Correlation Between Increase of Axial Length and Height Growth in Chinese School-Age Children

Can fundus features tell us something about 3D eye shape?

PURPOSE

To determine whether imaging features derived from fundus photographs contain 3D eye shape information beyond that available from spherical equivalent refraction (SER).

METHODS

We analysed 99 eyes of 68 normal adults in the UK Biobank. An ellipsoid was fitted to the entire volume of each posterior eye (vitreous chamber without the lens)-segmented from magnetic resonance imaging of the brain. Asphericity was computed based on the semidiameters of the ellipsoid's axes to describe posterior eye shape along the horizontal (temporal-nasal) and vertical (superior-inferior) meridians, while volume was calculated as the total number of foreground voxels. Mixed-effects linear regression models were used to test the association of SER with asphericity and volume, controlling for age and sex. Then, the association between various fundus features and asphericity was tested-both before and after controlling for SER, age and sex.

RESULTS

Posterior eyes were generally oblate (asphericity > 0), but the degree of oblateness reduced as SER decreased, with the shape tending towards prolateness in high myopia. Neither sex nor age influenced asphericity. However, males had larger posterior eyes on average (this difference disappeared after height was additionally controlled for). Optic disc (OD) orientation, OD-fovea angle, vessel tortuosity, vessel fractal dimension and central retinal arteriolar or venular equivalent (CRAE or CRVE) showed significant univariable associations with asphericity along at least one meridian. After controlling for SER, age and sex, a more negative OD-fovea angle (larger OD-fovea angular separation) remained significantly associated with reduced horizontal oblateness (p = 0.01). Similarly, decreasing CRAE (narrower arterioles) remained significantly associated with reduced oblateness along both the horizontal (p = 0.04) and vertical (p < 0.01) meridians.

CONCLUSIONS

Variations in OD-fovea angle and CRAE are associated with differences in ocular asphericity-even in eyes with similar SER-suggesting that fundus imaging provides eye shape information beyond what is available from refractive error alone.

Seasonal variation in axial elongation in children with orthokeratology treatment

PURPOSE

To investigate seasonal variations in changes of axial length (AL) among myopic children wearing orthokeratology (ortho-K) lenses.

METHODS

The data of 600 children receiving ortho-K treatment, aged 7-13 years, were collected retrospectively. Data were classified as 'summer' or 'winter' based on the midpoint of the 6-month period between visits. For each interval, AL from the right eye was used for statistical analysis. Paired sample t-tests were used to compare the seasonal differences in AL. Furthermore, the relationship between seasonal differences in AL, age and initial AL was analysed using Pearson correlation and multiple regression analysis, respectively.

RESULTS

The AL at 1 year after the initial ortho-K treatment was 24.96 ± 0.85 mm, representing an increase of 0.19 ± 0.15 mm. The semi-annual axial elongation was 0.07 ± 0.09 and 0.12 ± 0.09 mm for the summer and winter, respectively (p < 0.001). Linear regression analysis revealed that the control of axial growth in the summer was better than in the winter (β = -0.05, p < 0.001). A similar seasonal pattern was found among children aged 7-12 years as well as for those with an initial AL < 26 mm (but not in children aged 13 years).

CONCLUSIONS

The inhibition of axial growth by ortho-K treatment in the summer months is superior to that seen in the winter. Seasonal differences decrease with age and the initial AL.

Effects of racemic anisodamine in combination with orthokeratology and defocus incorporated multiple segment spectacle lenses for myopia control in adolescents

This study aimed to evaluate the clinical application of different myopia correction methods in the prevention and control of myopia in adolescents. A total of 145 myopic adolescents aged 8 to 15 years were included, and their eyes were divided into four groups based on the treatment modality: wearing Defocus Incorporated Multiple Segments (DIMS) spectacle lenses alone (Group A), orthokeratology (OK) lenses alone (Group B), DIMS spectacle lenses combined with racemic anisodamine eye drops (Group C), and OK lenses combined with racemic anisodamine eye drops (Group D). The primary outcomes, including axial length and refractive error (expressed as spherical equivalent refraction, SER), were measured at baseline and at the 12-month follow-up. The clinical effects of each group were compared. The results showed significant differences in myopia progression across the groups, with Group D showing the least axial elongation. OK lenses were more effective than DIMS spectacle lenses in controlling myopia progression, and the combination of racemic anisodamine eye drops further enhanced the correction effect. This study provides important clinical evidence for myopia control interventions in adolescents.

