Age of myopia onset in a British population-based twin cohort

Association Between Serum Vitamin D Levels and Myopia in the National Health and Nutrition Examination Survey (2001-2006)

PURPOSE

To assess the relationship between serum vitamin D levels and myopia in people aged 12-50 years using the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

Demographics, vision, and serum vitamin D levels from NHANES (2001-2006) were analyzed. Multivariate analyses were performed to examine the relationship between serum vitamin D levels and myopia while controlling for sex, age, ethnicity, education level, serum vitamin A, and poverty status. The main outcome was presence or absence of myopia, defined as a spherical equivalent of -1 diopters or more.

RESULTS

Of the 11669 participants, 5,310 (45.5%) had myopia. The average serum vitamin D concentration was 61.6 ± 0.9 nmol/L for the myopic group and 63.1 ± 0.8 nmol/L for the non-myopic group (p = .01). After adjusting for all covariates, having higher serum vitamin D was associated with lower odds of having myopia (odds ratio 0.82 [0.74-0.92], p = .0007). In linear regression modeling that excluded hyperopes (spherical equivalent > +1 diopters), there was a positive relationship between spherical equivalent and serum vitamin D levels. Specifically, as serum vitamin D doubled, spherical equivalent increased by 0.17 (p = .02) indicating a positive dose-response relationship between vitamin D and myopia.

CONCLUSIONS

Participants with myopia, on average, had lower serum concentrations of vitamin D compared to those without myopia. While further studies are needed to determine the mechanism, this study suggests that higher vitamin D levels are associated with lower incidence of myopia.

Myopia: An ounce of prevention is worth a pound of cure

PURPOSE

Myopia severity has a profound impact on visual impairment in later life. A patient's final level of myopia may be lowered by myopia control, but also by delaying onset. Here, we evaluate the influence of the age of onset on the final recorded level of myopia.

METHODS

Data were extracted from: (1) Three prospective cohort studies of myopia progression in East Asia and the United States where the final recorded level of myopia is presented as a function of the established age of onset. (2) Four retrospective studies of myopia progression in Finland, India, the Netherlands and China and two cross-sectional studies in Argentina and the UK where the age of onset was based on self-report of age at first spectacle prescription. (3) A cohort study of Finnish subjects originally recruited for a clinical trial and followed into adulthood. Subjects were divided into five groups according to age at recruitment that was used as a surrogate for the age of onset.

RESULTS

Final recorded level of myopia was plotted as a function of age of onset for all studies. Among the three East Asian studies, the slopes are between 0.68 and 0.97 D/year, meaning that each later year of onset is associated with between 0.68 and 0.97 less myopia at the final recorded refraction. For six of the seven non-East Asian studies, the slopes are substantially flatter, with slopes between 0.23 and 0.50 D/year. By contrast, the slope for the Finnish study was 0.87 D/year. Increasing age of final recorded refraction tended to be associated with higher levels of myopia.

CONCLUSION

Among East Asians, delaying the onset of myopia by 1 year has the potential to lower the final myopia level by 0.75 D or more-equivalent to 2-3 years of myopia control with existing modalities. The benefit is lower, but meaningful, among non-East Asians.

A Cross-Sectional Observational Study of the Relationship between Outdoor Exposure and Myopia in University Students, Measured by Conjunctival Ultraviolet Autofluorescence (CUVAF)

Myopia is the most common refractive error worldwide. This cannot be explained by genetic factors alone, therefore, environmental factors may play an important role. Hence, the main objective of this study was to analyse whether outdoor exposure could exert a protective effect against the development of myopia in a cohort of young adults and to investigate ultraviolet autofluorescence (CUVAF), as a biomarker of time spent outdoors. A cross-sectional observational study was carried out using two cohorts. A total of 208 participants were recruited, 156 medical students and 52 environmental science students. The data showed that 66.66% of the medical students were myopic, while 50% of the environmental science students were myopic (p = 0.021). Environmental science students spent significantly more hours per week doing outdoor activities than medical students (p < 0.0001), but there was no significant difference with respect to near work activities between them. In both cohorts, the degree of myopia was inversely associated with CUVAF, and a statistically significant positive correlation was observed between spherical equivalent and CUVAF (Pearson’s r = 0.248). In conclusion, outdoor activities could reduce the onset and progression of myopia not only in children, but also in young adults. In addition, CUVAF represents an objective, non-invasive biomarker of outdoor exposure that is inversely associated with myopia.

The optimal cut-off value of non-cycloplegic autorefraction for diagnosing myopia in school-aged children

PURPOSE

To determine the optimal cut-off value of non-cycloplegic autorefraction for diagnosing myopia and estimating myopia prevalence in school-aged children.

