Prevalence of myopia and hyperopia in a population of Polish schoolchildren

Risk Factors for Myopia: A Review

Due to the myopia prevalence increase worldwide, this study aims to establish the most relevant risk factors associated with its development and progression. A review search was carried out using PubMed, Web of Science, and Scopus databases to identify the main myopia risk factors. The inclusion criteria for the articles were those related to the topic, carried out in subjects from 5 to 30 years, published between January 2000 and May 2023, in English, and with the full text available. Myopia etiology has proven to be associated with both genetic and environmental factors as well as with gene-environment interaction. The risk of developing myopia increases in children with myopic parents (one parent ×2 times, two parents ×5 times). Regarding environmental factors, education is the main risk factor correlated with myopia prevalence increase. Further, several studies found that shorter distance (<30 cm) and longer time spent (>30 min) for near work increase the risk of myopia. Meanwhile, increased outdoor activity (>40 min/day) has been shown to be a key factor in reducing myopia incidence. In conclusion, the interventional strategy suggested so far to reduce myopia incidence is an increase in time outdoors and a reduction in the time spent performing near-work tasks.

Correlation between spherical equivalent and biometry parameters in adult Cynomolgus macaque

PURPOSE

To characterize the distribution of refractive and ocular biometry parameters and analyze the effect factors of the refractive status in cynomolgus monkey colonies.

METHODS

A Population-based cross-sectional study was conducted in adult cynomolgus macaque colonies. Animals were anesthetized with Zoletil 50. Intraocular pressure was measured using the Icare tonometer. Cycloplegic refraction (three drops of 1% tropicamide) and corneal radius of curvature (CRC) were measured using an autorefractor. The spherical equivalent (SE) was calculated. Biometric measurements, including the anterior chamber depth (ACD), lens thickness (LT), and axial length (AL), were obtained by A-scan ultrasonography. The AL-to-CR ratio (AL/CRC) was calculated. Central corneal thickness (CCT) and choroidal thickness (ChT) were measured using the Heidelberg Spectralis HRA OCT. Multiple regression analysis was performed to explore the association between refraction and ocular biometry.

RESULTS

Among 263 cynomolgus monkeys (aged 5-26 years), which consisted of 520 eyes, 29.42% had hyperopia, 27.12% had emmetropia, 33.27% had mild-to-moderate myopia and 10.19% had high myopia. The mean SE was -1.27 ± 3.44 Diopters (D). The mean CRC, CCT, AL, and ChT was 5.70 ± 0.22 mm, 454.30 ± 32.40 μm, 18.76 ± 0.89 mm and 188.96 ± 38.19 μm, respectively. The LT was the thickest in the hyperopic eyes. CRC was the lowest, and CCT was the thickest in high myopic eyes. AL increased, while ChT decreased as SE decreased. For the SE variance, AL alone explained 40.5%; age, AL, and CRC together explained 57.5%.

CONCLUSIONS

The refractive characteristics and biometry parameters of cynomolgus monkeys are highly comparable to those of humans. AL, CRC, and ChT showed the similar variation tendency in cynomolguses when compared to humans. Cynomolgus monkeys with naturally-occurring refractive errors may be a good animal model for refractive studies.

Refractive Errors and Their Associated Factors in Schoolchildren: A Structural Equation Modeling

PURPOSE

To determine the prevalence of myopia and hyperopia in Shahroud schoolchildren and their risk factors.

METHODS

Optometric examinations including the measurement of uncorrected and corrected visual acuity as well as non-cycloplegic and cycloplegic refraction using retinoscopy were done for students. Generalized Structural Equation Modeling (GSEM) was used to determine direct and indirect effects of independent variables on myopia and hyperopia.

RESULTS

The data of 5581 students with a mean age of 9.24 ± 1.7 years were used in this study. The prevalence of myopia was 5.0% (95%CI: 4.3-5.7) and the prevalence of hyperopia was 4.8% (95%CI: 4.0 - 5.5) in all schoolchildren. According to the GSEM results, the odds of myopia in rural areas were 0.55 compared to urban areas. A one-unit increase in the ocular AL increased the odds of myopia by 4.91 times. The interaction of sex and age on myopia was significant such that in girls, the odds of myopia increased by 20% for every one-year increase in age while no significant change was seen in boys. A one-unit increase in the ocular AL decreased the odds of hyperopia by 0.49 times. Moreover, the interaction of outdoor activity hours and sex on the prevalence of hyperopia was significant such that increased outdoor activity reduced the odds of hyperopia in girls while no significant correlation was found in boys.

