Near Work Related Parameters and Myopia in Chinese Children: the Anyang Childhood Eye Study

Prevalence and Time Trends in Myopia Among Children and Adolescents

BACKGROUND

Myopia (near-sightedness) is increasing worldwide, especially in Asia. The aim of this study was to describe trends in the prevalence of myopia in Germany.

METHODS

We analyzed data from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS; baseline survey 2003-2006, N = 17 640; wave 2, 2014-2017, N = 15 023). The presence of myopia was determined from a parent questionnaire and validated by the use of a visual aid. The population prevalence of myopia was calculated. Based on the KiGGS wave 2 data, potential risk factors for myopia were identified by means of logistic regression.

RESULTS

The prevalence of myopia at the age of 0-17 years in Germany was 11.6% (95% confidence interval [11.0; 12.2]) in the period 2003-2006 and 11.4% [10.7; 12.2] in 2014-2017. No age group of either sex exhibited a relevant, statistically significant change in the prevalence of myopia. In the adjusted model (adjusted for age, sex, family socioeconomic status, family history of migration), no association was found between myopia and use of digital media. More time spent reading books was associated with myopia: reading for more than 2 h/day showed an odds ratio of 1.69 [1.3; 2.2].

CONCLUSION

The prevalence of myopia in children and adolescents in Germany has remained virtually unchanged over a period of approximately 10 years. Changes in media consumption, such as the increased use of smartphones in this age group, have therefore had no detectable impact on the development of myopia, at least not so far. Future studies should investigate the influences of further increases in media use and examine the long-term effects.

Effect of reading with a mobile phone and text on accommodation in young adults

Purpose

To investigate the effects of reading with mobile phone versus text on accommodation accuracy and near work-induced transient myopia (NITM) and its subsequent decay during near reading in young adults with mild to moderate myopia.

Methods

The refractions of 31 young adults were measured with an open-field autorefractor (WAM-5500, Grand Seiko) for two reading tasks with a mobile phone and text at 33 cm. The mean age of the young adults was 24.35 ± 1.80 years. The baseline refractive aspects were determined clinically with full distance refractive correction in place. The initial NITM and its decay time and accommodative lag were assessed objectively immediately after binocularly viewing a mobile phone or text for 40 min.

Results

The mean ± standard deviation (SD) initial NITM magnitude was greater for reading with text (0.23 ± 0.26 D) than for reading with mobile phone (0.12 ± 0.17 D), but there was no significant difference between the two reading tasks (p = 0.082). The decay time (median, first quartile, and third quartile) was 60 s (16, 154) and 70 s (32, 180) in the phone task and text task groups, respectively. There was also no significant difference in the decay time between the two reading types in general (p = 0.294). The accommodative lags of text tasks and mobile phones tasks were equivalent (1.27 ± 0.52 D vs 1.31 ± 0.64 D, p = 0.792).

Conclusion

There were no significant differences in accommodative lags and the initial NITM and its decay time between reading with a mobile phone and text in young adults.

Screen Time and Bone Status in Children and Adolescents: A Systematic Review

Introduction: Technological advances over the last 2 decades have led to an increase in the time spent by children and youth engaged in screen-based activities, and growing recognition of deleterious effects on health. In this systematic review of cohort and cross-sectional studies, we assess current data on the relationship between screen time and bone status in children and teenagers. Methods: We searched PUBMED and SCOPUS databases for studies of children and adolescents that assessed screen time and bone status, determined by measuring bone mineral content or density, bone stiffness index, bone speed of sound, bone broadband ultrasound attenuation, or frame index. Searches were limited to studies published between 1900 and 2020, and performed in accordance with Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. The studies included were evaluated using the Newcastle-Ottawa quality assessment scale. Results: Ten cohort and cross-sectional studies including pediatric population were selected. The combined study population was 20,420 children/adolescents, of whom 18,444 participated in cross-sectional studies. Four studies assessed the effects of total screen time, seven the consequences of TV viewing time, and six the effects of recreational computer use on bone health. Our findings indicate an inverse association between total and weekly screen time and bone health in children and adolescents. In 57% of the studies included also a negative correlation between television viewing time and bone status was observed, while recreational computer time did not have a significant impact on bone health. According to the only four studies that included dietetic factors, no relevant differences were found between calcium intake and screen time or bone broadband ultrasound attenuation and bone speed of sound. Conclusions: Review of the literature of the past three decades provides strong support for comprehensive education of screen time on bone status. The findings of this systematic review support a negative association between screen time and bone status in children and adolescents, with a different impact when considering the different technological devices. As peak bone mass in adolescents is the strongest predictor of osteoporosis risk, strategies aimed at improving bone health should incorporate conscious use of digital technology.

Axial Length and Prevalence of Myopia among Schoolchildren in the Equatorial Region of Brazil

The prevalence of myopia is increasing globally, and the outdoor light environment is considered as a possible factor that can retard myopia. The aim of this study was to evaluate the prevalence of myopia and the light environment in Aracati, equatorial Brazil. We surveyed 421 children (421 right eyes; mean age, 10.6 years) and performed ocular examinations that included non-cycloplegic refraction and axial length (AL). Multiple regression analyses were performed to identify factors affecting myopia such as time spent outdoors and in near work. We measured illuminance and violet light irradiance in Aracati. The mean spherical equivalent (SE) and AL were −0.44 ± 1.38 diopters (D) and 22.98 ± 0.87 mm, respectively. The prevalence of myopia (SE ≤ −0.75 D) and high myopia (SE ≤ −6.0 D/AL ≥ 26.0 mm) was 20.4 and 1.4/0.48%, respectively. Multiple regression analyses showed that myopia was not associated with lifestyle factors. The average illuminance in Aracati was about 100,000 lux from morning to evening. The current results reflect the ALs and the prevalence of myopia among Brazilian schoolchildren. There is a possibility that the light environment in addition to other confounding factors including racial differences affects the ALs and refractive errors.

A Novel Approach to Quantify Environmental Risk Factors of Myopia: Combination of Wearable Devices and Big Data Science

Purpose

To develop a practical approach to quantify the exposure to environmental risk factors of myopia.

Methods

In total, 179 children (age, mean ± standard deviation [SD] 9.17 ± 0.52 years) were requested to wear Clouclip, designed to measure working distance (WD) and light intensity (LI), for a whole week. The spherical equivalent refraction (SER) was determined by cycloplegic autorefraction. The raw data of WD and LI were preprocessed through several steps, including data denoising, constructing a two-dimensional WD-LI space, and data sparseness disposing. Weighted linear regression was used to explore the relationship between WD/LI and SER. A novel parameter visual behaviour index (VBI) was developed to summarize the overall impact of WD/LI on SER.

Results

The mean ± SD SER of 179 participants was 0.22 ± 1.18 D. WD and LI were positively associated with SER. However, their magnitude of effect on SER varied with the relative level between them. When WD and LI were split up, the detrimental threshold was approximately 40 cm for WD and 6300 lux for LI. VBI was significantly positively associated with SER (β = 0.0623, R² = 0.031, P < 0.05).

