What is the association between the prevalence and severity of myopia and different study styles?
In this nationwide cross-sectional study that included 22 823 male adolescents, the odds of having myopia for those who were studying in the ultra-Orthodox and Orthodox educational systems were much higher compared with adolescents in the secular educational system.
These findings suggest that educational systems that require extensive reading and other near-work activities (those done at a short working distance) are associated with increased prevalence and severity of myopia.
A substantial portion of the public is diagnosed with myopia, which increases the risk of potential sight-threatening complications. The association between study style and the development of myopia is unclear.
To analyze the association between studying in different educational systems and the prevalence and severity of myopia among Jewish male adolescents in Israel.
Design, Setting, and Participants
A nationwide, population-based study was conducted of 22 823 male candidates for military service in Israel aged 17 to 18 years attending the military draft board in 2013 who underwent a medical examination and a visual acuity assessment. Statistical analysis was performed from January 1 to March 31, 2018.
The participants studied in 1 of 3 Israeli educational systems: secular, Orthodox, or ultra-Orthodox. The ultra-Orthodox system and, to a lesser extent, the Orthodox system involve intensive reading starting in early childhood compared with the secular system.
Main Outcomes and Measures
The odds ratio (OR) for the association between educational system and the prevalence and severity of myopia.
Among the 22 823 participants (mean [SD] age, 17.7 [0.6] years), there was a higher proportion of adolescents in the ultra-Orthodox educational system with myopia (1871 of 2276 [82.2%]) compared with adolescents in the Orthodox educational system (1604 of 3189 [50.3%]) and those in the secular educational system (5155 of 17 358 [29.7%]). Compared with adolescents in the secular educational system, those in the Orthodox educational system were more likely to have myopia (OR, 2.3; 95% CI, 2.1-2.5; P < .001), as were those in the ultra-Orthodox educational system (OR, 9.3; 95% CI, 8.2-10.7; P < .001), after adjustment for age, country of origin, socioeconomic status, years of education, and body mass index. The multivariable adjusted OR for high myopia (refractive error of at least −6.0 diopters) was 4.6 (95% CI, 3.8-5.5; P < .001) for adolescents in the Orthodox educational system and 38.5 (95% CI, 30.7-48.2; P < .001) for adolescents in the ultra-Orthodox educational system compared with adolescents in the secular educational system.
Conclusions and Relevance
This study provides evidence of the independent association between educational systems and the prevalence and severity of myopia. Male adolescents in the ultra-Orthodox educational system have higher odds of having myopia and high myopia. These findings suggest that study styles that involve intensive reading and other near-work activities (those done at a short working distance) play a role in the development of myopia and warrant consideration of prevention strategies.
The prevalence of myopia has increased worldwide in recent years.1-3 In addition, there has been a constant increase in the prevalence of high myopia (refractive error of at least −6.0 diopters [D]).1 Uncorrected myopia is the most common cause of vision impairment worldwide, whereas high myopia can cause serious, sight-threatening ocular damage and is associated with several ocular diseases, including myopic retinal degeneration, retinal detachment, glaucoma, cataract, and blindness.4,5 Hence, it is important to identify the possible risks and preventive factors in the development of myopia and, particularly, high myopia.