CONCLUSION

Myopia and hyperopia had moderate prevalence. Axial Length had the largest direct association on myopia and hyperopia. Age and outdoor activity had weak associations on refractive errors.

The Evolution and the Impact of Refractive Errors on Academic Performance: A Pilot Study of Portuguese School-Aged Children

The relationship between vision and academic performance has been discussed for a long time, with special emphasis on visual factors associated with learning problems. The objective of this pilot study is to obtain an initial idea about the evolution and the impact of refractive errors on school-aged children. A visual examination was performed on 252 children between the ages of 6 and 11 years, which consisted of objective refraction, subjective refraction, and accommodative and binocular tests. No significant differences were observed regarding the refractive state when taking academic performance into account (p > 0.05). However, it was determined that academic performance was better among children with a negative spherical equivalent. Studies with a larger sample size must be conducted to verify the results that were attained in this present pilot study, and these must likewise look at possible ways in which strategies can be implemented in schools to reduce myopia progression.

Myopia in Bulgarian school children: prevalence, risk factors, and health care coverage

Background

The prevalence of myopia has increased in recent years, with changes being dynamic and uneven in different regions. The purpose of this study is to evaluate the prevalence of visual impairment caused by myopia in Bulgarian school children, associated risk factors, and health care coverage.

Methods

A cross-sectional study among 1401 children (mean age 10.38, standard deviation 2.70) is conducted in three locations in Bulgaria from 2016 to 2020. Refractive error is measured with an auto-refractor in the absence of cycloplegia, the visual acuity is assessed without refractive error correction. A paper-based preliminary questionnaire is used to collect data on previous eye examinations, prescribed optical vision correction, regularity of wearing corrective glasses and risk factors.

Results

Children with myopic objective refraction ≤ -0.75 D and decimal visual acuity ≤ 0.8 on at least one of the eyes are 236 out of 1401 or 16.85%. The prevalence of myopia varies depending on age, geographical location, and school profile. The rate of myopic children in age group 6–10 is 14.2% compared to 19.9% in age group 11–15. The prevalence of myopic children in the urban populations is 31.4% (capital) and 19.9% (medium-sized town) respectively, and only 8.4% in the rural population. Our results show 53% increase of the prevalence of myopia in the age group 11–15 compared to a 2009 report. The analysis of data associated with health care coverage factors of all myopic pupils shows that 71.6% had a previous eye examination, 43.2% have prescription for corrective glasses, 27.5% wear their glasses regularly. Risk factors for higher odds of myopia are gender (female), age (adolescence), and parents with impaired vision. Residence in a small town and daily sport activities correspond to lower odds for myopia. The screen time (time in front of the screen calculated in hours per day) is self-reported and is not associated with increased odds of myopia when accounted for the other risk factors.

Conclusions

The prevalence of myopia in this study is higher compared to previous studies in Bulgaria. Additional studies would be helpful in planning adequate prevention and vision care.

Prevalence and Factors Associated with Myopia Among High School Students in Hawassa City, South Ethiopia, 2019

PURPOSE

Myopia is one of the avoidable causes of visual impairment. Twenty-seven percent of the world population were myopic in 2010 and after 30 years it is expected half of the peoples in the planet will become myopic. The aim of this study was to determine the prevalence and factors associated with myopia among high school students.

MATERIALS AND METHODS

A cross-sectional school-based study design using stratified simple random sampling technique was used to select 349 high school students from 21 high schools in Hawassa city. The study was conducted from April 24 to May 7, 2019. Structured questionnaire, six meter Snellen visual acuity chart, trial frame, trial set, retinoscope and cyclopentolate 1% eye drops were used to collect data. Data were analyzed using Statistical Package for Social Science (SPSS) version 20 computer software. Variables having p-value <0.05 in multivariate logistic regression were considered as statistically significant.

