoolchildren: A longitudinal study

PURPOSE

The prevalence of myopia in Scandinavia tends to be lower than in other parts of the world. This study aimed to investigate the incidence of myopia and its predictors in Swedish children to characterise this trend.

METHODS

A 2-year longitudinal study was conducted following a cohort of schoolchildren aged 8-16 years. Myopia was defined as a spherical equivalent refraction (SER) ≤ -0.50 D. The study enrolled 128 participants, 70 (55%) females with a mean age of 12.0 years (SD = 2.4).

RESULTS

The cumulative incidence of myopia during the follow-up period was 5.5%, and the incidence rate of myopia was 3.2 cases per 100 person-years. Participants with myopia at baseline exhibited a faster increase in refractive error during the follow-up period. Likewise, participants with two myopic parents exhibited a more marked change towards myopia, regardless of their initial refractive error.

CONCLUSION

In the current study, similar to prevalence, the incidence of myopia was low when compared with other parts of the world. These results lead us to formulate a new hypothesis that the normal emmetropisation process may be protected by low educational pressure practised in Sweden during early childhood. Further research is necessary to test this new hypothesis.

Knowledge, attitude, and practice of non-ophthalmic medical staff toward myopia-related fundus lesions

This study assessed the knowledge, attitude, and practice (KAP) of non-ophthalmic medical staff towards myopia-related fundus lesions. This multicenter, cross-sectional study enrolled non-ophthalmic medical staff of Suining City between January and May 2023 using a self-designed questionnaire. A total of 505 (93.19%) valid questionnaires were included. Their mean KAP scores were 8.10 ± 2.32 (range: 0-12), 20.27 ± 2.68 (range: 0-24), and 17.77 ± 5.04 (range: 0-28), respectively. Structural equation modeling indicated that knowledge has a positive effect on attitude (β = 0.307, P < 0.001), and attitude has a positive effect on practice (β = 0.604, P < 0.001). Moreover, a higher degree of myopia exhibited a positive effect on knowledge (β = 0.510, P < 0.001). Nurses and other medical staff showed a negative effect on knowledge (β = - 0.706, P < 0.001) compared to doctors. Working in secondary and tertiary public hospitals, as well as private hospitals, demonstrated a negative effect on practice (β = - 1.963, P < 0.001) compared to those working in primary hospitals. Non-ophthalmic medical staff exhibited moderate knowledge, positive attitudes, and moderate practices toward myopia-related fundus lesions. The degree of myopia, doctors vs. other medical staff, and the hospital level influence the KAP of non-ophthalmic medical staff.

Refractive Errors, Amplitude of Accommodation, and Myopia Progression in Kazakhstani Medical Students: 5-Year Follow-Up

Background/Objectives: this longitudinal study aimed to investigate the refractive errors, the amplitude of accommodation, and myopia progression in Kazakhstani medical students as they progressed from the first to the fifth course of their studies. Methods: A total of 696 students from Semey Medical University underwent non-cycloplegic and cycloplegic autorefraction in the first course, and 655 were available for examination in the fifth year of study. The amplitude of accommodation was measured before the instillation of cycloplegics using the push-up and push-down methods. A self-administered questionnaire was applied to evaluate the risk factors associated with myopia progression. Results: In the first course, the median spherical equivalent was -0.75 Diopters before cycloplegia and -0.25 Diopters after cycloplegia. In the fifth course, it constituted -1.125 Diopters before cycloplegia and -0.5 Diopters after cycloplegia. The proportion of students with myopia following cycloplegic refraction increased from 44.7% in the first course to 47.5% in the fifth course. The proportion of emmetropic students declined from 31.5% to 30.3%, and hyperopia decreased from 23.8% to 16.8%. The dioptric power of accommodative excess increased from 0.375 in the first year to 0.50 in the fifth year. The hours spent on near-work activities, such as reading books, writing, working at a computer, and using a mobile device, were significantly associated with a myopia progression of ≥0.5 Diopters. Conclusions: the findings of this study suggest implications for public health policy and educational practice.