STUDY DESIGN

Retrospective case-control study.

SUBJECTS AND METHODS

Based on age and sex, case-control data were extracted from the medical records of children who underwent autorefraction before and after instillation of 1% cyclopentolate eye drops. We regarded a spherical equivalent (SEQ) of -0.50 D or less found by cycloplegic autorefraction as myopia and determined the optimal cut-off value of non-cycloplegic autorefraction for diagnosing myopia using a receiver operating characteristic (ROC) curve and diagnostic performance (DP) plots.

RESULTS

Of a total of 232 children (mean age 8.2 [range: 6-12] years, 126 boys [54.3%]), 116 (50.0%) had myopia. In this cohort, the optimal cut-off SEQ for diagnosing myopia was -0.75 D with a sensitivity of 90.5% and specificity of 95.7%. However, the DP-plots indicated that the cut-off value significantly varied with prevalence of myopia: -1.31 D, -0.81 D, and -0.65 D for the prevalence of 30%, 50%, and 80%, respectively. For non-cycloplegic autorefraction, we found greater accommodation in children aged 6 years and hyperopic eyes (p < 0.001).

CONCLUSION

 When diagnosing myopia using non-cycloplegic autorefraction alone with a theoretical cut-off SEQ of -0.50 D, the prevalence of myopia will be overestimated, and we need to set the cut-off value lower (more myopic) especially in younger children with low prevalence.

Development and validation of a questionnaire-based myopia proxy in adults: the LifeLines Cohort Study

AIMS

To build a questionnaire-based myopia proxy and to validate the proxy by confirming its association with educational attainment and a Polygenic Risk Score (PRS) for myopia.

METHODS

Data were collected between 2014 and 2017 from 88 646 Dutch adults from the LifeLines Cohort. First, we performed principal component analysis (PCA) to responses of five refraction-status questions. Second, we measured the refractive state in a subset of LifeLines participants (n=326) and performed logistic regression using myopia (mean spherical equivalent <-0.5 D) as a dependent variable and the principal components (PCs) as independent variables. We identified specificity, sensitivity and the classification threshold. Third, the classification equation was applied to the remaining LifeLines participants. The value of the proxy was then explored by calculating its association with educational attainment and a PRS of myopia.

RESULTS

A total of 77 096 participants (58.1% women) were eligible for the PCA. The first two PCs had a specificity of 91.9% (95% CI 87.8% to 95.4%) and a sensitivity of 90.4% (95% CI 84.3% to 96.4%) for myopia. The area under the receiver operating characteristic curve was 95.0% (95% CI 92.2% to 97.8%). The age-standardised prevalence of proxy-inferred myopia was 33.8% (95% CI 33.4% to 34.3%). Compared with low education level, the ORs of proxy-inferred myopia were 1.66 (95% CI 1.58 to 1.74, p=5.94×10^-90) and 2.54 (95% CI 2.41 to 2.68, p=4.04×10^-271) for medium and high education levels, respectively. Similarly, individuals at the top 10% of PRS (vs lower 90%) had an OR of 2.18 (95% CI 1.98 to 2.41, p=6.57×10^-56) for proxy-inferred myopia, whereas those at the highest decile had an OR of 4.51 (95% CI 3.9 to 5.21, p=1.74×10^-89) when compared with the lowest decile.

CONCLUSION

Self-administered refractive error-related questions could be used as an effective tool to capture proxy-inferred myopic cases in a population-based setting.

Association of Age at Myopia Onset With Risk of High Myopia in Adulthood in a 12-Year Follow-up of a Chinese Cohort

Importance

Early-onset myopia is well known to progress to high myopia in adulthood. However, no accurate estimation of how a specific age at myopia onset is associated with the probability of developing high myopia in adulthood is available, and a very-long-term follow-up study with data from annual visits is needed.

Objective

To estimate the risk of developing high myopia in adulthood associated with a specific age at myopia onset from a data set with a 12-year annual follow-up.

Design, Setting, and Participants

This ongoing, population-based prospective cohort study of twins was conducted in Guangzhou, China, on July 11, 2006. Data from baseline to August 31, 2018, were analyzed. The first-born twins completed follow-up until 17 years or older, and the 443 participants (after exclusions) who developed myopia were included in the analysis. Data were analyzed from September 1, 2018, to January 20, 2020.

Main Outcomes and Measures

Age at myopia onset was determined by prospective annual cycloplegic refractions (365 participants [82.4%]) or with a questionnaire. Refraction in adulthood was defined as the cycloplegic refraction measured at the last follow-up visit.