RESULTS

A total of 349 participants having a response rate of 97% were involved with the mean age of 16.90±1.32 years. Prevalence of myopia was 16.05% (95%CI: 12.6, 20.1). Early age of schooling (adjusted odds ratio, AOR=3.14; 95%CI: 1.16, 10.06), parents being myopic (AOR=8.46; 95%CI: 7.11, 12.08), prolonged near work (AOR=11.65; 95%CI: 2.11, 64.5), short working distance (AOR=10.90; 95%CI: 0.57, 20.55), lack of outdoor sport activities (AOR=7.37; 95%CI: 2.71, 20.03) and visual display unit (VDU) usage (AOR=8.36; 95%CI: 2.39, 29.33) were variables significantly associated with myopia.

CONCLUSION AND RECOMMENDATIONS

The prevalence of myopia was high in the study area. Early age of schooling, parents being myopic, prolonged near work, short working distance, lack of outdoor sport activities, and visual display unit usage were variables significantly associated with myopia. There should be strategies to prevent visual impairments secondary to myopia with affordable optical corrections and appropriate use of visual display units.

The Prevalence of Myopia in Children in Spain: An Updated Study in 2020

Background: In recent years, there was a significant increase in myopia incidence worldwide. However, it is still not clear how it affects Spanish children. Since 2016, this research team analyzed myopia prevalence and risk in 9668 children aged between 5 and 7 years. It was shown that the prevalence rates increased from 16.8% in 2016 to 20.4% in 2019. The objective of this study is to update the prevalence rate of myopia in Spain in 2020 and analyze the risk and prevention factors of myopia. Methods: The participants underwent an optometric examination, and a questionnaire on their lifestyle, family history, and geographical origin was carried out. Finally, data were analyzed using the SPSS version 27 program. Results: 1601 children from various Autonomous Communities of Spain were examined. In 2020 the myopia rates did not increase compared to 2019 (p < 0.05), although the number of hyperopes decreased and the number of emmetropes increased. Regarding age, the prevalence of myopia increased progressively over the years (p < 0.001). There was no association between gender and myopia (p > 0.05). There was a link between the time spent in near vision and family history with the prevalence of myopia (p < 0.05). Conclusions: The prevalence of myopia in Spain in children between 5 and 7 years old increased significantly between 2016 and 2020.

Prevalence and pattern of refractive error and visual impairment among schoolchildren: the Lhasa childhood eye study

Background

Early and effective ocular screening may help to eliminate treatable eye disorders. The Lhasa Childhood Eye Study (LCES) revealed the particular prevalence of refractive error and visual impairment in grade one schoolchildren (starting age of 6 years old) in Lhasa.

Methods

This is a cross-sectional part of school-based cohort study. One thousand nine hundred forty-three children were enrolled (median age, 6.78 years, range, 5.89 to 10.32). Each child underwent general and ocular examinations, including logarithm of the minimum angle of resolution (logMAR) visual acuity, cycloplegic autorefraction, and slit-lamp biomicroscopy evaluation. Multivariate and correlation analyses were performed to evaluate the association between refractive error with gender and ethnics.

Results

The prevalence of visual impairment (logMAR visual acuity ≥0.3 in the better-seeing eye) of uncorrected, presenting and best-corrected visual acuity (BCVA) was 12.2, 11.7 and 2.7%, respectively. Refractive error presented in 177 (78.0%) out of 227 children with bilateral visual impairment. Myopia (spherical equivalent refractor [SER] ≤ − 0.50 diopter [D] in either eye) was present in 4.7% children when measured after cycloplegic autorefraction. Hyperopia (SER ≥ + 2.00 D) affected 12.1% children. Hyperopia was significantly associated with female gender (P<0.001). Astigmatism (cylinder value ≤ − 0.75 D) was present in 44.8% children. In multivariate regression and correlation analysis, SER had no significant difference between ethnic groups.

Conclusion

The Lhasa Childhood Eye Study is the first school-based cohort study to reveal the prevalence and pattern of refractive error and visual impairment in Lhasa. Effective strategies such as corrective spectacles should be considered to alleviate treatable visual impairment.

