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Myopia (near-sightedness) is an important public health issue. Spending more time outdoors can prevent myopia but the long-term association between this exposure and myopia has not been well characterised. We investigated the relationship between time spent outdoors in childhood, adolescence and young adulthood and risk of myopia in young adulthood. The Kidskin Young Adult Myopia Study (KYAMS) was a follow-up of the Kidskin Study, a sun exposure-intervention study of 1776 children aged 6–12 years. Myopia status was assessed in 303 (17.6%) KYAMS participants (aged 25–30 years) and several subjective and objective measures of time spent outdoors were collected in childhood (8–12 years) and adulthood. Index measures of total, childhood and recent time spent outdoors were developed using confirmatory factor analysis. Logistic regression was used to assess the association between a 0.1-unit change in the time outdoor indices and risk of myopia after adjusting for sex, education, outdoor occupation, parental myopia, parental education, ancestry and Kidskin Study intervention group. Spending more time outdoors during childhood was associated with reduced risk of myopia in young adulthood (multivariable odds ratio [OR] 0.82, 95% confidence interval [CI] 0.69, 0.98). Spending more time outdoors in later adolescence and young adulthood was associated with reduced risk of late-onset myopia (≥ 15 years of age, multivariable OR 0.79, 95% CI 0.64, 0.98). Spending more time outdoors in both childhood and adolescence was associated with less myopia in young adulthood.

Background To explore the relationship between outdoor time and academic performance among school-aged children. Methods This study was designed as a cross-sectional study. Data were derived from a school-based prospective children myopia intervention study (STORM). Outdoor time was recorded by self-developed algorithm-validated wristwatches in real-time and calculated as the cumulative average of 10 months. The academic performance was recorded and provided by the participating schools and further standardized. Other information was collected using an online standardized questionnaire. Mixed-effects model and B-Spline method were used to investigate the association between time spent on different types of daily activity, including outdoor activity and academic performance. Results A total of 3291 children with mean age 9.25 years were included in the final analysis. Overall, outdoor time was associated with academic performance in a non-linear manner; specifically, not exceeding 2.3 h per day, outdoor time was positively associated with academic performance; exceeding 2.3 h per day, this association became non-significant. Likewise, daily sleep duration and out-of-school learning time were associated with academic performance in a non-linear manner, resulting in turning points of 11.3 and 1.4 h per day, respectively. Separate analysis showed that outdoor time and sleep duration but not out-of-school learning time were positively associated with academic performance in Chinese, mathematics and English. Conclusion Outdoor time, sleep duration and out-of-school learning time were associated with academic performance in a non-linear manner. Promotion of outdoor time may not negatively impact on academic performance. Trial registration Our study was registered in ClinicalTrials.gov (Identifier: NCT02980445).

Carbon dioxide release during deglaciation At the end of the last ice age, rising atmospheric carbon dioxide levels coincided with a decline in carbon-14 levels, suggesting the release of very 'old' (radiocarbon-depleted) carbon dioxide from the deep ocean to the atmosphere. Rose et al . present radiocarbon records of surface and intermediate depth waters from two sediment cores in the southwest Pacific and Southern Ocean, and find a steady 170 per mil decrease in Δ 14 C that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial–interglacial climatic transition. The initial rise in carbon dioxide levels may have originated from intermediate Southern Ocean water masses that were not strongly depleted in radiocarbon, followed by the release of radiocarbon-depleted carbon dioxide from deeper North Pacific waters. At the end of the last ice age, rising atmospheric CO 2 levels coincided with a decline in radiocarbon activity, suggesting the release of highly radiocarbon-depleted CO 2 from the deep ocean to the atmosphere. These authors present radiocarbon records of surface and intermediate-depth waters from two sediment cores and find an decrease in radiocarbon activity that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial–interglacial climatic transition. Radiocarbon in the atmosphere is regulated largely by ocean circulation, which controls the sequestration of carbon dioxide (CO 2 ) in the deep sea through atmosphere–ocean carbon exchange. During the last glaciation, lower atmospheric CO 2 levels were accompanied by increased atmospheric radiocarbon concentrations that have been attributed to greater storage of CO 2 in a poorly ventilated abyssal ocean 1 , 2 . The end of the ice age was marked by a rapid increase in atmospheric CO 2 concentrations 2 that coincided with reduced 14 C/ 12 C ratios (Δ 14 C) in the atmosphere 3 , suggesting the release of very ‘old’ ( 14 C-depleted) CO 2 from the deep ocean to the atmosphere 3 . Here we present radiocarbon records of surface and intermediate-depth waters from two sediment cores in the southwest Pacific and Southern oceans. We find a steady 170 per mil decrease in Δ 14 C that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial–interglacial climatic transition. The atmospheric decrease in the radiocarbon signal coincides with regionally intensified upwelling and marine biological productivity 4 , suggesting that CO 2 released by means of deep water upwelling in the Southern Ocean lost most of its original depleted- 14 C imprint as a result of exchange and isotopic equilibration with the atmosphere. Our data imply that the deglacial 14 C depletion previously identified in the eastern tropical North Pacific 5 must have involved contributions from sources other than the previously suggested carbon release by way of a deep Southern Ocean pathway 5 , and may reflect the expanded influence of the 14 C-depleted North Pacific carbon reservoir across this interval. Accordingly, shallow water masses advecting north across the South Pacific in the early deglaciation had little or no residual 14 C-depleted signals owing to degassing of CO 2 and biological uptake in the Southern Ocean.

