Publications by authors named "Kathryn A Rose"

52 Publications

IMI Risk Factors for Myopia.

Invest Ophthalmol Vis Sci 2021 Apr;62(5)

School of Optometry & Vision Sciences, Cardiff University, Cardiff, United Kingdom.

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.
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http://dx.doi.org/10.1167/iovs.62.5.3DOI Listing
April 2021

Time spent outdoors in childhood is associated with reduced risk of myopia as an adult.

Sci Rep 2021 Mar 18;11(1):6337. Epub 2021 Mar 18.

Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute), The University of Western Australia, Perth, Australia.

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.
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http://dx.doi.org/10.1038/s41598-021-85825-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7973740PMC
March 2021

Independent Influence of Parental Myopia on Childhood Myopia in a Dose-Related Manner in 2,055 Trios: The Hong Kong Children Eye Study.

Am J Ophthalmol 2020 10 23;218:199-207. Epub 2020 May 23.

Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong; Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Hong Kong; Hong Kong Eye Hospital, Hong Kong. Electronic address:

Purpose: To determine the effects on childhood myopia of parental myopia, parental education, children's outdoor time, and children's near work.

Design: Population-based cross-sectional study.

Methods: A total of 6,155 subjects in 2,055 family trios (1 child and both parents). Cycloplegic autorefraction was measured for children and noncycloplegic autorefraction for parents. Parental education, children's outdoor time, and near work were collected by questionnaires. Children were categorized into 10 groups based on parental myopia levels. Associations of the above factors with myopia were evaluated by regression analyses. The areas under the receiver operating characteristic curve (AUROCs) for myopia were evaluated.

Results: Mild parental myopia did not increase childhood myopia's risk, but the risk was 11.22-folds when both parents were highly myopic. Higher parental education (Father: OR 1.08, P = .046; Mother: OR 1.11, P = .001) and more reading time of children were risk factors (OR 1.21, P = .044). Reduced odds of myopia were associated with more time spent on outdoor activities (OR 0.78, P = .017). Notably, all these factors became insignificant after adjustment, except for parental myopia. Children with more severe parental myopia spent more time on reading, but less on electronic devices. Parental myopic status alone accounted for 11.82% of myopia variation in children. With age and parental myopia, the AUROC for myopia was 0.731.

Conclusions: Among parental and environmental factors, parental myopia confers, in a dose-related manner, the strongest independent effect on childhood myopia. Therefore children with high risk of myopia can be identified for early prevention, based on parental myopia data.
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http://dx.doi.org/10.1016/j.ajo.2020.05.026DOI Listing
October 2020

Rationale and protocol for the 7- and 8-year longitudinal assessments of eye health in a cohort of young adults in the Raine Study.

BMJ Open 2020 03 25;10(3):e033440. Epub 2020 Mar 25.

Centre for Ophthalmology and Visual Science, University of Western Australia, Nedlands, Western Australia, Australia.

Introduction: Eye 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 Analysis: Participants 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 Dissemination: The 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 Number: ACTRN12617001599369; Active, not recruiting.
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http://dx.doi.org/10.1136/bmjopen-2019-033440DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7170556PMC
March 2020

Association of Parental Myopia With Higher Risk of Myopia Among Multiethnic Children Before School Age.

JAMA Ophthalmol 2020 05;138(5):501-509

Southern California Eye Institute, CHA Hollywood Presbyterian Medical Center, Los Angeles.

Importance: Parental myopia is an important risk factor for preschool myopia in Asian children. Further investigation of the association between parental myopia and early-onset myopia risk in other racial/ethnic groups, such as African American and Hispanic white children, could improve understanding of the etiology and treatment of this condition.

Objective: To investigate the association of parental myopia with refractive error and ocular biometry in multiethnic children aged 6 to 72 months.

Design, Setting, And Participants: This cohort study pooled data from children in 3 population-based studies with comparable design from the US, Singapore, and Australia. Parental myopia was defined as the use of glasses or contact lenses for distance viewing by the child's biological parent(s). Multivariable regressions were conducted to assess the association of parental myopia. Data were collected from 2003 to 2011 and analyzed from 2017 to 2019.

Main Outcomes And Measures: Cycloplegic refraction and prevalence of myopia (spherical equivalent refractive error of≤-0.5 diopters [D]) in the more myopic eye.

