Myopia and Childhood Migration: A Study of 607 862 Adolescents

Weight Status and Myopia in Children and Adolescents: A Nationwide Cross-Sectional Study of China

BACKGROUND/OBJECTIVES

The prevalence of both myopia and obesity is increasing among children and adolescents around the world. We aimed to examine the association between weight status and myopia in Chinese children and adolescents.

METHODS

The analysis included 35,108 participants aged 6-17 from a nationwide cross-sectional survey.

RESULTS

Our results indicated that girls with overweight and obesity had higher odds ratio (OR) of myopia and mild myopia: ages 6-8 (OR = 1.33, 95% CI: 1.01-1.76; OR = 1.71, 95% CI: 1.14-2.55) and 9-11 (OR = 1.22, 95% CI: 1.03-1.44; OR = 1.31, 95% CI: 1.06-1.62). Myopic boys had higher body fat percentages (BFP) at ages 6-8 (β = 1.18, 95% CI: 0.38-1.98), 9-11 (β = 0.58, 95% CI: 0.08-1.07), and 15-17 (β = 0.42, 95% CI: 0.03-0.80), and higher body mass index (BMI) at ages 9-11 (β = 0.30, 95% CI: 0.12-0.48) and 12-14 (β = 0.19, 95% CI: 0.02-0.38). Girls had higher BFP at ages 9-11 (β = 0.62, 95% CI: 0.19-1.05) and 12-14 (β =0.53, 95% CI: 0.19-0.88) and higher BMI at 9-11 (β = 0.53, 95% CI: 0.34-0.73). Furthermore, the dose-response curves revealed a significant gender- and age-specific association between BMI, BFP, and myopia odds ratio.

CONCLUSIONS

the study found an association between overweight or obesity and myopia in girls aged 6-11, and indicated that high BFP and BMI are associated with myopia, varying by sex and age.

Myopia and systemic manifestation of tissue hyperlaxity: A population-based cross-sectional study

BACKGROUND

Whether non-syndromic connective tissue hyperlaxity is associated with myopia is unknown. The aim of this study was to examine the association between systemic signs of tissue hyperlaxity and myopia among adolescents.

METHODS

Included were adolescents assessed before mandatory military service at the age of 16-18 years between 2011 and 2022. Diagnoses of hernias, pes planus, genu varus, genu valgum, and scoliosis, as well as joint injuries were used as surrogate markers for tissue hyperlaxity. The prevalence of these events among adolescents with myopia was evaluated and compared to the non-myopic population.

RESULTS

Included were 920 806 adolescents. The mean age was 17.4 ± 1.4 years and 58.6% were men. Myopia was diagnosed in 290 759 adolescents (31.6%) and high myopia in 24 069 adolescents (2.6%). The prevalence of hernias was higher among adolescents with myopia, (2.76%, 95% confidence interval (95% CI): 2.69%-2.82% vs. 2.60%, 95% CI: 2.57%-2.65%), as were pes planus (14.92%, 95% CI: 14.79-15.05 vs. 13.51%, 95% CI: 13.42-13.59) and scoliosis (9.14%, 95% CI: 9.03-9.24 vs. 7.69%, 95%CI: 7.62-7.76). The prevalence of joint injuries was clinically similar between groups (less than 0.1% difference for ankle, shoulder, and knee injuries), as were genu varum and genu valgum (0.66%, 95%CI: 0.64%-0.69% vs. 0.68%, 95% CI: 0.66-0.70, respectively). Adjusted for possible confounders results remained consistent.

CONCLUSIONS

Among a large sample of Israeli adolescents, those with myopia had a higher prevalence of hernias, pes planus, and scoliosis. These results could suggest a propensity for systemic conditions related to tissue laxity among myopic adolescents.

Shaping school for childhood myopia: the association between floor area ratio of school environment and myopia in China

AIM

To investigate the association of floor area ratio (FAR), an indicator of built environments, and myopia onset.