Results

Among the 443 eligible participants (247 [55.8%] female; mean [SD] age at myopia onset, 11.7 [2.0] years), 54 (12.2%) developed high myopia (spherical equivalent, -6.00 diopters or worse determined by cycloplegic refractions) in adulthood. Among participants with age at myopia onset of 7 or 8 years, 14 of 26 (53.9%; 95% CI, 33.4%-73.4%) developed high myopia in adulthood; among those with onset at 9 years of age, 12 of 37 (32.4%; 95% CI, 18.0%-49.8%); among those with onset at 10 years of age, 14 of 72 (19.4%; 95% CI, 11.1%-30.5%); among those with onset at 11 years of age, 11 of 78 (14.1%; 95% CI, 7.3%-23.8%); and among those with onset at 12 years or older, 3 of 230 (1.3%; 95% CI, 0.2%-3.8%). Results of multivariate logistic regression analysis suggested that the risk of developing high myopia in adulthood decreased significantly with delay in the age at myopia onset (odds ratio, 0.44; 95% CI, 0.36-0.55; P < .001), from greater than 50% for 7 or 8 years of age to approximately 30% for 9 years of age and 20% for 10 years of age.

Conclusions and Relevance

These findings suggest that the risk of high myopia is relatively high in children with myopia onset during the early school ages. Each year of delay in the age at onset substantially reduces the chance of developing high myopia in adulthood, highlighting the importance of identifying effective prevention strategies under investigation, such as increasing outdoor time.

Early Age of the First Myopic Spectacle Prescription, as an Indicator of Early Onset of Myopia, Is a Risk Factor for High Myopia in Adulthood

Purpose

The present study investigated the risk factors for high myopia in adulthood, with a focus on the age at which children wore their first spectacles.

Methods

Adults aged between 20 and 45 years were invited to complete a questionnaire about age, sex, current refractive error, high myopia in parents, early onset of myopia presented by the age of the first myopic spectacle prescription, refractive power of the first spectacles, and life habits at different educational stages. The associations between these factors and high myopia in adulthood were then evaluated and analyzed.

Results

In total, 331 participants were enrolled. Their average refractive error was −4.03 diopters, and high myopia was noted in 27.5% of the study participants. Only 3.3% of participants had fathers with high myopia, while 6.0% had mothers with high myopia. The participants received their first myopic spectacle prescription at a mean age of 13.35 years, with a mean refractive error of −1.63 diopters. The significant risk factors for developing high myopia in adult life were earlier age of the first spectacles prescribed (p < 0.001), higher refractive power of the first spectacles (p < 0.001), mother with high myopia (p=0.015), and after-school class attendance in senior high school (p=0.018). Those who wore their first spectacles at <9 years of age were more predisposed to high myopia than those who did so at ≧13 years, with an odds ratio of 24.9.

Conclusion

The present study shows that earlier onset of myopia, which is presented by the age of the first myopic spectacle prescription, higher myopic refraction of the first spectacles, mothers with high myopia, and after-school class attendance in senior high school are risk factors for high myopia in adulthood. It suggests that delaying the onset of myopia in children is important for the prevention of high myopia in later life.

IMI Impact of Myopia

The global burden of myopia is growing. Myopia affected nearly 30% of the world population in 2020 and this number is expected to rise to 50% by 2050. This review aims to analyze the impact of myopia on individuals and society; summarizing the evidence for recent research on the prevalence of myopia and high myopia, lifetime pathological manifestations of myopia, direct health expenditure, and indirect costs such as lost productivity and reduced quality of life (QOL). The principal trends are a rising prevalence of myopia and high myopia, with a disproportionately greater increase in the prevalence of high myopia. This forecasts a future increase in vision loss due to uncorrected myopia as well as high myopia-related complications such as myopic macular degeneration. QOL is affected for those with uncorrected myopia, high myopia, or complications of high myopia. Overall the current global cost estimates related to direct health expenditure and lost productivity are in the billions. Health expenditure is greater in adults, reflecting the added costs due to myopia-related complications. Unless the current trajectory for the rising prevalence of myopia and high myopia change, the costs will continue to grow. The past few decades have seen the emergence of several novel approaches to prevent and slow myopia. Further work is needed to understand the life-long impact of myopia on an individual and the cost-effectiveness of the various novel approaches in reducing the burden.

Trends in research related to high myopia from 2010 to 2019: a bibliometric and knowledge mapping analysis

AIM

To evaluate the global trends in and explore hotspots of high myopia (HM) research.

METHODS

This bibliometric analysis was used to reveal the publication trends in HM research field based on the Web of Science Core Collection (WoSCC). VOSviewer version 1.6.13 software was used to analyze the data and construct a knowledge map including the yearly publication number, journals, countries, international collaborations, authors, research hotspots, and intellectual base in HM.