Relationship Between Poor Visual Acuity and Lifestyle: A Longitudinal and Cross-Sectional Study of Japanese Students Using Secondary Data

Background The incidence of myopia-related vision loss among Japanese children is increasing, indicating that efforts to prevent this vision loss remain insufficient. School-aged Japanese children are thought to be more prone to myopia due to physical and lifestyle changes during their growth stages. This study aimed to clarify the relationship between changes in visual acuity (VA) from fourth-grade elementary school to junior high school and students' lifestyle habits and to examine efforts to maintain visual acuity among elementary and junior high school students in Japan. Methods The participants of the analysis included 49 Japanese junior high school students. Secondary data used in the study were the results of vision tests and lifestyle questionnaires administered at the students' elementary and junior high schools. A longitudinal analysis was performed by comparing visual acuity and lifestyle conditions at two time points: fourth grade of elementary school and junior high school. Furthermore, the relationship between changes in visual acuity from elementary to junior high school and lifestyle habits in junior high school was examined. Results Poor visual acuity in junior high school was significantly associated with poor visual acuity in the fourth grade (p=0.003). Students with poor vision (PV) had a significantly higher percentage of the following characteristics compared to those without poor vision: studying for more than two hours per day on their days off (p=0.043), spending less than one hour per day on the computer on weekdays (p=0.020), perceiving insufficient sleep duration (p=0.018), and not paying attention to taking breaks while studying or watching TV (p=0.038). Conclusion This study indicated that poor vision in school-aged children may progressively worsen without improvement. The poor vision group spent more time studying on weekends and less time on the computer during the week, reported insufficient sleep time, and neglected taking breaks while studying or watching TV. As students grow, they tend to spend more time studying and changing their living environment to one that demands the overuse of their eyes, increasing strain on them. It is necessary to teach students to prevent poor vision starting at school age while their eyesight is still good.

Sleep Duration, Sleep Habits, and Social Jetlag From 4 to 6 years Their Impacts on Myopia Among School-Aged Children: The Ma'anshan Birth Cohort Study

Purpose

To examine the associations of sleep parameters and their trajectories at preschool age with myopia among school-aged children by using a birth cohort study design.

Patients and methods

All participants were recruited from the Ma'anshan Birth Cohort Study. Sleep duration, sleep habits, and social jetlag were collected in 4 years, 5.5 years, and 6 years. Cycloplegic refraction and ocular biometry were performed at 7 years. Key statistical analyses were performed using the latent class growth models, binary logistic regression, generalized linear models, and linear mixed models, respectively.

Results

A total of 1561 children were included in the study (mean age of 7.93 years, 52.6% boys). Social jetlag of at least 1 hour at age 4 was positively linked to an increased risk of myopia in school-age children and axial length (AL) but negatively correlated with spherical equivalent refraction (SER) (P<0.05). Inadequate sleep duration at 5.5 years was associated with an increase in AL among school-age children (β=0.16; 95% CI: 0.07-0.24). A pattern of increasing-declining social jetlag was positively correlated with AL/CR ratio (RR=1.55; 95%CI: 1.01-2.37). Poor sleep habits, higher social jetlag at age 4, and the declining-increasing trajectory of social jetlag were negatively associated with SER in school-aged children (P<0.05). Furthermore, the declining-increasing and increasing-declining trajectories of social jetlag were positively correlated with the elongation of AL.

Conclusion

The correlations between sleep parameters at preschool age and myopia in school-aged children reveal that maintaining regular sleep habits in preschool may contribute to the early prevention of myopia.

Ocular Biometry Distribution and One-Year Growth in Eight-Year-Old Southern European Schoolchildren Under the CISViT Project