METHODS

This prospective cohort study recruited 136 753 children aged 6-10 years from 108 schools in Shenzhen, China at baseline (2016-2017). Refractive power was measured with non-cycloplegic autorefraction over a 2-year follow-up period. FAR was objectively evaluated using geographical information system technology. Mixed-effects logistic regression models were constructed to examine the association of FAR with a 2-year cumulative incidence of myopia among individuals without baseline myopia; multiple linear regression model, with a 2-year cumulative incidence rate of myopia at each school.

RESULTS

Of 101 624 non-myopic children (56.3% boys; mean (SE) age, 7.657±1.182 years) included in the study, 26 391 (26.0%) of them developed myopia after 2 years. In the individual-level analysis adjusting for demographic, socioeconomic and greenness factors, an IQR in FAR was associated with a decreased risk of 2-year myopia incidence (OR 0.898, 95% CI 0.866 to 0.932, p<0.001). Similar findings were observed in the analysis additionally adjusted for genetic and behavioural factors (OR 0.821, 95% CI 0.766 to 0.880, p<0.001). In the school-level, an IQR increase in FAR was found to be associated with a 2.0% reduction in the 2-year incidence rate of myopia (95% CI 1.3% to 2.6%, p<0.001).

CONCLUSIONS

Exposure to higher FAR was associated with a decreased myopia incidence, providing insights into myopia prevention through school built environments in China.

Body mass index and astigmatism: A nationwide study

BACKGROUND

Existing research on the relationship between body mass index (BMI) and astigmatism yields inconsistent results. This study analyses this association in a nationally representative sample of adolescents.

METHODS

This retrospective, cross-sectional study included Israeli adolescents who underwent medical assessments before mandatory military service between 2011 and 2022. BMI was categorised based on the US age- and sex-matched percentiles. Astigmatism was categorised by magnitude [low-moderate: 0.75 to <3.00 diopters (D), high: ≥3.00 D], and axis orientation [with-the-rule (WTR), against-the-rule (ATR), or oblique (OBL)]. Sex-stratified regression models adjusted for sociodemographic variables were used.

RESULTS

Of 935 989 adolescents evaluated, 887 325 were included [511 465 (57.6%) males, mean age 17.2 years]. Astigmatism was diagnosed in 123 675 (13.9%) adolescents, of whom 117 081 (13.2%) had low-moderate and 6594 (0.7%) had high astigmatism. WTR astigmatism was the most prevalent (8.2%), followed by ATR (4.1%) and OBL (1.6%) types. Compared with low-normal BMI (5th to 50th percentile), the adjusted ORs for total astigmatism increased with increasing BMI, peaking at 1.65 (1.57-1.74) in males and 1.74 (1.64-1.86) in females with severe obesity. ORs were accentuated for high astigmatism, reaching 3.51 (3.01-4.09) in males, and 3.45 (2.83-4.22) in females with severe obesity. WTR astigmatism demonstrated the strongest association with BMI, with ORs reaching 2.26 (2.13-2.40) in males and 2.04 (1.90-2.20) in females with severe obesity. The results persisted in a series of subgroup analyses.

CONCLUSIONS

Obesity is associated with higher odds of astigmatism in adolescence. Further investigation into the role of weight management in astigmatism development is warranted.

Visual impairment and cognitive performance: A nationwide study of 1.4 million adolescents

PURPOSE

Previous research highlights the adverse effects of visual impairment (VI) on academic achievement in children, yet its impact on cognitive performance among adolescents and young adults remains under-studied. Therefore, this investigation aimed to analyse this association in a nationwide sample of Israeli adolescents.

