Education, reading, and familial tendency as risk factors for myopia in Hong Kong fishermen

Myopia and Near Work: A Systematic Review and Meta-Analysis

BACKGROUND

Myopia is a global public health problem affecting quality of life and work productivity. Data is scarce regarding the effects of near work on myopia. Providing a larger meta-analysis with life-long perspective, including adults and occupational exposure seemed needed.

METHODS

We searched PubMed, Cochrane Library, Embase and Science Direct for studies reporting myopia prevalence in near work. Myopia was defined as a mean spherical equivalent ≤ -0.50 diopter. We performed a meta-analysis using random-effects model on myopia prevalence, myopia progression per year, and odds ratio (OR) of myopia in near work, completed by subgroup analyses and meta-regressions on patients' characteristics, type of work in adults, geographic zones, time and characteristics of near work.

RESULTS

We included 78 studies, representing a total of 254,037 participants, aged from 6 to 39 years. The global prevalence of myopia in near work was 35% (95% CI: 30 to 41%), with a prevalence of 31% (95% CI: 26 to 37%) in children and 46% (95% CI: 30 to 62%) in adults. Myopia progression was -0.39 diopters per year (-0.53 to -0.24 D/year), ranging from -0.44 (-0.57 to -0.31) in children to -0.25 D/year (-0.56 to 0.06) in adults. The odds of myopia in workers exposed vs. non-exposed to near work were increased by 26% (18 to 34%), by 31% (21 to 42%) in children and 21% (6 to 35%) in adults. Prevalence of myopia was higher in adults compared to children (Coefficient 0.15, 95% CI: 0.03 to 0.27).

CONCLUSIONS

Near work conditions, including occupational exposure in adults, could be associated with myopia. Targeted prevention should be implemented in the workplace.

Children in Tokyo Have a Long Sustained Axial Length from Age 3 Years: The Tokyo Myopia Study

Background: myopia prevalence is high among Japanese schoolchildren, but the underlying causes are unclear. Objective: To examine the distributions of ocular biometry and refraction and their associations with lifestyle variables among Japanese schoolchildren. Methods: This cross-sectional school-based study included 2140 children aged 3−14 years in Tokyo, Japan, and evaluated the distributions under non-cycloplegic conditions and the associated environmental factors. Results: The prevalence of spherical equivalent (SE) ≤−0.75 diopter among preschoolers (aged 3−6 years), elementary school students (aged 6−11 years), and junior high school students (aged 12−14 years) was 49.7%, 72.4%, and 87.7%, respectively. Multiple linear regression analyses showed that the time spent using digital devices was associated positively with lens thickness (β = 0.010; p < 0.050) but not SE, axial length, or vitreous chamber depth. The time spent reading was associated negatively with lens thickness (β = −0.012; p < 0.050), SE (β = −0.152; p < 0.010), axial length (β = 0.110; p < 0.001), and vitreous chamber depth (β = 0.110; p < 0.001). Conclusions: The data indicated that almost half of preschoolers may be myopic. The association with the lens thickness differed depending on the type of near work performed.

Impact of online classes and home confinement on myopia progression in children during COVID-19 pandemic: Digital eye strain among kids (DESK) study 4

Purpose

This study was performed to compare the rate of progression of myopia before and during the COVID-19 pandemic and to assess the risk factors of hastened progression.

Methods

All children with myopia of spherical equivalence ≤ -0.5 D with at least two prior documented refractions 6 months and 1 year before were included. The annual progression rate before COVID-19 and during COVID-19 was calculated. Annual myopia progression was categorized as no progression (0), slow progression (<1 D), and fast progression (≥1 D).

Results

A total of 133 children (266 eyes) aged 6-18 years were included in the study. Mean annual myopia progression was found to be statistically significant during COVID-19 as compared with pre-COVID-19 (0.90 vs 0.25 D, P < 0.00001). A total of 45.9% of children showed an annual progression of ≥1 D during the pandemic as compared with 10.5% before the COVID-19 (p < 0.00001). In multivariate analysis, history of rapid progression in pre-COVID-19 era (P = 0.002) and sun exposure <1 h/day (P < 0.00001) were found to be independent risk factors for rapid myopia progression.

Conclusion

Parents should consider risk of rapid myopia progression in children during current pandemic and children should be provided with socially distant outdoor activities to increase their sun exposure and diminish the rate of myopia progression.

Short-term Comparison of Refractive Errors between Two Different Age Groups after LASEK for Moderate Myopia

Purpose: To investigate the safety of laser epithelial keratomileusis (LASEK) by drawing a comparison between two groups divided according to age (18-19 vs. 20-21 years old).Methods: The study was conducted as a retrospective analysis including 339 patients (678 eyes) who underwent LASEK between January 2017 and April 2020. Patients were divided by age group, group I (18-19 years old) and group II (20-21 years old). The objectives of the study included determination of visual acuity and refractive errors before and at 1, 3, and 6 months after the procedure.Results: The preoperative mean spherical equivalents (SEs) were -4.73 ± 0.88 diopters (D) in group I and -4.58 ± 0.87 D in group II (<i>p</i> = 0.34). At 1 month postoperatively, mean SEs were 0.32 ± 0.46 D in group I and 0.26 ± 0.59 D in group II (<i>p</i> = 0.18). At 3 months postoperatively, the mean SEs were 0.30 ± 0.47 D in group I and 0.28 ± 0.50 D in group II (<i>p</i> = 0.67). At 6 months postoperatively, the mean SEs were 0.15 ± 0.47 D in group I and 0.14 ± 0.50 D in group II (<i>p</i> = 0.89). There were no significant differences in postoperative best corrected visual acuity between group I and group II at 1, 3, or 6 months (<i>p</i> = 0.20, <i>p</i> = 0.13, and <i>p</i> = 0.11, respectively).Conclusions: There were no significant differences in postoperative mean SE or safety of LASEK between moderate myopia patients 18-19 years old and those 20-21 years old.

A synopsis of the prevalence rates and environmental risk factors for myopia

The prevalence rates of myopia are higher in urban Asian cities such as Hong Kong and Singapore. One observation over the past few decades is that the prevalence rates of myopia have been rising and there is an epidemic of myopia in Asia. The age-old question of the roles of nature and nurture in this process remains unanswered. The strongest evidence for an environmental link to myopia is near work activity. Childhood exposure to night lighting has also been explored in different studies but the results have been mixed. Twin studies, segregation analysis and association studies have demonstrated that hereditary factors play an important role in myopia development. The exact nature and interplay of genetic and environmental factors is not known and data suggest that environmental factors may interact with genetic factors to increase the risks of developing myopia. Future research is needed to identify specific modifiable lifestyle factors and genetic markers for myopia. This will enable preventive measures such as health education to be instituted.