Association between sleep and myopia in children and adolescents: a systematic review and meta-analysis

PURPOSE

There is a scarcity of literature focusing on sleep's impact on myopia in children despite an epidemic rise of myopia among the age group and the importance of early prevention. As such, this systematic review-meta-analysis aims to evaluate the association between various aspects of sleep and myopia in children and adolescents aged 0-19 years.

METHODS

We searched PubMed, EMBASE, and Cochrane Library on 08/12/2022 for studies reporting sleep in relation to myopia among children and adolescents. Myopia was defined as spherical equivalent refraction < -0.5 diopter. The primary outcome was the relationship between sleep duration and myopia prevalence. Secondary outcomes include the effect of sleep quality, bedtime, and waketime on myopia prevalence, incidence, and progression. Odds ratio (OR) was estimated with a 95% confidence interval (95% CI).

RESULTS

Eighteen studies (49,277 participants) were included in the review, and six studies (14,116 participants) were included in the meta-analysis for the primary outcome. There was no significant correlation between sleep and myopia prevalence (OR = 0.905, 95% CI = 0.782 to 1.047). Some studies suggested that better sleep quality (2 of 6 studies), earlier bedtime (3 of 5 studies), and later waketimes (2 of 3 studies) had protective effects on myopia.

CONCLUSION

Sleep duration did not affect myopia prevalence in children, while other aspects of sleep had plausible but inconclusive impacts on myopia development and progression. More research with diverse populations and standardized methods of reporting is needed.

The CroMyop study: myopia progression in Croatian children and adolescents-a 15-year retrospective analysis

Purpose

Myopia is a major global health issue, especially among children and adolescents. Understanding its traits and progression is vital for proper management and prevention. This study aimed to fill a gap in research by analyzing demographic and refractive data concerning myopia among children and adolescents in Croatia, with the goal of providing insights into myopia prevalence, progression rates, and associated risk factors within the Croatian population.

Design

This retrospective study utilized a comprehensive dataset from pediatric ophthalmology clinics at the University Eye Department, University Hospital "Sveti Duh," Zagreb, Croatia. The dataset included electronic medical records spanning from January 2008 to July 2023, encompassing demographic and refractive data.

Methods

Data analysis focused on individuals aged 4 to 18 years who were diagnosed with primary myopia and/or compound myopic astigmatism. Ophthalmic examinations, including visual acuity tests, cycloplegic refraction, and assessments for eye comorbidities, were conducted by experienced pediatric ophthalmologists. Statistical analysis, including t-tests, survival analysis, and logistic regression, was performed to assess myopia prevalence, progression rates, and associated factors. These analyses were adjusted for covariates such as age, parental myopia, and gender.

Results

The study included 895 individuals, 51 premyopes, 813 low myopes, and 31 high myopes. The average age of diagnosis was 11.37 ± 3.59 years for premyopes, 11.18 ± 3.53 years for low myopes, and 11.44 ± 4.35 years for high myopes. The fastest progression occurred in 2021 and 2022, -0.5 ± 0.12 D/y for premyopes and - 0.45 ± 0.1 D/y for low myopes. Premyopic progression to low myopia was associated with age 7-9 years (HR 2.42, 1.53 to 3.21) and both parents being myopic (HR 920.27. 850.16 to 950.53). Low myopic individuals with both myopic parents displayed the fastest 11-24 months after first visit progression rates, -0.69 (-0.52 to -0.87) D/y, while the 7-9 age group demonstrated -0.36 (-0.24 to -0.45) D/y. Low myopes aged 7-9 years with baseline SE between -6 D and -4 D were more strongly associated with ≤ - 0.5 D progression (OR = 2.0, 95% CI -1.00 to 2.39).

Conclusion

This study highlights the importance of environmental factors, genetics, and age in addressing myopia progression among Croatian youth, urging further research for effective local intervention strategies.

Prevalence of myopia among children and adolescents aged 6-16 during COVID-19 pandemic: a large-scale cross-sectional study in Tianjin, China

PURPOSE

This study aimed to determine the prevalence of myopia among children and adolescents aged 6-16 years during COVID-19 pandemic in Tianjin, China.