Both genetics and environmental factors play a role in the development and progression of myopia. Near work is activity performed at a short working distance, such as reading and use of electronic devices. Near-work activity is one of the environmental factors that has been considered to be a potential cause of myopia.6-8 However, other studies do not support this claim.9-11 One theory that might explain this association is that the combined influence of biomechanical factors (eg, extraocular muscle forces and ciliary muscle contraction) associated with near-work tasks in downward gaze increases axial length.12
There are 3 educational systems in Israel: secular, Orthodox, and ultra-Orthodox schools, which differ in their study style. Ultra-Orthodox Jews in Israel have a unique educational system that involves intensive sustained near-work activity and prolonged accommodation effort beginning at a young age compared with the Orthodox and secular systems. Before primary school, children in secular and Orthodox educational systems attend prekindergarten and kindergarten. Children in the ultra-Orthodox system do not enroll in kindergarten but, instead, begin formal schooling with an emphasis on intensive studying and reading at the age of 3 years.13 Secular schools offer a state education core curriculum that includes different subjects, such as arts, mathematics, and science. Orthodox schools are similar to secular schools except for having additional 2 to 3 weekly study hours dedicated to intensive reading of religious texts, as well as having single-sex education.14 Ultra-Orthodox schools, on the other hand, focus mainly on intensive reading of religious texts.15 Most of the reading texts are printed with relatively small font sizes, which may be as small as 1 mm in height. Male and female students are separated in Ultra-Orthodox schools, and they have different curricula and study conditions.15 The number of study hours is gradually increased up to 16 hours a day in ultra-Orthodox schools compared with 6 to 8 hours in secular schools.16 In addition, adolescents in ultra-Orthodox schools are less exposed to technology, and specifically to devices with screens, in schools and in their everyday life.17
The objective of this study was to analyze the association between different educational systems (secular, Orthodox, and ultra-Orthodox) with the prevalence and severity of myopia among Israeli male adolescents.
The study population comprises 22 823 Israeli candidates for military service who were examined by the military draft board in 2013. In Israel, military service is mandatory by law for all Jewish adolescents, except for exclusive populations who are exempted from it, including religious (ie, Orthodox and ultra-Orthodox) females. In February 2012, military service became mandatory for ultra-Orthodox males in Israel.18 We therefore consider the data that were collected in 2013 for this study to be representative of males aged 17 to 18 years in the general Jewish population. The candidates undergo draft board assessment to check their eligibility for military service. The assessment includes demographic information, medical information (including a physical examination conducted by a physician), and visual acuity measurements. Myopia severity does not exclude one from military service, although it can affect one’s assignment. The study protocol was approved by the Israel Defense Forces Medical Corps Institutional Review Board. Patient consent was waived as the raw data were deidentified.
The screening for myopia and other refractive errors, which was conducted in a single military draft center, was performed in the following manner: a medical history was obtained, and the candidate’s unaided visual acuity was evaluated using a standard Snellen chart at 6 m. All candidates with unaided visual acuity lower than 6/6 in either eye underwent noncycloplegic refraction by using an automated refractometer (Speedy K; Nikon Corp; KR-8000, KR7000S, and earlier models; Topcon), and the results were recorded. This procedure was followed by a complement subjective refraction for validation using a Snellen chart. For each participant, refractive error was calculated as the spherical equivalent (SEQ = sphere + [cylinder/2]). Myopia was defined as an SEQ of −0.50 D or less.19 Low myopia was defined as an SEQ between −0.50 and −2.99 D, moderate myopia was defined as an SEQ between −3.00 and −5.99 D, and high myopia was defined as an SEQ of −6.00 D or more.19 The classification for each individual was made based on the worse SEQ between both eyes. Worse SEQ was chosen to be used for myopia definitions after preliminary analysis that demonstrated a satisfactory correlation between both eyes (Pearson correlation coefficient, 0.92).