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.

The measurement of time spent outdoors in child myopia research: a systematic review

The purpose of this article is to summarize the methods most commonly used to measure time spent outdoors and provide a comprehensive review of time and activity recording methods with the aim of encouraging the development of new methods. PubMed, Embase and the Cochrane Library were searched from Jan. 1^st, 1990 to Aug. 31^th, 2017. Studies including the following specific terms: "outdoor", "outside", "outdoor activity", "outside activity", "outdoor time", "outside time", and "outdoor AND measurement of time spent outdoors" were considered for this review. In total, three kinds of outdoor time measurements were discussed. Questionnaires have the longest history and are the most thoroughly revised instruments for assessing time spent outdoors, but recall bias is their most substantial drawback. Global positioning system (GPS) tracking can distinguish between indoor and outdoor locations, but its utility is limited due to several factors such as subject compatibility. Light exposure measurement devices are newly emerging, but all of these devices require good subject cooperation. Further efforts and exploration are needed to develop better methods and new tools to record exposure to the outdoors in real time. Moreover, inventing a new device by combining two or more types of devices mentioned above and using the latest technology of en ergy supplementation and autoswitching may make the best use of the advantages and bypass the disadvantages of each tool.

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.

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.

Bio-environmental factors associated with myopia: An updated review

Experimental studies in animals, as well as observational and intervention studies in humans, seem to support the premise that the development of juvenile myopia is promoted by a combination of the effect of genetic and environmental factors, with a complex interaction between them. The very rapid increase in myopia rates in some parts of the world, such as Southeast Asia, supports a significant environmental effect. Several lines of evidence suggest that humans might respond to various external factors, such as increased activity in near vision, increased educational pressure, decreased exposure to sunlight outdoors, dietary changes (including increased intake of carbohydrates), as well as low light levels indoors. All these factors could be associated with a higher prevalence of myopia.

Meta-analysis of gene-environment-wide association scans accounting for education level identifies additional loci for refractive error

Myopia is the most common human eye disorder and it results from complex genetic and environmental causes. The rapidly increasing prevalence of myopia poses a major public health challenge. Here, the CREAM consortium performs a joint meta-analysis to test single-nucleotide polymorphism (SNP) main effects and SNP × education interaction effects on refractive error in 40,036 adults from 25 studies of European ancestry and 10,315 adults from 9 studies of Asian ancestry. In European ancestry individuals, we identify six novel loci (FAM150B-ACP1, LINC00340, FBN1, DIS3L-MAP2K1, ARID2-SNAT1 and SLC14A2) associated with refractive error. In Asian populations, three genome-wide significant loci AREG, GABRR1 and PDE10A also exhibit strong interactions with education (P<8.5 × 10(-5)), whereas the interactions are less evident in Europeans. The discovery of these loci represents an important advance in understanding how gene and environment interactions contribute to the heterogeneity of myopia.

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.

Topical Atropine in the Control of Myopia

Atropine has been used for more than a century to arrest myopia progression. Compelling evidence of its protective effect has been reported in well-designed clinical studies, mainly performed during the last two decades. However, its exact mechanism of action has not been determined. Experimental findings have shown that the mechanism is not related to accommodation, as was thought for decades. A review of the published literature revealed a significant amount of evidence supporting its safety and efficacy at a concentration of 1.0%, and at lower concentrations (as low as 0.01%).

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

Purpose

To examine the associations of near work related parameters with spherical equivalent refraction and axial length in Chinese children.

Methods

A total of 1770 grade 7 students with mean age of 12.7 years were examined with cycloplegic autorefraction and axial length. Questions were asked regarding time spent in near work and outdoors per day, and near work related parameters.

Results

Multivariate models revealed the following associations with greater odds of myopia: continuous reading (> 45min), odds ratio [OR], 1.4; 95% confidence interval [CI], 1.1-1.8; close television viewing distance (≤ 3m), OR, 1.7; 95% CI, 1.2-2.3; head tilt when writing, OR, 1.3; 95% CI, 1.1-1.7, and desk lighting using fluorescent vs. incandescent lamp, OR, 1.5; 95% CI, 1.2-2.0. These factors, together with close reading distance and close nib-to-fingertip distance were significantly associated with greater myopia (P<0.01). Among near work activities, only reading more books for pleasure was significantly associated with greater myopia (P=0.03). Television viewing distance (≤ 3 m), fluorescent desk light, close reading distance (≤20 cm) and close nib-to-fingertip distance (≤ 2 cm) were significantly associated with longer axial length (P<0.01). Reading distance, desk light, and reading books for pleasure had significant interaction effects with parental myopia.

Conclusions

Continuous reading, close distances of reading, television viewing and nib-to-fingertip, head tilt when writing, reading more books for pleasure and use of fluorescent desk light were significantly associated with myopia in 12-year-old Chinese children, which indicates that visual behaviors and environments may be important factors mediating the effects of near work on myopia.

Refractive error among urban preschool children in Xuzhou, China

The prevalence of refractive errors in urban preschool children in Xuzhou, China remains unknown. Children attending twelve randomly selected kindergartens participated in this study. Visual acuity, ocular alignment, cover-uncover test, cycloplegic refraction, slit-lamp and funduscopy were performed under a standardized testing environment. Cycloplegic streak retinoscopy was performed for all subjects. The mean spherical equivalent (SE) refractive error was the main outcome measure. Emmetropia was defined as refractive status between +1.75 diopters (D) and -0.75D. Myopia, hyperopia, astigmatism and anisometropia were defined as SE < -0.50D, SE > +2.0 D, cylindrical error > 1.0 D and SE difference ≥ 1 D between fellow eyes, respectively. Out of 2349 eligible children, 2255 (96%) children completed a refractive examination. Of the 2255 children, the mean SE of right eyes was +1.14 ± 0.95 diopters (D). Mean SE of the right eyes did not decline with age (r = -0.01; P = 0.56). The majority (86.6%) of children were emmetropia. The prevalence of myopia and hyperopia was 0.9% and 14.3%, respectively. The mean astigmatism for the right eyes was 0.87 ± 0.62 D. The prevalence of With-the-rule, against the rule and oblique astigmatism was 93.8%, 4.7% and 1.5%, respectively. The mean anisometropia between two eyes was 0.14 ± 0.38 D. The most common type of refractive error was hyperopia (14.3%), followed by astigmatism (8.8%), anisometropia (3.2%), and myopia (0.9%). The refractive status in this population of urban Xuzhou preschool children was stable and there was no evidence of a myopic refractive shift over this age range in our cross-sectional study.

