Refractive Error in Chinese Preschool Children: The Shanghai Study

Link between parental myopia and early-onset high myopia: Insights from a clinical retrospective analysis

INTRODUCTION

Genetic aetiology is suspected in the development of early-onset high myopia (spherical equivalent refractive error [SER] ≤-6.00 D at ≤6 years of age), considering that the role of environmental factors in inducing high myopia is improbable at an early age. Therefore, we aimed to understand if early-onset high myopia is associated with parental myopia in a clinical setting.

METHODS

A retrospective study was conducted in which information about demographics, age of apparent onset of myopia, refractive error, axial length, number of myopic parents, time spent outdoors and time spent on near-work was obtained from electronic medical records (EMR). It included 195 myopic individuals categorised into (1) Early-onset high myopes (EOHM): SER ≤ -6.00 D with age of presentation ≤6 years, (2) Early-onset low myopes (EOLM): SER > -6.00 D with age of apparent onset ≤6 years, (3) Late-onset high myopes (LOHM): SER ≤ -6.00 D with age of presentation and age of apparent onset >6 years and (4) Late-onset low myopes (LOLM): SER > -6.00 D with age of apparent onset >6 years.

RESULTS

Overall, 63% of individuals were found to have parental myopia. The proportion of individuals with EOHM, EOLM, LOHM and LOLM with parental myopia was 57%, 74%, 53% and 64%, respectively. After adjustment for age, gender and environmental factors, the odds of development of EOHM (Odds ratio: 0.78, 95% confidence interval: 0.25-2.48), EOLM (1.54, 0.65-3.67) or LOHM (0.70, 0.30-1.65) were similar in the presence of myopic parents, when compared with LOLM. The SER and axial length did not differ based on the number of myopic parents in any of these categories.

CONCLUSION

This retrospective analysis reveals that the presence of parental myopia, which was self-reported, did not induce additional risk for early-onset high myopia.

Refraction and ocular biometric parameters in 3-to 6-year-old preschool children : a large-scale population-based study in Chengdu, China

PURPOSE

To understand the ocular biometric parameters characteristics and refractive errors in 3-to 6-year-old preschool children in Chengdu, China, and to investigate the prevalence of refractive errors.

METHOD

A school-based cross-sectional study was conducted in Chengdu from 2020 to2022 with a total of 666 kindergartens. All children were measured by non-cycloplegic autorefraction and uncorrected visual acuity (UCVA) and ocular biometric parameters. Finally, univariate linear regression models were used to analyze the relationship between ocular biometric parameters and refraction.

RESULTS

A total of 108,578 preschool children aged 3-6 underwent examinations, revealing a myopia prevalence of 6.1%. The mean axial length (AL), keratometry (K), corneal radius (CR), axial length/corneal radius (AL/CR) Ratio, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) were 22.35 ± 0.69 mm, 43.35 ± 1.58 D, 7.80 ± 0.28 mm, 2.87 ± 0.08, 533.31 ± 32.51 μm, 2.70 ± 0.28 mm, 3.91 ± 0.27 mm, and 15.20 ± 0.68 mm, respectively. With increasing age, AL, CR, AL/CR ratio, CCT, ACD, LT, and VCD also increased. Regardless of age, males consistently exhibited longer AL, flatter corneal curvature, shallower ACD, thicker CCT, thinner LT, and longer VCD compared to females. AL, K, CR, LT, and VCD all showed significant linear relationships with SE (all P < 0.001) in univariate linear regression analysis after adjusting for gender and age.

CONCLUSION

The prevalence of myopia among preschool children aged 3-6 in Chengdu is relatively low. Ocular biometric parameters affecting refractive errors include AL, K, CR, LT, and VCD. The preschool period serves as a critical phase for myopia prevention and control.

Prevalence and risk factors for astigmatism in 7 to 19-year-old students in Xinjiang, China: a cross-sectional study

BACKGROUND

To investigate the prevalence and risk factors for astigmatism in 7-19-year-old students in Xinjiang, China.

METHODS

A school-based, cross-sectional study was conducted on students who underwent refraction examination in Xinjiang, China, between May and December 2019. The prevalence of astigmatism was determined. Astigmatism was defined as cylinder power (C) ≤-0.75 D, undefined astigmatism as ≤-1.50 D, and high astigmatism as C ≤-3.00 D. Astigmatism types were: against-the-rule astigmatism (maximum refraction of the main meridian in 180° ± 30°), with-the-rule astigmatism (maximum refraction of the main meridian at 90°±30°), and oblique astigmatism (all other cases).

RESULTS

Of the 71,838 students examined (51.0% boys, 7 - 19 years old), 25,945 (36.1%, 95%CI: 35.52-36.68%) had astigmatism and 1267 (1.8%, 95%CI: 1.07-2.53%) had high astigmatism. The prevalence of astigmatism was greater in Han individuals (39.6%) compared with the Hui (34.0%), Kazakh (34.0%), Kyrgyz (32.1%), and Uyghur (26.4%) populations. Among the 25,945 students with astigmatism, 19,947 had with-the-rule astigmatism (76.9%), 3405 had against-the-rule astigmatism (13.1%), and 2593 had oblique astigmatism (10.0%). Multivariable logistic regression analysis showed that ethnicity (Han individuals more susceptible), male gender, age, and refractive errors (myopia and hyperopia) were independently associated with astigmatism, high astigmatism, and with-the-rule astigmatism (all P < 0.05).