RESULTS

The search engine found 3544 peer-reviewed publications on HM between 2010 and 2019, and the yearly research output substantially elevated over the past decade. China is the top publishing country, and Sun Yat-sen University was the most active academic institution. Jonas JB is the top publishing scientist, and Investigative Ophthalmology and Visual Science (IOVS) was the most productive journal. The highest cited references mainly focused on epidemiology and management. The keywords formed 6 clusters: 1) refractive surgery; 2) etiology and clinical characteristics; 3) the mechanism of eye growth; 4) management for myopic maculopathy; 5) vitrectomy surgical treatment; 6) myopia-associated glaucoma-like optic neuropathy.

CONCLUSION

The evaluation of development trends based on the data extracted from WoSCC can provide valuable information and guidance for ophthalmologists and public health researchers to improve management procedures in HM field.

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

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.

Progression of myopia in children and teenagers: a nationwide longitudinal study

Background

Data on myopia prevalence and progression in European children are sparse. The aim of this work was to evaluate the progression of myopia in children and teenagers in a large prospective study.

Methods

A prospective study involving a nationwide cohort. Myopia was defined as a spherical equivalent (SE) of ≤ –0.50 diopters (D). Data on refractive error, gender and age were collected in 696 optical centres in France between 2013 and 2019, including 136 333 children (4–17 years old) in the analysis.

Progression of myopia was assessed between the first visit and the last visit over up to 6.5 years.

Results

Mean age was 11.3±3.8 years (55.0% of female). The proportion of children progressing more than –0.50 D per year was higher in age groups 7–9 years and 10–12 years and in children with SE ≤ –4.00 D at first visit, representing 33.1%, 29.4% and 30.0% of these groups, respectively. In multivariate analysis, progression during the first 11–24 months was higher in the 7–9 and 10–12 age groups (–0.43 D and –0.42 D, respectively), for higher SE at baseline (at least –0.33 D for SE ≤ –1 D) and for girls (–0.35 D).

Conclusion

This is the first French epidemiological study to investigate myopia progression in a large-scale cohort of children. Sex, age groups and myopia severity are associated with differing rates of progression.

Association Between Medication-Taking and Refractive Error in a Large General Population-Based Cohort

Purpose

Refractive errors, particularly myopia, are common and a leading cause of blindness. This study aimed to explore associations between medications and refractive error in an aging adult cohort and to determine whether childhood-onset refractive errors predict future medication use to provide novel insights into disease mechanisms.

Methods

The study compared the spherical equivalent values measured in 102,318 UK Biobank participants taking the 960 most commonly used medications. The strengths of associations were evaluated against the self-reported age of spectacle wear. The causality of refractive error changes was inferred using sensitivity and Mendelian randomization analyses.

Results

Anti-glaucoma drugs were associated with 1 to 2 diopters greater myopic refraction, particularly in subjects who started wearing correction in the first two decades of life, potentially due to the association of higher intraocular pressure since early years with both myopia and, later in life, glaucoma. All classes of pain-control medications, including paracetamol, opiates, non-steroidal antiinflammatory drugs, and gabapentinoids, were associated with greater hyperopia (+0.68–1.15 diopters), after correction for deprivation, education, and polypharmacy and sensitivity analyses for common diagnoses. Oral hypoglycemics (metformin, gliburonide) were associated with myopia, as was allopurinol, and participants using bronchodilators (ipratropium and salbutamol) were more hyperopic.

Conclusions

This study finds for the first time, to our knowledge, that medication use is associated with refractive error in adults. The novel finding that analgesics are associated with hyperopic refraction, and the possibility that multisite chronic pain predisposes to hyperopia, deserves further research. Some drugs, such as antihyperglycemic or bronchodilators, may directly alter refractive error. Intraocular pressure appears causative for myopia.

Low-dose (0.01%) atropine eye-drops to reduce progression of myopia in children: a multicentre placebo-controlled randomised trial in the UK (CHAMP-UK)-study protocol

BACKGROUND/AIMS

To report the protocol of a trial designed to evaluate the efficacy, safety and mechanism of action of low-dose atropine (0.01%) eye-drops for reducing progression of myopia in UK children.