METHODS

A retrospective population-based cross-sectional study was conducted among 1,410,616 Israeli-born adolescents aged 16-19 years, who were assessed before mandatory military service between 1993 and 2017. The definition of VI was based on best-corrected visual acuity (BCVA) measurements using a standard Snellen chart. Adolescents with BCVA worse than 6/9 in either or both eyes were classified as having unilateral or bilateral VI, respectively. Cognitive performance was measured using the General Intelligence Score (GIS), based on a validated four-domain test. Relationships were analysed using regression models yielding adjusted odds ratios (ORs) for low (<-1 standard deviation [SD]) and high (≥1 SD) cognitive Z-scores.

RESULTS

Of 1,410,616 adolescents (56.1% men), 13,773 (1.0%) had unilateral and 3980 (0.3%) had bilateral VI. Unilateral VI was associated with adjusted ORs for low and high cognitive Z-scores of 1.24 (1.19-1.30) and 0.84 (0.80-0.89), respectively. ORs were accentuated for bilateral VI, reaching 1.62 (1.50-1.75) and 0.81 (0.74-0.90) for low and high cognitive Z-scores, respectively. Cognitive performance subscores mirrored these results, with the visual-spatial functioning subtest demonstrating the greatest effect size. These associations persisted in sub-analyses restricted to adolescents with amblyopia-related VI, mild VI and unimpaired health status.

CONCLUSIONS

Visual impairment, including mild and unilateral cases, is associated with reduced cognitive performance scores assessed in late adolescence. Further research is required to gain a comprehensive understanding of the dynamics underlying this relationship.

Myopia, Sodium Chloride, and Vitreous Fluid Imbalance: A Nutritional Epidemiology Perspective

Theories of myopia etiology based on near work and lack of outdoor exposure have had inconsistent support and have not prevented the rising prevalence of global myopia. New scientific theories in the cause and prevention of myopia are needed. Myopia prevalence is low in native people consuming traditional diets lacking in sodium chloride, and nutritional epidemiological evidence supports the association of rising myopia prevalence with dietary sodium intake. East Asian populations have among the highest rates of myopia associated with high dietary sodium. Similar associations of sodium and rising myopia prevalence were observed in the United States in the late 20th century. The present perspective synthesizes nutritional epidemiology evidence with pathophysiological concepts and proposes that axial myopia occurs from increased fluid retention in the vitreous of the eye, induced by dietary sodium chloride intake. Salt disturbs ionic permeability of retinal membranes, increases the osmotic gradient flow of fluid into the vitreous, and stretches ocular tissue during axial elongation. Based on the present nutritional epidemiology evidence, experimental research should investigate the effect of sodium chloride as the cause of myopia, and clinical research should test a very low-salt diet in myopia correction and prevention.

Body mass index and visual impairment in Israeli adolescents: A nationwide study

BACKGROUND

Previous research on the association between body mass index (BMI) and visual impairment (VI) in youth has reported inconsistent findings. We aimed to investigate this association in a national cohort of Israeli adolescents.

METHODS

This retrospective, population-based, cross-sectional study included 1 697 060 adolescents (56.4% men; mean age 17 years) who underwent mandatory pre-military service assessments from 1993 to 2017. BMI was classified based on the US age- and sex-matched percentiles. Unilateral or bilateral VI was classified as best-corrected visual acuity (BCVA) worse than 6/9 in either or both eyes, respectively. Sex-stratified regression models adjusted for sociodemographic variables were used to analyse the BMI-VI relationship.

RESULTS

Overall, 17 871 (1.05%) and 5148 (0.30%) adolescents had unilateral and bilateral VI, respectively. Compared with high-normal BMI (50th to 85th percentile), adjusted odds ratios (ORs) for unilateral and bilateral VI gradually increased with higher BMI, reaching 1.33 (1.13-1.55) and 1.80 (1.37-2.35) in men with severe obesity, and 1.51 (1.24-1.84) and 1.52 (1.08-2.14) in women with severe obesity, respectively. Men with underweight also had increased ORs for unilateral and bilateral VI (1.23; 1.14-1.33 and 1.59; 1.37-1.84, respectively), a pattern not observed in women (0.96; 0.86-1.07 and 1.02; 0.83-1.25, respectively). Results were maintained when the outcome was restricted to mild VI, as well as in subgroups of adolescents with unimpaired health and those without moderate-to-severe myopia.