METHODS

This was a cross-sectional study using data from the Tianjin Child and Adolescent Research of Eye between March and June in 2021. A total of 909 835 children and adolescents aged 6-16 years from 1348 primary and secondary schools in Tianjin, China were recruited. Prevalence of myopia with 95% CIs was described in different regions, sexes and ages. The regions-standardised prevalence rate and chain growth rate of myopia in different ages were described the characteristics of myopia.

RESULTS

A total of 864 828 participants (95.05% participation rate) were included in the analysis. The age range was 6-16 with a mean age of 11.50±2.79 years. The overall prevalence of myopia was 54.71% (95% CI 54.60% to 54.81%). The prevalence of myopia was 57.58% (95% CI 57.43% to 57.73%) for girls and 52.05% (95% CI 51.91% to 52.20%) for boys. Students living in the six central districts had the highest prevalence of moderate myopia (19.09% (95% CI 19.01% to 19.17%)) and high myopia (5.43% (95% CI 5.39% to 5.48%)). The regions-standardised prevalence of myopia was increased by age and the highest chain growth rate of myopia was up to 47.99% at 8 years.

CONCLUSIONS

The prevalence of myopia in Tianjin is high during COVID-19 pandemic. The progression of myopia started to increase dramatically at 8 years, and the increasing slowed down at 14 years. For policy-makers, intervention in the lower age groups may be important to control myopia progression.

Myopia prevalence and ocular biometry in children and adolescents at different altitudes: a cross-sectional study in Chongqing and Tibet, China

OBJECTIVE

To investigate the differences in myopia prevalence and ocular biometry in children and adolescents in Chongqing and Tibet, China.

DESIGN

Cross-sectional study.

SETTING

The study included children and adolescents aged 6-18 years in Chongqing, a low-altitude region, and in Qamdo, a high-altitude region of Tibet.

PARTICIPANTS

A total of 448 participants in Qamdo, Tibet, and 748 participants in Chongqing were enrolled in this study.

METHODS

All participants underwent uncorrected visual acuity assessment, non-cycloplegic refraction, axial length (AL) measurement, intraocular pressure (IOP) measurement and corneal tomography. And the participants were grouped according to age (6-8, 9-11, 12-14 and 15-18 years group), and altitude of location (primary school students: group A (average altitude: 325 m), group B (average altitude: 2300 m), group C (average altitude: 3250 and 3170 m) and group D (average altitude: 3870 m)).

RESULTS

There was no statistical difference in mean age (12.09±3.15 vs 12.2±3.10, p=0.549) and sex distribution (males, 50.4% vs 47.6%, p=0.339) between the two groups. The Tibet group presented greater spherical equivalent (SE, -0.63 (-2.00, 0.13) vs -0.88 (-2.88, -0.13), p<0.001), shorter AL (23.45±1.02 vs 23.92±1.19, p<0.001), lower prevalence of myopia (39.7% vs 47.6%, p=0.008) and flatter mean curvature power of the cornea (Km, 43.06±1.4 vs 43.26±1.36, p=0.014) than the Chongqing group. Further analysis based on age subgroups revealed that the Tibet group had a lower prevalence of myopia and higher SE in the 12-14, and 15-18 years old groups, shorter AL in the 9-11, 12-14 and 15-18 years old groups, and lower AL to corneal radius of curvature ratio (AL/CR) in all age subgroups compared with the Chongqing group, while Km was similar between the two groups in each age subgroup. Simple linear regression analysis showed that SE decreased with age in both the Tibet and Chongqing groups, with the Tibet group exhibiting a slower rate of decrease (p<0.001). AL and AL/CR increased with age in both the Tibet and Chongqing groups, but the rate of increase was slower in the Tibet group (p<0.001 of both). Multiple linear regression analysis revealed that AL had the greatest effect on SE in both groups, followed by Km. In addition, the children and adolescents in Tibet presented thinner corneal thickness (CCT, p<0.001), smaller white to white distance (WTW, p<0.001), lower IOP (p<0.001) and deeper anterior chamber depth (ACD, p=0.015) than in Chongqing. Comparison of altitude subgroups showed that the prevalence of myopia (p=0.002), SE (p=0.031), AL (p=0.001) and AL/CR (p<0.001) of children at different altitudes was statistically different but the Km (p=0.189) were similar. The highest altitude, Tengchen County, exhibited the lowest prevalence of myopia and greatest SE among children, and the mean AL also decreased with increasing altitude.