CONCLUSIONS

The prevalence of astigmatism among children and adolescents in Xinjiang was 36.1%, including 1.8% of high astigmatism. In this population, astigmatism was mainly of the with-the-rule astigmatism type (76.9%). Han ethnicity, male gender, and myopia or hyperopia were independently associated with a high risk of astigmatism.

Association between body stature with ocular biometrics and refraction among Chinese preschoolers

PURPOSE

To evaluate the association of body stature with ocular biometrics and refraction in preschool children.

METHODS

A cross-sectional, school-based study was conducted in Shenzhen, China. Preschool children aged 3 to 6 from 10 randomly-selected kindergartens were recruited. Ocular biometric parameters, including axial length (AL), anterior chamber depth (ACD), vitreous chamber depth (VCD), corneal radius curvature (CR), axial length to corneal radius ratio (AL-to-CR ratio) and lens thickness (LT) were measured using non-contact partial-coherence laser interferometry. Cycloplegic refractions were obtained by a desktop autorefractor. Body height and weight were measured using standard procedures. The association between body stature and ocular biometrics were analyzed with univariable and multivariable regression model.

RESULTS

A total of 373 preschoolers were included. AL, ACD, VCD, CR, and AL-to-CR ratio, were positively associated with height and weight (p < 0.05), whereas LT was negatively associated with height and weight (p < 0.01). No association was observed between stature and central cornea thickness and refraction. After adjusted for age and gender in a multivariable regression model, AL had positive associations with height (p < 0.01) and weight (p < 0.01). However, refraction had no significant association with stature parameters.

CONCLUSION

Taller and heavier preschoolers had eyes with longer AL, deeper vitreous chamber, and flatter cornea. The significant associations between body stature and ocular biometric parameters reveal the driving influence of body development on the growth of eyeballs in preschoolers.

Axial length to corneal radius of curvature ratio and refractive error in Chinese preschoolers aged 4-6 years: a retrospective cross-sectional study

OBJECTIVE

This study aims to investigate the associations of axial length to corneal radius of curvature (AL/CRC) ratio with refractive error and to determine the effect of AL/CRC ratio on hyperopia reserve and myopia assessment among Chinese preschoolers.

METHODS

This was a retrospective cross-sectional study that evaluated subjects aged 4-6 years. AL and CRC were obtained using a non-contact ocular biometer. Correlation analysis was performed to explore the associations of AL/CRC ratio with spherical equivalent refractive error (SER). The accuracy of AL/CRC ratio for hyperopia reserve and myopia assessment was analysed using cycloplegic refraction by drawing receiver operating characteristic (ROC) curves.

RESULTS

The analysis included 1024 participants (537 boys, 52.4%). The mean AL/CRC ratios in hyperopes, emmetropes and myopes were 2.90±0.06, 2.95±0.05 and 3.08±0.07, respectively. The SER was found to be more strongly correlated with AL/CRC ratio (ρ=-0.66, p<0.001) than either AL or CRC alone (ρ=-0.52, p<0.001; ρ=-0.03, p=0.33, respectively). AL/CRC was correlated with SER in hyperopes (ρ=-0.54, p<0.001), emmetropes (ρ=-0.33, p<0.001) and myopes (r=-0.67, p<0.001). For low hyperopia reserve assessment, the area under the ROC curves of AL/CRC ratio was 0.861 (95% CI 0.829 to 0.892), the optimal cut-off value of the AL/CRC ratio was ≥2.955. For myopia assessment, the area under the ROC curves of AL/CRC ratio was 0.954 (95% CI 0.925 to 0.982), the optimal cut-off value of the AL/CRC ratio was ≥2.975.

CONCLUSIONS

The SER showed a better correlation with AL/CRC ratio than either AL or CRC alone, especially in myopes, among children aged 4-6 years. These findings indicate that when cycloplegic refraction is unavailable, AL/CRC ratio could be used as an alternative indicator for identifying low hyperopia reserve and myopia among preschoolers, helping clinicians and parents screen children with low hyperopia reserve before primary school in a timely manner.

Establishment of noncycloplegic methods for screening myopia and pre-myopia in preschool children

Purpose

Pre-myopia, a non-myopic refractive state, is a key concern for myopia prevention because of its association with a significantly higher risk of myopia in children under 3 years of age. Amid the myopia pandemic, its onset at younger ages is increasing, yet research on screening methods for myopia and pre-myopia in preschool children remains limited. This study aimed to establish effective noncycloplegic screening methods for myopia and pre-myopia in preschool children.

Methods

This cross-sectional study included 16 kindergartens in Shanghai, China. Uncorrected distance visual acuity (UDVA) was recorded using a logMAR visual acuity chart. Pre- and post-cycloplegic refractions were obtained using an auto-refractor (TopconKR-800). Noncycloplegic axial length (AL) and corneal curvature radius (CR) were measured using the IOL Master-700. Logistic regression models were developed to establish accurate noncycloplegic screening methods for myopia and pre-myopia.

Results

A total of 1,308 children with a mean age of 4.3 ± 0.9 years were included; among them 640 (48.9%) were girls. The myopia prevalence rate was 2.8% (n = 36), and the prevalence of pre-myopia was 21.9% (n = 286). Pre-myopia screening (cycloplegic spherical equivalent [SE] ≤ -0.5 < SE ≤0.75 diopters [D]) using UDVA exhibited an area under the receiver operating curve (AUC) of 0.52, noncycloplegic SE had an AUC of 0.70 and AL had an AUC of 0.63. The accuracy of combining the SE and AL/CR ratio was among the best with the least number of checks used, and the AUC was 0.74 for pre-myopia screening and 0.94 for myopia screening (cycloplegic SE ≤ -0.5 D). The addition of UDVA did not further improve the accuracy.