Results: The analysis cohort included 9793 children, including 4003 Asian, 2201 African American, 1998 Hispanic white, and 1591 non-Hispanic white participants (5106 boys [52.1%]; mean [SD] age, 40.0 [18.9] months). Compared with children without parental myopia, the odds ratios for early-onset myopia were 1.42 (95% CI, 1.20-1.68) for children with 1 parent with myopia, 2.70 (95% CI, 2.19-3.33) for children with 2 parents with myopia, and 3.39 (95% CI, 1.99-5.78) for children with 2 parents with childhood-onset myopia. Even among children without myopia, parental myopia was associated with a greater ratio of axial length to corneal curvature radius (regression coefficient for myopia in both parents, 0.023; P < .001) and more myopic refractive error (regression coefficient for myopia in both parents, -0.20 D; P < .001). Effects of parental myopia were observed in all 4 racial/ethnic groups and across age groups except those younger than 1 year. However, parental myopia was not associated with the age-related trends of refractive error (regression coefficient for children without parental myopeia, 0.08; for children with 2 parents with myopia, 0.04; P = .31 for interaction) and ratio of axial length to corneal curvature radius (regression coefficient for children without parental myopeia, 0.031; for children with 2 parents with myopia, 0.032; P = .89 for interaction) beyond infancy.

Conclusions And Relevance: Parental myopia, especially childhood-onset parental myopia, was associated with a greater risk of early-onset myopia in Asian, Hispanic, non-Hispanic white, and African American children. The observed associations of parental myopia in children as early as 1 year of age and in children without myopia suggests that genetic susceptibility may play a more important role in early-onset myopia and that parental myopia may contribute to myopia in children by setting up a more myopic baseline before school age.
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http://dx.doi.org/10.1001/jamaophthalmol.2020.0412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7082765PMC
May 2020

Prevalence, Characteristics, and Risk Factors of Moderate or High Hyperopia among Multiethnic Children 6 to 72 Months of Age: A Pooled Analysis of Individual Participant Data.

Ophthalmology 2019 07 26;126(7):989-999. Epub 2019 Feb 26.

Southern California Eyecare and Vision Research Institute, CHA Medical Group PC, Hollywood Presbyterian Medical Center, Los Angeles, California.

Purpose: To describe the prevalence, ocular characteristics, and associated risk factors of moderate to high hyperopia in early childhood.

Design: Pooled analysis of individual participant data from population-based studies.

Participants: Six- to 72-month-old multiethnic children who participated in 4 population-based studies of pediatric eye diseases.

Methods: The pooled studies conducted comparable parental interviews and ocular examinations including cycloplegic autorefraction. Presence of hyperopia was defined based on cycloplegic refractive error in the worse eye. Multivariate analyses were performed to evaluate the association of potential risk factors with hyperopia risk.

Main Outcome Measures: Prevalence and odds ratios of moderate to high hyperopia (≥4.0 diopters [D]).

Results: Cycloplegic refraction was completed in 15 051 children 6 to 72 months of age. Among these children, the overall prevalence of moderate to high hyperopia (≥4.0 D) in the worse eye was 3.2% (95% confidence interval, 2.9%-3.5%), accounting for 15.6% of all hyperopia (≥2.0 D). Among children with moderate to high hyperopia, both eyes were affected in 64.4%, 28.9% showed spherical anisometropia of 1.0 D or more, and 19.5% showed astigmatism of 1.5 D or more. Among 36- to 72-month-old children with moderate to high hyperopia, 17.6% wore glasses. Prevalence of moderate to high hyperopia was slightly less in 12- to 23-month-old children and was relatively stable in children 24 months of age and older. Non-Hispanic and Hispanic white race and ethnicity, family history of strabismus, maternal smoking during pregnancy, and being a participant in the United States studies were associated with a higher risk of moderate to high hyperopia (P < 0.05).

Conclusions: By assembling similarly designed studies, our consortium provided robust estimates of the prevalence of moderate to high hyperopia in the general population and showed that in 6- to 72-month-old children, moderate to high hyperopia is not uncommon and its prevalence does not decrease with age. Risk factors for moderate to high hyperopia differ from those for low to moderate hyperopia (2.0-<4.0 D) in preschool children, with family history of strabismus and maternal smoking during pregnancy more strongly associated with moderate to high hyperopia than low to moderate hyperopia.
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http://dx.doi.org/10.1016/j.ophtha.2019.02.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6589395PMC
July 2019

IMI - Clinical Management Guidelines Report.