Clinical prediction of the need for interventions for the control of myopia

The prevalence of myopia is increasing in Western populations but in East Asian countries, it is increasing to epidemic levels, where there are also markedly increased rates of progression to pathological myopia. Measures to more effectively control the development and progression of myopia are urgently needed. Notwithstanding a large volume of research, especially regarding the different mechanisms for the development of myopia and the efficacy of particular methods of intervention, there is still a great need and scope for improvements in clinical efforts to prevent and/or control myopic progression. Too often clinical efforts may involve only one method of intervention; however, the heterogenous nature of myopia suggests that clinical intervention may be more successful when interventions are employed in combination. The decision to prescribe interventions for the control of myopia in children, especially prior to onset, may be better framed by a comprehensive estimation of the degree of risk for the development and/or progression of myopia. For example, rather than ascribing equal weight to any degree of parental myopia, more accurate estimates may be obtained, if risk is judged to increase with the degree of parental myopia and the extent of any associated degenerative pathology. Risk estimates may be limited to broad mild, moderate and severe classifications due to lack of accurate weighting of risk factors. Nevertheless, comprehensive assessment of risk factors appears likely to better inform a prognosis and discussions with parents. Consideration of numerous environmental influences, for example, such as continuity and intensity of near work and time spent outdoors, may contribute to better risk estimation. Family-based practice appears to be ideally suited for risk estimation and the clinical application of approaches to control myopia. A proactive approach to estimating risk of developing myopia prior to its onset may be beneficial. Earlier implementation of interventions to control myopia could significantly reduce the chance of progression to pathological myopia.

The impact of intermittent exotropia and surgery for intermittent exotropia on myopic progression among early school-aged children with myopia

AIM

To investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early school-aged children (from 7 years to 12 years of age).

METHODS

Medical records of early school-aged patients with myopia were reviewed. Patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia when 7-12 years old; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Main outcome measurements were the simple rate of myopic progression per year, the preoperative and postoperative rates of refractive growth with regards to the logarithmic age model in Group A, and the rate of high myopia development at the end of the early school period.

RESULTS

The rates of myopic progression were -0.43±0.14 dioptre (D) per year in Group A, -0.49±0.17 D/year in Group B and -0.42±0.24 D/year in Group C. There was no significant difference in the rate of myopic progression among three groups. There was no significant intergroup difference in the preoperative and postoperative rates of refractive growth in Group A. There were no significant intergroup differences in the rates of high myopia development among three groups.

CONCLUSIONS

Whether patients with intermittent exotropia underwent surgical correction for intermittent exotropia did not influence the rate of myopic progression. There was no significant difference in the rate of myopic progression between patients with accompanying intermittent exotropia and myopia and those with myopia alone.

Education influences the association between genetic variants and refractive error: a meta-analysis of five Singapore studies

Refractive error is a complex ocular trait governed by both genetic and environmental factors and possibly their interplay. Thus far, data on the interaction between genetic variants and environmental risk factors for refractive errors are largely lacking. By using findings from recent genome-wide association studies, we investigated whether the main environmental factor, education, modifies the effect of 40 single nucleotide polymorphisms on refractive error among 8461 adults from five studies including ethnic Chinese, Malay and Indian residents of Singapore. Three genetic loci SHISA6-DNAH9, GJD2 and ZMAT4-SFRP1 exhibited a strong association with myopic refractive error in individuals with higher secondary or university education (SHISA6-DNAH9: rs2969180 A allele, β = -0.33 D, P = 3.6 × 10(-6); GJD2: rs524952 A allele, β = -0.31 D, P = 1.68 × 10(-5); ZMAT4-SFRP1: rs2137277 A allele, β = -0.47 D, P = 1.68 × 10(-4)), whereas the association at these loci was non-significant or of borderline significance in those with lower secondary education or below (P for interaction: 3.82 × 10(-3)-4.78 × 10(-4)). The evidence for interaction was strengthened when combining the genetic effects of these three loci (P for interaction = 4.40 × 10(-8)), and significant interactions with education were also observed for axial length and myopia. Our study shows that low level of education may attenuate the effect of risk alleles on myopia. These findings further underline the role of gene-environment interactions in the pathophysiology of myopia.

A New Community-Based Outdoor Intervention to Increase Physical Activity in Singapore Children: Findings from Focus Groups

Introduction: Myopia is a significant public health problem in Singapore with estimates that more than 50% of the population is affected by it by the time of adulthood. Childhood obesity is also increasing and has been linked to long-term health problems. Recent studies have found that Singaporean children in Primary 1 spend less than 3 hours a day outdoors which is less than children in other countries. Physical activity has been shown to be protective against obesity and recently, there has been some evidence to suggest that time spent outdoors may reduce the prevalence and severity of myopia. This study aims to explore the barriers and enablers to children in Singapore participating in outdoor activities. Materials and Methods: Qualitative data, gathered from focus group discussions was thematically analysed against the PRECEDE component of the PRECEDE-PROCEED model which provided a conceptual framework for examining factors relevant to children participating in an outdoor activity intervention. A total of 31 people participated in 4 focus groups held over a 6-month period. Results: This feasibility study was exploratory in nature but provided valuable information concerning barriers and enablers to participation. Data informed the development of a larger study. Conclusion: Results indicated that families preferred structured activities such as orienteering and a choice of weekend attendance days and times. Key words: Myopia, Physical activity, Qualitative research, Singapore

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

PURPOSE

To examine the risk factors for incident myopia in Australian schoolchildren.

DESIGN

Population-based, longitudinal cohort study.

PARTICIPANTS

The Sydney Adolescent Vascular and Eye Study (SAVES) was a 5- to 6-year follow-up of the Sydney Myopia Study (SMS). At follow-up, 2103 children were reexamined: 892 (50.5%) from the younger cohort and 1211 (51.5%) from the older cohort. Of these, 863 in the younger cohort and 1196 in the older cohort had complete refraction data.