CONCLUSIONS

Myopia prevalence in Tibet was comparable with that in Chongqing for students aged 6-8 and 9-11 years but was lower and myopia progressed more slowly for students aged 12-14 and 15-18 years than in Chongqing, and AL was the main contributor for this difference, which may be related to higher ultraviolet radiation exposure and lower IOP in children and adolescents at high altitude in Tibet. Differences in AL and AL/CR between Tibet and Chongqing children and adolescents manifested earlier than in SE, underscoring the importance of AL measurement in myopia screening.

Prevalence of and risk factors for myopia among urban and rural children in Northeast China: protocol for a school-based cross-sectional study

INTRODUCTION

The worldwide prevalence of myopia is high and continues to increase. In this study, a school screening programme for myopia will be implemented using the whole-process information method. The purpose of this study is to investigate the prevalence of myopia in urban and rural areas of Northeast China and to determine the factors related to myopia.

METHODS AND ANALYSIS

This is a school-based cross-sectional study. Our study population will include 6000 school-aged children from 2 urban and 2 rural schools in Jinzhou, China. The study will be conducted using our self-developed internet-based intelligent data collection, transmission, storage and analysis system. Examination parameters include uncorrected distance visual acuity, presenting distance visual acuity, non-cycloplegic autorefraction, height, weight, waist circumference, hip circumference, spinal curvature and dental caries. The examination report will be automatically sent to parents, who will complete the questionnaire, and appropriate statistical analysis will be performed. The main outcome is the prevalence of myopia, defined as an equivalent spherical degree ≤-0.5 D.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Third Affiliated Hospital of Jinzhou Medical University (number: JYDSY-KXYJ-IEC-2023-018). Findings will be published in a peer-reviewed journal. Subjects and their parents (or other authorised agents) give informed consent prior to study participation.

TRIAL REGISTRATION NUMBER

ChiCTR2300072893.

Associations between axial length, corneal refractive power and lens thickness in children and adolescents: The Ural Children Eye Study

PURPOSE

To assess relationships between ocular biometric parameters in dependence of age and sex in children and adolescents.

METHODS

In the Ural Children Eye Study, a school-based cohort study, 4933 children underwent an ophthalmological and general examination.

RESULTS

Complete biometric measurements were available for 4406 (89.3%) children. Cycloplegic refractive error (mean: -0.87 ± 1.73 diopters (D); median: -0.38 D; range: -19.75 D to +11.25 D) increased (multivariable analysis; r2  = 0.73) with shorter axial length (β: -0.99; non-standardized regression coefficient B: -1.64; 95% CI: -1.68, -1.59) and lower corneal refractive power (β: -0.55; B: -0.67; 95% CI: -0.70, -0.64), in addition to higher cylindrical refractive error (β: 0.10; B: 0.34; 95% CI: 0.27, 0.41), thinner lens (β: -0.11; -0.85; 95% CI: -1.02, -0.69) and male sex (β: 0.15; B: 0.50; 95% CI: 0.42, 0.57). In univariate analysis, decrease in refractive error with older age was more significant (β: -0.38 vs. β: -0.25) and steeper (B: -0.22 (95% CI: -0.24, -0.20) vs. B: -0.13 (95% CI: -0.15, -0.11)) in girls than boys, particularly for an age of 11+ years. Axial length increased with older age (steeper for age <11  years) (B: 0.22 (95% CI: 0.18, 0.25) vs. 0.07 (95% CI: 0.05, 0.09)). In multivariable analysis, axial length increased with lower refractive error (β: -0.77; B: -0.42; 95% CI: -0.43, -0.40) and lower corneal refractive power (β: -0.54; B: -0.39; 95% CI: -0.41, -0.38), in addition to older age (β: 0.04; B: 0.02; 95% CI: 0.01, 0.03), male sex (β: 0.13; B: 0.23; 95% CI: 0.21, 0.32), higher cylindrical refractive error (β: 0.05; B: 0.09; 95% CI: 0.05, 0.14) and thinner lens (β: -0.14; B: -0.62; 95% CI: -0.72, -0.51). The axial length/corneal curvature (AL/CR) ratio increased until the age of 14 years (β: 0.34; B: 0.017; 95% CI: 0.016, 0.019; p < 0001), and then became independent of age. The AL/CR ratio increased (r2  = 0.78) mostly with higher corneal refractive power (β: 0.25; B: 0.02; 95% CI: 0.02, 0.02; p < 0.001), lower refractive error (β: -0.75; B: -0.05; 95% CI: -0.05, -0.05; p < 0.001), thinner lens thickness (β: -01.6; B: -0.09; 95% CI: -0.10, -0.08; p < 0.001) and older age (β: 0.16; B: 0.006; 95% CI: 0.005, 0.007; p < 0.001).