Objective: To analyse variations in axial length (AL), corneal radius (CR) and the AL/CR ratio over one year in eight-year-old schoolchildren, considering sex, ethnicity and refractive error. Methods: Vision screenings were conducted in 16 schools in Terrassa (Barcelona, Spain) with eight-year-old children as part of the CISViT project. Measurements included ocular biometrics (AL and CR) and non-cycloplegic autorefraction for refractive error. Parental questionnaires provided demographic data (birth date, ethnicity). The same procedures were repeated after one year. Results: Ocular biometric parameters differed by sex and ethnicity. Boys and children of Maghreb descent had longer AL and flatter CR than girls and Caucasian children (p < 0.001 for both visits). The AL/CR ratio was higher in boys than girls (p = 0.002 in the initial visit and p = 0.011 in the follow-up visit) but consistent across ethnicities (p = 0.291 and p = 0.390). AL and AL/CR ratio differed significantly by refractive error status (p < 0.001 in both visits), increasing in more myopic children, while CR showed no significant difference. In myopic children, the AL/CR ratio exceeded 3.0, and typical sex-based biometric differences diminished. Growth rates for AL and AL/CR ratio were similar across sex and ethnicity, indicating minimal demographic influence. Conclusions: AL and CR differ significantly by sex and ethnicity, with demographic differences evident in baseline measurements but not in growth rates over one year. The consistency of the AL/CR ratio across ethnicities, despite sex-based differences, supports its utility as a reliable metric for assessing refractive development in diverse populations.

Deep anterior chamber depth may be a risk factor for axial length growth in children

Objective

To investigate and evaluate the progression of myopia and associated factors of axial length (AL) growth among children in Chongqing.

Methods

This six-month prospective study was conducted on students in grades 1 to 8 at a school in Chongqing, China. All participants underwent a standard ophthalmologic examination including uncorrected visual acuity (UCVA), noncycloplegic refraction, AL, and corneal topography in March 2023. Six months later, the above examinations were repeated to obtain follow-up data. Visual habits questionnaire was gained to analyze the correlation between the AL growth and vision-related behavior.

Results

A total of 417 students from Chongqing were enrolled in this study. The myopia prevalence was higher in follow-up (38.6%) than in baseline (33.3%) and the AL was longer in follow-up than in baseline (23.69 ± 1.03 mm vs. 23.57 ± 1.03 mm, p < 0.001). The anterior chamber depth (ACD) in students with AL growth greater than or equal to 0.2 mm (3.16 ± 0.23 mm) was deeper than that in students with AL growth less than or equal to 0.05 mm (3.02 ± 0.28 mm, p = 0.001), lens thickness (LT) was thinner (3.29 ± 0.10 mm vs. 3.33 ± 0.10 mm, p = 0.004). Furthermore, ACD was positively correlated with AL growth. (r = 0.181, p < 0.001).

Conclusion

Compared to SE, AL serves as a more sensitive indicator for monitoring myopia progression. ACD was positively correlated with AL growth, and deeper ACD may be contributed to longer AL growth.

Causal association of obesity-related anthropometric traits with myopia and the mediating role of educational attainment: a Mendelian randomization study

AIM

To study the causal relationship between obesity-related anthropometric traits and myopia and the mediating role of educational attainment (EA).

METHODS

Univariable Mendelian randomization (UVMR) was performed to evaluate the causal association between body mass index (BMI), height, waist-hip ratio (WHR, adjusted for BMI), and mean spherical equivalent (MSE). BMI was divided into fat and fat-free mass and included in multivariable Mendelian randomization (MVMR) to explore the roles of different BMI components in the causal relationship between BMI and MSE. A mediation analysis based on two-step Mendelian randomization (MR) was carried out. Specifically, UVMR was conducted to estimate the causal effect of BMI on EA. The direct effect of EA on MSE was estimated from MVMR. The mediation effect of EA in the BMI-EA-MSE model was calculated by the product of coefficients method. Expression quantitative trait loci (eQTL)-MR, reverse MR, and Linkage Disequilibrium Score Regression (LDSC) were performed to assess the robustness.

RESULTS

Genetically predicted higher BMI had a positive total effect on MSE (βIVW=0.26 D, 95%CI=0.14 to 0.37 D, P<0.001), whereas there was no significant association between height, WHR, and MSE. Fat mass was found to play a significant role in the effect of body mass on MSE (βIVW=0.50 D, 95%CI=0.21 to 0.78 D, P=0.001), but there was no significant association between fat-free mass and MSE. The causal effect of BMI on EA was -0.14 (95%CI=-0.16 to -0.11, P<0.001), and the direct effect of EA on MSE was -0.63 D (95%CI=-0.81 to -0.44 D, P<0.001). The mediating effect of EA in the BMI-EA-MSE model was 0.09 D (95%CI=0.06 to 0.12 D), with a mediation proportion of 33% (95%CI=22.1% to 44.6%). No reverse causal associations were detected except for BMI on EA. The results of eQTL-MR and LDSC were consistent with each MR analysis.