Conclusions

The current study provides a novel approach to quantify environmental risk factors of myopia. Despite the complexity of the interaction between these risk factors and their impact on SER, this information can be summarized as one single-parameter VBI, which provides a useful tool to investigate the effect of environmental factors on myopia development and progression.

Translational Relevance

We developed a novel approach to quantify environmental risk factors of myopia.

Status of Eye Health among School Children in South India - Sankara Nethralaya School Children Eye Examination Study (SN-SEES)

Purpose: To define the prevalence of visual impairment, refractive errors and other ocular problems among school children from the public schools of South India between 2011 and 2015.Methods: This was a cross-sectional study covering 296 schools in the three districts of Tamil Nadu. The school eye screening included visual acuity assessment, external eye examination, objective and subjective refraction, and direct ophthalmoscopy. Vision impairment was defined as logMAR visual acuity of less than 0.2 (Snellen equivalent of 6/9).Results: A total of 91545 children were included with a mean age of 12.9 ± 3.0 years. The prevalence of vision impairment was found to be 5.67% (95%CI 5.53-5.83) and spherical equivalent refractive error was 4.42% (95%CI 4.29-4.56). The prevalence of myopia, hyperopia, and 'other refractive errors' was found to be 3.57% (95%CI 4.01-4.27), 0.03% (95%CI 0.02-0.04), and 0.82% (95%CI 0.76-0.88) respectively. Strabismus, retina and neuro-ophthalmology-related abnormalities, ptosis, and corneal scars were the common ocular problems. In the rural region the prevalence of the refractive errors and the ocular problems were 2.92% and 2.32%, respectively.Conclusion: The study reports a lower prevalence of refractive errors and myopia in this population, much lesser compared to other reported studies from India. Rural regions exhibit an equal need for both refractive services and management of other ocular problems.

Validation of the Clouclip and utility in measuring viewing distance in adults

PURPOSE

To validate the Clouclip, a continuously measuring objective rangefinder, and examine viewing behaviours during various near tasks in non-myopic and myopic adults.

METHODS

In experiment 1, five Clouclip devices were utilised. An infrared camera was used to visualise and measure infrared beam size and angle. Repeatability for distance tracking was assessed from 5 to 120 cm in 5 cm increments. Accuracy of distance tracking was investigated for paper and iPad targets, spatial integration was calculated, effects of target tilt were determined and light measurements were compared to a lux meter. In experiment 2, viewing behaviour was assessed in 41 subjects (21 non-myopic, 20 myopic) during four 15-min near tasks; (1) passive reading of printed material, (2) active writing on printed material, (3) passive viewing on an electronic device and (4) active engagement on an electronic device. Working distance was compared between tasks and refractive error groups.

RESULTS

Clouclip distance tracking showed good repeatability, with a mean difference of 0.34 cm and limits of agreement of ±2.0 cm. Clouclip-measured and actual distances were highly correlated for paper and electronic targets from 5 to 120 cm, with mean differences and limits of agreement of 3.96 ± 13.78 cm and 4.48 ± 8.92 cm, respectively; variability increased for distances >100 cm. Tracking ability increased with larger target sizes; tracking was accurate when the target occupied 1.5%-20.3% of tracking beam area, depending on distance and with target tilt up to ±60 degrees. Clouclip- and lux meter-measured ambient illumination were highly correlated for a wide range of intensities (r = 0.96, p < 0.001), but with greater variability for intensities >20 000 lux. The Clouclip infrared beam was measured to have a diameter of 25.6 ± 2.2° and a downward angle of 10.3 ± 0.5°. For subject testing, viewing distance was significantly closer for active and passive printed tasks (29.5 ± 6.7 cm and 33.2 ± 8.8 cm, respectively) than for active and passive electronic tasks (35.4 ± 8.0 cm and 40.8 ± 10.4 cm, respectively), with no differences between refractive error groups (p = 0.88).

CONCLUSIONS

The Clouclip performed well in measuring near and intermediate distances and could distinguish between indoor (<1000 lux) and outdoor (>1000 lux) illumination. A closer working distance was observed for printed tasks compared to those on an iPad, with no difference in viewing distance between non-myopic and myopic adults.

Prevalence and risk factors of pseudomyopia in a Chinese children population: the Anyang Childhood Eye Study

AIMS

To investigate the prevalence and predictors of pseudomyopia in Chinese children and its association with myopia progression.

METHODS

A prospective, school-based, cohort study of 6- and 13-year-old children was conducted in Anyang, China. Pre-cycloplegic and post-cycloplegic autorefraction were performed at baseline and 1 year later. Pseudomyopia was defined as spherical equivalent refractive (SER) error in the better-seeing eye ≤-0.50 D before cycloplegia and >-0.50 D after cycloplegia. Among pseudomyopic children, pseudomyopic power was defined as non-cycloplegic SER subtracted from cycloplegic SER. Market survey was collected in all optometry stores in Anyang city to investigate how cycloplegia is used for refracting children.

RESULTS

A total of 2612 children aged 6 years and 1984 children aged 13 years were included. Of the two cohorts, median cycloplegic SER (IQR) was 1.00 D (0.50, 1.38) and -1.13 D (-2.63, 0.13) respectively, myopia prevalence was 5.2% and 61.0%, pseudomyopia prevalence was 24.1% and 18.9%, and median pseudomyopic power was 1.13 D (0.63, 1.63) and 0.38 D (0.13, 0.88). In both cohorts, greater baseline hyperopia was the strongest predictor of pseudomyopia (p<0.001), whereas time spent on near work was not associated with pseudomyopic power (p>0.05). After 1 year, 15.6% (98/629) of 6-year-olds and 10.7% (40/374) of 13-year-olds with pseudomyopia developed myopia. Compared with myopes, pseudomyopic children with the same pre-cycloplegic SER had slower myopic progression (p<0.001). Among all 127 optometry stores in Anyang, only 4 (3.15%) used cycloplegia for refracting children.

CONCLUSION

Pseudomyopia is more prevalent in younger, more hyperopic children. Pseudomyopia is not an independent risk factor for myopic progression in this setting.

Probability of myopia in children with high refined carbohydrates consumption in France

BACKGROUND

Evaluate risk factors for paediatric myopia in a contemporary French cohort taking into account consumption of refined carbohydrates (starches and sugars).

METHODS

An epidemiological cross-sectional study was conducted between May 2017 and May 2018. Two hundred sixty-four children aged 4 to 18 years attending the Centre Hospitalier Universitaire Gui de Chauliac in Montpellier were recruited. Ophthalmologic or optometric cycloplegic refraction were measured. Evaluated risk factors for myopia were collected, including family history of myopia, outdoor time, reading time, screen time, physical activity, and consumption of refined carbohydrates. Association between the probability of at least one eye showing myopia (defined as < 0 D) and frequency of refined carbohydrates consumption adjusted for risk factors and control factors was tested.