CONCLUSIONS

Abnormal BMI, and particularly obesity, is associated with increased OR for VI in late adolescence.

Blepharoptosis and cognitive performance: a population-based study of 1.4 million adolescents

The purpose of this study is to examine the association between blepharoptosis and cognitive performance in late adolescence. This population-based, retrospective, cross-sectional study included 1,411,570 Israeli-born adolescents (620,107 women, 43.9%) aged 16-19 years who were medically examined before compulsory military service between 1993 and 2017. The diagnosis of blepharoptosis was verified by an ophthalmologist. Cognitive performance was assessed by a validated intelligence-quotient-equivalent test, comprising four domains (problem-solving, verbal abstraction and categorization, verbal comprehension, and mathematical abilities). Cognitive Z-scores were calculated and categorized as high (≥ 1 standard deviation (SD)), medium (- 1 to < 1 SD), and low (less than - 1 SD). Relationships were analyzed using regression models adjusted for sociodemographic variables including sex, year of birth, residential socioeconomic status, education level, body mass index, and familial country of origin. A total of 577 (41 per 100,000, 32.2% women) adolescents were diagnosed with blepharoptosis. The proportions of unilateral and bilateral visual impairment among adolescents with blepharoptosis were 13.0% and 3.5%, respectively. In a multivariable analysis, blepharoptosis was associated with a 0.18 SD reduction in cognitive Z-score (p < 0.001). The adjusted odds ratios for low and high cognitive Z-scores in adolescents with blepharoptosis were 1.54 (1.25-1.89) and 0.80 (0.62-1.04), respectively. This relationship persisted when adolescents with normal best-corrected visual acuity or unimpaired health status were analyzed separately.  Conclusions: Blepharoptosis is associated with reduced cognitive performance determined in late adolescence. Future prospective studies should investigate the causes of this link and their underlying mechanisms. What is Known: • While earlier investigations have examined the effects of blepharoptosis on vision and quality of life, the association between blepharoptosis and cognitive outcomes in youth has remained unexplored. What is New: • This nationwide study involving 1.4 million Israeli adolescents found a correlation between blepharoptosis and reduced cognitive performance. • Our findings suggest a potential interplay between blepharoptosis and cognitive development in the pediatric population, calling for increased focus on the educational needs of affected individuals.

The Definition-Dependent Nature of Myopia Prevalence: A Nationwide Study of 1.5 Million Adolescents

PURPOSE

The application of myopia definition varies considerably within the literature. The purpose of this study was to examine the relationship between different myopia and high myopia definitions and resultant prevalence estimates.

METHODS

A population-based cross-sectional study of 1,588,508 Israeli adolescents assessed for medical fitness before mandatory military service at the age of 17 years between 1993 through 2015. Participants underwent non-cycloplegic autorefraction. Nine definitions of myopia and seven definitions of high myopia were examined. Prevalence estimates for each definition were calculated and compared with the reference definition (right eye spherical equivalent (SE)≤-0.50D and ≤-6.00D for myopia and high myopia, respectively), to yield a rate ratio (RR) across definitions.

RESULTS

Applying the right eye SE≤-0.50D reference definition yielded 31.0% myopia prevalence. While some definitions resulted in similar prevalence estimates, using the right eye SE of ≤-0.75D; ≤-1.00D or least minus meridian of ≤-0.75D definitions yielded 28.8%, 26.3%, and 26.9% myopia prevalence, respectively, which corresponded to a 7.1%, 15.1% and 13.4% reduction in myopia RR, respectively. The prevalence of high myopia demonstrated considerable alternations, with a 1.7-fold increase in prevalence for the narrower threshold of SE≤-5.00D compared with SE≤-6.00D reference definition (4.2% and 2.4%, respectively).