Conclusion

Using UDVA alone did not achieve good accuracy in pre-myopia or myopia screening of young children. Under non-cycloplegic conditions, the combination of AL/CR and SE demonstrated favorable results for pre-myopia and myopia screening of preschool children.

Refractive and corneal astigmatism in Chinese 4-15 years old children: prevalence and risk factors

BACKGROUND

To investigate the prevalence and risk factors of refractive astigmatism (RA) and corneal astigmatism (CA) in preschool children and school-aged children in Shanghai, China.

METHODS

In this school-based, cross-sectional study, 4-15 years old children across three learning stages of kindergarten, primary school, and junior high school underwent noncycloplegic autorefraction and completed comprehensive questionnaires involving time spent on daily homework and outdoor activities. Data from the right eyes were analysed.

RESULTS

Overall, 7084 children (mean ± standard deviation (SD) of age: 8.08 ± 3.11 years) were included, and the prevalence rates of RA/CA ( ≤ - 1.0 D) in children were 15.8%/64% in kindergartens, 16.5%/65% in primary schools, and 32.8%/76.9% in junior high schools. The magnitude and prevalence of RA and CA all increased with age or with learning stage (all P < 0.001). The presence of RA was associated with more myopic spherical power (odds ratio (OR) 0.956, P = 0.021), junior high school (OR 1.973, P < 0.001), longer homework time on weekdays (OR 1.074, P = 0.029), and shorter outdoor activity time on weekends (odds ratio 0.929, P = 0.013).

CONCLUSION

In the wide age range of 4 to 15 years, the magnitude and prevalence of RA and CA increased with the learning stage, and these increases mainly began at the primary school stage. Factors, including longer homework time and shorter outdoor time were correlated with the presence of RA.

The Guiding Significance of Ocular Biometry in Evaluating the Refractive Status of Preschool Children

INTRODUCTIONS

This study aimed to analyze the correlation between refractive status and ocular biological parameters in preschool-age children (3-6 years old), establish a regression curve, guide the clinical judgment of children's refractive status, and improve the accuracy of refractive screening for this age group.

METHODS

A total of 508 children, aged 3-6 years, were admitted to the hospital, exhibiting symptoms of ametropia and a need for dilation optometry. Among these, 326 children were included in the statistics group, having been examined between August 2021 and October 2022, and 182 children were included in the validation group, having been examined between November 2022 and March 2023. Using IOL Master700, ocular biometry parameters were measured for all participants, including axial length (AL), keratometry readings (K1 and K2), anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT). One percent atropine sulfate eye gel was administered, and then the spherical equivalent (SE) was calculated by Bennett's formula. The correlation between SE and other ocular biometrics was analyzed, followed by the establishment of an SE prediction equation. The SE prediction equation was used to calculate the spherical equivalent (SE#) using ocular biometry data from the validation group, and the consistency between SE and SE# was evaluated.

RESULTS

SE showed a negative correlation with AL/CR (r = -0.936), AL (r = -0.811), ACD (r = -0.500), age (r = -0.396), and Km (r = -0.213) (p < 0.001), and positive correlation with LT (r = 0.301), LP (r = 0.176) (p < 0.001). A multiple linear regression equation was established for SE using the stepwise selection method, SE = 49.232 - 23.583 × AL/CR + 1.703 × ACD + 0.589 × Km - 0.609 × LP + 1.103 × LT (R2 = 0.997). Based on the regression equation, the predicted SE# highly correlated with SE after cycloplegia in the validation group (r = 0.998, p < 0.001).

CONCLUSION

The main ocular biological factors of ocular diopter in children aged 3-6 years are AL/CR, ACD, Km, LP, and LT, which are jointly influenced by multiple factors. Ocular biometry is a reliable predictor of real refraction among children aged 3-6.

Machine learning to analyze the factors influencing myopia in students of different school periods

Purpose

We aim to develop myopia classification models based on machine learning algorithms for each schooling period, and further analyze the similarities and differences in the factors influencing myopia in each school period based on each model.

Design

Retrospective cross-sectional study.

Participants

We collected visual acuity, behavioral, environmental, and genetic data from 7,472 students in 21 primary and secondary schools (grades 1-12) in Jiamusi, Heilongjiang Province, using visual acuity screening and questionnaires.

Methods

Machine learning algorithms were used to construct myopia classification models for students at the whole schooling period, primary school, junior high school, and senior high school period, and to rank the importance of features in each model.

Results

The main influencing factors for students differ by school section, The optimal machine learning model for the whole schooling period was Random Forest (AUC = 0.752), with the top three influencing factors being age, myopic grade of the mother, and Whether myopia requires glasses. The optimal model for the primary school period was a Random Forest (AUC = 0.710), with the top three influences being the myopic grade of the mother, age, and extracurricular tutorials weekly. The Junior high school period was an Support Vector Machine (SVM; AUC = 0.672), and the top three influencing factors were gender, extracurricular tutorial subjects weekly, and whether can you do the "three ones" when reading and writing. The senior high school period was an XGboost (AUC = 0.722), and the top three influencing factors were the need for spectacles for myopia, average daily time spent outdoors, and the myopic grade of the mother.

Conclusion

Factors such as genetics and eye use behavior all play an essential role in students' myopia, but there are differences between school periods, with those in the lower levels focusing on genetics and those in the higher levels focusing on behavior, but both play an essential role in myopia.

Prevalence of refractive errors in children of Puerto Rico

AIM

To determine the prevalence of refractive error in 5- to 17-year-old schoolchildren in Puerto Rico.