Educational System Classification
All the participants studied in one of the 3 major educational systems in Israel (secular, Orthodox, and ultra-Orthodox schools). We classified participants based on the educational system their school belonged to according to the Israeli Ministry of Education list.20 Each school’s educational system is clearly defined, and there are no schools that combine 2 or more of these systems.21 Throughout childhood, the transfer of students between educational systems is less than 2%. If a transfer occurred, it was generally to a less religious system.21
Covariates and Study Variables
Sociodemographic and anthropometric data were recorded as part of the draft board evaluation process. Age, country of origin, socioeconomic status (SES), years of education, and body mass index (BMI) were obtained from the data. Country of origin was determined by the birthplace of the father and was categorized into 6 groups: Israel, former Union of Soviet Socialist Republics countries, Asia, North Africa, Ethiopia, and Western countries. Socioeconomic status was determined according to the classification method developed by the Israeli Central Bureau of Statistics, which ranks municipal authorities on a scale of 1 to 10 based on the inhabitants’ financial resources (from work, benefits, and other), housing density and quality, home appliances, motorization level, educational level, employment profile, and other demographic characteristics.22 Socioeconomic status was classified into the following 3 categories: low (municipal ranking, 1-3), medium (municipal ranking, 4-6), and high (municipal ranking, 7-10); each recruit was allocated to 1 of the categories based on locality of residence at the time of examination. Educational level was grouped according to the formal schooling years that the participant attended: 9 years or less, 10 to 11 years, and 12 years or more (includes higher and academic studies). Body mass index was calculated as measured weight in kilograms divided by measured height in meters squared. Body mass index values were coded according to the age- and sex-adjusted growth charts of the US Centers for Disease Control and Prevention.23
A total of 87 875 military candidates were examined by the military draft board in 2013 (Figure 1). Female candidates were excluded from the analysis (n = 31 968) because religious females who study in the Orthodox or ultra-Orthodox schools do not undergo draft board assessments because they are exempted from mandatory military service. Hence, it was not possible to compare myopia prevalence by educational system among female candidates in the present study because data for religious females were incomplete and not representative. Candidates who were born abroad (n = 10 535) were also excluded because they had been enrolled in different education systems (ie, non-Israeli) throughout childhood and were exposed to heterogeneous study conditions that we could not account for. We excluded candidates who were not aged 17 to 18 years (n = 36 018), and we used a relatively narrow range of ages because refractory error varies with age.24 We also removed from the data set candidates who had a prior surgical correction of refraction (n = 395), non-Jewish candidates because only a minority of the non-Jewish population is examined by the military draft board (n = 7227), and individuals with missing data or likely data entry errors (n = 1732). Missing data were apportioned proportionately across the 3 educational systems. This process left 22 823 participants with data available for analysis. The data set was specially created by our own study group.
Statistical analysis was performed from January 1 to March 31, 2018. Univariable logistic regression models were used to evaluate the associations between myopia, as an outcome variable, and each of the independent variables and covariates. The χ2 test was used for categorical variables, and 1-way analysis of variance was used for continuous variables. The association between educational system and myopia was assessed using multivariable logistic regression models, adjusted for all the covariates that were found to be statistically significant (by 2-sided P < .001) in the univariable regression models: age, country of origin, SES, years of education, and BMI. Similar multivariable regression models were used to estimate the association between educational system and the 3 myopia severity categories (low, moderate, and high). The results of the regression models are reported as odds ratios (ORs) with 95% CIs. All analyses were conducted using SPSS, version 22.0 (IBM Corp).
There were 22 823 male adolescents aged 17 to 18 years with data available for analysis: 17 358 secular adolescents (76.1%), 3189 Orthodox adolescents (14.0%), and 2276 ultra-Orthodox adolescents (10.0%). There were several differences between the educational systems in the baseline characteristics of adolescents (Table 1). Ultra-Orthodox adolescents were older (mean [SD], 18.1 [0.6] years) compared with Orthodox (mean [SD], 17.4 [0.4] years) and secular adolescents (mean [SD], 17.4 [0.4]; P < .001), had lower SES (1821 [80.1%] vs 1320 [42.0%] of Orthodox adolescents and 3957 [22.9%] of secular adolescents; P < .001), and originated mainly from Western countries (741 [32.7%] vs 706 [22.3%] of Orthodox adolescents and 3339 [19.4%] of secular adolescents; P < .001). Univariate analysis showed that age, country of origin, SES, years of education, and BMI were associated with myopia (Table 2).
The prevalence of myopia in the total study population was 37.8% (8627 individuals) (19.7%  with low myopia, 12.8%  with moderate myopia, and 5.3%  with high myopia) (eTable in the Supplement). Ultra-Orthodox adolescents had the highest rate of myopia compared with Orthodox and secular adolescents (82.2%  vs 50.3%  vs 29.7% ; Figure 2). In addition, ultra-Orthodox adolescents had the highest rate of high myopia compared with Orthodox and secular adolescents (27.6%  vs 7.1%  vs 2.0% ; eTable in the Supplement).