METHODS

Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1; Canon, Tokyo, Japan) was measured at baseline and follow-up. Myopia was defined as a spherical equivalent refraction of ≤-0.50 diopters (D). Children were classified as having incident myopia if they were nonmyopic at baseline and myopic in either eye at follow-up. A comprehensive questionnaire determined the amount of time children spent outdoors and doing near work per week at baseline, as well as ethnicity, parental myopia, and socioeconomic status.

MAIN OUTCOME MEASURES

Incident myopia.

RESULTS

Children who became myopic spent less time outdoors compared with children who remained nonmyopic (younger cohort, 16.3 vs. 21.0 hours, respectively, P<0.0001; older cohort, 17.2 vs. 19.6 hours, respectively, P=0.001). Children who became myopic performed significantly more near work (19.4 vs. 17.6 hours; P=0.02) in the younger cohort, but not in the older cohort (P=0.06). Children with 1 or 2 parents who were myopic had greater odds of incident myopia (1 parent: odds ratio [OR], 3.2, 95% confidence interval [CI], 1.9-5.2; both parents: OR, 3.3, 95% CI, 1.6-6.8) in the younger but not the older cohort. Children of East Asian ethnicity had a higher incidence of myopia compared with children of European Caucasian ethnicity (both P<0.0001) and spent less time outdoors (both P<0.0001). A less hyperopic refraction at baseline was the most significant predictor of incident myopia. The addition of time outdoors, near work, parental myopia, and ethnicity to the model significantly improved the predictive power (P<0.0001) in the younger cohort but had little effect in the older cohort.

CONCLUSIONS

Time spent outdoors was negatively associated with incident myopia in both age cohorts. Near work and parental myopia were additional significant risk factors for myopia only in the younger cohort.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Variation in prevalence of myopia between generations of migrant indians living in Singapore

PURPOSE

To assess the influence of factors related to migration and acculturation on myopia in migrant Indians in Singapore.

DESIGN

Population-based cross-sectional study.

METHODS

A total of 3400 Singaporean Indians (75.6% response rate) aged over 40 years participated in this study. Information regarding country of birth, migration age, and language of interview were collected from interviews. Indians born outside of Singapore were defined as "first-generation" immigrants, while Indians born in Singapore were defined as "second-generation (or higher)" immigrants. Refraction was determined by autorefraction and refined by subjective refraction. Ocular biometry including axial length (AL), anterior chamber depth (ACD), and corneal radius (CR) were measured by partial coherence interferometry. Myopia and high myopia were defined as spherical equivalents (SE) of less than -0.5 diopter (D) for myopia, and < -5 D for high myopia, respectively.

RESULTS

The prevalence of myopia (30.2% vs 23.4 %) and high myopia (4.8% vs 2.5%) were higher in second-generation immigrants compared with first-generation immigrants. Second-generation immigrants had longer AL (23.50 mm vs 23.37 mm, P = .004) than first-generation immigrants after multivariate adjustment. The excess prevalence of myopia was reduced by 37.5% but remained statistically significant (P = .02) after further controlling for educational level. Among first-generation immigrants, those migrating to Singapore before the age of 21 had significantly higher prevalence of myopia (odds ratio [OR]: 1.85; 95% confidence interval [CI]: 1.32, 2.59) and longer AL (regression coefficient: 0.27; 95% CI: 0.11, 0.43) than those migrating after 21 years of age. Also, first-generation immigrants interviewed in English had higher prevalence of myopia (OR: 1.46; 95% CI: 1.00, 2.17) than their non-English-interviewed counterparts.

CONCLUSIONS

The prevalence of myopia among second-generation (or higher) Indian immigrants in Singapore is higher than first-generation immigrants. Country-specific environmental factors may be important for the increasing prevalence of myopia in Asia.

Refractive error in school children in an urban and rural setting in Cambodia

PURPOSE

To assess the prevalence of refractive error in schoolchildren aged 12-14 years in urban and rural settings in Cambodia's Phnom Penh and Kandal provinces.

METHODS

Ten schools from Phnom Penh Province and 26 schools from Kandal Province were randomly selected and surveyed in October 2010. Children were examined by teams of Australian and Cambodian optometrists, ophthalmic nurses and ophthalmologists who performed visual acuity (VA) testing and cycloplegic refraction.

RESULTS

A total of 5527 children were included in the study. The prevalence of uncorrected, presenting and best-corrected VA ≤ 6/12 in the better eye were 2.48% (95% confidence interval [CI] 2.02-2.83%), 1.90% (95% CI 1.52-2.24%) and 0.36% (95% CI 0.20-0.52%), respectively; 43 children presented with glasses whilst a total of 315 glasses were dispensed. The total prevalence of refractive error was 6.57% (95% CI 5.91-7.22%), but there was a significant difference between urban (13.7%, 95% CI 12.2-15.2%) and rural (2.5%, 95% CI 2.03-3.07%) schools (P < 0.0001). Refractive error accounted for 91.2% of visually impaired eyes, cataract for 1.7%, and other causes for 7.1%. Myopia (spherical equivalent ≤ -0.50 diopters [D] in either eye) was associated with increased age, female gender and urban schooling.

CONCLUSIONS

The prevalence of refractive error was significantly higher in urban Phnom Penh schools than rural schools in Kandal Province. The prevalence of refractive error, particularly myopia was relatively low compared to previous reports in Asia. The majority of children did not have appropriate correction with spectacles, highlighting the need for more effective screening and optical intervention.

School Myopia in Hong Kong

The short article is about school myopia in Hong Kong and the high prevalence rates of myopia in primary school children.

A novel instrument for logging nearwork distance

PURPOSE

To validate a novel ultrasonic sensor for logging reading distances. In addition, this device was used to compare the habitual reading distances between low and high myopes.

METHODS

First, the stability and sensitivity of the ultrasonic device were determined by repeated measures using artificial targets. Then, thirty Hong Kong Chinese (20-30 years) were recruited, of whom fifteen were considered to be high myopes (mean ± S.D. = -8.7 ± 0.5 D) and 15 to be low to non-myopes (mean ± S.D. = -2.0 ± 0.2 D). Each subject read a newspaper with their habitual visual aid continuously for 10 min in two sessions at their preferred working distance(s). The reading distances were recorded continuously using a novel nearwork analyzer. The modal working distance was considered as the 'habitual' reading distance. In addition, habitual reading distance was reported orally by each subject.