Invest Ophthalmol Vis Sci 2019 02;60(3):M184-M203

Brien Holden Vision Institute, Sydney, New South Wales, Australia.

Best practice clinical guidelines for myopia control involve an understanding of the epidemiology of myopia, risk factors, visual environment interventions, and optical and pharmacologic treatments, as well as skills to translate the risks and benefits of a given myopia control treatment into lay language for both the patient and their parent or caregiver. This report details evidence-based best practice management of the pre-, stable, and the progressing myope, including risk factor identification, examination, selection of treatment strategies, and guidelines for ongoing management. Practitioner considerations such as informed consent, prescribing off-label treatment, and guides for patient and parent communication are detailed. The future research directions of myopia interventions and treatments are discussed, along with the provision of clinical references, resources, and recommendations for continuing professional education in this growing area of clinical practice.
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http://dx.doi.org/10.1167/iovs.18-25977DOI Listing
February 2019

Myopia: is the nature-nurture debate finally over?

Clin Exp Optom 2019 01 31;102(1):3-17. Epub 2018 Oct 31.

Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Ultimo, New South Wales, Australia.

In the nineteenth century, the prevalence of myopia began to rise, and Cohn stressed the role of education. Later, based on twin studies, Sorsby argued that refraction was almost totally genetically determined. This became the dominant view. However, rapid increases in the prevalence of myopia were then reported, especially in East and Southeast Asia, where the prevalence of myopia in children completing secondary school is now 80-90 per cent, with around 20 per cent highly myopic, and at risk of ocular pathology. It is not possible to explain these rapid changes genetically, since gene pools cannot change that fast. Nevertheless, there are at least 200 genetic forms of myopia, but these account for myopia in only a low percentage of the population. Genome-wide association studies have identified over 150 single-nucleotide polymorphisms (SNPs) associated with myopia, but they account for < 10 per cent of the variation in refraction. In contrast, twin studies have given consistently high heritability estimates for myopia. The high twin study heritability may be explained by the limited environmental variation within twin pairs, combined with basic assumptions made in twin studies. The SNP-heritability approach suggests that 25-35 per cent of the variation may be accounted for by hundreds or even thousands of SNPs. The apparent conflicts in the literature can be explained by the aetiological heterogeneity of myopia, and the fact that estimates of heritability are population-specific. It has been proposed that environmental variation is more relevant to variations between populations; however, the current differences between populations are due to changes within populations, driven by educational pressures, and limited time spent outdoors. Ethnic differences in myopia and the effects of parental myopia now seem more likely to be explained by environmental influences. Genetic studies have not yet defined molecular pathways and preventive interventions, and the predictive power of current genetic data is limited.
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http://dx.doi.org/10.1111/cxo.12845DOI Listing
January 2019

Intense schooling linked to myopia.

BMJ 2018 Jun 6;361:k2248. Epub 2018 Jun 6.

Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Ultimo, NSW, Australia.

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http://dx.doi.org/10.1136/bmj.k2248DOI Listing
June 2018

The epidemics of myopia: Aetiology and prevention.

Prog Retin Eye Res 2018 01 23;62:134-149. Epub 2017 Sep 23.

Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Ultimo, NSW, Australia.

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.
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http://dx.doi.org/10.1016/j.preteyeres.2017.09.004DOI Listing
January 2018

EPIDEMIC OF PATHOLOGIC MYOPIA: What Can Laboratory Studies and Epidemiology Tell Us?

Retina 2017 May;37(5):989-997

*Research School of Biology, Australian National University, Canberra, ACT, Australia; †Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China; ‡Centre for Eye Research Australia, University of Melbourne, Melbourne, Victoria, Australia; and §Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Ultimo, New South Wales, Australia.

Purpose: To systematically review epidemiologic and laboratory studies on the etiology of high myopia and its links to pathologic myopia.

Methods: Regular Medline searches have been performed for the past 20 years, using "myopia" as the basic search term. The abstracts of all articles have been scrutinized for relevance, and where necessary, translations of articles in languages other than English were obtained.

Results: Systematic review shows that there is an epidemic of myopia and high myopia in young adults in East and Southeast Asia, with similar but smaller trends in other parts of the world. This suggests an impending epidemic of pathologic myopia. High myopia in young adults in East and Southeast Asia is now predominantly associated with environmental factors, rather than genetic background. Recent clinical trials show that the onset of myopia can be reduced by increasing the time children spend outdoors, and methods to slow the progression of myopia are now available.