METHODS

A quantitative descriptive study of 2867 children aged 5 to 17y from all seven educational regions of Puerto Rico was conducted from 2016-2019. Refractive error was determined via static and subjective refraction. Children with distance acuity ≤20/40 or near visual acuity ≤20/32 had a cycloplegic refraction. Data analysis included descriptive statistics, correlation coefficient, Kruskal-Wallis, Chi-square, and t test calculations.

RESULTS

Twenty percent of the children had a spherical equivalent refractive error ≤ -0.50 D, 3.2% had a spherical equivalent ≥ +2.00 D, and 10.4% had astigmatism ≥1 D. There was a statistically (but non-clinically) significant myopic change in spherical equivalent refractive error with age (P<0.001). The prevalence of myopia increased with age (P<0.001) but not hyperopia (P=0.59) or astigmatism (P=0.51). Males had a significantly higher hyperopic spherical equivalent than females (P<0.001). Females had a higher prevalence of myopia (P<0.001) than males, but there was no difference in the hyperopia (P=0.74) or astigmatism prevalence (P=0.87).

CONCLUSION

The prevalence of a spherical equivalent equal to or less than -0.50 D (myopia, 20.7%) is one of the highest among similar-aged children worldwide. Further studies should explore the rate of myopia progression in children in Puerto Rico. Individual children must be monitored to examine the need for treatment of myopia progression.

Parents' intentions toward preschool children's myopia preventive behaviors: Combining the health belief model and the theory of planned behavior

Objective

This study aimed to develop an integrated model based on the health belief model (HBM) and the theory of planned behavior (TPB) to explore the influencing factors of parents' intentions toward preschool children's myopia preventive behaviors.

Methods

This cross-sectional study was conducted in Minhang District, Shanghai, China in January 2022. One thousand six hundred and twenty-eight parents of preschool children from seven preschools were recruited in the study. A four-part questionnaire was used to collect data on socio-demographic characteristics, HBM variables, TPB variables and parental intentions. This study used exploratory factor analysis to analyze HBM and TPB items. Hierarchical multiple regression analysis was performed to explore the relationship between independent variables and parents' intentions toward preschool children's myopia preventive behaviors.

Results

The final integrative model showed that perceived severity, perceived barriers, attitudes, subjective norms, and perceived behavioral control were associated with parents' intentions toward preschool children's myopia preventive behaviors. In model 1, Child's age was entered as a control variable and explained 0.6% of the variance (F = 7.241, p = 0.007). When the HBM variables were entered in model 2, the proportion of variance increased to 25.4% (F = 73.290, P < 0.001). In model 3, TPB variables were entered and explained 63.2% of the variance (F = 246.076, p < 0.001).

Conclusion

The integrated model of HBM and TPB constructed in this study significantly improved the degree of explanation of parents' intentions toward preschool children's myopia preventive behaviors. Parents' perceived severity, perceived barriers, attitudes, subjective norms, and perceived behavioral control can be prioritized intervention targets for myopia preventive practices in preschool children.

Normal range of ocular biometry in healthy children: A systemic review and meta-analysis of 33,559 individuals under seven years of age

PURPOSE

To conduct a systemic review and meta-analysis on the normative range of ocular biometry in healthy children under seven years of age.

METHODS

A literature search was performed using the PubMed (MEDLINE) database. The main outcomes were normative values of axial length (AL), central corneal thickness (CCT), cornea curvature (CC), anterior chamber depth (ACD), lens thickness (LT) and vitreous chamber depth (VCD). Pooled estimates were obtained with a random-effects meta-analysis. Multivariate meta-regressions ascertained the moderator-related trends.

RESULTS

We included 47 studies for a total of 33,559 subjects. The pooled ALs for 0.0-1.9 years, 2.0-3.9 years and 4.0-6.9 years were 18.33 mm (95% confidence interval [CI] 17.57-19.09), 21.71 mm (21.49-21.93) and 22.37 mm (22.29-22.45), respectively. Children aged 0.0-1.9 years had a greater CCT (576.70 μm, 567.20-586.21), steeper cornea (7.41 mm, 7.16-7.65) and shallower ACD (2.46 mm, 2.23-2.69). LT ranged from 3.65 to 3.74 mm for 0-6 years, and VCD increased from 11.94 mm at birth to 15.36 mm at 4.0-6.9 years. Differences in AL between East Asian and non-East Asian children were found below two years of age (17.30 mm vs. 18.40 mm, p = 0.008) and for CC at 4.0-6.9 years of age (7.82 mm vs. 7.79 mm, p = 0.004). In a multivariate meta-regression, AL, CC, ACD and VCD increased with age (p < 0.05 for all), while CCT decreased with age (p = 0.0007).

CONCLUSIONS

This study reports normative data for ocular biometry in children. Few differences were found with ethnicity in the ocular biometry of infants and pre-schoolers.

Progression of Vision in Chinese School-Aged Children Before and After COVID-19

Objectives: To investigate the changes of vision, including the prevalence of myopia, hyperopia, poor vision, and the spherical equivalent refraction (SER), in school-aged children before and after the pandemic of Coronavirus Disease 2019 (COVID-19).

Methods: A school-based vision screening study was performed on children in 133 primary schools in Wuhan. This study was conducted in 4 consecutive years (2018–2021).

Results: A total of 468,094 children (936,188 eyes) were recruited, 255,863 (54.7%) were boys. The SER decreased in 2020 compared to other years after the age of 10. A positive myopia shift was found in younger children aged 6 (0.1 D), 7 (0.05D), and 8 (0.03 D) in 2020 compared to 2019. The progression of vision has improved slightly in 2021. Among the students included in the study, 33.7% were myopia.