RESULTS

Overall, 86/264 (32.6%) children investigated showed myopia in at least one eye. We included 180 children exhibiting refraction < 3 D in both eyes: 88 (48.9%) girls and 92 (51.1%) boys. The consumption of refined carbohydrates significantly increased the probability of myopia for girls (odds ratio [OR] = 1.07; 95% confidence interval [CI], 1.02-1.13; P = 0.009) but decreased it for boys (OR = 0.94; 95% CI, 0.89-0.98; P = 0.011). The probability of myopia was marginally increased with increased screen time (OR = 2.32; 95% CI, 0.94-6.47; P = 0.083). Outdoor time seemed marginally protective (OR = 0.74; 95% CI, 0.54-1.01; P = 0.057).

CONCLUSION

Refined carbohydrates consumption could be associated with child myopia, with increased probability for girls and unexpected reduced probability for boys, possibly due to the fact that frequency of carbohydrates consumption do not really capture boy's chronic hyperglycemia, boys being more physically active than girls at all ages. Some known risk/protective factors of myopia were marginally significant: screen time (risk) and outdoor time (protective). This study reinforces the belief that modifiable risk factors for myopia could be targets for future public health actions.

Prevalence and associated factors of myopia among rural school students in Chia-Yi, Taiwan

Background

The prevalence of myopia has increased rapidly worldwide over the past few decades. The aim of this study was to evaluate the prevalence and associated risk factors for myopia in elementary and junior high school students in Chia-Yi, Taiwan.

Methods

We included 5417 students in total from Grade 1–6 (n = 4763) and Grade 7–9 (n = 654) from Chia Yi County in this population-based study. The students underwent noncycloplegic autorefractometry and an interview with a structured questionnaire.

Results

For this study population, the prevalence of myopia and high myopia was 42.0 and 2.0%, respectively, revealing a statistically significant increase with increasing age (p < 0.05). Junior high school students (aged 13–15) showed a greater prevalence of myopia than elementary school students (aged 7–12) (55.8% vs. 40.1%, respectively, p < 0.001). Multiple logistic regression analysis showed that associated factors of myopia were body height (odds ratio [OR]: 1.05, 95% confidence interval [CI]: 1.05–1.06), body mass index (OR: 0.98, 95% CI: 0.96–1.00), and ocular alignment (horizontal heterophoria vs. orthophoria, OR: 2.37, 95% CI: 2.08–2.70; tropia vs. orthophoria, OR: 1.94, 95% CI: 1.50–2.52) for elementary school students, whereas in junior high school students, they included body height (OR: 1.02, 95% CI: 1.01–1.04) and ocular alignment (heterophoria vs. orthophoria, OR: 2.20, 95% CI: 1.56–3.10).

Conclusions

This study provided epidemiological data on myopia in rural school students in Chia-Yi, Taiwan, and demonstrated the association between heterophoria and myopia. Correction of refractive errors in the students remained a challenge.

The diversified defocus profile of the near-work environment and myopia development

Purpose

To quantify the defocus characteristics in the near‐work environment at home and investigate the relationship with subsequent myopia progression.

Methods

Fifty subjects (aged 7–12 years) were recruited and followed for 1 year. The home near‐work environment (writing desk) was measured at a baseline home‐visit using the Kinect‐for‐Windows to capture a 3‐dimensional image. The depth values of the image were then converted into scene defocus with respect to the subject’s viewpoint. The defocus characteristics were quantified as the dioptric volume (the total amount of net defocus, or DV) and standard deviation of the defocus values (SD_D). Information on home size, time spent outdoors, and in front of a desk were also obtained. Univariate correlation, and multivariate regression were used to assess the association between myopia progression, defocus characteristics, and other co‐variates.

Results

The baseline spherical equivalent refraction (M) and refraction change over 1 year (∆M) were − 1.51 ± 2.02 D and − 0.56 ± 0.45 D respectively. DV was not significantly correlated with ∆M (Spearman’s ρ = −0.25, p = 0.08), while SD_D was negatively correlated to ∆M (Spearman’s ρ = −0.42, p = 0.003). Although SD_D was not a significant predictor in multivariate analysis, the regional DV at 15°–20° eccentricity was significant (p = 0.001). Home size (F_2,50 = 7.01, p = 0.002) and time spent outdoors (Independent t = −2.13, p = 0.04) were also associated with ∆M, but not time spent in front of desk (Independent t = 0.78, p = 0.44).

Conclusion

The defocus profile in the home environment within the para‐central field of view is associated with childhood refractive error development.

Association of Myopia with cognitive function among one million adolescents

BACKGROUND

Myopia is a leading cause of visual impairment worldwide, and its increasing incidence is of public health concern. Cognitive function was associated with myopia among children, but evidence for adolescents is scarce. The purpose of this study was to determine whether myopia is associated with cognitive function, and which cognitive ability, verbal or non-verbal, is involved.

METHODS

We conducted a population-based cross-sectional study of 1,022,425 Israeli candidates for military service aged 16.5-18 years. Participants underwent a comprehensive battery of tests assessing verbal and non-verbal intelligence, which yields a summarized cognitive function score (CFS). In addition, subjective visual acuity examination followed by objective non-cycloplegic refraction was carried out for each participant. Association between myopia and cognitive function was evaluated by multivariable logistic regression models adjusted for gender, age, country of origin, socioeconomic status, years of education, body mass index, height and year of examination.

RESULTS

Compared to the intermediate CFS of the entire cohort, participants who had the highest CFS had 1.85-fold (95% CI, 1.81 to 1.89; P < .001) higher odds of having myopia and 2.73-fold (95% CI, 2.58 to 2.88; P < .001) higher odds of high myopia, while participants with the lowest CFS had 0.59-fold (95% CI, 0.57 to 0.61, P < .001) lower odds of having myopia. The verbal components of the cognitive function assessment had stronger associations with myopia than the non-verbal components (P < .001, for all).

CONCLUSIONS

Cognitive function, especially verbal intelligence, is strongly and consistently associated with myopia among adolescents.

Objectively measured near work, outdoor exposure and myopia in children

Aim

To reassess the association between near work, outdoor exposure and myopia in children through an objective approach.

Methods

Eighty-six children (10.13±0.48 years) were asked to wear Clouclip, a newly developed wearable device that is able to measure working distance and eye-level illuminance, for a complete week to obtain information on near work and outdoor exposure. The mean daily Clouclip wearing time was 11.72±1.14 hour. The spherical equivalent refraction was determined by cycloplegic autorefraction.

Results

The myopic children were found to be exposed to light intensities >3000 lux (0.68±0.50 hour vs 1.02±0.53 hour, p=0.012) and >5000 lux (0.42±0.35 hour vs 0.63±0.31 hour, p=0.004) for shorter durations on average each day than the non-myopic children. Additionally, the myopic children spent more time on average each day on activities at a distance of <20 cm than non-myopic children (1.89±0.61 hour vs 1.52±0.77 hour, p=0.019). In the multivariate logistic analysis, the time spent with a higher light intensity (>3000 lux (OR=0.27, 95% CI: 0.10 to 0.72, p=0.009); >5000 lux (OR=0.11, 95% CI: 0.02 to 0.56, p=0.008)) and a working distance of <20 cm (in a circumstance of >3000 lux (OR=1.17, 95% CI: 1.09 to 1.86, p=0.038) or in that of >5000 lux (OR=1.12, 95% CI: 1.03 to 1.77, p=0.046)) were the independent protective factors and risk factors, respectively.

