Effect of Myopic Undercorrection on Habitual Reading Distance in Schoolchildren: The Hong Kong Children Eye Study.

INTRODUCTION: This study aimed to evaluate the habitual reading distance among non-myopic children and also myopic children with undercorrection and with full correction. METHODS: This was a population-based cross-sectional study with a total of 2363 children aged 6-8 years who were recruited from the Hong Kong Children Eye Study. Cycloplegic autorefraction, subjective refraction, habitual visual acuity, and best corrected visual acuity were measured. The entire reading process (9 min) was recorded using a hidden video camera placed 5 m away from the reading desk. Reading distances were taken at 6, 7, 8, and 9 min after the child began reading and were measured using a customized computer program developed in MATLAB. The main outcome was the association of habitual reading distances with refraction status. Habitual reading distances of children were documented via video camera footage. RESULTS: The habitual reading distances of undercorrected myopic children (23.37 ± 4.31 cm) were the shortest when compared to non-myopic children (24.20 ± 4.73 cm, P = 0.002) and fully corrected myopic children (24.81 ± 5.21 cm, P < 0.001), while there was no significant difference between the last two children groups (P = 0.17). A shorter reading distance was associated with myopia (OR 1.67; 95% CI 1.11-2.51; P = 0.013) after adjusting for age, sex, height, near work time, outdoor time, and parental myopia. The association of reading distance with myopia did not hold after undercorrected myopic children were excluded (OR 0.97, 95% CI 0.55-1.73; P = 0.92). A shorter reading distance correlated with poorer vision under habitual correction (ß = - 0.003, P < 0.001). CONCLUSION: A shorter reading distance was present among undercorrected myopic children. Myopia undercorrection is not recommended as a strategy for slowing myopic progression.

Vision Screening in Children: The New South Wales Statewide Eyesight Preschooler Screening Program.

PURPOSE: The aim was to investigate universality of access, screening rate, and outcomes from the New South Wales (NSW) Statewide Eyesight Preschooler Screening (StEPS) over the period of 2009 to 2016. DESIGN: Cross-sectional, observational study. METHODS: The StEPS program provides vision screening to 4-year-old children residing in NSW and is administered within Local Health Districts (LHDs). Visual acuity (VA) was examined by trained lay and nurse screeners using HOTV logMAR. Children who had VA <6/9-2 were referred to local practitioners while those with VA <6/18 were referred to public hospital pediatric ophthalmic outpatient clinics where available. Activity data were collected by NSW Health and screening rates determined from population projections of 4-year-olds per LHD based on adjusted 2014 Census data. To determine factors impacting screening and referral rates, a random effects panel analysis was undertaken. RESULTS: A total of 719,686 (96.4%) NSW 4-year-old children were offered StEPS vision screening between 2009 and 2016, 84% accepted and 564,825 children (75.6%) were screened. The screening rate increased from 67.3% in 2009 to 74.5% in 2016, with an 80% target reached for 3 consecutive years from 2013 to 2015. Of those screened, 19.2% were referred to an eye health professional or advised to have a vision retest in 12 months. This referral rate remained steady over the period studied, with little variation between metropolitan, and rural and regional LHDs. CONCLUSIONS: StEPS is an ideal service model for preschool vision screening providing coverage that is comparable to school-based screening programs and at an age likely to facilitate optimal treatment outcomes.

IMI Risk Factors for Myopia.

Risk factor analysis provides an important basis for developing interventions for any condition. In the case of myopia, evidence for a large number of risk factors has been presented, but they have not been systematically tested for confounding. To be useful for designing preventive interventions, risk factor analysis ideally needs to be carried through to demonstration of a causal connection, with a defined mechanism. Statistical analysis is often complicated by covariation of variables, and demonstration of a causal relationship between a factor and myopia using Mendelian randomization or in a randomized clinical trial should be aimed for. When strict analysis of this kind is applied, associations between various measures of educational pressure and myopia are consistently observed. However, associations between more nearwork and more myopia are generally weak and inconsistent, but have been supported by meta-analysis. Associations between time outdoors and less myopia are stronger and more consistently observed, including by meta-analysis. Measurement of nearwork and time outdoors has traditionally been performed with questionnaires, but is increasingly being pursued with wearable objective devices. A causal link between increased years of education and more myopia has been confirmed by Mendelian randomization, whereas the protective effect of increased time outdoors from the development of myopia has been confirmed in randomized clinical trials. Other proposed risk factors need to be tested to see if they modulate these variables. The evidence linking increased screen time to myopia is weak and inconsistent, although limitations on screen time are increasingly under consideration as interventions to control the epidemic of myopia.