Conclusion: The vision of older children decreased significantly during the COVID-19. After the pandemic, there is still a high risk for them. In the future, the focus on vision prevention and control should move forward to preschool children.

Prevalence of Myopia and Its Associated Factors Among Japanese Preschool Children

Purpose

To investigate the prevalence of myopia and factors associated with spherical equivalent (SE), axial length (AL), and axial length to corneal radius of curvature (AL/CR) ratio among Japanese preschool children.

Study Design

Prospective observational study.

Methods

This cross-sectional study evaluated subjects aged 4–6 years from a preschool. Non-cycloplegic autorefraction was measured using the Spot Vision Screener, while AL and corneal radius (CR) were measured using the Myopia Master. Parental myopia and environmental factors were investigated using the myopia-related factor questionnaire. The worse eye with higher myopic SE was chosen for analysis, and multiple linear regression models was performed using AL, SE, and AL/CR ratio as dependent variables.

Results

A total of 457 out of 514 participants (239 males, 52.3%) aged 4–6 years (mean 4.77 ± 0.65 years) were included. The mean SE was 0.13 ± 0.63 D, AL was 22.35 ± 0.67 mm, CR was 7.76 ± 0.25 mm, and AL/CR ratio was 2.88 ± 0.72. The overall prevalence of myopia and high myopia were 2.9 and 0.2%, respectively. Multiple regression analysis showed that myopic SE was significantly associated with male sex (β = −0.14, p = 0.02) and parental myopia (β = −0.15, p = 0.04). Meanwhile, longer AL was significantly associated with older age (β = 0.13, p = 0.02), male sex (β = 0.44, p < 0.001), parental myopia (β = 0.24, p = 0.01), and screen time (including smartphones, tablets, and computers) (>1 h, β = 0.14, p = 0.04). A higher AL/CR was significantly associated with older age (β = 0.02, p < 0.001), male sex (β = 0.03, p < 0.001), ratio and parental myopia (β = 0.03, p = 0.02).

Conclusion

The prevalence of myopia and high myopia were 2.9 and 0.2%, respectively, among Japanese preschool children in 2021. Longer AL was associated with older age, male sex, parental myopia, and screen time in children aged 4–6 years. Children with a high risk of myopia can be identified early based on parental myopia information for early prevention.

Prevalence of Myopia and Influencing Factors among High School Students in Nantong, China: A Cross-Sectional Study

INTRODUCTION

Myopia is an increasingly serious health problem in China. The aim of this study was to investigate the prevalence of myopia and the factors associated with it among students in Nantong, China, to show the current status of myopia prevention.

METHODS

This school-based, cross-sectional study examined students from all high schools in an urban area of Nantong, China. At least two classes were randomly selected from each grade of each school. A self-reported questionnaire was used to collect the required information. Univariate analyses were performed to identify associations between myopia and various parameters. Noncycloplegic autorefraction and visual acuity were assessed for each student. Factors that were statistically significant in univariate analyses were selected for multivariate analyses. Myopia was defined as a spherical equivalent refraction of ≤-0.5 diopters.

RESULTS

The completion percentage of students out of the whole high school was 6.5%. The overall prevalence of myopia was 94%. The response percentage of the number of validated questionnaires was 90.2%, of which 50.2% (n = 1,466) were from male participants, and 49.8% (n = 1,452) were from female participants. The mean (SD) of age was 15.22 ± 1.75 years, ranging from 12 to 18 years. Factors such as female sex, older age, parental myopia, sitting in the back of the classroom, increased homework time, and minimal outdoor activity were significantly associated with a higher risk of myopia (p < 0.05). In the myopic population, most students (67.9%) did not take measures to prevent further progression of myopia.

CONCLUSION

The prevalence of myopia among high school students was 94%. Female sex, older age, parental myopia, sitting in the back of the classroom, increased homework time, and minimal outdoor activity were significantly associated with a higher risk of myopia. Most students with myopia (67.9%) did not take measures to prevent further progression of myopia.

Distribution, Progression, and Associated Factors of Refractive status of Children in Lhasa, Tibet after COVID-19 Quarantine

Introduction Uncorrected refractive error is one of the major causes of visual impairment in children and adolescents worldwide. During the COVID-19(Coronavirus Disease 2019) epidemic,home isolation is considered a boost to the progression of children's myopia. Under geographical conditions of high altitude and strong sunshine, the Tibetan plateau is the main residence of the Tibetan population, where little information is available about the refractive status and developmental trajectory.Therefore,this article aimed to evaluate the distribution,progression,and associated factors of the refractive status in second grade children in Lhasa after COVID-19 quarantine. Materials and Methods Students from 7 elementary schools completed comprehensive ocular examinations in the Lhasa Childhood Eye Study. Data regarding cycloplegic refraction and corneal biometry parameters, including axial length (AL),corneal power,anterior chamber depth(ACD),and other demographic factors,were analyzed. Results A total of 1,819 students were included, with a mean age of 7.9±0.5 years, of which 961 were boys (52.8%), and 95.1% were Tibetan. The prevalence of myopia, emmetropia, mild hyperopia and hyperopia was 10.94%, 24.02%, 60.80% and 4.24%, respectively. Besides, the average cycloplegic spherical equivalent refraction(SER) was +1.07±0.92D before the COVID-19 quarantine and +0.59±1.08D after the quarantine, with a growth rate of 7%. Moreover, the prevalence of hyperopia in girls was significantly higher than that of boys. Nonetheless, the proportion of myopia and emmetropia was similar. Meanwhile, children in suburban schools had a significantly lower proportion of myopia. The average AL, ACD, lens power (LP) and axial length-to-corneal radius(AL/CR) ratio were 22.79±0.78mm, 3.54±0.21mm, 25.12±1.48D and 2.93±0.08, respectively. The result of AL,ACD,and AL/CR for girls were significantly lower than for boys while the result of LP is the opposite. Finally, multivariate regression analysis revealed that SER was negatively correlated with AL, LP, and AL-to-CR ratio, while positively correlated with CR and ACD. Conclusion This study found that after the COVID-19 confinement, myopia progressed faster in Lhasa children but was still significantly lower than that of plain cities in China. Compared to short-term confinement, this acceleration was more likely related to the growth and general trend of myopia in children. Collectively, these findings help to explore the differences in ocular growth and development among children of different ethnic groups.