Conclusion

The current study provides novel evidence, based on objective data, to support the association between the intensity of near work, light intensity and myopia. However, the causality and the dose-effect relationship need to be investigated further.

A Serial Cross-Sectional Analysis of the Prevalence, Risk Factors and Geographic Variations of Reduced Visual Acuity in Primary and Secondary Students from 2000 to 2017 in Hong Kong

Background: We would like to investigate the prevalence trend, potential risk factors and geographic features of reduced visual acuity (VA) in primary and secondary schoolchildren of Hong Kong. Methods: This was a serial cross-sectional study using historical data of schoolchildren aged 6 to 15 years from the annual health checks conducted at Student Health Service Centers across Hong Kong, for the school years of 2000/2001 to 2016/2017. Results: The prevalence of reduced VA increased from 49.23% (95% CI, 48.99-49.47) in 2000/2001 to 54.34% (95% CI, 54.10-54.58) in 2011/2012 but decreased to 51.42% (95% CI, 51.17-51.66) in 2016/2017. Girls were less susceptible than boys at age 6-7 (and in grade primary 1-2), but more susceptible at older ages. The prevalence in junior grades increased while the risk effect of grade reduced over the past 17 years. Geographic variation on the risk for reduced VA existed and spatial autocorrelation was positive. The difference in prevalence of reduced VA between Hong Kong and mainland China has decreased in recent years. Cross-border students living in mainland China were associated with a lower risk for reduced VA. Conclusions: Further study was proposed to investigate the environmental association between students living in and outside Hong Kong with the prevalence of reduced VA. Multi-level research should also be conducted to investigate the influence of compositional and contextual factors on the prevalence of reduced VA.

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.

IMI - Interventions Myopia Institute: Interventions for Controlling Myopia Onset and Progression Report

Myopia has been predicted to affect approximately 50% of the world's population based on trending myopia prevalence figures. Critical to minimizing the associated adverse visual consequences of complicating ocular pathologies are interventions to prevent or delay the onset of myopia, slow its progression, and to address the problem of mechanical instability of highly myopic eyes. Although treatment approaches are growing in number, evidence of treatment efficacy is variable. This article reviews research behind such interventions under four categories: optical, pharmacological, environmental (behavioral), and surgical. In summarizing the evidence of efficacy, results from randomized controlled trials have been given most weight, although such data are very limited for some treatments. The overall conclusion of this review is that there are multiple avenues for intervention worthy of exploration in all categories, although in the case of optical, pharmacological, and behavioral interventions for preventing or slowing progression of myopia, treatment efficacy at an individual level appears quite variable, with no one treatment being 100% effective in all patients. Further research is critical to understanding the factors underlying such variability and underlying mechanisms, to guide recommendations for combined treatments. There is also room for research into novel treatment options.

Risk factors for high myopia: a 22-year follow-up study from childhood to adulthood

PURPOSE

To determine the effect of the definition of high myopia on its prevalence and risk factors for high myopia.

METHODS

A total of 240 myopic schoolchildren (119 boys and 121 girls) at the mean age of 10.9 years (range 8.8-12.8 years) were recruited to a randomized clinical trial of myopia treatment among children from 3rd- and 5th grades of school referred for an eye examination due to poor distant vision and having no previous spectacles. Clinical follow-ups, including refraction with cycloplegia, were conducted annually at 3 years [third follow-up here = clinical follow-up 1, (n = 237)], and thereafter twice at approximately 10-year intervals [clinical follow-ups 2 (n = 179) and 3, (n = 134)]. Additional refraction values between follow-ups 2 and 3 were received from ophthalmologists and opticians' prescriptions and records. The most recent adulthood refraction measure available was taken as the final refraction value for 204 (85%) of the original cohort [mean follow-up time (±standard deviation) 22.1 (±3.9) years]. Parental myopia, time spent on reading and close work, watching TV and outdoor activities were assessed with a questionnaire at the clinical follow-ups. The influence of different definitions of high myopia on its prevalence was analysed. The associations of different factors with high myopia were investigated.

RESULTS

Mean spherical equivalent (SE) at baseline was -1.43 (±0.60) D, ranging from -0.38 D to -3.00 D. At follow-up end, mean SE of the more myopic eye was -5.29 (±1.95) D, ranging from -1.00 D to -11.25 D. High myopia prevalence with the definitions SE < -6.00 D in the right eye and SE ≤ -6.00 D or ≤-5.00 D in either eye was 24%, 32% and 52%, respectively. In this study, high myopia was defined as spherical equivalent (SE) ≤ -6.00 D in either eye. If both parents were myopic, the odds ratio (OR) of having high myopia was 3.9 (95% CI: 1.5-10.4). Younger age at baseline predicted higher prevalence of high myopia; baseline ages between 8.8 and 9.7 and between 11.9 and 12.8 years gave prevalences 65% and 7%. Higher myopia at baseline, higher myopic progression between the first follow-ups and more time spent on reading and close work as compared with time spent outdoors were associated with high myopia.

CONCLUSION

About 32% of the children receiving first spectacles for myopia between ages of 8.8-12.8 years had high myopia (SE ≤ -6.00 D in either eye) in adulthood. Different definitions of high myopia ranging between -5 D and -6 D lead to large differences in prevalence. A generally accepted definition of high myopia is thus needed. Parental myopia, age at baseline, myopic progression during the first post onset year, and more time spent on reading and close work and less on outdoor activities in childhood were associated with adulthood high myopia.

Role of Gender in the Prevalence of Myopia among Polish Schoolchildren

Purpose

The aim of the paper was to study the role of gender in the progression of myopia among Polish schoolchildren.

Materials and Methods

4875 children from elementary schools and high schools were examined (2470 boys, aged 6–16 years, mean age 11.0, SD = 2.6 and 2405 girls, aged 6–16 years, mean age 11.1, SD = 2.6). The examined students were Caucasian and resided in and around Szczecin, Poland. The examination included retinoscopy under cycloplegia. The refractive error readings were reported as spherical equivalent (SE). Myopia was defined as SE of at least −0.5 D. Data analysis was performed using the Mann–Whitney U test and 2-sided Fisher's exact test. p values of less than 0.05 were considered statistically significant.

Results

It was found that the SE among Polish boys is similar to the SE among Polish girls before the age of 9 years. However, in older children, lower SE values and higher prevalence of myopia were found among girls than boys, both at 9–13 years range (0.45 ± 1.05 vs 0.55 ± 1.23 D, p=0.047 and 8.30% vs 5.71%, p=0.015, respectively) and at 13–16 years range (0.32 ± 1.14 vs 0.54 ± 1.08 D,  p=0.0093 and 10.37% vs 5.96%, p=0.0050), respectively.