Rural-urban differences in myopia prevalence among myopes presenting to Bhutanese retinal clinical services: a 3-year national study.

PURPOSE: To determine the prevalence and demographic characteristics of myopia among patients presenting to the national vitreo-retinal (VR) services in Bhutan. METHODS: The records of the VR clinic at the apex national referral centre, providing the only VR services in the country, were reviewed to identify all new myopia patients over three years. Thus, we surveyed all referrals nationally. The patients were categorised into urban and rural females and males. We assessed myopia prevalence in each group by occupational and educational categories. We examined univariate prevalence data and a multivariate logistic regression (MLR) identified independent factors. RESULTS: Of 2913 cases 1544 (53.0%) were males. Females presented earlier (mean ±SD): overall 45.7 ± 21.9 cf. 48.6 ± 21.6 years, p = 0.003, and among myopes 23.9 ± 13.5 cf. 27.6 ± 18.6 years, p = 0.032. Myopia constituted 92.1% of refractive error, an overall prevalence of 12.3%. Myopia was more common among females (p = 0.01) and urbanites (p = 0.02). Myopia prevalence was highest among urban females (20.9%), followed by urban males (11.9%), rural females (6.8%), and rural males (5.2%). Logistic regression revealed that the odds of having myopia were increased by being a student (4.96 ×) or professional (1.96 ×), and decreased by rural living (1.75 ×), all p ≤ 0.038. CONCLUSIONS: This is the first study on myopia in Bhutan. As observed throughout East and Southeast Asia, the prevalence of myopia was higher in females and urbanites and positively associated with formal education. Given known risk factors, these prevalences may be driven by educational pressures and reduced time spent outdoors.

The epidemics of myopia: Aetiology and prevention.

There is an epidemic of myopia in East and Southeast Asia, with the prevalence of myopia in young adults around 80-90%, and an accompanying high prevalence of high myopia in young adults (10-20%). This may foreshadow an increase in low vision and blindness due to pathological myopia. These two epidemics are linked, since the increasingly early onset of myopia, combined with high progression rates, naturally generates an epidemic of high myopia, with high prevalences of "acquired" high myopia appearing around the age of 11-13. The major risk factors identified are intensive education, and limited time outdoors. The localization of the epidemic appears to be due to the high educational pressures and limited time outdoors in the region, rather than to genetically elevated sensitivity to these factors. Causality has been demonstrated in the case of time outdoors through randomized clinical trials in which increased time outdoors in schools has prevented the onset of myopia. In the case of educational pressures, evidence of causality comes from the high prevalence of myopia and high myopia in Jewish boys attending Orthodox schools in Israel compared to their sisters attending religious schools, and boys and girls attending secular schools. Combining increased time outdoors in schools, to slow the onset of myopia, with clinical methods for slowing myopic progression, should lead to the control of this epidemic, which would otherwise pose a major health challenge. Reforms to the organization of school systems to reduce intense early competition for accelerated learning pathways may also be important.

Risk factors for incident myopia in Australian schoolchildren: the Sydney adolescent vascular and eye study.