Development of Refractive Parameters in 3- to 6-Year-Old Children and Its Application in Myopia Prediction and Intervention Guidance

OBJECTIVE

To investigate refractive development and prevalence of myopia in children aged 3-6 years in Hebei Province, China, and to explore the developmental law of refraction, so as to clinically guide the prediction and intervention of myopia.

METHODS

In May 2019, a total of 6120 people were inspected in 68 kindergartens in 11 cities in Hebei Province. Child refractive refraction was checked under noncycloplegia using a handheld binocular vision screener (SW-800, SUOER, Tianjin, China). Axial length (AL) and corneal radius of curvature (CR) were measured using an ocular biometry (IOLMaster 500, Carl Zeiss, Germany). Myopia was defined as spherical equivalent (SE) ≤ -0.75 D.

RESULTS

A total of 5506 children aged 3-6 years met the criteria and were included in the statistical analysis. The prevalence of myopia was 3.49% (1.93% at age 3, 2.90% at age 4, 3.78% at age 5, and 3.88% at age 6). Overall, the mean SE was +0.67 ± 1.05 D (+0.81 ± 1.00 D at age 3, +0.79 ± 1.05 D at age 4, +0.67 ± 1.08 D at age 5, and +0.13 ± 1.01 D at age 6); the mean CR was 7.76 ± 0.26 mm (7.78 ± 0.26 mm at age3, 7.75 ± 0.25 mm at age 4, 7.77 ± 0.26 mm at age 5, and 7.76 ± 0.25 mm at age 6); the mean AL was 22.31 ± 0.73 mm (21.98 ± 0.63 mm at age 3, 22.12 ± 0.69 mm at age 4, 22.34 ± 0.73 mm at age 5, and 22.49 ± 0.73 mm at age 6).

CONCLUSIONS

Prevalence of myopia increases with age in children aged 3-6 years in Hebei, China. With the increase of age, CR is basically stable, and AL increases gradually. AL/CR, which is closely related to SE, can be used as an indicator to predict myopia and guide clinical work.

Assessment of the retinal vasculature in healthy Chinese preschool children aged 4-6 years old using optical coherence tomography angiography

PURPOSE

To establish normal parameters of macular and optic disc vasculature by optical coherence tomography angiography (OCTA) in healthy preschool children aged 4-6 years old in China. OCTA reflects retinal metabolism and development in children at these ages and could be used clinically and in future studies to aid diagnosis and prediction of retinal abnormalities and developmental stagnation.

METHODS

In this cross-sectional study, we measured foveal, parafoveal, and perifoveal vessel density in the superficial capillary plexus (SCP); the deep capillary plexus (DCP), the foveal avascular zone (FAZ), and the radial capillary peripapillary (RPC) in the optic disc using investigational spectral-domain OCTA. The magnification effect of the FAZ area and microvasculature measurements was corrected by Littman and the modified Bennett formula.

RESULTS

A total of 242 eyes (116 males and 126 females, 5.31 ± 0.73 years) were recruited for the analysis. The mean macular vessel density was 48.10 ± 2.92% and 48.74 ± 6.51% in the SCP and the DCP, respectively. The RPC vessel density was 47.17 ± 2.52%, 47.99 ± 4.48%, and 48.41 ± 3.07% in the whole image, inside disc, and peripapillary, respectively; and the mean FAZ area was 0.28 ± 0.11 mm². A significant difference between male and female participants was found in the retinal vasculature (DCP, SCP, and RPC). None of these parameters were significantly different in age (P > 0.05), except that DCP slightly increased with aging. The right and left eyes had good consistency in the parameters of the macula and optic disc.

CONCLUSIONS

Our study establishes the macular and optic disc OCTA reference values in 4- to 6-year-old healthy preschool children. They may be used in longitudinal OCTA studies and clinical applications.

Prevalence and time trends of refractive error in Chinese children: A systematic review and meta-analysis

Background

To investigate the prevalence and time trends of refractive error (RE) among Chinese children under 18 years old.

Methods

PubMed, Embase, Web of Science were searched for articles that estimated prevalence of RE in Chinese children. Data of identified eligible studies was extracted by two investigators independently. Pooled prevalence of RE and its 95% confidence interval (95% CI) and the time trends of RE were investigated using Meta-analysis methods.

Results

Of the 41 studies covering 1 051 784 subjects, the pooled prevalence of myopia, high myopia, hyperopia and astigmatism in Chinese children was 38.0% (95% confidence interval (CI) = 35.1%-41.1%), 2.8% (95% CI = 2.3%-3.4%), 5.2% (95% CI = 3.1%-8.6%) and 16.5% (95% CI = 12.3%-21.8%), respectively. Subgroup analysis show that children living in urban were at higher risk of RE. Prevalence of myopia and hyperopia were higher in Northern China compared with Southern China and high myopia and astigmatism were higher in Hong Kong, Macau and Taiwan than in mainland China. Regression analysis showed an upward trend in myopia and hyperopia and a downward trend in high myopia and astigmatism with years.