Conclusions

Gender is associated with the prevalence of myopia among Polish schoolchildren ranging from 9 to 16 years of age.

Novel Method of Remotely Monitoring the Face-Device Distance and Face Illuminance Using Mobile Devices: A Pilot Study

Specially developed software (app) was written for handheld electronic devices that uses the device camera and light detector for real-time monitoring of near-work distance and environmental lighting. A pilot study of this novel app employed children using tablet computers in a classroom. Measurements of face-device distance and face illuminance were obtained from two schools where tablets were used regularly. Children were divided randomly into a control group (CG) and intervention group (IG). The app was calibrated in a lab and configured to store average values every 20 seconds in a remote database. In both groups, the app recorded data only when a child's face was present in the camera image. The app darkened the screen for the IG when the face-device distance was shorter than 40 cm. The total mean face-device distance was 36.8 ± 5.7 cm in CG and 47.2 ± 6.5 cm in IG. Children in IG had to accommodate approximately 0.6 D less when using their devices. The mean classroom face illuminance was 980 ± 350 lux in School #1 and 750 ± 400 lux in School #2. The novel method of remotely monitoring and controlling the face-device distance and illuminance can potentially open new paths for myopia prevention and myopia control.

Electronic devices and myopic refraction among children aged 6-14 years in urban areas of Tianjin, China

PURPOSE

To assess associations between different types of electronic devices, myopic refraction and ocular biometric parameters in children aged 6-14 years in urban areas of Tianjin, China.

METHODS

A school-based, cross-sectional study was performed on 566 children (302 boys and 264 girls). The children underwent a comprehensive eye examination, including cycloplegic autorefraction and ocular biometry. The children's parents completed a detailed questionnaire that included each child's demographics, the use of electronic devices and other related risk factors.

RESULTS

Myopia was not associated with time spent using various electronic devices. However, the mean spherical equivalent refraction (SER) decreased by 0.28 D (p = 0.042) and 0.33 D (p = 0.018) for each 1-h increase in the time spent using smart phones and computers, respectively. In the multiple linear regression analyses of factors associated with the SER, the standardised coefficient B for time spent reading and writing was approximately four to five times larger than the standardised coefficient for time spent using smart phones or computers. Time spent using tablets and watching television was not significantly associated with the SER. A longer axial length (AL) was associated with more time spent using smart phones (B = 0.23, p = 0.006) and computers (B = 0.26, p = 0.002) but not using tablets (p = 0.45) and watching television (p = 0.45). No significant association was found between other ocular biometric parameters and time spent using various electronic devices.

CONCLUSIONS

On average, a more myopic SER and longer AL were both associated with more time spent using smart phones and computers, but not with time spent using tablets and watching television. The magnitude of the association between SER and time spent reading and writing was a substantially larger than that for smart phone or computer use. Different types of electronic devices had differing levels of association with myopic refraction.

Continuous Objective Assessment of Near Work

Evidence regarding the role of near work in myopia is conflicting. We developed the RangeLife, a device for continuous, objective measurement of working distance. Four devices were built, calibrated, and validated. Then, adult subjects wore the device on weekdays and weekend days, while simultaneously wearing an actigraph device for objective measurements of light exposure and activity. Subjects maintained an activity log and answered a visual activity questionnaire. RangeLife data were downloaded and binned into 0.10 m intervals. Objective diopter hours (dh), a weighted measure of near work, were calculated. Diopter hours for all subjects were significantly higher on weekdays (14.73 ± 4.67 dh) compared to weekends (11.90 ± 4.84 dh, p = 0.05). 94 ± 1.85% of near and intermediate viewing distances were recorded when the subjects were exposed to mesopic and indoor photopic light levels (<1000 lux), and 80.03 ± 2.11% during periods of sedentary physical activity (<320 counts per minute). Subjective reports of time viewing near and intermediate distances significantly overestimated objective measures (p = 0.002). The RangeLife was shown to provide reliable measures of viewing distance, and can be further utilized to understand potential influences of viewing behaviors on refractive error.

Refractive Errors in University Students in Central China: The Anyang University Students Eye Study

Purpose

To assess the prevalence of refractive errors and associated factors in university students in urban areas of Anyang, Central China.

Methods

This is a cross-sectional university-based study of 16- to 26-year-old students in China. Subjects from two universities were invited to undergo a comprehensive eye examination. Cycloplegic refraction was acquired by autorefractor with two drops of 1% cyclopentolate. The prevalence of myopia, high myopia, hyperopia, astigmatism, and anisometropia was calculated. Only data from right eyes were included in analysis.

Results

A total of 7732 eligible subjects were included, with an average age of 20.2 ± 1.4 years. Overall, the mean spherical equivalent (SE) was -2.92 ± 2.48 diopters (D). The prevalence of myopia (SE ≤ -0.50 D), emmetropia, and hyperopia (SE ≥ +0.50 D) was 83.2%, 9.5%, and 7.3%, respectively. Female sex (OR = 1.542; P < 0.001) and science and engineering students (OR = 1.219; P = 0.004) were more likely to be myopic. The prevalence of high myopia, defined using SE ≤ -5.0 D, ≤ -6.0 D, and ≤ -10.0 D, respectively, occurred in 20.2%, 11.1 %, and 0.5%. High myopia (SE ≤ -6.0 D) was statistically associated with female sex (OR = 1.202; P = 0.029) and younger age (OR = 0.896; P = 0.001). The prevalence of astigmatism (cylinder of ≤ -0.75 D) was 28.8%. Astigmatism was associated with male sex (OR = 0.824; P = 0.001) and younger age (OR = 0.925; P = 0.001).

Conclusions

A prevalence of 83.2% for myopia and 11.1% for high myopia (SE ≤ -6.0 D) was found in central Chinese university students. In the future, this generation of university students may encounter long-term, vision-threatening effects, especially pathologic myopia.

Myopia is associated with education: Results from NHANES 1999-2008

Purpose

Myopia is increasing worldwide and possibly linked to education. In this study, we analyse the association of myopia and education in the U.S. and investigate its age-dependency.

Methods

We conducted a secondary data analysis using the public use files from the cross-sectional study National Health and Nutrition Examination Survey of the period from 1999 to 2008. 19,756 participants aged 20 to 85 years were included with data on education and ophthalmic parameters (distance visual acuity, objective refraction and keratometry). Spherical equivalent, astigmatism, corneal power and corneal astigmatism were evaluated for an association with education using linear regression analysis with adjustment of potential confounders.

Results

Analysis revealed an association between spherical equivalent and educational level in the univariate analysis (P < .001), and in the adjusted model (P < .001). Subjects who attend school to less than 9th grade had a mean spherical equivalent of 0.34 D, subjects with 9-11th grade -0.14 D, subjects that finished high school -0.33 D, subjects with partial college education -0.70 D, subjects that graduated from college or a higher formal education -1.22 D. Subjects that graduated from college or above were -1.47 D more myopic compared to subjects that completed less than 9^th grade school in the adjusted analyses. Astigmatism and corneal curvature was not associated with education.