Prevalence and time trends of refractive error in Chinese children: A systematic review and meta-analysis

Background

To investigate the prevalence and time trends of refractive error (RE) among Chinese children under 18 years old.

Methods

PubMed, Embase, Web of Science were searched for articles that estimated prevalence of RE in Chinese children. Data of identified eligible studies was extracted by two investigators independently. Pooled prevalence of RE and its 95% confidence interval (95% CI) and the time trends of RE were investigated using Meta-analysis methods.

Results

Of the 41 studies covering 1 051 784 subjects, the pooled prevalence of myopia, high myopia, hyperopia and astigmatism in Chinese children was 38.0% (95% confidence interval (CI) = 35.1%-41.1%), 2.8% (95% CI = 2.3%-3.4%), 5.2% (95% CI = 3.1%-8.6%) and 16.5% (95% CI = 12.3%-21.8%), respectively. Subgroup analysis show that children living in urban were at higher risk of RE. Prevalence of myopia and hyperopia were higher in Northern China compared with Southern China and high myopia and astigmatism were higher in Hong Kong, Macau and Taiwan than in mainland China. Regression analysis showed an upward trend in myopia and hyperopia and a downward trend in high myopia and astigmatism with years.

Conclusions

The prevalence of RE is higher in urban areas than in rural for Chinese children. The much higher prevalence of myopia and astigmatism in China compared with foreign countries indicates the important role played by environment and genetic factors. Considering the large magnitude of refractive errors, much more attention should still be paid to RE prevention and treatment strategy development in China.

Refractive error, axial length, environmental and hereditary factors associated with myopia in Swedish children

Clinical relevance: Investigation of refractive errors amongst Swedish schoolchildren will help identify risk factors associated with myopia development.Background: Genetic and hereditary aspects have been linked with the development of myopia. Nevertheless, in the case of 'school myopia' some authors suggest that environmental factors may affect gene expression, causing school myopia to soar. Additional understanding about which environmental factors play a relevant role can be gained by studying refractive errors in countries like Sweden, where prevalence of myopia is expected to be low.Methods: Swedish schoolchildren aged 8-16 years were invited to participate. Participants underwent an eye examination, including cycloplegic refraction and axial length (AL) measurements. Predictors such as time spent in near work, outdoor activities and parental myopia were obtained using a questionnaire. Myopia was defined as spherical equivalent refraction (SER) ≤ -0.50D and hyperopia as SER ≥ +0.75D.Results: A total of 128 children (70 females and 58 males) participated in this study with mean age of 12.0 years (SD = 2.4). Based on cycloplegic SER of the right eye, the distribution of refractive errors was: hyperopia 48.0% (CI95 = 38.8-56.7), emmetropia 42.0% (CI95 = 33.5-51.2) and myopia 10.0%. (CI95 = 4.4-14.9). The mean AL was 23.1 mm (SD = 0.86), there was a correlation between SER and AL, r = -0.65 (p < 0.001). Participants with two myopic parents had higher myopia and increased axial length than those with one or no myopic parents. The mean time spent in near work, outside of school, was 5.3 hours-per-day (SD = 3.1), and mean outdoor time reported was 2.6 hours-per-day (SD = 2.2) for all the participants. The time spent in near work and outdoor time were different for different refractive error categories.Conclusion: The prevalence of myopia amongst Swedish schoolchildren is low. Hereditary and environmental factors are associated with refractive error categories. Further studies with this sample are warranted to investigate how refractive errors and environmental factors interact over time.

Myopia prevalence in Denmark - a review of 140 years of myopia research

PURPOSE

To evaluate potential changes in myopia prevalence in Denmark by revising more than 100 years of myopia research.

METHODS

A systematic literature search was performed in the PubMed, Embase and Cochrane Library databases. Only studies reporting a myopia prevalence in Denmark were included. Myopia was defined using the definition in individual references. We did not restrict inclusion of studies to specific methods of measuring or evaluating refraction. As refraction changes throughout life, information from available studies was divided in relevant age groups. Chi-squared test was used when analysing the effect of sex and education on myopia prevalence except when the expected values were beneath 5, where Fisher's exact test was used. To further compare the effect of sex, we calculated the odds ratio of being myopic for females compared to males.