CONCLUSION

Genetically predicted higher BMI decreases the degree of myopia with a 33% mediation proportion by EA, and fat mass provides a dominant protective role in body mass-myopia. As a supplement to previous observational studies, it provides strong evidence for the relationship between anthropometric traits and refractive errors and offers a theoretical basis for future measures to prevent and control myopia.

Association between body stature and prevalence of reduced visual acuity in high school graduates in Hangzhou, China

CLINICAL RELEVANCE

The association between myopia and body stature is of great significance for understanding prevention and control of myopia. It has been extensively studied in previous studies but without consistent conclusions.

BACKGROUND

The aim of this study is to investigate the association between body stature and prevalence of reduced visual acuity in high school graduates in Hangzhou, China.

METHODS

50,620 high school graduates who finished the physical examination of the national college entrance examination in 2020 were included. Data were derived from the database of physical examination of the national college entrance examination. Height and weight were measured, and body mass index (BMI) was calculated according to the general formula. Visual acuity was measured by the standard logarithmic visual acuity chart.

RESULTS

The prevalence of reduced visual acuity was 90.38% in high school graduates. Girls had a higher prevalence of reduced visual acuity than boys (93.07% vs 87.60%, P < 0.001). Boys with normal visual acuity were significantly taller (P < 0.001) and heavier (P < 0.001) than those with reduced visual acuity. Girls with normal visual acuity were significantly taller than those with reduced visual acuity (P < 0.001). The prevalence of reduced visual acuity was significantly inversely associated with height in both boys (P < 0.001) and girls (P < 0.001). The risk of reduced visual acuity was the lowest in the fourth quartile of height. The prevalence of reduced visual acuity was significantly associated with BMI only in boys (P < 0.001). The risk of reduced visual acuity was the lowest in the third quartile of BMI.

CONCLUSIONS

The prevalence of reduced visual acuity was inversely associated with height in both boys and girls, and there was a U-shaped association with BMI only in boys.

Causal relationships between height, screen time, physical activity, sleep and myopia: univariable and multivariable Mendelian randomization

Background

This study aims to investigate the independent causal relation between height, screen time, physical activity, sleep and myopia.

Methods

Instrumental variables (IVs) for exposures and outcome were obtained from the largest publicly available genome-wide association studies (GWAS) databases. First, we performed a bidirectional univariate MR analysis using primarily the inverse variance weighted method (IVW) with height, screen time, physical activity and sleep as the exposure and myopia as the outcome to investigate the causal relationship between exposures and myopia. Sensitivity analysis was used to demonstrate its robustness. Then the multivariable MR (MVMR) and MR-based mediation approach was further used to estimate the mediating effect of potential confounders (education and time outdoors) on causality.

Results

The results of univariate MR analysis showed that taller height (OR = 1.009, 95% CI = 1.005-1.012, p = 3.71 × 10-7), longer time on computer (OR = 1.048, 95% CI = 1.029-1.047, p = 3.87 × 10-7) and less moderate physical activity (OR = 0.976, 95% CI = 0.96-0.991 p = 2.37 × 10-3) had a total effect on the increased risk of developing myopia. Meanwhile our results did not have sufficient evidence to support the causal relationship between chronotype (p = 0.637), sleep duration (p = 0.952) and myopia. After adjusting for education, only taller height remains an independent risk factor for myopia. After adjusting for education, the causal relationship between height, screen and myopia still had statistical significance. A reverse causal relationship was not found in our study. Most of the sensitivity analyses showed consistent results with those of the IVW method.

Conclusion

Our MR study revealed that genetically predicted taller height, longer time on computer, less moderate physical activity increased the risk of myopia. After full adjustment for confounders, only height remained independently associated with myopia. As a complement to observational studies, the results of our analysis provide strong evidence for the improvement of myopia risk factors and provide a theoretical basis for future measures to prevent and control myopia in adolescents.

Axial length elongation profiles from 3 to 6 years in an Asian paediatric population: the Growing Up in Singapore Towards Healthy Outcomes birth cohort study (GUSTO)

AIMS

To determine axial length (AL) elongation profiles in children aged 3-6 years in an Asian population.