CONCLUSIONS

In this multiethnic group of school children in Russia, the age-related increase in myopic refractive error was more significant and steeper in girls, particularly for the age group of 11+ years. Determinants of higher myopic refractive error were longer axial length, higher corneal refractive power, lower cylindrical refractive error, thicker lens and female sex.

Trajectories of spherical equivalent refraction from grades 1 to 4 in Chinese children

BACKGROUND

The development trajectories of children's SER remain unknown. This study aimed to characterize spherical equivalent refraction (SER) trajectories during grades 1-4 in Chinese children.

METHODS

This prospective cohort study included 1226 first-grade non-myopic children from 12 public primary schools, randomly selected in two districts in Guangzhou, China. From November 2018 to March 2022, four-wave ocular examinations and questionnaire surveys have been completed. The group-based trajectory modeling was used to explore SER trajectories in grades 1-4.

RESULTS

All five trajectories showed an upward trend and rose faster after grade 2. Children in the sharp-developing (n = 44), high-developing (n = 136), and rapid-developing (n = 237) myopia groups developed myopia before grades 2, 3, and 4, respectively. Their SER development speed remained at a relatively high level after myopia, almost consistent with that before myopia. Children in the moderate-developing (n = 418) and low-developing (n = 391) non-myopia groups did not develop myopia before grade 4. Some characteristics in grade 1 were independently associated with SER trajectories, including sex, axial length, number of parents with myopia, residence, academic achievement, and the duration of outdoor activity. Based on the baseline characteristics, we established the model predicting the probability of children belonging to each group.

CONCLUSIONS

Myopia interventions are best started in grade 1 or preschool age. If interventions are not taken in time, the latest intervention window might be in grades 1, 2, and 3 for children with a high probability of belonging to the sharp-developing, high-developing, and rapid-developing myopia groups, respectively. The above probabilities might be predicted using the model we established. Moreover, the interventions for myopic children shouldn't be ignored.

Myopia & painful muscle form of temporomandibular disorders: connections between vision, masticatory and cervical muscles activity and sensitivity and sleep quality

The main aim of this study is to evaluate the effects of painful muscle form of temporomandibular disorders and myopia on the connections between the visual organ, the bioelectrical activity and sensitivity of the masticatory and cervical muscles, and sleep quality. Subjects were divided into 4 groups (Myopia & TMDs, Myopia (Without TMDs), Emmetropic & TMDs and Emmetropic (Without TMDs)). The study was conducted in the following order of assessment: examination for temporomandibular disorders, assessment of the muscle activity by electromyograph, pressure pain thresholds examination, ophthalmic examination and completion of the Pittsburgh Sleep Quality Index. It was observed that the Myopia & TMDs group had higher muscle tenderness, higher resting and lower functional muscle bioelectrical activity. The visual organ is clinical related to the masticatory and cervical muscles. TMDs and myopia alter masticatory and cervical muscle activity. The thickness of the choroid in people with myopia is related to muscle tenderness. TMDs and myopia impair sleep quality. It is recommended to determine the number of people with refractive error and its magnitude in the sEMG study in order to be able to replicate the research methodology.