IntroductionEye diseases and visual impairment more commonly affect elderly adults, thus, the majority of ophthalmic cohort studies have focused on older adults. Cohort studies on the ocular health of younger adults, on the other hand, have been few. The Raine Study is a longitudinal study that has been following a cohort since their birth in 1989–1991. As part of the 20-year follow-up of the Raine Study, participants underwent a comprehensive eye examination. As part of the 27- and 28-year follow-ups, eye assessments are being conducted and the data collected will be compared with those of the 20-year follow-up. This will provide an estimate of population incidence and updated prevalence of ocular conditions such as myopia and keratoconus, as well as longitudinal change in ocular parameters in young Australian adults. Additionally, the data will allow exploration of the environmental, health and genetic factors underlying inter-subject differential long-term ocular changes.Methods and analysisParticipants are being contacted via telephone, email and/or social media and invited to participate in the eye examination. At the 27-year follow-up, participants completed a follow-up eye screening, which assessed visual acuity, autorefraction, ocular biometry and ocular sun exposure. Currently, at the 28-year follow-up, a comprehensive eye examination is being conducted which, in addition to all the eye tests performed at the 27-year follow-up visit, includes tonometry, optical coherence tomography, funduscopy and anterior segment topography, among others. Outcome measures include the incidence of refractive error and pterygium, an updated prevalence of these conditions, and the 8-year change in ocular parameters.Ethics and disseminationThe Raine Study is registered in the Australian New Zealand Clinical Trials Registry. The Gen2 20-year, 27-year and 28-year follow-ups are approved by the Human Research Ethics Committee of the University of Western Australia. Findings resulting from the study will be published in health or medical journals and presented at conferences.Trial registration numberACTRN12617001599369; Active, not recruiting.

Education systems must change to protect children’s vision

AimTo examine ethnic differences in optic nerve head and retinal nerve fibre layer (RNFL) parameters between European Caucasian and East Asian children aged 6–12 years.MethodsOf 4118 children examined in the Sydney Childhood Eye Study (incorporating the Sydney Myopia Study) from 34 randomly selected primary and 21 secondary schools during 2003–5, 3382 (82.1%) had optical coherence tomography (OCT; Zeiss Stratus) data suitable for analysis. ‘Fast’ optic disc and RNFL scans were used. Ethnicity was defined only when both parents were of the same ethnicity.ResultsEast Asian children tended to have a lower birth weight, were shorter with a smaller body mass index and were less hyperopic than European Caucasian children of the same age. After adjusting for age, gender, axial length, birth weight and optic-disc area, East Asian children had similar mean vertical disc diameters to European Caucasians (p=0.38, p=0.64 for 6–12 years, respectively) but 30–43% larger mean vertical cup diameters (p<0.0001 for both), resulting in larger mean cup/disc ratios (p<0.0001 for both). Compared with European Caucasians (101.95 μm and 104.57 μm, respectively), East Asian children had thicker mean average RNFL (105.45 μm and 107.92 μm, respectively; p=0.0006 and 0.0001) and thicker non-nasal RNFL quadrants in both ages.ConclusionsCompared with European Caucasian children, East Asian children generally had thicker RNFL and larger mean cup/disc ratios. Given the relatively lower prevalence of open angle glaucoma in Asians, these anatomical variations could contribute to better understanding of apparent racial differences in glaucoma susceptibility.

Aim To establish the range of normal stereoacuity thresholds and evaluate the diagnostic reliability of stereoacuity tests in preschool-aged children. Methods 1606 children, aged 24–72 months, had detailed eye examinations and stereoacuity testing. Lang-Stereotest II (LangII) was attempted on all children, Stereo Smile Stereoacuity II Test (SSST) was conducted on children aged <30 months and on older children who could not complete the Randot Preschool Stereoacuity Test (RPST). The RPST was conducted on children aged ≥30 months and on some younger children who passed both the LangII and SSST. Results Modes for the age groups 24–47 months and 48–72 months were: 200 arcsec for both age groups with the LangII test; 120 arcsec and 60 arcsec, respectively, with the SSST; 100 arcsec and 60 arcsec, respectively, with the RPST. Age-adjusted areas under the curve for detecting amblyopia, strabismus and anisometropia were: for the LangII test, 0.72, 0.68 and 0.60, respectively; for the SSST, 0.73, 0.80 and 0.57, respectively; for the RPST, 0.92, 0.82 and 0.73, respectively. Conclusions Normative data for the LangII, RPST and SSST stereoacuity tests were determined for children aged 24–72 months. Sensitivity and specificity at individual disparity levels for detecting anisometropia, amblyopia and strabismus were also determined for RPST and SSST. Using area under age-adjusted receiver operating curves, the RPST was found to be the most reliable in detecting ocular conditions compared with the LangII and SSST tests.