METHODS

Multicentre, double-masked, superiority, placebo-controlled, randomised trial. We will enrol children aged 6-12 years with myopia of -0.50 dioptres or worse in both eyes.We will recruit 289 participants with an allocation ratio of 2:1 (193 atropine; 96 placebo) from five centres. Participants will instil one drop in each eye every day for 2 years and attend a research centre every 6 months. The vehicle and preservative will be the same in both study arms.The primary outcome is SER of both eyes measured by autorefractor under cycloplegia at 2 years (adjusted for baseline). Secondary outcomes include axial length, best corrected distance visual acuity, near visual acuity, reading speed, pupil diameter, accommodation, adverse event rates and allergic reactions, quality of life (EQ-5D-Y) and tolerability at 2 years. Mechanistic evaluations will include: peripheral axial length, peripheral retinal defocus, anterior chamber depth, iris colour, height and weight, activities questionnaire, ciliary body biometry and chorioretinal thickness. Endpoints from both eyes will be pooled in combined analysis using generalised estimating equations to allow for the correlation between eyes within participant. Three years after cessation of treatment, we will also evaluate refractive error and adverse events.

CONCLUSIONS

The Childhood Atropine for Myopia Progression in the UK study will be the first randomised trial reporting outcomes of low-dose atropine eye-drops for children with myopia in a UK population.

TRIAL REGISTRATION NUMBER

ISRCTN99883695, NCT03690089.

Evaluation of changes in choroidal thickness after surgical implantation of collamer lens in patients with different degrees of high myopia

The aim of the present study was to investigate the potential changes in the choroidal thickness (CT) after surgical implantation of collamer lens (ICL) and to determine whether the variations in CT were associated with the degree of myopia. In the study, 98 eyes from 98 myopia patients were divided into two groups according to the degree of myopia: High myopia and super-high myopia. All eyes were measured using the swept-source optical coherence tomography (SS-OCT) technique. CT and CT variations were also recorded. The foveal CT increased significantly in high-myopia patients at 2 h after surgery and 3 months after surgery; the same tendency was observed in the inner nasal CT and outer nasal CT at the same time-points. In patients with super-high myopia, the subfoveal CT increased significantly at 2 h and 3 months after surgery compared with the pre-operative values. No statistically significant differences were obtained in any of the nine different choroidal regions evaluated at post-operative week 1 and post-operative month one. Furthermore, the increase in the subfoveal CT in the super-myopia group was significantly higher than that in the high-myopia group at 2 h and at 3 months after ICL. The results of the present study indicated that the CT significantly increased 2 h after the surgery and then reached a peak at 3 months, particularly in the subfoveal and nasal areas. A higher degree of myopia was associated with greater subfoveal choroidal changes.

IMI - Myopia Control Reports Overview and Introduction

With the growing prevalence of myopia, already at epidemic levels in some countries, there is an urgent need for new management approaches. However, with the increasing number of research publications on the topic of myopia control, there is also a clear necessity for agreement and guidance on key issues, including on how myopia should be defined and how interventions, validated by well-conducted clinical trials, should be appropriately and ethically applied. The International Myopia Institute (IMI) reports the critical review and synthesis of the research evidence to date, from animal models, genetics, clinical studies, and randomized controlled trials, by more than 85 multidisciplinary experts in the field, as the basis for the recommendations contained therein. As background to the need for myopia control, the risk factors for myopia onset and progression are reviewed. The seven generated reports are summarized: (1) Defining and Classifying Myopia, (2) Experimental Models of Emmetropization and Myopia, (3) Myopia Genetics, (4) Interventions for Myopia Onset and Progression, (5) Clinical Myopia Control Trials and Instrumentation, (6) Industry Guidelines and Ethical Considerations for Myopia Control, and (7) Clinical Myopia Management Guidelines.

IMI - Clinical Management Guidelines Report

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.

Genome-wide association meta-analysis highlights light-induced signaling as a driver for refractive error

Refractive errors, including myopia, are the most frequent eye disorders worldwide and an increasingly common cause of blindness. This genome-wide association meta-analysis in 160,420 participants and replication in 95,505 participants increased the number of established independent signals from 37 to 161 and showed high genetic correlation between Europeans and Asians (>0.78). Expression experiments and comprehensive in silico analyses identified retinal cell physiology and light processing as prominent mechanisms, and also identified functional contributions to refractive-error development in all cell types of the neurosensory retina, retinal pigment epithelium, vascular endothelium and extracellular matrix. Newly identified genes implicate novel mechanisms such as rod-and-cone bipolar synaptic neurotransmission, anterior-segment morphology and angiogenesis. Thirty-one loci resided in or near regions transcribing small RNAs, thus suggesting a role for post-transcriptional regulation. Our results support the notion that refractive errors are caused by a light-dependent retina-to-sclera signaling cascade and delineate potential pathobiological molecular drivers.

Age of onset of myopia predicts risk of high myopia in later childhood in myopic Singapore children

PURPOSE

To investigate the effect of age of myopia onset on the severity of myopia later in life among myopic children.