RESULTS

We identified 29 Danish studies reporting on prevalence of myopia. The studies were performed between year 1882 and 2018. We found no strong evidence of an increase in myopia prevalence in Denmark. Increasing age was associated with an increased myopia prevalence up to the age of 60 years where after the prevalence decreased. Longer education and more intensive educational load were associated with myopia. Fourteen studies compared the prevalence of myopia between males and females and two of these studies found a significant higher prevalence in females.

CONCLUSION

We evaluated nearly 140 years of myopia research in Denmark and did not find a convincing change in prevalence of myopia which is in contrast to the high prevalence of myopia reported in some parts of the world and the expected rise in myopia as predicted by WHO.

Low physical activity and higher use of screen devices are associated with myopia at the age of 16-17 years in the CCC2000 Eye Study

PURPOSE

To determine the myopia prevalence in a Danish cohort aged 16-17 years and its relation to physical activity and use of screen-based electronic devices.

METHODS

The Copenhagen Child Cohort 2000 Eye Study is a prospective, population-based, observational study. Information about use of screen devices and physical activity was obtained using questionnaires. Myopia was defined as non-cycloplegic subjective spherical equivalent refraction ≤-0.50 D in right eye.

RESULTS

We included 1443 participants (45% boys) with a median age (±IQR) of 16.6 years (±0.3). The prevalence of myopia was 25% (CI95% 23-28, n = 360) with no differences between sexes (p = 0.10). The odds ratio (OR) for myopia was 0.57 (CI95% 0.42-0.76, p = 0.0002) in participants physically active 3-6 hr/week (n = 502) and 0.56 (CI95% 0.42-0.76, p = 0.0002) if active >6 hr/week (n = 506), both compared with participants physically active <3 hr/week (n = 396). The use of screen devices >6 hr/day was associated with increased OR for myopia compared with screen device use <2 hr/day in both weekdays (OR = 1.95, CI95% 1.16-3.30, p = 0.012) and weekends (OR = 2.10, CI95% 1.17-3.77, p = 0.013).

CONCLUSION

In this cohort of healthy 16-17-year olds, lower physical activity and more use of screen devices contributed significantly to the observed 25% prevalence of myopia with a roughly doubled risk of having myopia if physically active <3 hr/week or if using screen devices >6 hr/day. Our results support physical activity being a protective factor and near work a risk factor for myopia in adolescents.

Should Pearson's correlation coefficient be avoided?

PURPOSE

To survey the use of Pearson's correlation coefficient (r) and related statistical methods in the ophthalmic literature, to consider the limitations of r, and to suggest suitable alternative methods of analysis.

RECENT FINDINGS

Searching Ophthalmic and Physiological Optics (OPO), Optometry and Vision Science (OVS), and Clinical and Experimental Optometry (CXO) online archives using correlation and Pearson's r as search terms resulted in 4057 and 281 hits respectively. Coefficient of determination, r square, or r squared received fewer hits (65, 8, and 22 hits respectively). The assumption that r follows a bivariate normal distribution was rarely encountered (3 hits) although several studies applied Spearman's rank correlation (70 hits). The intra-class correlation coefficient (ICC) was widely used (178 hits), but fewer hits were recorded for partial correlation (43 hits) and multiple correlation (13) hits. There was little evidence that the problem of sample size was addressed in correlation studies.

SUMMARY

Investigators should be alert to whether: (1) the relationship between two variables could be non-linear, (2) the data are bivariate normal, (3) r accounts for a significant proportion of the variance in Y, (4) outliers are present, the data are clustered, or have a restricted range, (5) the sample size is appropriate, and (6) a significant correlation indicates causality. In addition, the number of significant digits used to express r and the problems of multiple testing should be addressed. The problems and limitations of r suggest a more cautious approach regarding its use and the application of alternative methods where appropriate.

Refractive error and visual impairment in Ireland schoolchildren

Aim

To report refractive error prevalence and visual impairment in Republic of Ireland (henceforth 'Ireland') schoolchildren.