RESULTS

The nearwork analyzer gave accurate and repeatable measurements over a range of distances and angles. Using this instrument, high myopes were found to have a significantly shorter reading distance than low myopes or non-myopes (mean ± S.D. = 35.9 ± 9.8 cm vs 50.9 ± 24.8 cm; two-sample t-test, p = 0.04, df = 18). The reading distances reported orally by the subjects were not correlated with those recorded by the nearwork analyzer.

CONCLUSIONS

The nearwork analyzer was found to be an effective tool for measuring nearwork reading distance in a small group of emmetropic and myopic adults over a 10 min interval. Differences between the reading distance between high myopes and low/non-myopes was detected by the device. Further study is needed to determine if a closer working distance is a cause or effect of myopia development.

Effects of confined space and near vision stimulation on refractive status and vitreous chamber depth in adolescent rhesus monkeys

This study aimed to investigate the effects of sustained near vision stimulation, on the refractive development and elongation of the vitreous chamber in adolescent rhesus monkeys. A total of 12 adolescent rhesus monkeys (1.5-2.0 years old) were randomly assigned to 3 groups. In groups A (n=4) and B (n=4), monkeys were reared in close-vision cages for 8 and 4 h d(-1), respectively; tiny granules were added on the cage floor to avoid visual deprivation and to encourage near gaze. In group C (n=4), monkeys were reared in open-vision cages, with non-granule food as a control. Vitreous chamber depth, refractive status, and corneal refractive power were assessed over 18 months. Paired t-test was used to compare the differences and a P-value<0.05 was considered to be statistically significant. In group A, vitreous chamber depth and optical axis elongated significantly, and refractive error shifted towards myopia during the observation period. In group B, vitreous chambers and optical axis elongated but the refractive power did not show significant changes. In group C, there was no significant elongation in vitreous chambers and optical axis, and the refractive power changed slightly towards hypermetropia. There were no significant changes in corneal refractive power in each group. Sustained near vision can promote vitreous chamber growth and induce myopic shifts in refractive power in adolescent monkeys. Our results demonstrate the potential for a primate model of near-work-related myopia.

Refractive status and prevalence of refractive errors in suburban school-age children

OBJECTIVE

This study investigated the distribution pattern of refractive status and prevalence of refractive errors in school-age children in Western China to determine the possible environmental factors.

METHODS

A random sampling strategy in geographically defined clusters was used to identify children aged 6-15 years in Yongchuan, a socio-economically representative area in Western China. We carried out a door-to-door survey and actual eye examinations, including visual acuity measurements, stereopsis examination, anterior segment and eyeball movements, fundus examinations, and cycloplegic retinoscopy with 1% cyclopentolate.

RESULTS

A total of 3469 children living in 2552 households were selected, and 3070 were examined. The distributions of refractive status were positively-skewed for 6-8-year-olds, and negatively-skewed for 9-12 and 13-15-year-olds. The prevalence of hyperopia (≥+2.00 D spherical equivalent [SE]), myopia (≤-0.50 D SE), and astigmatism (≥1.00 diopter of cylinder [DC]) were 3.26%, 13.75%, and 3.75%, respectively. As children's ages increased, the prevalence rate of hyperopia decreased (P<0.001) and that of myopia increased significantly (P<0.001). Children in academically challenging schools had a higher risk of myopia (P<0.001) and astigmatism (≥1.00DC, P =0.04) than those in regular schools.

CONCLUSION

The distribution of refractive status changes gradually from positively-skewed to negatively-skewed distributions as age increases, with 9-year-old being the critical age for the changes. Environmental factors and study intensity influence the occurrence and development of myopia.

Estimation of heritability in myopic twin studies

PURPOSE

To examine the genetic and environmental factors for myopia at the family level, as well as risk factors such as ocular measurements and environmental covariates at the individual level, by analysis of myopic twin data.

METHODS

A myopic twin study was conducted on participants from the 2000 Guinness World Records for twins in Taiwan. A total of 130 participants comprising 58 twin pairs and 13 siblings were recruited. The generalized estimating equation approach was used to evaluate the covariate effects. A Bayesian linear mixed model was then used to estimate the heritability.

RESULTS

Pearson's intrapairwise correlation coefficients for ocular refraction and its components were higher among monozygotic twins than among dizygotic twins. The significance of sex suggested that women are more myopic than men. Both axial length and anterior chamber depth were significant factors associated with myopia. The results also showed that people with higher education levels were more likely to have a higher degree of myopia. After accounting for genetic and environmental effects and other covariates, the estimate of heritability of myopia was as high as 0.306.

CONCLUSIONS

After adjusting for environmental covariates, heritability still plays a decisive genetic role in the development of myopia.

Heritability analysis of spherical equivalent, axial length, corneal curvature, and anterior chamber depth in the Beaver Dam Eye Study

OBJECTIVE

To examine genetic influences for quantitative refraction. Spherical equivalent and its related binary traits of myopia and hyperopia are highly correlated within families. Many linkage regions have been reported for myopia, high myopia, and quantitative refraction. However, the measured phenotype of spherical equivalent is in large part dictated by the relationship between the underlying optical components of axial length, corneal curvature, and anterior chamber depth.

METHODS

Using data from the fourth visit of the Beaver Dam Eye Study, we conducted familial correlation and heritability analysis of quantitative spherical equivalent, axial length, anterior chamber depth, and corneal curvature using data from 715 individuals in 189 pedigrees.

RESULTS

Overall, every trait was highly heritable. Heritability estimates were 0.58 (SE 0.13) for spherical equivalent after adjustment for age, education, and nuclear sclerosis; 0.95 (SE 0.11) for corneal curvature after adjustment for height; 0.67 (SE 0.14) for axial length after adjustment for height and education; and 0.78 (SE 0.14) for anterior chamber depth after adjustment for age, education, height, and nuclear sclerosis.

CONCLUSION

Refraction and the underlying traits of axial length, corneal curvature, and anterior chamber depth are highly heritable. Genetic analysis of these traits may provide greater insight into the development of refractive errors.