Conclusion: High myopia is now largely associated with environmental factors that have caused the epidemic of myopia in East and Southeast Asia. An important clinical question is whether the pathologic consequences of acquired high myopia are similar to those associated with classic genetic high myopia. Increased time outdoors can be used to slow the onset of myopia, whereas methods for slowing progression are now available clinically. These approaches should enable the current epidemics of myopia and high myopia to be turned around, preventing an explosion of pathologic myopia.
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http://dx.doi.org/10.1097/IAE.0000000000001272DOI Listing
May 2017

ALSPAC study does not support a role for vitamin D in the prevention of myopia.

Invest Ophthalmol Vis Sci 2014 Dec 29;55(12):8559. Epub 2014 Dec 29.

Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Sydney, Australia;

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http://dx.doi.org/10.1167/iovs.14-15998DOI Listing
December 2014

Normative visual acuity in infants and preschool-aged children in Sydney.

Acta Ophthalmol 2014 Nov 9;92(7):e521-9. Epub 2014 Mar 9.

Discipline of Orthoptics, The University of Sydney, Lidcombe, NSW, Australia.

Purpose: To provide population-based normative visual acuity (VA) by age, in children participating in the Sydney Paediatric Eye Disease Study aged 6 to <72 months.

Methods: Monocular VA was measured using the Amblyopia Treatment Study (ATS HOTV) protocol (24 to <72 months). Some children were also tested using linear ETDRS or HOTV logMAR VA charts (30 to <72 months). If unable to perform recognition acuity, the Teller Acuity Cards II (TAC II) was performed (6 to <42 months). Children with significant refractive error or ocular disease were excluded.

Results: Improvement in VA with age was shown on all three vision tests (all p < 0.0001). Mean VA using ATS HOTV (n = 836) was 0.13 logMAR (6/8) at <36 months, which improved to -0.01 (6/6) at 66 to <72 months. Mean ETDRS/HOTV (n = 399) VA was 0.26 logMAR (6/11) at <36 months, which improved to 0.1 (6/7.5) at 66 to <72 months. Mean monocular TAC II (n = 442) was 5.7 cycles/degree (0.72 logMAR) at 6 to <9 months and improved to 12.4 cycles/degree (0.38 logMAR) at age 30 to <33 months. Associations with ATS HOTV VA included prematurity (p = 0.027) and socio economic status (SES) factors such as home ownership (p = 0.039) and employment of one (p = 0.019) or both parents (p = 0.003).

Conclusions: VA norms in children improved with age and were different according to the VA test used. Low SES was associated with poorer VA, supporting the need for test specific VA norms to be established for different populations. The ATS HOTV appears to be the best test to use for vision screening due to its lower false positive referral rate.
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http://dx.doi.org/10.1111/aos.12366DOI Listing
November 2014

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

Ophthalmology 2013 Oct 11;120(10):2100-8. Epub 2013 May 11.

Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia.

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.
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http://dx.doi.org/10.1016/j.ophtha.2013.02.035DOI Listing
October 2013

Myopia and international educational performance.

Ophthalmic Physiol Opt 2013 May;33(3):329-38

Research School of Biology, ARC Centre of Excellence in Vision Science, Australian National University, Canberra, Australia.

Purpose: To analyse the relationship between myopia, educational performance and engagement in after-school tutorial classes.

Methods: Educational performance data and data on engagement in after-school tutorial classes were taken from the results of the Organisation for Economic Cooperation and Development (OECD) Program in Secondary Assessment (PISA) reports for 2009, which tested educational outcomes in representative samples of 15 year-old school children from 65 jurisdictions. High prevalence of myopia (>70%) and low prevalence of myopia (<40%) locations were identified by systematic literature search.

Results: Six locations with a high prevalence of myopia were identified from among the participants in PISA 2009 - Shanghai-China, Hong Kong-China, Taiwan, Singapore, Japan and South Korea. All were ranked in the top quartile on educational performance. Other participants in the top educational performance quartile were identified as locations with a low prevalence of myopia, including Australia and Finland. The locations with a high prevalence of myopia combined high educational performance and high engagement in after-school tutorials, whereas the locations with a low prevalence of myopia combined high educational performance with little engagement in tutorials.