PURPOSE: To examine the risk factors for incident myopia in Australian schoolchildren. DESIGN: Population-based, longitudinal cohort study. PARTICIPANTS: The Sydney Adolescent Vascular and Eye Study (SAVES) was a 5- to 6-year follow-up of the Sydney Myopia Study (SMS). At follow-up, 2103 children were reexamined: 892 (50.5%) from the younger cohort and 1211 (51.5%) from the older cohort. Of these, 863 in the younger cohort and 1196 in the older cohort had complete refraction data. METHODS: Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1; Canon, Tokyo, Japan) was measured at baseline and follow-up. Myopia was defined as a spherical equivalent refraction of ≤-0.50 diopters (D). Children were classified as having incident myopia if they were nonmyopic at baseline and myopic in either eye at follow-up. A comprehensive questionnaire determined the amount of time children spent outdoors and doing near work per week at baseline, as well as ethnicity, parental myopia, and socioeconomic status. MAIN OUTCOME MEASURES: Incident myopia. RESULTS: Children who became myopic spent less time outdoors compared with children who remained nonmyopic (younger cohort, 16.3 vs. 21.0 hours, respectively, P<0.0001; older cohort, 17.2 vs. 19.6 hours, respectively, P=0.001). Children who became myopic performed significantly more near work (19.4 vs. 17.6 hours; P=0.02) in the younger cohort, but not in the older cohort (P=0.06). Children with 1 or 2 parents who were myopic had greater odds of incident myopia (1 parent: odds ratio [OR], 3.2, 95% confidence interval [CI], 1.9-5.2; both parents: OR, 3.3, 95% CI, 1.6-6.8) in the younger but not the older cohort. Children of East Asian ethnicity had a higher incidence of myopia compared with children of European Caucasian ethnicity (both P<0.0001) and spent less time outdoors (both P<0.0001). A less hyperopic refraction at baseline was the most significant predictor of incident myopia. The addition of time outdoors, near work, parental myopia, and ethnicity to the model significantly improved the predictive power (P<0.0001) in the younger cohort but had little effect in the older cohort. CONCLUSIONS: Time spent outdoors was negatively associated with incident myopia in both age cohorts. Near work and parental myopia were additional significant risk factors for myopia only in the younger cohort. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Time outdoors and the prevention of myopia.

Recent epidemiological evidence suggests that children who spend more time outdoors are less likely to be, or to become myopic, irrespective of how much near work they do, or whether their parents are myopic. It is currently uncertain if time outdoors also blocks progression of myopia. It has been suggested that the mechanism of the protective effect of time outdoors involves light-stimulated release of dopamine from the retina, since increased dopamine release appears to inhibit increased axial elongation, which is the structural basis of myopia. This hypothesis has been supported by animal experiments which have replicated the protective effects of bright light against the development of myopia under laboratory conditions, and have shown that the effect is, at least in part, mediated by dopamine, since the D2-dopamine antagonist spiperone reduces the protective effect. There are some inconsistencies in the evidence, most notably the limited inhibition by bright light under laboratory conditions of lens-induced myopia in monkeys, but other proposed mechanisms possibly associated with time outdoors such as relaxed accommodation, more uniform dioptric space, increased pupil constriction, exposure to UV light, changes in the spectral composition of visible light, or increased physical activity have little epidemiological or experimental support. Irrespective of the mechanisms involved, clinical trials are now underway to reduce the development of myopia in children by increasing the amount of time they spend outdoors. These trials would benefit from more precise definition of thresholds for protection in terms of intensity and duration of light exposures. These can be investigated in animal experiments in appropriate models, and can also be determined in epidemiological studies, although more precise measurement of exposures than those currently provided by questionnaires is desirable.

Patterns of myopigenic activities with age, gender and ethnicity in Sydney schoolchildren.

PURPOSE: To examine the patterns of myopigenic activity (high near work, low time outdoors) in children growing up in Sydney, Australia, by age, ethnicity and gender. METHODS: The Sydney Adolescent Vascular and Eye Study (SAVES) re-examined children from the two age cohorts (6 and 12 years at baseline) from the Sydney Myopia Study (SMS). At 5-6 year follow-up, 863 in the younger cohort and 1196 in the older cohort had complete refraction data. Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1) was measured at baseline and follow-up. Children who became myopic (≤-0.50 dioptres spherical equivalent refraction) were those classified as non-myopic at baseline and myopic at follow-up. A detailed questionnaire was administered to measure weekly activities, including time spent outdoors and near work at both baseline and follow-up examination. RESULTS: Overall, 128 (14.8%) children in the younger cohort and 210 (17.6%) in the older cohort became myopic. At follow-up, for both cohorts, children had significantly reduced the amount of time spent outdoors (younger cohort, p = 0.001, older cohort, p < 0.0001) and increased near work time (younger cohort, p < 0.0001, older cohort, p = 0.006). Children of East Asian ethnicity spent significantly less time outdoors by more than 7 h per week (both cohorts at baseline and follow-up, all p < 0.0001) and more time in near work activities by close to 3 h compared to European Caucasian children at all ages examined (both cohorts at baseline and follow-up all, p < 0.03). The average pattern of activity for girls differed from that of boys in a similar way (both cohorts at baseline and follow-up all, p < 0.0001). The two independent samples of 12 year-old children provided by follow-up in the younger cohort and baseline in the older cohort gave very similar answers to the questionnaire, with significant differences only evident for computer use (p = 0.001) and books read (p < 0.0001). CONCLUSIONS: Answers to the activity questionnaire were very similar in the two cohorts of 12 year-olds, suggesting that the questionnaire gives reproducible answers. However, further work is required for validation. Children's pattern of activities become more myopigenic with age, and differed by gender and by ethnicity at all ages, with girls having a more myopigenic activity pattern than boys, and children of East Asian ancestry having a more myopigenic activity pattern than European Caucasian children.