METHODS

In this prospective study, school children aged 7-9 years from the Singapore Cohort Of the Risk factors for Myopia (SCORM) were followed up till 11 years (n = 928). Age of myopia onset was defined either through questionnaire at baseline (age 7-9 years) or subsequent annual follow-up visits. Age of onset of myopia was a surrogate indicator of duration of myopia progression till age 11 years. Cycloplegic refraction and axial length were measured at every annual eye examination. High myopia was defined as spherical equivalent of ≤-5.0 D. A questionnaire determined the other risk factors.

RESULTS

In multivariable regression models, younger age of myopia onset (per year decrease) or longer duration of myopia progression was associated with high myopia (odds ratio (OR) = 2.86; 95% CI: 2.39 to 3.43), more myopic spherical equivalent (regression coefficient (β) = -0.86 D; 95% CI: -0.93 to -0.80) and longer axial length (β = 0.28 mm; 95% CI: 0.24 to 0.32) at aged 11 years, after adjusting for gender, race, school, books per week and parental myopia. In Receiver Operating Curve (ROC) analyses, age of myopia onset alone predicted high myopia by 85% (area under the curve = 0.85), while the addition of other factors including gender, race, school, books per week and parental myopia only marginally improved this prediction (area under the curve = 0.87).

CONCLUSIONS

Age of myopia onset or duration of myopia progression was the most important predictor of high myopia in later childhood in myopic children. Future trials to retard the progression of myopia to high myopia could focus on children with younger age of myopia onset or with longer duration of myopia progression.

Retinal Microvascular Network and Microcirculation Assessments in High Myopia

PURPOSE

To investigate the changes of the retinal microvascular network and microcirculation in high myopia.

DESIGN

A cross-sectional, matched, comparative clinical study.

PARTICIPANTS

Twenty eyes of 20 subjects with nonpathological high myopia (28 ± 5 years of age) with a refractive error of -6.31 ± 1.23 D (mean ± SD) and 20 eyes of 20 age- and sex-matched control subjects (30 ± 6 years of age) with a refractive error of -1.40 ± 1.00 D were recruited.

METHODS

Optical coherence tomography angiography (OCTA) was used to image the retinal microvascular network, which was later quantified by fractal analysis (box counting [D_box], representing vessel density) in both superficial and deep vascular plexuses. The Retinal Function Imager was used to image the retinal microvessel blood flow velocity (BFV). The BFV and microvascular density in the myopia group were corrected for ocular magnification using Bennett's formula.

RESULTS

The density of both superficial and deep microvascular plexuses was significantly decreased in the myopia group in comparison to the controls (P < .05). The decrease of the microvessel density of the annular zone (0.6-2.5 mm), measured as D_box, was 2.1% and 2.9% in the superficial and deep vascular plexuses, respectively. Microvessel density reached a plateau from 0.5 mm to 1.25 mm from the fovea in both groups, but that in the myopic group was about 3% lower than the control group. No significant differences were detected between the groups in retinal microvascular BFV in either arterioles or venules (P > .05). Microvascular densities in both superficial (r = -0.45, P = .047) and deep (r = -0.54, P = .01) vascular plexuses were negatively correlated with the axial lengths in the myopic eye. No correlations were observed between BFV and vessel density (P > .05).

CONCLUSIONS

Retinal microvascular decrease was observed in the high myopia subjects, whereas the retinal microvessel BFV remained unchanged. The retinal microvascular network alteration may be attributed to ocular elongation that occurs with the progression of myopia. The novel quantitative analyses of the retinal microvasculature may help to characterize the underlying pathophysiology of myopia and enable early detection and prevention of myopic retinopathy.

Myopia is an Adaptive Characteristic of Vision: Not a Disease or Defect

This article proposes that myopia (nearsightedness) is an adaptive characteristic of human vision. Most theories of the evolution of vision assume myopia is a disease or defect that would have resulted in decreased reproductive fitness in the absence of modern corrective lenses. In contrast, the present article argues that myopic individuals may have played important roles in hunter–gatherer groups such as making tools and weapons, and identifying medicinal plants, contributing to individual and group survival. This idea is called the “adaptive myopia hypothesis.” Evidence favoring this hypothesis is reviewed in the context of the metatheory of evolutionary psychology.