METHODS

Eligible subjects were recruited from the Growing Up in Singapore Towards Healthy Outcomes birth cohort. AL measurement was performed using IOLMaster (Carl Zeiss Meditec, Jena, Germany) at 3 and 6 years. Anthropometric measurements at birth, cycloplegic refraction at 3 and 6 years, questionnaires on the children's behavioural habits at 2 years and parental spherical equivalent refraction were performed. Multivariable linear regression model with generalised estimating equation was performed to determine factors associated with AL elongation.

RESULTS

273 eyes of 194 children were included. The mean AL increased from 21.72±0.59 mm at 3 years to 22.52±0.66 mm at 6 years (p<0.001). Myopic eyes at 6 years had greater AL elongation (1.02±0.34 mm) compared with emmetropic eyes (0.85±0.25 mm, p=0.008) and hyperopic eyes (0.74±0.16 mm, p<0.001). The 95th percentile limit of AL elongation was 1.59 mm in myopes, 1.34 mm in emmetropes and 1.00 mm in hyperopes. Greater birth weight (per 100 g, β=0.010, p=0.02) was significantly associated with greater AL elongation from 3 to 6 years, while parental and other behavioural factors assessed at 2 years were not (all p≥0.08).

CONCLUSION

In this preschool cohort, AL elongates at an average length of 0.80 mm from 3 to 6 years, with myopes demonstrating the greatest elongation. The differences in 95th percentile limits for AL elongation between myopes, emmetropes and hyperopes can be valuable information in identifying myopia development in preschool children.

Repeatability and reproducibility of a new fully automatic measurement optical low coherence reflectometry biometer and agreement with swept-source optical coherence tomography-based biometer

AIMS

To assess the repeatability and reproducibility of the ocular measurements obtained with the Suoer SW-9000 μm Plus, a new fully automatic biometer based on optical low coherence reflectometry (OLCR) biometer, and to compare them to those obtained by a swept-source optical coherence tomography (SS-OCT)-based biometer.

METHODS

This prospective study consisted of 115 eyes of 115 healthy subjects. The measurements were taken by the two optical biometers in random order. The measured parameters were axial length (AL), central corneal thickness (CCT), aqueous depth (AQD), anterior chamber depth (ACD), mean keratometry (Km), lens thickness (LT) and corneal diameter (CD). To evaluate the intraobserver repeatability and interobserver reproducibility, the within-subject SD, test-retest variability, coefficient of variation (CoV) and intraclass correlation coefficient (ICC) were adopted. The Bland-Altman plot was drawn to assess the agreement.

RESULTS

The repeatability and reproducibility of all parameters for the new device were excellent (ICC>0.960 and CoV<0.71%). The Bland-Altman plots showed high agreement between the OLCR-based and SS-OCT-based devices for AL, CCT, AQD, ACD, Km and LT, with narrow 95% limit of agreements (LoAs) (-0.08 mm to 0.06 mm, -15.91 µm to -1.01 µm, -0.09 mm to 0.09 mm, -0.09 mm to 0.08 mm, -0.47 D to 0.35 D, -0.05 mm to 0.16 mm, respectively) and moderate agreement for CD (95% LoA: -0.67 mm to -0.01 mm).

CONCLUSIONS

The new Suoer SW-9000 μm Plus biometer showed excellent repeatability and reproducibility. All the parameters obtained by this biometer were similar to those measured by SS-OCT-based biometer.

Distribution of Axial Length in Australians of Different Age Groups, Ethnicities, and Refractive Errors

Purpose

Treatments are available to slow myopic axial elongation. Understanding normal axial length (AL) distributions will assist clinicians in choosing appropriate treatment for myopia. We report the distribution of AL in Australians of different age groups and refractive errors.

Methods

Retrospectively collected spherical equivalent refraction (SER) and AL data of 5938 individuals aged 5 to 89 years from 8 Australian studies were included. Based on the SER, participants were classified as emmetropes, myopes, and hyperopes. Two regression model parameterizations (piece-wise and restricted cubic splines [RCS]) were applied to the cross-sectional data to analyze the association between age and AL. These results were compared with longitudinal data from the Raine Study where the AL was measured at age 20 (baseline) and 28 years.