Orthokeratology in controlling myopia of children: a meta-analysis of randomized controlled trials

BACKGROUND

Delaying the development and lowering the progression of myopia in children is the focus of current ophthalmology researches. We aimed to evaluate the role of orthokeratology in controlling myopia of children, to provide insights to the clinical treatment and care of children with myopia.

METHODS

Two investigators searched the The Cochrane Library, Embase, Pubmed, China national knowledge infrastructure, China biomedical literature database, WanFang and Weipu databases for randomized controlled trials(RCTs) on the role of orthokeratology in controlling myopia of children up to November 5, 2022. Two researchers independently searched, screened and extracted the studies according to the inclusion and exclusion standards. RevMan5.3 software was used for statistical analysis.

RESULTS

A total of 14 RCTs involving 2058 children were included in this meta-analysis. Synthesized outcomes indicated that orthokeratology improved the uncorrected visual acuity(MD = 0.40, 95%CI: 0.05 ~ 0.74), reduced the diopter change(MD=-3.19, 95%CI: -4.42~-1.95), changes of corneal curvature(MD=-3.21, 95%CI: -3.64~-2.79), the length of ocular axis (MD=-0.66, 95%CI: -1.27~-0.06) and amount of ocular axis change(MD=-0.42, 95%CI: -0.64~-0.21) after 1 year of wearing orthokeratology(all P < 0.05). Besides, orthokeratology reduced the diopter change (MD=-3.22, 95%CI: -4.86~-1.58), the length of ocular axis (MD=-1.15, 95%CI: -2.25~-0.06) and the amount of ocular axis change after 2 year of wearing orthokeratology (MD=-0.53, 95%CI: -0.96~-0.11) after 2 year of wearing orthokeratology (all P < 0.05). No publication biases were found amongst the synthesized outcomes (all P > 0.05).

CONCLUSIONS

Orthokeratology delays the progression of myopia in children, the long-term effects of orthokeratology need further investigations in future studies.

The association between sleep duration and risk of myopia in Chinese school-aged children: a cross-sectional study

BACKGROUND

Myopia is one of the most commonly diagnosed refractive disorders worldwide. Identifying risk factors for myopia at an early age may help to characterize children who would benefit most from individualized lifestyle advice and early interventions. The influence of sleep duration on myopia risk remains controversial and thus needs to be evaluated.

METHODS

A population-based cross-sectional study of Chinese school-aged children was conducted. Information on sleep duration was derived. The association between sleep duration and myopia risk was investigated by logistic regression analysis.

RESULTS

Myopia prevalence among 9530 Chinese school-aged children was 75.4% and decreased from 84.9%, 76.5%, 65.8%, to 61.3% along with the extension of sleep duration. Univariate logistic regression found longer sleep duration of 8-9 h (OR = 0.58, 95% CI: 0.51-0.66), 9-10 h (OR = 0.34, 95% CI: 0.30-0.39), and ≥ 10 h (OR = 0.28, 95% CI: 0.24-0.33) were protective factors for myopia in all participants (P for trend < 0.001). In the multivariate analyses, sleep duration was inversely associated with the risk of myopia, and a dose-effect relationship was observed when the analysis was split by age category.

CONCLUSIONS

Long sleep duration was associated with decreased risk of myopia in Chinese school-aged children.

Prevalence of myopia among senior students in Fenghua, Eastern China, before and during the COVID-19 pandemic

Background

Myopia is a common cause of vision impairment worldwide. In China, the prevalence, the affected population, and the onset age of myopia are prominent issues. Prevention and intervention of myopia are great public health concerns.

Methods

This school-based retrospective study retrieved visual acuity and refractive data of senior students (grade 12th) from six high schools in Fenghua City, Zhejiang Province, eastern China, from 2016 and 2022. Noncycloplegic autorefraction was performed for refractive status. Students were divided into three subgroups by their school types. The overall myopia prevalence, as well as the prevalence of low myopia, moderate myopia, and high myopia, were calculated separately for each year. Statistical analyzes were performed using SPSS 25.0 and Graphpad Prism software.