Conclusions

The prevalence of RE is higher in urban areas than in rural for Chinese children. The much higher prevalence of myopia and astigmatism in China compared with foreign countries indicates the important role played by environment and genetic factors. Considering the large magnitude of refractive errors, much more attention should still be paid to RE prevention and treatment strategy development in China.

The Sankara Nethralaya Tamil Nadu Essilor Myopia (STEM) Study-Defining a Threshold for Non-Cycloplegic Myopia Prevalence in Children

The aim of this study was to investigate the agreement between cycloplegic and non-cycloplegic autorefraction with an open-field auto refractor in a school vision screening set up, and to define a threshold for myopia that agrees with the standard cycloplegic refraction threshold. The study was conducted as part of the Sankara Nethralaya Tamil Nadu Essilor Myopia (STEM) study, which investigated the prevalence, incidence, and risk factors for myopia among children in South India. Children from two schools aged 5 to 15 years, with no ocular abnormalities and whose parents gave informed consent for cycloplegic refraction were included in the study. All the children underwent visual acuity assessment (Pocket Vision Screener, Elite school of Optometry, India), followed by non-cycloplegic and cycloplegic (1% tropicamide) open-field autorefraction (Grand Seiko, WAM-5500). A total of 387 children were included in the study, of whom 201 were boys. The mean (SD) age of the children was 12.2 (±2.1) years. Overall, the mean difference between cycloplegic and non-cycloplegic spherical equivalent (SE) open-field autorefraction measures was 0.34 D (limits of agreement (LOA), 1.06 D to −0.38 D). For myopes, the mean difference between cycloplegic and non-cycloplegic SE was 0.13 D (LOA, 0.63D to −0.36D). The prevalence of myopia was 12% (95% CI, 8% to 15%) using the threshold of cycloplegic SE ≤ −0.50 D, and was 14% (95% CI, 11% to 17%) with SE ≤ −0.50 D using non-cycloplegic refraction. When myopia was defined as SE of ≤−0.75 D under non-cycloplegic conditions, there was no difference between cycloplegic and non-cycloplegic open-field autorefraction prevalence estimates (12%; 95% CI, 8% to 15%; p = 1.00). Overall, non-cycloplegic refraction underestimates hyperopia and overestimates myopia; but for subjects with myopia, this difference is minimal and not clinically significant. A threshold of SE ≤ −0.75 D agrees well for the estimation of myopia prevalence among children when using non-cycloplegic refraction and is comparable with the standard definition of cycloplegic myopic refraction of SE ≤ −0.50 D.

Age-Related Change of Axial Length, Spherical Equivalent, and Prevalence of Myopia and High Myopia in School-Age Children in Shanghai: 2014–2018

Purpose. To investigate the age-related change of axial length (AL), spherical equivalent (SE), and prevalence of myopia and high myopia in children at 7–18-year-olds in Shanghai in 2014 and 2018, respectively. Methods. This was an observational study in Shanghai. The same 3 schools were selected in 2014 and 2018, respectively. AL, SE, prevalence of myopia and high myopia, height, and weight were measured. A questionnaire regarding the lifestyles was completed. Results. Mean age was smaller in 2018 than in 2014 ( $P<0.001$ ), and mean AL was shorter in 2018 than in 2014 ( $P=0.003$ ), whereas mean SE was greater in 2018 than in 2014 ( $P<0.001$ ). The prevalence of myopia and high myopia was lower in 2018 than in 2014 ( $P<0.001$ and $P=0.013$ , respectively). Mean AL increased with age from 7-year-olds to 18-year-olds in 2014 and 2018 (both $P<0.001$ ), respectively. Mean SE decreased with age in 2014 and 2018 (both $P<0.001$ ), respectively. The prevalence of myopia and high myopia increased with age in 2014 and 2018 (all $P<0.001$ ), respectively. Less mean time outdoors and more mean time of study of all children were observed in 2018 than in 2014 ( $P=0.018$ and $P<0.001$ , respectively). Conclusion. This study shows normative growth values for AL and SE in Shanghai children at the age of 7–18-year-olds, as well as the age-specific prevalence of myopia and high myopia.

Time trend of axial length and associated factors in 4- and 5-year-old children in Shanghai from 2013 to 2019

Purpose

To evaluate the time trend of axial length (AL) and associated factors in 4- and 5-year-old children in Shanghai from 2013 to 2019.

Methods

This was a 7-year observational study of 985 four-year-old and 1059 five-year-old children in Shanghai. AL, horizontal and vertical corneal curvature, spherical equivalent (SE), and body height and weight were measured. Furthermore, a questionnaire was collected, including time outdoors and bad eyesight habits.

Results

In 4-year-old children, no significant difference was found in AL (P = 0.526), but significant differences were observed in SE (P = 0.001), horizontal corneal curvature (P = 0.006), vertical corneal curvature (P = 0.004), height (P < 0.001), and weight (P = 0.022) from 2013 to 2019. In 5-year-old children, no significant differences were found in AL (P = 0.304), SE (P = 0.200), or weight (P = 0.292), but significant differences were observed in horizontal corneal curvature (P = 0.040), vertical corneal curvature (P = 0.015), and height (P < 0.001) from 2013 to 2019. Multivariate analyses revealed that AL was mainly significantly associated with boys and time outdoors in the 4- and 5-year-old children.