Conclusions

Myopia is associated with higher education in the U.S. Our analysis shows that corneal curvature does not contribute to this association, therefore axial elongation or lens power are likely to contribute to myopia.

HOXA9 is a novel myopia risk gene

Purpose

A recent meta-analysis revealed PAX6 as a risk gene for myopia. There is a link between PAX6 and HOXA9. Furthermore, HOXA9 has been reported to activate TGF-β that is a risk factor for myopia. We speculate HOXA9 may participate in myopia development.

Methods

The Singapore GUSTO birth cohort provides data on children’s cycloplegic refraction measured at age of 3 years and their methylation profile based on the umbilical cord DNA. The HOXA9 expression levels were measured in the eyes of mono-ocular form deprivation myopia in mice. The plasmid with the mouse HOXA9 cDNA was constructed and then transfected to mouse primary retinal pigment epithelial (RPE) cells. The expression levels of myopia-related genes and cell proliferation were measured in the HOXA9-overexpressed RPE cells.

Results

A total of 519 children had data on methylation profile and cycloplegic refraction. The mean spherical equivalent refraction (SE) was 0.90D. Among 8 SE outliers (worse than -2D), 7 children had HOXA9 hypomethylation. The HOXA9 levels in the retina of myopic eyes was 2.65-fold (p = 0.029; paired t-test) higher than the uncovered fellow eyes. When HOXA9 was over-expressed in the RPE cells, TGF-β, MMP2, FGF2 and IGF1R expression levels were dose-dependently increased by HOXA9. However, over-expression of HOXA9 had no significant influence on IGF1 or HGF expression. In addition, HOXA9 also increased RPE proliferation.

Conclusion

Based on the human, animal and cellular data, the transcription factor HOXA9 may promote the expression of pro-myopia genes and RPE proliferation, which eventually contribute to myopia development.

Association of visual acuity with educational outcomes: a prospective cohort study

BACKGROUND/AIM

To quantify the impact of baseline presenting visual acuity (VA), refractive error and spectacles wear on subsequent academic performance among Chinese middle school children.

METHODS

A prospective, longitudinal, school-based study on grade 7 Chinese children (age, mean±SD, 12.7±0.5 years, range=11.1-15.9) at four randomly selected middle schools in Anyang, China. Comprehensive eye examinations including cycloplegic autorefraction were performed at baseline, and information on demographic characteristics, known risk factors for myopia and spectacle wear was collected. Academic test scores for all subjects in the curriculum were obtained from the local Bureau of Education. Main outcome measure was total test scores for five subjects at the end of grade 9, adjusted for total scored at the beginning of grade 7.

RESULTS

Among 2363 eligible children, 73.1% (1728/2363) had seventh grade test scores available. 93.9% (1623/1728) completed eye examinations, and 98.5% (1599/1623) of these had ninth grade test scores. Adjusting only for baseline test score, the following were significantly associated with higher ninth grade scores: younger age, male sex, less time outdoors, better baseline presenting VA, higher parental education and income and parental myopia, but refractive error and spectacle wear were not. In the full multivariate model, baseline test score (p<0.001), presenting VA (p<0.01), age (p<0.001), quality of life (p<0.05) and parental education (p<0.001) and myopia (either: p<0.05; both: p<0.05) remained significantly associated with better ninth grade scores.

CONCLUSIONS

In this longitudinal study, better presenting VA, but not cycloplegic refractive error or spectacle wear, was significantly associated with subsequent academic performance.

Genome-wide DNA hypermethylation and homocysteine increase a risk for myopia

AIM

To test for the association between genome-wide methylation and myopia in human and mice.

METHODS

Long interspersed nucleotide element 1 (LINE-1) methylation levels were used to surrogate genome-wide methylation level. We first tested for the association between high myopia (<-6 D) and LINE-1 methylation in leukocytes in 220 cases and 220 control subjects. Secondly, we validated the results of LINE-1 methylation in eyes from the form deprivation myopia (FDM) mice. Furthermore, we calculated the correlation of LINE-1 methylation levels between leukocyte DNA and ocular DNA in the mice. We also tested whether dopamine can alter LINE-1 methylation levels.

RESULTS

The LINE-1 methylation level was significantly higher in the myopic human subjects than controls. The upper and middle tertiles of the methylation levels increased an approximately 2-fold (P≤0.002) risk for myopia than the lower tertile. Similarly, FDM mice had high LINE-1 methylation levels in the leukocyte, retina and sclera, and furthermore the methylation levels detected from these three tissues were significantly correlated. Immunohistochemical staining revealed higher levels of homocysteine and methionine in the rodent myopic eyes than normal eyes. Dopamine treatment to the cells reduced both LINE-1 methylation and DNA methyltransferase levels.

CONCLUSION

LINE-1 hypermethylation may be associated with high myopia in human and mice. Homocysteine and methionine are accumulated in myopic eyes, which may provide excess methyl group for genome-wide methylation.

Retardation of Myopia Progression by Multifocal Soft Contact Lenses

Myopia is an important public health problem due to its prevalence and significant public health cost. Elevating levels of myopia increase the risk of vision impairment, and therefore, high myopia has become one of the main causes of untreatable vision loss throughout the world due to its irreversible complications. At present, many options for slowing progression of myopia have already been proposed and evaluated such as progressive addition of executive bifocal spectacle lenses, peripheral defocusing lenses, overnight orthokeratology, pharmacological agents such as atropine eye drops, and multifocal soft contact lenses (MFSCLs). Use of MFSCLs has especially increased in recent years due to the growing demand to slow myopia progression during patient's adolescent growth period to avoid pathological myopia in adulthood. Compared with the other traditional methods of controlling myopia, MFSCLs allow myopic patients to better maintain their clear visual quality and slow myopia progression. In this manuscript, we aim to review the basics of myopia, recent advances in contact lenses to control myopia with emphasis on MFSCLs, define the elements for proper MFSCL fittings (such as pupil size, aberrations, accommodation and centering), discuss the potential rebound effect after discontinuation of contact lenses, and future directions for improvements of contact lenses for the control of myopia.

A Review of Current Concepts of the Etiology and Treatment of Myopia

Myopia occurs in more than 50% of the population in many industrialized countries and is expected to increase; complications associated with axial elongation from myopia are the sixth leading cause of blindness. Thus, understanding its etiology, epidemiology, and the results of various treatment regiments may modify current care and result in a reduction in morbidity from progressive myopia. This rapid increase cannot be explained by genetics alone. Current animal and human research demonstrates that myopia development is a result of the interplay between genetic and the environmental factors. The prevalence of myopia is higher in individuals whose both parents are myopic, suggesting that genetic factors are clearly involved in myopia development. At the same time, population studies suggest that development of myopia is associated with education and the amount time spent doing near work; hence, activities increase the exposure to optical blur. Recently, there has been an increase in efforts to slow the progression of myopia because of its relationship to the development of serious pathological conditions such as macular degeneration, retinal detachments, glaucoma, and cataracts. We reviewed meta-analysis and other of current treatments that include: atropine, progressive addition spectacle lenses, orthokeratology, and multifocal contact lenses.