AimsTo establish the prevalence of heterophoria and its association with refractive error and ethnicity in a population-based study of Australian schoolchildren.MethodsThe Sydney Myopia Study is a stratified, random cluster (school-based) sample of 4093 students (examined: 2003–2005). Two samples aged 6 (n=1692) and 12 years (n=2289) without heterotropia were included. Prevalent heterophoria was assessed using cover un-cover and prism bar alternate cover testing at 33 cm and 6 m distance fixation. Cycloplegic autorefraction (1% cyclopentolate) was performed. Significant refractive error was defined as ≤−0.50SE and ≥+2.00SE.ResultsExophoria was highly prevalent at near fixation (age 6: 58.3%, age 12: 52.2%). Orthophoria predominated at distance fixation (age 6: 85.4%, age 12: 90.9%). Hyperopia was associated with esophoria at near (age 6: OR 1.7, 95% CI 1.1 to 2.8, age 12: OR 2.9, CI 1.1 to 2.8) and distance fixation (age 6: OR 9.7, CI 3.5 to 26, age 12: 9.6 OR, CI 4.2 to 22). Myopia was associated with exophoria at near (OR 2.1, CI 1.5 to 2.7) and distance fixation (OR 3.1, CI 2.1 to 4.4) for 12-year-old children only. Exophoria was more frequent in children of East Asian than European Caucasian origins, even after adjusting for refraction; at near (age 6: OR 1.4, CI 1.0 to 2.0, age 12: OR 1.4, CI 1.0 to 1.9) and distance (age 12: OR 1.7, CI 1.1 to 2.7).ConclusionContrary to other studies, exophoria, not orthophoria, was predominant for near. Exophoria was more prevalent in children of East Asian origin. Longitudinal studies are needed to establish if incident heterotropia is preceded by heterophoria.

Abstract Aim To determine the age and ethnicity-specific prevalence of anisometropia in Australian preschool-aged children and to assess in this population-based study the risk of anisometropia with increasing ametropia levels and risk of amblyopia with increasing anisometropia. Methods A total 2090 children (aged 6–72 months) completed detailed eye examinations in the Sydney Paediatric Eye Disease Study, including cycloplegic refraction, and were included. Refraction was measured using a Canon RK-F1 autorefractor, streak retinoscopy and/or the Retinomax K-Plus 2 autorefractor. Anisometropia was defined by the spherical equivalent (SE) difference, and plus cylinder difference for any cylindrical axis between eyes. Results The overall prevalence of SE and cylindrical anisometropia ≥1.0 D were 2.7% and 3.0%, for the overall sample and in children of European-Caucasian ethnicity, 3.2%, 1.9%; East-Asian 1.7%, 5.2%; South-Asian 2.5%, 3.6%; Middle-Eastern ethnicities 2.2%, 3.3%, respectively. Anisometropia prevalence was lower or similar to that in the Baltimore Pediatric Eye Disease Study, Multi-Ethnic Pediatric Eye Disease Study and the Strabismus, Amblyopia and Refractive error in Singapore study. Risk (OR) of anisometropic amblyopia with ≥1.0 D of SE and cylindrical anisometropia was 12.4 (CI 4.0 to 38.4) and 6.5 (CI 2.3 to 18.7), respectively. We found an increasing risk of anisometropia with higher myopia ≥−1.0 D, OR 61.6 (CI 21.3 to 308), hyperopia > +2.0 D, OR 13.6 (CI 2.9 to 63.6) and astigmatism ≥1.5 D, OR 30.0 (CI 14.5 to 58.1). Conclusions In this preschool-age population-based sample, anisometropia was uncommon with inter-ethnic differences in cylindrical anisometropia prevalence. We also quantified the rising risk of amblyopia with increasing SE and cylindrical anisometropia, and present the specific levels of refractive error and associated increasing risk of anisometropia.

The term “gene-environment interactions” in statistical genetics refers to the possibility of different genotypes responding differentially to environmental exposures. Myopia is an etiologically heterogeneous disorder, in which there is a low prevalence of clearly genetic myopias, which are generally strongly familial, early in onset and severe. In the last few decades, there has been a marked increase in the prevalence of mild to moderate myopia, particularly in urban East Asia. This increase appears to be strongly associated with changing environmental exposures involving increasingly intensive education and less time spent outdoors. With analysis restricted to this form of acquired or school myopia, there is abundant evidence for environmental impacts, but only limited evidence for genetic contributions. Until the relevant genetic variation has been identified, scientific analysis of gene-environment interactions will not be possible. Currently, it is more parsimonious to interpret school myopia as a disorder caused by environmentally induced excessive axial elongation.