The educational system category was strongly associated with myopia after adjustment for age, country of origin, SES, years of education, and BMI (Table 3). With secular adolescents as the reference category, the adjusted OR of having myopia was 2.3 (95% CI, 2.1-2.5; P < .001) for Orthodox adolescents and 9.3 (95% CI, 8.2-10.7; P < .001) for ultra-Orthodox adolescents.
Multivariable logistic regression confirmed that educational system was also associated with myopia severity after adjustment for age, country of origin, SES, years of education, and BMI (Table 3). We observed that the OR gap between the groups increased with myopia severity. Orthodox adolescents had an adjusted OR for high myopia of 4.6 (95% CI, 3.9-5.5; P < .001), and ultra-Orthodox adolescents had an adjusted OR of 38.5 (95% CI, 30.7-48.2; P < .001), compared with the secular group.
In this population-based study, we found evidence of disparity in myopia prevalence among male adolescents in different educational systems: ultra-Orthodox (82.2%), Orthodox (50.3%) and secular (29.7%), with a very high prevalence of myopia among adolescents in the ultra-Orthodox educational system. Similar and even stronger associations were found for high myopia. This association persisted after adjustment for age, BMI, and sociodemographic factors.
The association between different educational systems and myopia has been studied in the past among teenagers and military conscripts in Singapore.25,26 An association was found between myopia and an increased number of hours during elementary school and a better educational system. In Israel, this association has been studied previously in small-scale populations. One study among high school students in Israel found that the incidence of myopia among 167 Orthodox students was higher than that among 187 secular students (46.7% vs 24.6%).27 Furthermore, Orthodox students had a higher incidence than secular students of high myopia (13.1% vs 1.6%). Another study of 870 teenagers reported a much higher prevalence of myopia among Orthodox male teenagers than among non-Orthodox teenagers (81.3% vs 27.4%).28 One study examined 917 Israeli students in the third grade and found that male students from ultra-Orthodox schools had the highest rate of reduced unaided vision (72.5%) compared with male students from secular schools (27.3%), male students from Orthodox schools (59.3%), and female students from all 3 groups.29
There are several differences between our study and previous works. The present study is a population-based cross-sectional study that examines the association between the educational system and the prevalence and severity of myopia. In addition, our study adjusted for demographic factors that may confound the association between educational system and myopia. Furthermore, the educational systems may resemble a natural “experiment” of participants to “exposure groups” that differ in the likelihood of near-work exposure at school; therefore, this presents a rare opportunity to examine this association on a large scale.
We found a much higher prevalence of myopia in the ultra-Orthodox group compared with the Orthodox and secular groups. This high proportion of myopia also was seen in Asian populations, where myopia is reaching epidemic proportions, with prevalence rates among adolescents being as high as 66% in Japan, 79% in Singapore, 80% in China, 84% in Taiwan, and 97% in South Korea.30-34 Ultra-Orthodox adolescents had the highest odds of having myopia and, specifically, high myopia compared with secular adolescents. Orthodox adolescents also had a higher risk than secular adolescents of having high myopia, but to lesser extent than ultra-Orthodox adolescents.
The association may possibly be explained by the near-work theory. It has been proposed that near-work activity contributes to the increase in myopia in East Asian countries. A 2014 report of the Organization for Economic Co-operation and Development showed that the average 15-year-old student in Shanghai spends 14 hours per week on homework compared with 5 hours in the United Kingdom and 6 hours in the United States.35 The ultra-Orthodox educational system involves sustained near work from a very young age because most of their daily life is dedicated to reading biblical texts, often with a very small font size.13,16 Orthodox adolescents also dedicate a large portion of their daily life to reading religious text, albeit not as much as ultra-Orthodox adolescents.14 In light of this theory, our results suggest a dose-response association between near-work activity (specifically reading) and myopia because the odds of developing myopia increase with educational systems that incorporate extended reading activity from a young age.