Breastfeeding and myopia: A cross-sectional study of children aged 6-12 years in Tianjin, China

This study aimed to determine whether an association existed between breastfeeding and myopia in children aged 6-12 years in Tianjin, China, using a cross-sectional study of 527 children. The spherical equivalent refraction (SER) and axial length (AL) were determined by ocular examination, and information regarding the children's demographics, breastfeeding history and other myopia-related risk factors were investigated using a questionnaire. The myopia prevalence rate, mean SER, and mean AL were 53.9%, -0.99 ± 1.69 D, and 23.56 ± 1.11 mm, respectively. In total, 442 (83.9%) participants were breastfed; among the breastfed participants, 132 (29.9%) were breastfed <6 months. Children who were breastfed were less likely to have myopia (breastfeeding duration <6 months: OR = 0.399, P = 0.011; >6 months: OR = 0.502, P = 0.033, multiple logistical regression). The mean SER of children breastfed <6 months was 0.653 D more hyperopic than that of non-breastfed children (P = 0.008, multiple linear regression). No significant association was observed between breastfeeding and AL. In conclusion, breastfeeding was associated with a decreased risk of myopia among children aged 6-12 years in Tianjin. Breastfeeding during the first 6 months of infancy was associated with more hyperopic SER. Furthermore, breastfeeding was associated with myopic refraction and was not related to AL, and this association could exist in childhood.

Early Intervention and Nonpharmacological Therapy of Myopia in Young Adults

Myopia is a condition of the eye where parallel rays focus in front of, instead of on, the retina, which results in excessive refractive power of the cornea or the lens or eyeball elongation. Studies carried out in recent years show that the etiology of myopia is complex with genetic and environmental factors playing a role. Refraction defects decrease the quality of vision, while progressing myopia can lead to partial loss of vision, which can be particularly dramatic in young adults. Therefore, it is so crucial to take appropriate actions aimed at preventing myopia progression. This is a review of nonpharmacological therapeutic possibilities of refraction defect prevention in young adults, with special regard to myofascial therapy, osteopathy, and massage of acupuncture points surrounding the eye.

Allergic Conjunctivitis-induced Retinal Inflammation Promotes Myopia Progression

Myopia is a highly prevalent eye disease. There is limited information suggesting a relationship between myopia and inflammation. We found children with allergic conjunctivitis (AC) had the highest adjusted odds ratio (1.75, 95% confidence interval [CI], 1.72-1.77) for myopia among the four allergic diseases. A cohort study was conducted and confirmed that children with AC had a higher incidence and subsequent risk of myopia (hazard ratio 2.35, 95%CI 2.29-2.40) compared to those without AC. Lower refractive error and longer axial length were observed in an AC animal model. Myopia progression was enhanced by tumor necrosis factor (TNF)-α or interleukin (IL)-6 administration, two cytokines secreted by mast cell degranulation. The TNF-α or IL-6 weakened the tight junction formed by corneal epithelial (CEP) cells and inflammatory cytokines across the layer of CEP cells, which increased the levels of TNF-α, IL-6, and IL-8 secreted by retinal pigment epithelial cells. The expression levels of TNF-α, IL-6, IL-8, monocyte chemoattractant protein-1, and nuclear factor kappa B were up-regulated in eyes with AC, whereas IL-10 and the inhibitor of kappa B were down-regulated. In conclusion, the experimental findings in mice corroborate the epidemiological data showing that allergic inflammation influences the development of myopia.

Prevalence and Related Factors for Myopia in School-Aged Children in Qingdao

Purpose

To investigate the prevalence and related factors for myopia in school-aged children in the Economic and Technological Development Zone of Qingdao, Eastern China.

Methods

A total of 4890 (aged 10 to 15 years) students were initially enrolled in this study. 3753 (76.75%) students with completed refractive error and questionnaire data were analyzed. The children underwent a comprehensive eye examination. Multiple logistic regression models were applied to assess possible factors associated with myopia.

Results

The prevalence of myopia increased as the children's grade increased (χ² = 560.584, P < 0.001). Low myopia was the main form of myopia in adolescent students (30.22%). With the growth of age, students spent significantly more time on near work (P = 0.03) and less time on outdoor activity (P < 0.001). In multivariate models, only the following variables were significantly associated with myopia: age, two myopic parents, outdoor activity time, and continuous near work without 5 min rest.

Conclusions

The prevalence of myopia increased as the grade increased. Age, two myopic parents, and continuous near work time without 5 min rest were risk factors for myopia. Outdoor activities had protective effect for myopia.

Refractive and ocular biometric profile of children with a history of laser treatment for retinopathy of prematurity

PURPOSE

Indian children belong to a diverse socioeconomic strata with retinopathy of prematurity (ROP) developing in mature, higher birth weight babies as well. The purpose of our study is to analyze the long-term status of refractive errors and its relationship with ocular biometry in children with ROP who were laser treated at a tertiary center in North India.

METHODS

Cross sectional study. Children (<16 years) enrolled from January 2014 to December 2014 with a history of laser treatment for ROP and examined for refractive and biometric status.

RESULTS

Thirty-six children presenting to us at the mean age of 7.37 ± 3.07 years (6-15 years) were included. Mean spherical equivalent (SE) was -4.05 D ± 5.10. 75% were myopic, with high astigmatism in 31%. Higher lens thickness (P = 0.03) and higher SE (P = 0.002) at 1 year postnatal age were predictors of larger SE. 79.4% achieved a favorable functional outcome (visual acuity ≥20/40). 5.88% achieved unsatisfactory outcome (<20/200) despite having a favorable structural outcome.

CONCLUSION

There are a substantial number of children who develop myopia and high astigmatism while undergoing laser treatment for ROP. We found myopia in our cohort to be lenticular and greater axial length contributing to the development of high myopia. An initial large refractive error predicts the future development of myopia in these children. Nearly 6% of patients with good structural outcome have unexplained subnormal vision. Our threshold for prescribing glasses in these children should be low.

The Influence of Environmental Factors on the Prevalence of Myopia in Poland

Purpose

In the paper, we describe and discuss the results of epidemiological studies concerning myopia carried out in Poland.

Materials and Methods

Results from the examination of 5601 Polish school children and students (2688 boys and 2913 girls) aged 6 to 18 years were analyzed. The mean age was 11.9 ± 3.2 years. Every examined student had undergone the following examinations: distance visual acuity testing, cover test, anterior segment evaluation, and cycloplegic retinoscopy after instillation of 1% tropicamide, and a questionnaire was taken.

Results

We have found that (1) intensive near work (writing, reading, and working on a computer) leads to a higher prevalence of myopia, (2) watching television does not influence the prevalence of myopia, and (3) being outdoors decreases the prevalence of myopia.