Results

The mean myopia prevalence in Fenghua was 84.5% (95% CI: 84.0-85.0%), and a slightly downward trend was found in myopia prevalence after 2019, but the change was not statistically significant (p = 0.078). The overall prevalence of myopia was 79.6, 85.2, and 86.1% in vocational high schools, general high schools, and key high schools, respectively, with statistically significant differences (p < 0.001). The prevalence of myopia among senior students in the vocational high school was significantly lower than that in the other two high schools. There's no significant change in the overall prevalence of myopia (84.7% vs. 84.3%, p = 0.265) before and during the COVID-19 pandemic, and it remained statistically insignificant after stratifying by gender (male p = 0.207, female p = 0.918) or school types (vocational high school p = 0.112; general high school p = 0.299; key high school p = 0.393).

Conclusion

The prevalence of myopia among senior students in Fenghua is relatively high, and the COVID-19 pandemic has no significant impact on it. The prevalence of myopia among vocational high school students is lower than that of general high school and key high school. Attention should be paid to the effects of educational pressure on the prevalence of myopia among students.

IMI 2023 Digest

Myopia is a dynamic and rapidly moving field, with ongoing research providing a better understanding of the etiology leading to novel myopia control strategies. In 2019, the International Myopia Institute (IMI) assembled and published a series of white papers across relevant topics and updated the evidence with a digest in 2021. Here, we summarize findings across key topics from the previous 2 years. Studies in animal models have continued to explore how wavelength and intensity of light influence eye growth and have examined new pharmacologic agents and scleral cross-linking as potential strategies for slowing myopia. In children, the term premyopia is gaining interest with increased attention to early implementation of myopia control. Most studies use the IMI definitions of ≤-0.5 diopters (D) for myopia and ≤-6.0 D for high myopia, although categorization and definitions for structural consequences of high myopia remain an issue. Clinical trials have demonstrated that newer spectacle lens designs incorporating multiple segments, lenslets, or diffusion optics exhibit good efficacy. Clinical considerations and factors influencing efficacy for soft multifocal contact lenses and orthokeratology are discussed. Topical atropine remains the only widely accessible pharmacologic treatment. Rebound observed with higher concentration of atropine is not evident with lower concentrations or optical interventions. Overall, myopia control treatments show little adverse effect on visual function and appear generally safe, with longer wear times and combination therapies maximizing outcomes. An emerging category of light-based therapies for children requires comprehensive safety data to enable risk versus benefit analysis. Given the success of myopia control strategies, the ethics of including a control arm in clinical trials is heavily debated. IMI recommendations for clinical trial protocols are discussed.

The Prevalence of Myopia Among Primary School Male Students in Bisha, Saudi Arabia

Background Myopia (shortsightedness) is considered a major health problem globally which has increased in the last few decades. This study aims to determine the prevalence of myopia and the associated risk factors among primary school students in Bisha, Saudi Arabia. Methods This descriptive cross-sectional study included 330 male students from five boys' schools in Bisha city. Students underwent an interview questionnaire that composed of (sociodemographic data, risk factors, and ocular history). Students' vision was assessed by an optometrist through the use of a Snellen chart and the result was converted to a Diopter unit (D). Myopia was defined as the spherical equivalent (SE) of ≤ - 0.5 D. Binomial statistical test was used to get a prevalence of myopia with a confidence interval (CI) of 95%. Chi-square analytical test was used to compare myopic and non-myopic groups on multiple variables. Results were considered statistically significant at p-value ≤ 0.05. Results The mean age of 330 male students was 11.29 ± 0.97. The prevalence of myopia was (32.7%, 95% CI: 27.7-38.1%), and the mean of the SE of participants was - 0.25 ± 0.60 D. Myopia prevalence was increased with age and school grade of participants (p ≤ 0.05). Students who spent a long time (more than three hours) on near activity are at risk of developing myopia (p ≤ 0.001). having one or both parents affected by myopia was not statistically significant with the prevalence of myopia (p = 0.175). Children who spent a long time outdoors tend to have a lower risk of myopia (p ≤ 0.001). Conclusion The study showed a high prevalence of myopia among schoolchildren in Bisha city. Therefore, it is recommended to plan for future screening programs for myopia.