Results

A piece-wise regression model (with 1 knot) showed that myopes had a greater increase in AL before 18 years by 0.119 mm/year (P < 0.001) and after 18 years by 0.011 mm/year (P < 0.001) compared to emmetropes and hyperopes, with the RCS model (with 3 knots) showing similar results. The longitudinal data from the Raine Study revealed that, when compared to emmetropes, only myopes showed a significant change in the AL in young adulthood (by 0.016 mm/year, P < 0.001).

Conclusions

The AL of myopic eyes increases more rapidly in childhood and slightly in early adulthood. Further studies of longitudinal changes in AL, particularly in childhood, are required to guide myopia interventions.

Translational Relevance

The axial length of myopic eyes increases rapidly in childhood, and there is a minimal increase in the axial length in non-myopic eyes after 18 years of age.

Baseline metrics that may predict future myopia in young children

PURPOSE

We used baseline data from the PICNIC longitudinal study to investigate structural, functional, behavioural and heritable metrics that may predict future myopia in young children.

METHODS

Cycloplegic refractive error (M) and optical biometry were obtained in 97 young children with functional emmetropia. Children were classified as high risk (HR) or low risk (LR) for myopia based on parental myopia and M. Other metrics included axial length (AXL), axial length/corneal radius (AXL/CR) and refractive centile curves.

RESULTS

Based on the PICNIC criteria, 46 children (26 female) were classified as HR (M = +0.62 ± 0.44 D, AXL = 22.80 ± 0.64 mm) and 51 (27 female) as LR (M = +1.26 ± 0.44 D, AXL = 22.77 ± 0.77 mm). Based on centiles, 49 children were HR, with moderate agreement compared with the PICNIC classification (k = 0.65, p < 0.01). ANCOVA with age as a covariate showed a significant effect for AXL (p < 0.01), with longer AXL and deeper anterior chamber depth (ACD) (p = 0.01) in those at HR (differences AXL = 0.16 mm, ACD = 0.13 mm). Linear regression models showed that central corneal thickness (CCT), ACD, posterior vitreous depth (PVD) (=AXL - CCT - ACD-lens thickness (LT)), corneal radius (CR) and age significantly predicted M (R = 0.64, p < 0.01). Each 1.00 D decrease in hyperopia was associated with a 0.97 mm elongation in PVD and 0.43 mm increase in CR. The ratio AXL/CR significantly predicted M (R = -0.45, p < 0.01), as did AXL (R = -0.25, p = 0.01), although to a lesser extent.

CONCLUSIONS

Although M and AXL were highly correlated, the classification of pre-myopic children into HR or LR was significantly different when using each parameter, with AXL/CR being the most predictive metric. At the end of the longitudinal study, we will be able to assess the predictability of each metric.

Associations between anthropometric indicators and refraction in school-age children during the post-COVID-19 era

Purpose

To explore the associations between anthropometric indicators and refraction in school-aged children in the post-COVID-19 era.

Methods

Data were collected from 25,644 children aged 7 to 12 years in 48 elementary schools in Tianjin. The comprehensive examination included height, weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), refraction, and calculation of BMI, with a follow-up visit after 6 months. Myopia was defined as spherical equivalent refraction (SER) ≤-0.50 diopter (D). Bivariate correlation coefficients and multiple linear regression models were used to explore the cross-sectional and longitudinal associations between anthropometric indicators (height, weight, BMI, SBP, and DBP) and refraction.

Results

The mean changes in height, weight, BMI, SBP, DBP, and SER of the participants were 4.03 ± 2.18 cm, 3.10 ± 2.39 kg, 0.45 ± 1.16 kg/m², 2.26 ± 14.74 mmHg, 2.18 ± 11.79 mmHg and -0.17 ± 0.51 D, respectively. Overall, height, weight, BMI, SBP, and DBP were all correlated with SER (r = -0.324, r = -0.234, r = -0.121, r = -0.112, r = -0.066, both p < 0.001), and changes in height and weight were correlated with changes in SER (r = -0.034, -0.031, both p < 0.001). Furthermore, multiple linear regression analysis revealed that the association of BMI, SBP, and DBP with SER was significant in myopic children but not in non-myopic children. The association between changes in weight and changes in SER was only present in non-myopic children but not in myopic children.

Conclusion

Height and weight were negatively correlated with SER in both cross-sectional analysis and longitudinal changes, indicating that children's height, weight and growth rate may be used as a reference indicator for myopia risk prediction and myopia progression monitoring.

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.