Conclusions

The results of our study point to insufficiency of accommodation contributing to the pathogenesis of myopia.

Near work, outdoor activity, and myopia in children in rural China: the Handan offspring myopia study

BACKGROUND

The near work and outdoor activity are the most important environmental risk factors for myopia. However, data from Chinese rural children are relatively rare and remain controversial. Therefore, the purpose of this study was to evaluate the relationship of both near work and outdoor activities with refractive error in rural children in China.

METHODS

In this cross-sectional study, 572 (65.1%) of 878 children (6-18 years of age) were included from the Handan Offspring Myopia Study (HOMS). Information from the parents on these children, as well as the parent's non-cycloplegic refraction, were obtained from the database of the Handan Eye Study conducted in the years 2006-2007. A comprehensive vision examination, including cycloplegic refraction, and a related questionnaire, were assessed on all children.

RESULTS

The overall time spent on near work and outdoor activity in the children was 4.8 ± 1.6 and 2.9 ± 1.4 h per day, respectively. Myopic children spent more time on near work (5.0 ± 1.7 h vs.4.7 ± 1.6 h, p = 0.049), while no significant difference was found in outdoor activity hours (2.8 ± 1.3 h vs. 3.0 ± 1.4 h, p = 0.38), as compared to non-myopic children. In the multiple logistic analysis, in general, no association between near work and myopia was found after adjusting for the children's age, gender, parental refractive error, parental educational level, and daily outdoor activity hours [odds ratio (OR), 95% confidence interval (CI): 1.10, 0.94-1.27]. However, a weak protective effect of the outdoor activity on myopia was found (OR, 95% CI: 0.82, 0.70-0.96), after adjusting for similar confounders.

CONCLUSIONS

In general, no association between near work and myopia was found, except for the high near work subgroup with moderate outdoor activity levels. A weak protective effect of outdoor activity on myopia in Chinese rural children was observed.

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

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.

Distribution and associations of intraocular pressure in 7- and 12-year-old Chinese children: The Anyang Childhood Eye Study

Purpose

To report the intraocular pressure (IOP) and its association with myopia and other factors in 7 and 12-year-old Chinese children.

Methods

All children participating in the Anyang Childhood Eye Study underwent non-contact tonometry as well as measurement of central corneal thickness (CCT), axial length, cycloplegic auto-refraction, blood pressure, height and weight. A questionnaire was used to collect other relevant information. Univariable and multivariable analysis were performed to determine the associations of IOP.

Results

A total of 2760 7-year-old children (95.4%) and 2198 12-year-old children (97.0%) were included. The mean IOP was 13.5±3.1 mmHg in the younger cohort and 15.8±3.5 mmHg in older children (P<0.0001). On multivariable analysis, higher IOP in the younger cohort was associated with female gender (standardized regression coefficient [SRC], 0.11, P<0.0001), increasing central corneal thickness (SRC, 0.39, P<0.0001), myopia (SRC, 0.05, P = 0.03), deep anterior chamber (SRC, 0.07, P<0.01), smaller waist (SRC, 0.07, P<0.01) and increasing mean arterial pressure (SRC, 0.13, P<0.0001). In the older cohort, higher IOP was again associated with female gender (SRC, 0.16, P<0.0001), increasing central corneal thickness (SRC, 0.43, P<0.0001), deep anterior chamber (SRC, 0.09, P<0.01), higher body mass index (SRC, 0.07, P = 0.04) and with increasing mean arterial pressure (SRC, 0.09, P = 0.01), age at which reading commenced (SRC, 0.10, P<0.01) and birth method (SRC, 0.09, P = 0.01), but not with myopia (SRC, 0.09, P = 0.20).

Conclusion

In Chinese children, higher IOP was associated with female gender, older age, thicker central cornea, deeper anterior chamber and higher mean arterial pressure. Higher body mass index, younger age at commencement of reading and being born of a caesarean section was also associated with higher IOP in adolescence.

Effect of Accommodation on Peripheral Eye Lengths of Emmetropes and Myopes

PURPOSE

To investigate the effect of accommodation on central and peripheral axial lengths in young adult emmetropes and myopes.

METHODS

On-axis and peripheral axial lengths were measured with the Haag-Streit Lenstar in 83 young adult participants for 0D and 6D accommodation demands. A Badal system was used to both correct refractive errors and induce accommodation. Participants were emmetropes (n = 29, mean spherical equivalent refraction +0.35 ± 0.35D), low myopes (32, -1.38 ± 0.73D), and higher myopes (22, -4.30 ± 0.73D). Ages were similar for all groups (22 ± 2 years). Pupils were dilated with 2.5% phenylephrine to allow a large field of measurement while maintaining active accommodation. Axial lengths were measured in 5° steps to ±30° across the horizontal visual field.

RESULTS

With accommodation, axial length increased for all refractive groups at all positions, but with lessening effect away from fixation. Axial length changes were greater for higher myopes than for emmetropes on-axis (higher myopes 41 ± 14 μm, emmetropes 30 ± 12 μm, P = .005), for higher myopes than for low myopes at 30° nasal (P = .03), and for the higher myopes than for the other groups at 20° nasal (P < .05). There were significant correlations between myopia and changes in axial length at all positions, with the highest correlation on-axis (R = 0.30, P < .001).

CONCLUSIONS

During accommodation, eye length increased out to at least ±30° visual angle in young adult myopes and emmetropes. The increase was significantly greater for higher myopes than for the other groups at some positions. At all positions, there were significant correlations between myopia and accommodation-induced changes in axial length.

Time Outdoors at Specific Ages During Early Childhood and the Risk of Incident Myopia

Purpose

Time outdoors during childhood is negatively associated with incident myopia. Consequently, additional time outdoors has been suggested as a public health intervention to reduce the prevalence of myopia. We investigated whether there were specific ages during early childhood when the time outdoors versus incident myopia association was strongest.

Methods

Children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) were studied from age 2 to 15 years. Parentally reported time outdoors and time spent reading were assessed longitudinally in early childhood (ages 2, 3, 4, 5, 7, and 9 years). Noncycloplegic autorefraction was carried out longitudinally in later childhood (ages 10, 11, 12, and 15 years). Information was available for 2833 participants. Cox proportional hazards regression was used to test for association between time outdoors and incident myopia.

Results

From 3 years of age onward, greater time outdoors was associated with a reduced risk of incident myopia. The hazard ratio for myopia changed progressively from 0.90 (95% CI 0.83–0.98, P = 0.012) at age 3 years, to 0.86 (95% CI 0.78–0.93, P = 0.001) at age 9 years, for each additional SD of time spent outdoors per day. These associations were independent of two major risk factors for myopia: time reading and number of myopic parents.

Conclusions

Additional time spent outdoors across the 3 to 9 years age range was associated with a reduced incidence of myopia between ages 10 and 15 years. There was a trend for the association to increase toward the older end of the 3 to 9 years range.