TikTok and adolescent vision health: Content and information quality assessment of the top short videos related to myopia

Background

Despite the increasing recognition of the public health value of social media platforms, TikTok short videos focusing on adolescent vision health have not received much attention. We aimed to evaluate the content, sources, and information quality of myopia-related videos on TikTok.

Methods

The top 200 most-liked myopia-related videos on the Chinese version of TikTok were queried and screened on March 12, 2022. The descriptive characteristics, contents, and sources of the selected 168 videos were obtained, and their overall quality, reliability, understandability, and actionability were assessed using the validated scoring instruments DISCERN and PEMAT-A/V.

Results

Medical professionals were the main source (45.8%, 77/168) of videos. Misinformation (10.1%, 17/168) was mainly attributable to for-profit organizations (20%, 3/15) and individual non-medical users (31.3%, 10/32). However, their videos enjoyed the highest numbers of "likes," "comments," and "shares" (P < 0.05). The mean reliability and overall quality regarding treatment choice were (2.5 ± 0.5) and (3.1 ± 0.9), respectively. Videos on TikTok showed relatively high understandability (84.7%) and moderate actionability (74.9%). Video producers tended to partly or fully provide information regarding management (81.5%, 137/168) and outcome (82.1%, 138/168), and to ignore or only slightly mention content related to definition (86.9%, 146/169) and signs (82.1%, 138/168). The five video sources showed significant differences in the prevalence of misleading information (P < 0.001), publication reliability (P < 0.001), overall quality (P = 0.039), content score (P = 0.019), and understandability (P = 0.024).

Conclusion

Considering the moderate-to-poor reliability and variable quality across video sources, the substantial myopia-related content on TikTok should be treated with caution. Nevertheless, TikTok videos may serve as a surrogate or supplement for information dissemination if providers can ensure more comprehensive and accurate content.

Increasing prevalence of myopia and the impact of education in primary-school students in Xi'an, north-western of China

Purpose

The present study was performed to detect the prevalence of myopia among primary-school students in Xi'an, north-western of China.

Methods

The present study was a school-based study with students aged from 6 to 13 years old. All the individuals underwent ophthalmological examination and spherical equivalent (SE) of refractive error were measured with non-cycloplegic refraction. Myopia was defined as a SE of ≤ -0.5 diopters (D), and further divided into three stratified groups based on SE: low myopia (≤ -0.5 to >-3.0 D), moderate myopia (≤ -3.0 to >-6.0 D), and high myopia (≤ -6.0 D). Relative risk factors, including age, sex, grade and ethnicity were investigated using questionnaire.

Results

A total of 4,680 individuals were eligible for this survey and 4,654 (99.4% participation rate) were finally included (51.2% boys). The mean age of participants was 8.756 ± 1.727 years. The whole city-level prevalence of total myopia was 57.1% (95% CI: 55.7-58.6%). Additionally, the prevalence of low, moderate, and high myopia was 45.0% (95% CI: 43.5-46.4%), 11.1% (95% CI: 10.2-12.0%), and 1.0% (95% CI: 0.7-1.3%), respectively. Moreover, grade (education level) instead of age, sex and ethnicity was the most essential risk factor for prevalence of overall myopia (OR = 1.844, 95% CI: 1.605-2.119), and an increase of prevalence by 84.4% per grade was seen. Furthermore, similar associations of grade were significant with low myopia (OR = 1.613, 95% CI: 1.385-1.877) and moderate myopia (OR = 2.186, 95% CI: 1.693-2.823), meanwhile, prevalence of low myopia and moderate myopia demonstrated an increase of prevalence by 61.3 and 118.6% per grade, respectively. None of the factors included in the present study was significant risk factor for high myopia.

Conclusions

The present study investigated a non-negligible high prevalence of myopia among primary-school students in Xi'an, north-western of China, and a gradual increasing in proportion with education level.