CONCLUSIONS

The prevalence of myopia and especially high myopia varies between frequently applied definitions, considering diverse thresholds, eye lateralization, and spherical vs. astigmatic refractive components. This variability highlights the pressing need for standardization of myopia definition in ophthalmic research. The results of this study provide crude estimates of a "conversion rate" across data, allowing comparisons between studies that utilize different myopia definitions.

Myopia and BMI: a nationwide study of 1.3 million adolescents

OBJECTIVE

This study analyzed the association between adolescent BMI and myopia severity.

METHODS

This cross-sectional study comprised 1,359,153 adolescents who were medically examined before mandatory military service. Mild-to-moderate and high myopia were defined based on right-eye refractive data. BMI was categorized based on the US age- and sex-matched percentiles. Logistic regression models were applied separately for women and men to estimate odds ratios (ORs) for myopia per BMI category.

RESULTS

A total of 318,712 adolescents had mild-to-moderate myopia and 23,569 had high myopia. Compared with low-normal BMI (reference group), adjusted ORs for mild-to-moderate and high myopia increased with increasing BMI status, reaching 1.39 (95% CI: 1.23-1.57) and 1.73 (95% CI: 1.19-2.51) for men with severe obesity, respectively, and 1.19 (95% CI: 1.12-1.27) and 1.38 (95% CI: 1.14-1.65) for women with mild obesity, respectively. ORs for mild-to-moderate and high myopia were also higher in men with underweight (OR = 1.20; 95% CI: 1.18-1.23 and OR = 1.39; 95% CI: 1.30-1.47) and women with underweight (OR = 1.06; 95% CI: 1.03-1.09 and OR = 1.12; 95% CI: 1.04-1.22). The overall size effect was greater for men than women (pinteraction  < 0.001), in whom the group with severe obesity did not reach statistical significance.

CONCLUSIONS

BMI was associated with myopia in a J-shaped pattern, with the size effect being greater for adolescent men than women. This study indicates that both low BMI and high BMI are associated with mild-to-moderate and severe myopia.

Myopia and Early-Onset Type 2 Diabetes: A Nationwide Cohort Study

CONTEXT

A correlation between myopia and insulin resistance has been suggested.

OBJECTIVE

We investigated the association between myopia in adolescence and type 2 diabetes (T2D) incidence in young adulthood.

METHODS

This population-based, retrospective, cohort study comprised 1 329 705 adolescents (579 543 women, 43.6%) aged 16 to 19 years, who were medically examined before mandatory military service during 1993 to 2012, and whose data were linked to the Israel National Diabetes Registry. Myopia was defined based on right-eye refractive data. Cox proportional models were applied, separately for women and men, to estimate hazard ratios (HRs) for T2D incidence per person-years of follow-up.

RESULTS

There was an interaction between myopia and sex with T2D (P < .001). For women, T2D incidence rates (per 100 000 person-years) were 16.6, 19.2, and 25.1 for those without myopia, and with mild-to-moderate and high myopia, respectively. These corresponded to HRs of 1.29 (95% CI, 1.14-1.45) and 1.63 (1.21-2.18) for women with mild-to-moderate and high myopia, respectively, compared to those without myopia, after adjustment for age at study entry, birth year, adolescent body mass index, cognitive performance, socioeconomic status, and immigration status. Results persisted in extensive sensitivity and subgroup analyses. When managed as a continuous variable, every 1-diopter lower spherical equivalent yielded a 6.5% higher adjusted HR for T2D incidence (P = .003). There was no significant association among men.

CONCLUSION

For women, myopia in adolescence was associated with a significantly increased risk for incident T2D in young adulthood, in a severity-dependent manner. This finding may support the role of insulin resistance in myopia pathogenesis.