Prevalence of refractive error in rural Myanmar: the Meiktila Eye Study

OBJECTIVE

To determine the prevalence of refractive error and associated risk factors in the Meiktila District of central rural Myanmar.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Randomized stratified cluster sampling of the inhabitants 40 years or older from villages in Meiktila was performed; 2481 eligible participants were identified, 2076 participated in the study, and adequate refractive data were obtained on 1863 individuals (75.1%).

METHODS

Demographic data including age, gender, and education level were obtained from all participants. The ophthalmic examination included autorefraction, nuclear opalescence (NO) grading at the slit lamp, and applanation tonometry.

MAIN OUTCOME MEASURES

Refractive errors were classified by type of ametropia and their prevalence was determined. Univariate and multivariate analyses were performed and odds ratios were calculated for the predictors of refractive error within the statistical models.

RESULTS

Mean refractive error measured -1.3 diopters (D) (standard deviation [SD], 2.9) and mean cylindrical error measured 1.1 D (SD, 1.5). Myopia of >-1.0 and >-6.0 D occurred in 42.7% (95% confidence interval [CI], 40.4%-44.9%) and 6.5% (95% CI, 5.4%-7.6%) of subjects, respectively. Myopic refractive error was associated significantly with a higher degree of NO (P<0.001) and age. Hypermetropia of >+1.0 D occurred in 15% (95% CI, 5.4%-7.6%) of the population and was associated with higher education levels (P<0.001). Astigmatism worse than 1.0 D occurred in 30.6% (95% CI, 28.5%-32.7%) of the population and was associated with age (P<0.001) and NO (P<0.001).

CONCLUSION

Myopia was more prevalent in older subjects and in those with increased NO. The prevalence rates of myopia in the > or =40 age group are higher than those found in other Asian regions and are likely to contribute to visual impairment.

Candidate gene and locus analysis of myopia

PURPOSE

A previous study has reported evidence of a strong linkage, but no association, between paired box gene 6 (PAX6) and myopia. We attempted to replicate these findings and to conduct a candidate gene and locus evaluation of genetic involvement in common forms of myopia.

METHODS

Samples were collected from 517 individuals in 123 families with a myopic child participating in the Orinda Longitudinal Study of Myopia or the Contact Lens and Myopia Progression Study. Myopia in the proband children was defined as -0.75 D or more and as being present in both meridians on cycloplegic autorefraction (1% tropicamide). Affected status in parents and siblings was determined by survey. After DNA was extracted from buccal mucosal cells and genotyped using assays for microsatellite markers and single nucleotide polymorphisms (SNPs), DNA was analyzed for linkage disequilibrium. Markers on chromosomes 12 and 18 were selected as regions previously associated with pathological myopia. SNPs were also analyzed in genes where their expression pattern or their association with syndromes conveys myopia as part of the phenotype (FGF2, BDNF, COL2A1, COL18A1, and PAX6).

RESULTS

The SNP rs1635529 for COL2A1 on 12q13.11 showed highly significant over-transmission to affected individuals (p=0.00007). No SNP for FGF2, BDNF, COL18A1, or PAX6 showed significant over-transmission to affected individuals after correction for multiple comparisons. Markers on chromosome 12 and 18 previously associated with pathological myopia also showed no significant associations with the more common form of myopia in this study.

CONCLUSIONS

As reported previously by others, PAX6 showed no association with myopia. Associations in the current analysis are suggestive of involvement of COL2A1. Future studies should focus on replication in other samples and in genome-wide approaches.

Evaluation of Accuracy in Proband-Reported Family History and Its Determinants: The Genes in Myopia Family Study

PURPOSE

Proband-reported family histories are widely used in epidemiological and genetic studies. The accuracy of these reports may have significant effects on the intended outcome, particularly in genetic studies. This study aims to determine the accuracy of proband-reported family history of myopia and to assess whether demographic or clinical factors are predictive of an accurate history.

METHODS

In 2004 to 2005, the study recruited 120 myopic probands (< or = -0.50 D spherical equivalent in both eyes) aged 18 to 72 years and 358 nuclear family members residing within Victoria, Australia as part of the Genes in Myopia (GEM) family study. Data collection used an examiner-administered questionnaire with an ocular examination. Proband-reported family history of myopia was evaluated for agreement with ophthalmic examination results of family members.

RESULTS

The statistical measures of accuracy used in this report were sensitivity, specificity, positive predictive value, and negative predictive value. Sensitivity varied from 85 to 98%, specificity from 84 to 96%, positive predictive value from 83 to 97%, and negative predictive value from 84 to 97%. Following multivariate analysis, an evaluation of demographic and clinical factors indicated that the highest predictive accuracy was obtained from proband reporting of their children [odds ratio (OR), 0.38; 95% confidence interval (CI), 0.15 to 0.94] whereas the most inaccurate reporting of a proband was when there was less-severe maternal myopia (per 0.50 D less myopic) (OR, 1.23; 95% CI, 1.06 to 1.43) or for increase in total education of the proband (per 1 year increase) (OR, 1.22; 95% CI, 1.04 to 1.42).

CONCLUSIONS

Several variables influence the accuracy of obtaining a family history of myopia. A questionnaire-based approach alone will introduce some error into the study and this should be taken into account when designing and undertaking family-based epidemiological or genetic studies of myopia.

Comparison of the experience sampling method and questionnaires to assess visual activities in pre-teen and adolescent children

AIM

A study was conducted to assess the feasibility of the experience sampling method (ESM) to quantify the daily visual tasks of children.

METHODS

Thirty-one children (9-14 years old, 39% male) were randomly paged after school (four times per day) and on weekends (eight times per day) for seven consecutive days. When paged, the children completed a voicemail survey regarding the nature, duration, working distance and type of visual correction worn during the activity. Responses of the subjects were grouped into 14 categories. Before beginning the paging, each child and one parent also reported, via survey, the number of hours and working distance for several visual activities.

RESULTS

The usable (complete voicemail responses) response rate was 87.1%. The most commonly reported activity category was watching television (17.8%). Other common responses included distance activities (12.5%), reading/studying (12.2%) and sports/outdoor activities (12.0%). Of the total number of responses, 25% were near work activities (reading/studying, computer use, near hobbies and playing Game Boy). The mean working distance (+/-S.D.) reported was 40.4 +/- 36.9 cm for reading/studying, 232.9 +/- 127.1 cm for watching television, 354.7 +/- 345.8 cm for distance activities and 438.5 +/- 421.0 cm for sports/outdoor activities. When comparing the ESM to surveys, the only significant difference was for the amount of time estimated to be spent in talking/conversation (p < 0.0001). No differences were found for any of the near work activities.