Prevalence and 5- to 6-year incidence and progression of myopia and hyperopia in Australian schoolchildren.

PURPOSE: To determine the prevalence, incidence, and change in refractive errors for Australian schoolchildren and examine the impact of ethnicity and sex. DESIGN: Population-based cohort study. PARTICIPANTS: The Sydney Adolescent Vascular and Eye Study, a 5- to 6-year follow-up of the Sydney Myopia Study, examined 2760 children in 2 age cohorts, 12 and 17 years. Longitudinal data were available for 870 and 1202 children in the younger and older cohorts, respectively. METHODS: Children completed a comprehensive examination, including cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1). Myopia was defined as ≤-0.50 diopters (D) and hyperopia as ≥+2.00 D right eye spherical equivalent refraction. MAIN OUTCOME MEASURES: Baseline and follow-up refraction. RESULTS: Prevalence of myopia increased between baseline and follow-up for both the younger (1.4%-14.4%; P<0.0001) and older cohorts (13.0%-29.6%; P<0.0001). The annual incidence of myopia was 2.2% in the younger cohort and 4.1% in the older. Children of East Asian ethnicity had a higher annual incidence of myopia (younger 6.9%, older 7.3%) than European Caucasian children (younger 1.3%, older 2.9%; all P<0.0001). The prevalence of myopia in European Caucasian children almost doubled between the older (4.4%; 95% confidence interval [CI], 3.0-5.8) and younger samples (8.6%; 95% CI, 6.7-10.6) when both were aged 12 years. Children with ametropia at baseline were more likely to have a significant shift in refraction (hyperopia: odds ratio [OR], 3.4 [95% CI, 1.2-9.8]; myopia: OR, 6.3 [95% CI, 3.7-10.8]) compared with children with no refractive error. There was no significant difference in myopia progression between children of European Caucasian and East Asian ethnicity (P = 0.7). CONCLUSIONS: In Sydney, myopia prevalence (14.4%, 29.6%) and incidence (2.2%, 4.1%) was low for both age cohorts, compared with other locations. However, in European Caucasian children at age 12, the significantly higher prevalence of myopia in the younger sample suggests a rise in prevalence, consistent with international trends. Progression of myopia was similar for children of East Asian and European Caucasian ethnicity, but lower than reported in children of East Asian ethnicity in East Asia, suggesting that environmental differences may have some impact on progression.

Comparison of refraction and ocular biometry in European Caucasian children living in Northern Ireland and Sydney, Australia.

PURPOSE: To compare refraction and ocular biometry in European Caucasian children aged 6 to 7 years and 12 to 13 years, living in Sydney, Australia, and Northern Ireland. METHODS: All children had a comprehensive eye examination, including cycloplegic (cyclopentolate 1%) autorefraction and ocular biometry. Hyperopia was defined as a right spherical equivalent refraction (SER) of ≥+2.00 diopters (D), myopia as ≤-0.50 D, and astigmatism as a cylindrical error of ≥1.00 D. RESULTS: The mean SER was similar at age 6 to 7 years (P = 0.9); however, at 12 to 13 years, children in Northern Ireland had a significantly less hyperopic mean SER (+0.66 D) than children in Sydney (+0.83 D, P = 0.008). The prevalence of myopia, hyperopia, and astigmatism was significantly greater in Northern Ireland than Sydney at both ages (all P < 0.03). The distribution of refraction was highly leptokurtic in both samples, but less so in Northern Ireland (kurtosis: 6-7 years of age, 7.2; 12-13 years of age, 5.9) than Sydney (kurtosis: 6-7 years of age, 15.0; 12-13 years of age, 19.5). CONCLUSIONS: European Caucasian children in Northern Ireland have a greater prevalence of myopia, hyperopia, and astigmatism when compared to children living in Sydney. Risk factors for myopia such as parental myopia, parental education, and educational standards do not appear to explain the differences. Further work on levels of near work and time spent outdoors is required.