Discussion: These results show that it is possible to achieve high educational outcomes without extensive engagement in after-school tutorials, and that the combination of high educational outcomes with extensive use of tutorials is associated with high prevalence rates of myopia. We suggest that extensive use of after-school tutorials may be a marker of educational environments which impose high educational loads. Further quantification of educational loads to include after- school educational activities, such as homework, tutorials and other after-school classes, as well as formal school classes, is desirable. Policy initiatives to decrease these loads may contribute to the prevention of myopia, perhaps, at least in part, by enabling children to spend more time outdoors.
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http://dx.doi.org/10.1111/opo.12040DOI Listing
May 2013

Time outdoors and the prevention of myopia.

Exp Eye Res 2013 Sep 2;114:58-68. Epub 2013 May 2.

Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Lidcombe, NSW 2011, Australia.

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.
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http://dx.doi.org/10.1016/j.exer.2013.04.018DOI Listing
September 2013

Prevalence of anisometropia and its association with refractive error and amblyopia in preschool children.

Br J Ophthalmol 2013 Sep 23;97(9):1095-9. Epub 2013 Apr 23.

Department of Ophthalmology, Westmead Millennium Institute, Centre for Vision Research, University of Sydney, New South Wales, Australia.

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.
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http://dx.doi.org/10.1136/bjophthalmol-2012-302637DOI Listing
September 2013

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

Ophthalmology 2013 Jul 22;120(7):1482-91. Epub 2013 Mar 22.

Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Sydney, New South Wales, Australia.

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.
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http://dx.doi.org/10.1016/j.ophtha.2012.12.018DOI Listing
July 2013

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

Ophthalmic Physiol Opt 2013 May 4;33(3):318-28. Epub 2013 Mar 4.

Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Sydney, Australia.

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.
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http://dx.doi.org/10.1111/opo.12045DOI Listing
May 2013

Diagnostic reliability and normative values of stereoacuity tests in preschool-aged children.

Br J Ophthalmol 2013 Mar 3;97(3):308-13. Epub 2013 Jan 3.

Department of Ophthalmology, Centre for Vision Research, Westmead Millennium Institute, University of Sydney, Sydney, New South Wales, Australia.

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.
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http://dx.doi.org/10.1136/bjophthalmol-2012-302192DOI Listing
March 2013

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

Invest Ophthalmol Vis Sci 2012 Jun 26;53(7):4021-31. Epub 2012 Jun 26.

Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Sydney, NSW, 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.
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http://dx.doi.org/10.1167/iovs.12-9556DOI Listing
June 2012

Testability of refraction, stereopsis, and other ocular measures in preschool children: the Sydney Paediatric Eye Disease Study.

J AAPOS 2012 Apr;16(2):185-92

Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia.

Purpose: To determine the testability and lower age limits for applying common eye tests to preschool children.

Methods: Investigators from the Sydney Paediatric Eye Disease Study examined 2,461 children aged 6 to 72 months between 2007 and 2009. Cycloplegic autorefraction was measured with Retinomax and Canon autorefractors. Ocular biometry was measured by the use of IOLMaster in children aged >30 months. The Randot Preschool Stereoacuity test, Lang-Stereotest II, and the Stereo Smile II test were administered to assess stereoacuity. Fundus photography was performed with the subjects' pupils dilated. Testability was defined as the ability to successfully complete tests in both eyes.

Results: There were 2,189 children with complete data. Most were testable with the Retinomax (71.8%) and Canon (66.0%) autorefractors. Testability improved with age (P for trend <0.0001) for both, and Retinomax achieved >70% testability when a subject was 24 months of age, half the age limit (48 months) found for Canon. IOLMaster was mostly testable in children aged 48+ months. Lang-Stereotest II could be used in children aged 6 months and achieved the greatest testability (94.4%) of all stereotests. White children performed better than children of some other ethnicities on Randot (P = 0.007), with girls performing better than boys (P = 0.01). Bilateral photography was achieved in >70% of preschool children 48 months of age.

Conclusions: The testability of all measures was strongly age related, with mostly no sex or ethnicity effects found. The handheld Retinomax could be tested in >70% of children aged 24 months, younger than that found for the stationary Canon autorefractor (48 months). Testability measures for most eye tests in this preschool sample are comparable to other preschool studies.
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http://dx.doi.org/10.1016/j.jaapos.2011.09.017DOI Listing
April 2012

Amblyopia prevalence and risk factors in Australian preschool children.

Ophthalmology 2012 Jan 2;119(1):138-44. Epub 2011 Oct 2.