CONCLUSIONS

The ESM provides a feasible way to quantify daily near work tasks in children.

Corneal Optics after Reading, Microscopy and Computer Work

PURPOSE

To compare lid-induced changes in corneal optics following reading, microscopy and computer work.

METHODS

Nine subjects with normal ocular health were recruited for the study. Five subjects were myopic, two were emmetropic, one was astigmatic and one was hyperopic. Corneal topography was measured before and after 60 mins of reading a novel, performing a blood cell counting task on a microscope and Internet searching. Corneal topography data were used to derive the corneal wavefront Zernike coefficients up to the fourth order. A meridian analysis of instantaneous corneal power along the upper 90-degree semi-meridian was performed to examine local changes caused by eyelid pressure. Digital photography was used to capture body posture and eyelid position during the tasks.

RESULTS

Each of the three tasks showed systematically different effects on both the characteristics and location of corneal topography changes. Reading and microscopy generally exhibited larger and more centrally located changes compared with the computer task. Differences in wavefront aberration characteristics between the three tasks were apparent in both lower and higher order aberrations. The location of corneal distortions differed significantly between microscopy and computer work, with microscopy causing distortions to occur closer to the videokeratoscope measurement axis compared with computer work (p = 0.015).

CONCLUSIONS

Reading, microscopy and computer work have different effects on corneal aberrations. The results are in agreement with the hypothesis that lid-induced corneal aberrations may play a role in myopia development.

Determinants of myopia among Omani school children: a case-control study

BACKGROUND

Our aim was to determine risk factors for myopia in students of 10th grade of eight regions of Oman.

METHODS

This was a case control study. Students of 10th grade with and without myopia were cases and controls respectively. In 2002 to 2003, their vision, refractive status, and physical measurements were recorded. The health records of all students were reviewed for their ocular and physical status in the 7th grade. The association of myopia to anthropometric variables, "Protein Energy Malnourishment" status, gender, history of myopia in parents and sibling, trachoma, and allergic conjunctivitis were analyzed.

RESULTS

Myopia in students was significantly associated to myopia in parents [OR = 2.11 (95% CI 1.8-2.47)] and their siblings [OR = 2.87 (95% CI 2.45-3.35)]. Height was significantly higher in myopes compared to non-myopes both at the 10th and 7th grades. Weight and body mass index were greater in myopes than non-myopes only at 7th grade. Myopia in parents and siblings and female gender were predictors of myopia in the students.

CONCLUSIONS

Hereditary and anthropometric factors seem to be associated with myopia in Omani children. The genetic etiology needs further confirmation.

How genetic is school myopia?

Myopia is of diverse aetiology. A small proportion of myopia is clearly familial, generally early in onset and of high level, with defined chromosomal localisations and in some cases, causal genetic mutations. However, in economically developed societies, most myopia appears during childhood, particularly during the school years. The chromosomal localisations characterised so far for high familial myopia do not seem to be relevant to school myopia. Family correlations in refractive error and axial length are consistent with a genetic contribution to variations in school myopia, but potentially confound shared genes and shared environments. High heritability values are obtained from twin studies, but rest on contestable assumptions, and require further critical analysis, particularly in view of the low heritability values obtained from parent-offspring correlations where there has been rapid environmental change between generations. Since heritability is a population-specific parameter, the values obtained on twins cannot be extrapolated to define the genetic contribution to variation in the general population. In addition, high heritability sets no limit to the potential for environmentally induced change. There is in fact strong evidence for rapid, environmentally induced change in the prevalence of myopia, associated with increased education and urbanisation. These environmental impacts have been found in all major branches of the human family, defined in modern molecular terms, with the exception of the Pacific Islanders, where the evidence is too limited to draw conclusions. The idea that populations of East Asian origin have an intrinsically higher prevalence of myopia is not supported by the very low prevalence reported for them in rural areas, and by the high prevalence of myopia reported for Indians in Singapore. A propensity to develop myopia in "myopigenic" environments thus appears to be a common human characteristic. Overall, while there may be a small genetic contribution to school myopia, detectable under conditions of low environmental variation, environmental change appears to be the major factor increasing the prevalence of myopia around the world. There is, moreover, little evidence to support the idea that individuals or populations differ in their susceptibility to environmental risk factors.

Prevalence of myopia in local and international schools in Hong Kong

PURPOSE

This study aims to investigate genetic and environmental influences on physiological myopia by studying the difference in myopia prevalence between local schools and international schools in Hong Kong.

METHODS

Vision screening was carried out in local and international schools for students 13 to 15 years old. Types of refractive error were identified by visual acuity measurement, the presence of spectacles, a simple refraction, and the use of plus and minus ophthalmic lenses.

RESULTS

Three local schools and six international schools participated in the study. Two hundred eighty-nine students were from the local schools, and 789 students were from the international schools. Prevalence of myopia at the local schools ranged from 85 to 88%, whereas it ranged from 60 to 66% in the international schools. Students in the international schools were subdivided into Chinese origin, white, mixed Chinese, and Asian. Prevalence of myopia was highest in the Chinese group (82.8%) and lowest in the white group (40.5%). There was no age or gender difference in the prevalence of myopia.

CONCLUSIONS

Hong Kong Chinese students had a higher prevalence of myopia regardless of whether they studied in local or international schools when compared with other ethnic groups, such as whites. This further supports a genetic input into myopia development.

Use of the experience sampling method to measure nearwork

PURPOSE

The purpose of this study was to use the Experience Sampling Method (ESM) to evaluate the daily visual activities of a group of optometry students and to determine whether the ESM could detect differences in visual activities when a difference was thought to exist.

METHODS

Sixty-two optometry students, at four different levels of training, at The Ohio State University College of Optometry were tested using the ESM during a 14-day period. A subgroup of 18 subjects in their fourth year of study was asked to repeat the 14-day ESM on a second occasion. The two ESM periods were specifically chosen at times when the subjects were expected to have markedly different nearwork profiles.

RESULTS

A comparison of members from the four optometry classes when the fourth-year students were taking final written examinations showed no significant differences in the proportion of nearwork among groups (p = 0.170); however, when the fourth-year students were primarily performing eye examinations during clinical rotations, there was a significant difference in the proportion of nearwork among training levels (13.8% for fourth-year students compared with 24.9%, 23.7%, and 30.4% for the other optometry classes; p = 0.0001). The percentage of time spent doing nearwork and performing eye examinations was significantly different between two ESM periods (paired t-test, p = 0.0001 for each activity).