Change in choroidal thickness and the relationship with accommodation following myopic excimer laser surgery

PurposeTo investigate early changes in choroidal thickness (CT) and the relationship with accommodation after myopic excimer laser surgery.MethodsWe enrolled the right eye of 70 patients with myopia and without other ophthalmic or systemic diseases who were suitable for myopic excimer laser surgery. The CT was measured at the fovea and at distances of 0.5 and 2.5 mm for the following: nasal; temporal; superior; and inferior to the fovea preoperatively and at 1 month postoperatively. Other data collected included demographic information (age, sex, and refractive error), the amplitude of accommodation (AA), intraocular pressure, axial length, corneal thickness, and surgical parameters. The data were analyzed with a paired Student's t-test, stepwise linear regression, and correlation analysis.ResultsThe CT was significantly thicker postoperatively compared with the preoperative CT. The AA significantly decreased postoperatively. The change in the AA was the most significant factor associated with the change in the CT at the fovea. Except for 2.5 mm inferior to the fovea, the increase in the CT at other locations was positively correlated with the decrease in the AA.ConclusionsThe CT increased following myopic excimer laser surgery and the change was most obvious when accompanied by a decrease in the AA early after the surgery.

Elevated light levels in schools have a protective effect on myopia

PURPOSE

To determine whether elevated light levels in classrooms in rural areas can protect school-age children from myopia onset or myopia progression.

METHODS

A total of 317 subjects from 1713 eligible students aged six to 14 in four schools located in northeast China participated in the study. Students received a comprehensive eye examination including cycloplegic refraction and ocular biometry, which included axial length (AL), anterior chamber depth (ACD), and corneal curvature (CC) measurement, and completed a questionnaire. The intervention arm included 178 students in two schools with rebuilt elevated lighting systems and the control arm included 139 students in which lighting systems were unchanged. Results for the two arms were compared with a Wilcoxon rank sum test, a chi-squared test or a t-test, as appropriate. Factors that might help explain any differences were explored with multivariate linear regression analysis.

RESULTS

The median average illuminance of blackboards and desks and uniformity of desk lighting were significantly improved, however, the uniformity of blackboard lighting declined after intervention. At baseline, the mean refraction, AL, CC, ACD and myopia prevalence between the two arms were not significantly different. After 1 year, compared with the control arm the intervention arm had a lower incidence of new myopia onset (4% vs 10%; p = 0.029), a smaller decrease in refractive error among no myopic subjects (-0.25 dioptre [D] vs -0.47 D; p = 0.001), and shorter axial growth for both non-myopic (0.13 vs 0.18 mm; p = 0.023) and myopic subjects (0.20 vs 0.27 mm; p = 0.0001). Multivariate linear regression analysis showed the intervention program, lower hyperopic baseline refraction, lower father's education level, longer time sleeping and less time in screen-viewing activities were associated with less refractive shift in the direction of myopia in non-myopic children. For myopic subjects, myopia progression was significantly associated with family income only. The intervention program and older age had a protective effect on axial growth for both myopic and non-myopic subjects. The father's education level and sleep duration were significantly associated with axial growth in non-myopic children.

CONCLUSIONS

Elevated light levels in classrooms have a significant effect on myopia onset, decreases in refraction, and axial growth; if the findings of lighting intervention are reproduced in future studies, the ambient light levels in schools should be improved.

Is myopia another clinical manifestation of insulin resistance?

Myopia is a multifactorial visual refraction disease, in which the light rays from distant objects are focused in front of retina, causing blurry vision. Myopic eyes are characterized by an increased corneal curvature and/or ocular axial length. The prevalence of myopia has increased in recent decades, a trend that cannot be attributed exclusively to genetic factors. Low and middle income countries have a higher burden of refractive error, which we propose could be a consequence of a shorter exposure time to a westernized lifestyle, a phenomenon that may also explain the rapid increase in cardiometabolic diseases, such as diabetes, among those populations. We suggest that interactions between genetic, epigenetic and a rapidly changing environment are also involved in myopia onset and progression. Furthermore, we discuss several possible mechanisms by which insulin resistance may promote abnormal ocular growth and myopia to support the hypothesis that insulin resistance and hyperinsulinemia are involved in its pathogenesis, providing a link between trends in myopia and those of cardiometabolic diseases. There is evidence that insulin have direct ocular growth promoting effects as well an indirect effect via the induction of insulin-like growth factors leading to decreases insulin-like growth factor-binding protein, also implicated in ocular growth.

Risk factors for myopia in a discordant monozygotic twin study

PURPOSE

Monozygotic (MZ) twin pairs discordant for disease allow careful examination of environmental factors whilst controlling for genetic variation. The purpose of this study was to examine differences in environmental risk factors in MZ twins discordant for myopia.

METHODS

Sixty four MZ twin pairs discordant for refractive error were interviewed. Discordant twins were selected from 1326 MZ twin pairs from the TwinsUK adult twin registry with non-cycloplegic autorefraction. Discordancy was defined as ≥ 2 Dioptres (D) difference in spherical equivalent (SphE) and discordant for class of refractive error. In a 35-item telephone questionnaire twins were separately asked (and scored) about the risk factors urban/rural residence, occupational status and highest educational level. They responded with more (1), less (-1) or the same (0) as their twin on time spent outside, playing outdoor sport, and on close work aged <16 and 16-25 years. The lower SphE twin's score was subtracted from the higher SphE twin's score, and mean values of the difference calculated for each variable.