Centre for Vision Research, Department of Ophthalmology, Westmead Millennium Institute, University of Sydney, Sydney, Australia.

Purpose: To determine the prevalence of and factors associated with amblyopia in a sample of Australian preschool children.

Design: Population-based, cross-sectional study.

Participants: The Sydney Paediatric Eye Disease Study examined 2461 (73.8% participation) children aged between 6 and 72 months from 2007 to 2009.

Methods: Visual acuity (VA) was assessed in children aged ≥ 30 months using the Electronic Visual Acuity system, and a subset using the logarithm of the minimum angle of resolution chart. Amblyopia was categorized into unilateral and bilateral subtypes: Unilateral amblyopia was defined as a 2-line difference in reduced VA between the 2 eyes, in addition to strabismus, anisometropia, and/or visual axis obstruction; bilateral amblyopia was defined as bilateral reduced VA with either bilateral visual axis obstruction or significant bilateral ametropia. Information on ethnicity, birth parameters, and measures of socioeconomic status were collected in questionnaires completed by parents.

Main Outcome Measures: Amblyopia.

Results: We included 1422 children aged 30 to 72 months, of whom 27 (1.9%) were found to have amblyopia or suspected amblyopia. Mean spherical equivalent for the amblyopic eyes was +3.57 diopters, with a mean VA of 20/50. Only 3 of the 27 amblyopic children had previous diagnoses or treatments for amblyopia. In regression analysis controlling for age, gender, and ethnicity, amblyopia was significantly associated with hyperopia (odds ratio [OR], 15.3; 95% confidence interval [CI], 6.5-36.4), astigmatism (OR, 5.7; 95% CI, 2.5-12.7), anisometropia (OR, 27.8; 95% CI, 11.2-69.3), and strabismus (OR, 13.1; 95% CI, 4.3-40.4). There were no significant associations of amblyopia with low birthweight (<2500 g), preterm birth (<37 weeks), maternal smoking, age, gender, ethnicity, or measures of socioeconomic status (all P>0.05).

Conclusions: Amblyopia was found in 1.9% of this Australian preschool sample, which is comparable with prevalence rates reported by other recent studies in preschool children. Refractive errors, particularly significant hyperopia and astigmatism, in addition to anisometropia and strabismus, were the major amblyogenic factors. There was a low amblyopia detection rate in this preschool population, which suggests that different strategies are required to improve current vision screening strategies in preschoolers.

Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.
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http://dx.doi.org/10.1016/j.ophtha.2011.06.024DOI Listing
January 2012

Prevalence and risk factors for visual impairment in preschool children the sydney paediatric eye disease study.

Ophthalmology 2011 Aug 29;118(8):1495-500. Epub 2011 Apr 29.

Centre for Vision Research, Westmead Millennium Institute (Westmead Hospital), University of Sydney, Sydney, Australia.

Purpose: To assess the prevalence and associations of visual impairment (VI) in preschool children.

Design: Cross-sectional, population-based study.

Participants: A total of 2461 children (73.8% participation rate), aged 6 to 72 months, were examined in the Sydney Paediatric Eye Disease Study during 2007-2009; of whom 1188, aged 30 to 72 months, with complete visual acuity (VA) data in both eyes, were included in this report.

Methods: Measurement of VA was attempted on all children using the Electronic Visual Acuity (EVA) system or a logarithm of the minimum angle of resolution (logMAR) chart. Visual impairment was defined as presenting VA <20/40 in children aged ≥48 months and <20/50 in those aged <48 months. Post-cycloplegic refraction was measured, and myopia was defined as spherical equivalent (SE) ≤-0.50 diopters (D), hyperopia was defined as SE ≥2.00 D, astigmatism was defined as cylinder ≥1.00 D, and anisometropia was defined as SE difference ≥1.00 D between 2 eyes. Ethnicity, birth parameters, and sociodemographic information were collected in questionnaires completed by parents.

Main Outcome Measures: Visual impairment prevalence and its associations with child demographic factors and birth parameters.

Results: Visual impairment was found in 6.4% of the worse eye and 2.7% of the better eye in our sample. Refractive errors (69.7%) and amblyopia (26.3%) were the principal causes of VI in the worse eye. Astigmatism (51.3%) and hyperopia (28.9%) were the main refractive errors causing VI. In regression analysis controlling for other factors, VI was independently associated with low birthweight of <2500 g (odds ratio 2.4, 95% confidence interval, 1.1-5.3), but not with age, gender, ethnicity, or measures of socioeconomic status (P > 0.05).