CONCLUSIONS

The ESM is capable of detecting differences in the proportion of time spent doing nearwork and performing eye examinations among groups of optometry students in different levels of training with different daily visual demands and between two ESM periods when these activities were expected to differ. The ESM can be used as an alternative method for nearwork quantification in future studies.

Prevalence of Myopia in a Group of Hong Kong Microscopists

PURPOSE

To study the prevalence and magnitude of myopia in a group of Hong Kong Chinese microscopists and compare it with that observed in microscopists working in the United Kingdom.

METHODS

Forty-seven microscopists (36 women and 11 men) with a median age of 31 years and working in hospital laboratories throughout Hong Kong were recruited to the study. Information about past refractive corrections, microscopy work, and visual symptoms associated with microscope use were collected. All subjects had a comprehensive eye examination at The Hong Kong Polytechnic University Optometry Clinic, including measures of refractive error (both noncycloplegic and cycloplegic), binocular vision functions, and axial length.

RESULTS

The prevalence of myopia in this group of microscopists was 87%, the mean (+/- SD) refractive error was -4.45 +/- 3.03 D and mean axial length was 25.13 +/- 1.52 mm. No correlation was found between refractive error and years spent working as a microscopist or number of hours per day spent performing microscopy. Subjects reporting myopia progression (N = 22) did not differ from the refractively stable group (N = 19) in terms of their microscopy working history, working hours, tonic accommodation level, or near phoria. However, the AC/A ratio of the progressing group was significantly greater than that of the stable group (4.59 delta/D cf. 3.34 delta/D).

CONCLUSION

The myopia prevalence of Hong Kong Chinese microscopists was higher than that of microscopists in the United Kingdom (87% cf. 71%), as well as the Hong Kong general population (87% cf. 70%). The average amount of myopia was also higher in the Hong Kong Chinese microscopists than the Hong Kong general population (-4.45 D cf. -3.00 D). We have confirmed that the microscopy task may slightly exacerbate myopia development in Chinese people.

Prevalence of refractive errors in teenage high school students in Singapore

We aimed to study the prevalence of refractive conditions in Singapore teenagers. Grade 9 and 10 students (n = 946) aged 15-19 years from two secondary schools in Singapore were recruited. The refractive errors of the students' eyes were measured using non-cycloplegic autorefraction. Sociodemographic data and information on risk factors for myopia (such as reading and writing) were also obtained using an interviewer-administered questionnaire. The prevalence of refractive conditions was found to be: myopia [spherical equivalent (SE) at least -0.50 D] - 73.9%, hyperopia (SE at least +0.50 D) - 1.5%, astigmatism (cylinder at least -0.50 D) - 58.7% and anisometropia (SE difference at least 1.00 D) - 11.2%. After adjusting for age and gender, currently doing more than 20.5 h of reading and writing a week was found to be positively associated with myopia [odds ratio 1.12 (95% CI 1.04-1.20, p = 0.003)], as was reading and writing at a close distance and a better educational stream. The prevalence of myopia (73.9%) in Singapore teenagers is high. Current reading and writing habits, reading at close distances and a better educational stream are possible risk factors for myopia.

Family history and reading habits in adult-onset myopia

PURPOSE

A retrospective study was developed to evaluate risk factors in adult-onset myopia.

METHODS

Subjects included were 25 to 35 years old. There were 116 non-myopic subjects in the control group and 66 myopic subjects with first lens prescription at age 17 or later. Subjects received a questionnaire about academic achievement, daily hours of reading during years of study, and family history of myopia.

RESULTS

The level of academic achievement was similar for myopic and non-myopic groups in this sample. Myopia was associated with family history (chi(2) = 6.131, p </= 0.013) and with daily hours of reading during years of study (chi(2) = 3.904, p </= 0.048). According to multiple logistic regression analysis, the correlation of myopia with family history adjusted for daily hours of reading remained significant (p </= 0.005), whereas the correlation with daily hours of reading adjusted for family history was not significant (p </= 0.061).

CONCLUSIONS

After multivariate analysis, adult-onset myopia was significantly associated only with family history of myopia.

An evolutionary analysis of the aetiology and pathogenesis of juvenile-onset myopia

The available evidence suggests that both genes and environment play a crucial role in the development of juvenile-onset myopia. When the human visual system is examined from an evolutionary perspective, it becomes apparent that humans, living in the original environmental niche for which our species is genetically adapted (as hunter-gatherers), are either slightly hypermetropic or emmetropic and rarely develop myopia. Myopia occurs when novel environmental conditions associated with modern civilization are introduced into the hunter-gatherer lifestyle. The excessive near work of reading is most frequently cited as the main environmental stressor underlying the development of myopia. In this review we point out how a previously unrecognized diet-related malady (chronic hyperinsulinaemia) may play a key role in the pathogenesis of juvenile-onset myopia because of its interaction with hormonal regulation of vitreal chamber growth.

Familial clustering and myopia progression in Singapore school children

BACKGROUND

Familial factors may be related to the progression of myopia in children. A cohort study was conducted to determine the relationship between familial factors and myopia progression in children.

METHODS

From a larger clinical trial (n = 311), 153 Singapore children aged 6--12 years were recruited to participate in a cohort study of the risk factors for myopia progression. An in-person interview was conducted whereby information on the history of myopia in first-degree relatives was obtained. Other information collected included housing type, parental education and income. Cycloplegic refractive error as measured by subjective refraction and autorefraction were ascertained every six months. The average length of follow-up was 28 months.

RESULTS

The adjusted mean rate of progression of myopia was -0.60 (95% confidence interval -0.66, -0.55) diopters per year. The average rate of progression of myopia for children with a parental history of myopia was -0.63 (95% confidence interval -0.69, -0.56) diopters per year compared to -0.42 (95% confidence interval -0.57, -0.27) diopters per year for children whose parents were not myopic. The different measures of family history of myopia were related to rate of change in refractive error and refractive error in the final visit. There was no association between close work and myopia progression.

CONCLUSIONS

A positive family history is related to the progression of myopia and final refractive error in Singapore children, thus supporting evidence that hereditary factors may play an important role in myopia progression.