Conclusions

The AL of 4- and 5-year-old children remained relatively stable in Shanghai from 2013 to 2019. Longitudinal studies are needed to confirm the relationship between AL elongation and environmental risk factors.

Reference curves for refraction in a German cohort of healthy children and adolescents

PURPOSE

Percentile curves of refractive development for German children were generated. We hypothesize that refraction in children in central Europe might differ from data in central Asia.

METHODS

Non-cycloplegic refraction was measured using the ZEISS i.Profiler plus (Carl Zeiss Vision GmbH, Germany) in 1999 children, of which were 1046 male and 953 female, aged 3 to 18 years. Reference curves were calculated with the R-package GAMLSS as continuous function of age.

RESULTS

There were only little differences for all centiles between the genders at 3 years and a general trend towards more myopia with increasing age. For the 97th centile and the 3rd centile, girls showed higher myopia/ less hyperopia than boys. Between the age of 3 and 18, the median refraction became -0.68 D and -0.74 D more myopic for boys and girls, respectively. At the same time, the 97th centile for boys changed +0.29 D towards hyperopia and in girls -0.52 D towards myopia. A general myopic trend was seen in the 3rd centile, which was -2.46 D for boys and -2.98 D for girls. For both genders, the median became less than zero at the age of 10 years but did not become myopic (less than -0.5 D) up to the age of 18.

CONCLUSION

Our analysis presents the first reference curve for refraction in central Europe. In comparison to data from China and Korea, there is only little difference at the age of 5 years in all centiles which then increases continuously. For all ethnicities, a trend towards myopia with increasing age could be observed, but myopia progression is much higher in China and Korea than in Germany. The most marked differences can be seen in the lower centiles. Further investigations should clarify whether commencement of preschool activities with prolonged near-work initiates the divergence in refractive development.

Axial length elongation in primary school-age children: a 3-year cohort study in Shanghai

OBJECTIVE

To investigate the axial length (AL) elongation in primary school-age children during 3-year follow-up period and evaluate the associations of AL elongation with spherical equivalent (SE), AL at baseline, body height and weight.

DESIGN

A 3-year observational cohort study from 2014 to 2017.

SETTING

Jinshan Hospital of Fudan University in Shanghai.

METHODS

A total of 452 children successfully completed their measurements in the 3-year follow-up period. The mean age of those children was 6.9±0.7 years, ranging from 6 to 8 years, and 217 (42.7%) were boys. AL was measured with an ocular biometry system. Refractive error was measured using an auto-refractor without cycloplegia.

RESULTS

The mean changes of ALs were 0.27±0.28 mm, 0.52±0.40 mm and 0.89±0.51 mm over 1, 2 and 3 years, respectively. The mean changes of SEs were -0.27±0.80 D, -0.56±1.00 D and -0.95±1.41 D over 1, 2 and 3 years, respectively. Multivariate linear regression analysis revealed that mean change of AL was associated with mean change of SE at all points (all p<0.001). In addition, linear regression analysis revealed that AL elongation in the 3year follow-up period was associated with AL at baseline (R²=0.009, p=0.045).

CONCLUSIONS

AL elongation is relatively high in the primary school-age children in Jinshan District, Shanghai. Effect strategies are needed to control AL elongation.

Prevalence of visual impairment and refractive errors in an urban area of Mexico

AIM

To determine the distribution of refractive errors in a school-age population in Quintana Roo (Mexico) in the framework of an international cooperation campaign for the prevention of blindness.

METHODS

A sample of 2647 school-age children (ranging from 5 to 14 years old) with a mean age of 9.1±1.9 years old were tested by trained volunteers for distance visual acuity (VA) and refractive errors. The first screening examination included uncorrected distance visual acuity (UDVA) and VA with a +2.00 D lens. Inclusion criteria for a second complete cycloplegic eye examination performed by an optometrist were UDVA <20/25 (0.10 logMAR or 0.8 decimal) and/or VA with +2.00 D ≥20/25.

RESULTS

A total of 633 (23.9%) children underwent the second complete eye examination. Mean logMAR UDVA was 0.035±0.094 (range 1.00 to 0.00 logMAR) for the right eyes and 0.036±0.160 (range 1.00 to 0.00 logMAR) for the left eyes. Bilateral amblyopia was found in 17 children (2.7% of refracted eyes; 0.64% of the total). The main reason for visual impairment (VI) in the sample analyzed was found to be refractive errors. In 12 children (1.9% of refracted eyes; 0.45% of the total) the VI was bilateral and 9 (1.4% of refracted eyes; 0.34% of the total) achieved a corrected distance visual acuity of 20/25 or better in both eyes. Mean magnitude of sphere and refractive cylinder was +0.20±0.96 D and -0.43±0.85 D in right eyes, and +0.24±1.08 and -0.43±0.83 D in left eyes. The proportion of myopic eyes [standard equivalent (SE) ≤-0.50 D] was 4.6% of the whole sample (5290 eyes). The mean magnitude of myopia was -0.84±3.44 D for the right eyes and -0.82±5.21 D for the left eyes. The proportion of hyperopic patients (SE≥+2.00 D) was 2.4% (15/633), which corresponded to 0.60% of the whole sample (32/5290 eyes). No statistically significant correlation of age to manifest sphere or cylinder was found.

CONCLUSION

VI due to uncorrected refractive errors can be easily corrected with glasses but it is still a burden to be treated. Myopia is prevalent in this sample. More efforts towards correcting uncorrected refractive errors are needed.