Several additional environmental factors may be associated with our results. Some studies suggest that increased outdoor time is an important modifiable environmental factor that protects children from myopia.36 French et al7 found an inverse association between time spent outdoors and the risk of incident myopia among 2103 children. The data are supported by animal models, in which myopia was induced by raising chicks under controlled conditions where only the light intensity was changed.37 Although all the participating schools in our study have state-regulated lighting conditions in each classroom, increased study hours among the ultra-Orthodox students could suggest that they spend more time in the classrooms and less time outdoors.
In the last few decades, exposure to display screen equipment, such as computers and television monitors, has increased.17 It was suggested that this almost universal and extensive exposure might represent a risk factor in the development or progression of myopia and might be associated with its increasing prevalence.38-40 We found the highest prevalence of myopia among ultra-Orthodox adolescents who are considered to have the least exposure to display screen equipment between the different groups.17 However, we did not have specific data on the use of display screen equipment, and it is not possible to conclude based on the present study whether display screen equipment is a risk factor for the development or progression of myopia.
The following limitations merit consideration. First, there was no information in the database on the refractory status of the adolescents’ parents. It has been demonstrated that genetic changes underlie the molecular basis of myopia development.41 However, the clinical effect of these changes remains largely unknown, and the dramatic and sudden increase in the prevalence of myopia during the past century in certain societies argues for a dominant environmental influence. In addition, the noncycloplegic refraction used in this study is a less accurate method than cycloplegic refraction for measuring refractive error in teenagers, which might have resulted in a slight overestimation of myopia among all groups.42 Moreover, because this is a cross-sectional study, the ORs are associated with having myopia rather than developing myopia. The association of near work with myopia may be cumulative over time. Because only adolescents aged 17 to 18 years were included in this study, our findings are limited to this age group only. Ku et al43 showed that children aged 7 to 12 years who attended after-school centers for extracurricular academic lessons on a weekly basis had a higher risk of developing myopia. Given that finding, it would appear that future research should further explore the association between educational system and myopia by conducting prospective studies of different age groups and with the inclusion of female students to find the critical period of myopia development for both sexes.
We found an independent association between educational systems that incorporate demanding near-work activities, specifically reading, and myopia. Male adolescents in the ultra-Orthodox educational system who are exposed to intensive near-work activity (eg, reading) on a daily basis have higher odds of having myopia or high myopia compared with adolescents in other educational systems. These results appear to support the hypothesis that near-work activities play a role in the development and progression of myopia. The observational design of this study identifies associations, not necessarily causation. Therefore, further research should evaluate potential prevention strategies that reduce the association of near work with the development of myopia in children and adolescents, such as limiting reading time or providing the students with books with larger fonts and improved reading conditions to determine whether this change would reduce the development or progression of myopia.
Accepted for Publication: March 29, 2019.
Corresponding Author: Hagai Levine, MD, MPH, Braun School of Public Health and Community Medicine, Hebrew University-Hadassah Faculty of Medicine, PO Box 12272, Kiryat Hadassah, Ein Kerem, Jerusalem, Israel 9112002 (email@example.com).
Published Online: May 30, 2019. doi:10.1001/jamaophthalmol.2019.1415
Author Contributions: Dr Levine had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: D. Bez, Barak, Levine.
Acquisition, analysis, or interpretation of data: D. Bez, Megreli, M. Bez, Avramovich, Levine.
Drafting of the manuscript: D. Bez, M. Bez, Barak, Levine.
Critical revision of the manuscript for important intellectual content: D. Bez, Megreli, Avramovich, Barak.
Statistical analysis: D. Bez, Megreli.
Administrative, technical, or material support: All authors.
Supervision: Avramovich, Barak, Levine.
Conflict of Interest Disclosures: Dr Barak reported receiving personal fees from Nanoretina and grants from Cellcure, Byonics, Novartis, and MicroSert outside the submitted work. No other disclosures were reported.
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