Conclusions: Visual impairment in at least 1 eye was found in 6.4% of Australian preschool children, with bilateral VI found in 2.7%. Uncorrected refractive errors and amblyopia were the principal ocular conditions associated with VI. Low birthweight was a significant risk factor independent of age, gender, and ethnicity.

Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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http://dx.doi.org/10.1016/j.ophtha.2011.01.027DOI Listing
August 2011

Upper-ocean-to-atmosphere radiocarbon offsets imply fast deglacial carbon dioxide release.

Nature 2010 Aug;466(7310):1093-7

Department of Geology, University of California, Davis, California 95616, USA.

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. The end of the ice age was marked by a rapid increase in atmospheric CO(2) concentrations that coincided with reduced (14)C/(12)C ratios (Delta(14)C) in the atmosphere, suggesting the release of very 'old' ((14)C-depleted) CO(2) from the deep ocean to the atmosphere. 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 Delta(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, 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 must have involved contributions from sources other than the previously suggested carbon release by way of a deep Southern Ocean pathway, 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.
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http://dx.doi.org/10.1038/nature09288DOI Listing
August 2010

Is emmetropia the natural endpoint for human refractive development? An analysis of population-based data from the refractive error study in children (RESC).

Acta Ophthalmol 2010 Dec;88(8):877-84

College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, Australia.

Purpose: To determine the natural end-point for refractive development during childhood.

Methods: Cycloplegic (1% cyclopentolate) autorefraction was performed on 38, 811 children aged 5 and 15 in population-based samples at eight sites in the Refractive Error Study in Children (RESC). Refractions (right eye) were categorized as myopic (≤-0.5 D), emmetropic (>-0.5 to ≤+0.5 D), mildly hyperopic (>+0.5 to ≤+2.0 D and hyperopic (>+2.0 D).

Results: At five sites (Jhapa - rural Nepal, New Delhi - urban India, Mahabubnagar - rural India, Durban - semi-urban South Africa and La Florida - urban Chile), there was <20% myopia by age 15. Mild hyperopia was the most prevalent category at all ages, except for Mahabubnagar where emmetropia became the marginally most prevalent category at ages 14 and 15. At the other sites (Gombak - semi-urban Malaysia, Shunyi - semi-rural China and Guangzhou - urban China), there was substantial (>35%) myopia by age 15. At these sites, mild hyperopia was the most prevalent category during early childhood, and myopia became the predominant category later. In Gombak district and Guangzhou, emmetropia was a minor category at all ages, with myopia increasing as mild hyperopia decreased. In Shunyi district, emmetropia was the most prevalent category over the ages 11-14.

Conclusion: Emmetropia was not the predominant outcome for refractive development in children. Instead, populations were predominantly mildly hyperopic or substantial amounts of myopia appeared in them. This suggests that mild hyperopia is the natural state of refractive development in children and that emmetropia during childhood carries the risk of subsequent progression to myopia.
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http://dx.doi.org/10.1111/j.1755-3768.2009.01800.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2891782PMC
December 2010

Prevalence of heterophoria and associations with refractive error, heterotropia and ethnicity in Australian school children.

Br J Ophthalmol 2010 May 22;94(5):542-6. Epub 2009 Oct 22.

Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney (Cumberland Campus), PO Box 170, Lidcombe NSW 1825, Australia.

AIMS To establish the prevalence of heterophoria and its association with refractive error and ethnicity in a population-based study of Australian schoolchildren. METHODS The 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 < or =-0.50SE and > or =+2.00SE. RESULTS Exophoria 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). CONCLUSION Contrary 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.
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http://dx.doi.org/10.1136/bjo.2009.163709DOI Listing
May 2010

Ethnic differences in optic nerve head and retinal nerve fibre layer thickness parameters in children.

Br J Ophthalmol 2010 Jul 12;94(7):871-6. Epub 2009 Oct 12.

Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia.

Aim: To 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.

Methods: Of 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.

Results: East 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 microm and 104.57 microm, respectively), East Asian children had thicker mean average RNFL (105.45 microm and 107.92 microm, respectively; p=0.0006 and 0.0001) and thicker non-nasal RNFL quadrants in both ages.

Conclusions: Compared 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.
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http://dx.doi.org/10.1136/bjo.2009.158279DOI Listing
July 2010

Macular and nerve fiber layer thickness in amblyopia: the Sydney Childhood Eye Study.