RESULTS

Sixty four twin pairs were included (mean age 56, range 30-79 years; mean difference in refraction 3.35 D, S.D. 1.55 D, median difference 2.78 D). Within discordant MZ twin pairs, the more myopic twin was associated with having a higher occupational status (mean score between 16 and 25 years -0.11; 95% CI -0.19 to -0.04; mean score aged >25 years -0.23, 95% CI -0.28 to -0.17), being resident in urban area (mean score -0.26; 95% CI -0.33 to -0.18) and performing more close work (mean score <16 years -0.11; 95% CI -0.18 to -0.05; mean score aged 16-25 years -0.17, 95% CI -0.24 to -0.10) than their twin. The twins who spent more time outdoors (mean score <16 years 0.09; 95% CI 0.03-0.15; mean score aged 16-25 years 0.28, 95% CI 0.15-0.41) or performed more outdoors sports (mean score <16 years 0.13; 95% CI 0.04-0.21; mean score aged 16-25 years 0.23, 95% CI 0.10-0.36) were less likely to be myopic than their twin.

CONCLUSIONS

This study has confirmed known environmental risk factors for myopia. These data will allow selection of discordant twins for epigenetic analysis to advance knowledge of mechanisms of refractive error development.

Prevalence of Refractive Errors in Students with and without Color Vision Deficiency

PURPOSE

To evaluate refractive errors in school age children with color vision deficiency (CVD) and those with normal color vision (NCV) in order to make a better understanding of the emmetropization process.

METHODS

A total of 4,400 primary school students aged 7-12 years were screened for color vision using Ishihara pseudoisochromatic color vision plate sets. Of these, 160 (3.6%) students had CVD. A total of 400 age- and sex-matched students with NCV were selected as controls. Refractive status was evaluated using objective cyclorefraction.

RESULTS

The CVD group included 136 male (85%) and 24 female (15%) subjects with mean age of 10.1 ± 1.8 years. The NCV group comprised of 336 male (84%) and 64 female (16%) subjects with mean age of 10.5 ± 1.2 years. The prevalence of myopia (7.7% vs. 13.9%, P < 0.001) and hyperopia (41% vs. 57.4%, P = 0.03) was significantly lower in the CVD group. Furthermore, subjects with CVD subjects demonstrated a lower magnitude of refractive errors as compared to the CVD group (mean refractive error: +0.54 ± 0.19 D versus + 0.74 ± 1.12 D, P < 0.001).

CONCLUSION

Although the lower prevalence of myopia in subjects with CVD group supports the role of longitudinal chromatic aberration in the development of refractive errors; the lower prevalence of hyperopia in this group is an opposing finding. Myopia is a multifactorial disorder and longitudinal chromatic aberration is not the only factor influencing the emmetropization process.

Why don't younger adults in England go to have their eyes examined?

PURPOSE

Most research on attitudes to eye health has focussed on older people, reflecting the higher prevalence of eye diseases in older age groups. Little is known about younger people's attitudes to eye health. This paper explores young adults understanding of eye health and the purpose of eye examinations and the reasons why they do or do not attend for eye examinations. The aim is to provide evidence to inform policy on recommendations relating to eye health for individuals at low risk of visual impairment.

METHODS

Six focus-group meetings were held in Leeds with 43 people aged 18-35 (mean age 22 years). Focus group participants were recruited using a snowballing approach from an initial group of young adults. Focus groups were transcribed and a thematic analysis approach was used.

RESULTS

Children who wore spectacles were often bullied. As people grew up it became more socially acceptable to wear spectacles. Practicalities, aesthetics and fashion were important issues. Knowledge about eye disease and the eye examination were generally poor. Many claimed to value vision, but recognised that young people do not have eye examinations as often as they should. Eye examinations were only perceived to be needed for younger people experiencing problems or to update prescriptions. Eye health was seen as issue for older people. Some had no idea or were shocked about how much spectacles cost. Optometrists were seen differently to other healthcare professionals. The retail aspect of optometry was seen as too dominant. More information was wanted from the NHS on eye health.

CONCLUSION

While young adults are at low risk of sight threatening disease, many do benefit from correction of refractive error. There is an argument for reducing the recommended frequency of eye examinations for low risk individuals from the 2 years currently advised. Nevertheless, young adults need to be made more aware of eye health issues, so that optometrists are seen as more than somewhere that sell spectacles. Increasing awareness of eye health in younger adulthood will also be important to ensure that services are appropriately accessed as they get older.