Ophthalmology 2009 Sep 27;116(9):1604-9. Epub 2009 Jun 27.

Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia.

Purpose: To examine macular and peripapillary retinal nerve fiber layer (RNFL) thickness in amblyopia.

Design: Population-based cross-sectional study.

Participants: Of 4118 children examined in the Sydney Childhood Eye Study (incorporating the Sydney Myopia Study) from 34 randomly selected primary schools and 21 secondary schools from 2003 to 2005, 3529 (85.7%) were included in this analysis. The median age of the 2 samples was 6 years (n = 1395) and 12 years (n = 2134), respectively.

Methods: A detailed eye examination was conducted on all children, including determination of best-corrected visual acuity (logarithm of the minimum angle of resolution [logMAR]), autorefraction (RK-F1 autorefractor, Canon, Tokyo, Japan) after cyclopentolate (1%), cover testing to identify strabismus, and optical coherence tomography (StratusOCT, Carl Zeiss Meditec, Dublin, CA) through dilated pupils to obtain macula and peripapillary RNFL thickness. Amblyopia was defined as best visual acuity <0.3 logMAR units not explained by any obvious underlying eye or visual pathway abnormalities. Anisometropia was defined as an interocular difference of at least 1.0 diopter of the spherical equivalent refraction.

Main Outcome Measures: Macular and peripapillary RNFL thickness.

Results: Amblyopic eyes had slightly greater foveal minimum thickness than the normal fellow eye (by 5.0 microm; 95% confidence interval 0.1-9.9) and right eyes of non-amblyopic children (by approximately 10 microm), both P<0.05. This was more pronounced in 6-year-old children (6.9 microm) than 12-year-old children (4.2 microm). Amblyopic eyes also had slightly thicker central macula (1 mm diameter region) in both comparisons, although these differences were not statistically significant. The inner macular ring (outer radius 1.5 mm) was thinner in amblyopic than normal fellow eyes. Peripapillary RNFL thickness was not significantly different between amblyopic and normal fellow eyes or normal eyes of non-amblyopic children.

Conclusions: In children aged predominantly 6 and 12 years, central macular thickness may be increased in eyes with amblyopia, although it is uncertain if this precedes or follows the development of amblyopia. No differences in peripapillary RNFL thickness were found when compared with normal eyes.

Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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http://dx.doi.org/10.1016/j.ophtha.2009.03.013DOI Listing
September 2009

Role of near work in myopia: findings in a sample of Australian school children.

Invest Ophthalmol Vis Sci 2008 Jul;49(7):2903-10

Centre for Vision Research, Department of Ophthalmology and the Westmead Millennium Institute, University of Sydney, Sydney, Australia.

Purpose: To examine the association of time spent in near work and reading with spherical equivalent refraction (SER) in a population-based sample of 12-year-old Australian schoolchildren.

Methods: Data on the time spent in near-work or outdoor activities per week and estimates for the duration of continuous reading and reading distances, were collected in questionnaires (2353 participants, 75.3% response) in the Sydney Myopia Study between 2004 and 2005; 2339 children underwent a comprehensive eye examination, including cycloplegia.

Results: Longer time spent on reading for pleasure and reports of close reading distance (< 30 cm) were associated with a more myopic refraction after adjustment for age, sex, ethnicity, and school type (P(trend) = 0.02 and P = 0.0003, respectively). Time spent in individual near-work activities, however, correlated poorly with SER (all r < or = 0.2) and was not significant in multivariate analyses for myopia (SER < or = -0.50 D), with adjustment for age, sex, ethnicity, parental myopia, school type, and outdoor activity. Children of European Caucasian ethnicity reported spending marginally less time in near work than children of East Asian ethnicity (26.0 h/wk vs. 32.5 h/wk, P < 0.0001). East Asian ethnicity, however, was associated with substantially greater odds of having myopia (odds ratio [OR], 11.0; 95% confidence interval [CI], 7.0-17.4). Near work such as close reading distance (< 30 cm) and continuous reading (> 30 minutes) independently increased the odds of having myopia in this sample of children.

Conclusions: Although myopia was not significantly associated with time spent in near work after adjustment for other factors, there were significant independent associations with close reading distance and continuous reading. These associations may indicate that the intensity rather than the total duration of near work is an important factor.
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http://dx.doi.org/10.1167/iovs.07-0804DOI Listing
July 2008