Methods

The Ireland Eye Study examined 1626 participants (881 boys, 745 girls) in two age groups, 6–7 years (728) and 12–13 years (898), in Ireland between June 2016 and January 2018. Participating schools were selected by stratified random sampling, representing a mix of school type (primary/postprimary), location (urban/rural) and socioeconomic status (disadvantaged/advantaged). Examination included monocular logarithm of the minimum angle of resolution (logMAR) presenting visual acuity (with spectacles if worn) and cycloplegic autorefraction (1% Cyclopentolate Hydrochloride). Parents completed a questionnaire to ascertain participants’ lifestyle.

Results

The prevalence of myopia (spherical equivalent refraction (SER): ≤−0.50 D), hyperopia (SER: ≥+2.00 D) and astigmatism (≤−1.00 DC) among participants aged 6–7 years old was 3.3%, 25% and 19.2%, respectively, and among participants aged 12–13 years old was 19.9%, 8.9% and 15.9%, respectively. Astigmatic axes were predominately with-the-rule. The prevalence of ‘better eye’ presenting visual impairment (≥0.3 logMAR, with spectacles, if worn) was 3.7% among younger and 3.4% among older participants. Participants in minority groups (Traveller and non-white) were significantly more likely to present with presenting visual impairment in the ‘better eye’.

Conclusions

The Ireland Eye Study is the first population-based study to report on refractive error prevalence and visual impairment in Ireland. Myopia prevalence is similar to comparable studies of white European children, but the levels of presenting visual impairment are markedly higher than those reported for children living in Northern Ireland, suggesting barriers exist in accessing eye care.

Visual and binocular status in elementary school children with a reading problem

PURPOSE

This descriptive study provides a summary of the binocular anomalies seen in elementary school children identified with reading problems.

METHODS

A retrospective chart review of all children identified with reading problems and seen by the University of Waterloo, Optometry Clinic, from September 2012 to June 2013.

RESULTS

Files of 121 children (mean age 8.6 years, range 6-14 years) were reviewed. No significant refractive error was found in 81% of children. Five and 8 children were identified as strabismic at distance and near respectively. Phoria test revealed 90% and 65% of patients had normal distance and near phoria. Near point of convergencia (NPC) was <5cm in 68% of children, and 77% had stereoacuity of ≤40seconds of arc. More than 50% of the children had normal fusional vergence ranges except for near positive fusional vergencce (base out) break (46%). Tests for accommodation showed 91% of children were normal for binocular facility, and approximately 70% of children had an expected accuracy of accommodation.

CONCLUSION

Findings indicate that some children with an identified reading problem also present with abnormal binocular test results compared to published normal values. Further investigation should be performed to investigate the relationship between binocular vision function and reading performance.

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.

Global and regional estimates of prevalence of refractive errors: Systematic review and meta-analysis

Purpose

The aim of the study was a systematic review of refractive errors across the world according to the WHO regions.

Methods

To extract articles on the prevalence of refractive errors for this meta-analysis, international databases were searched from 1990 to 2016. The results of the retrieved studies were merged using a random effect model and reported as estimated pool prevalence (EPP) with 95% confidence interval (CI).

Results

In children, the EPP of myopia, hyperopia, and astigmatism was 11.7% (95% CI: 10.5–13.0), 4.6% (95% CI: 3.9–5.2), and 14.9% (95% CI: 12.7–17.1), respectively. The EPP of myopia ranged from 4.9% (95% CI: 1.6–8.1) in South–East Asia to 18.2% (95% CI: 10.9–25.5) in the Western Pacific region, the EPP of hyperopia ranged from 2.2% (95% CI: 1.2–3.3) in South-East Asia to 14.3% (95% CI: 13.4–15.2) in the Americas, and the EPP of astigmatism ranged from 9.8% in South-East Asia to 27.2% in the Americas. In adults, the EPP of myopia, hyperopia, and astigmatism was 26.5% (95% CI: 23.4–29.6), 30.9% (95% CI: 26.2–35.6), and 40.4% (95% CI: 34.3–46.6), respectively. The EPP of myopia ranged from 16.2% (95% CI: 15.6–16.8) in the Americas to 32.9% (95% CI: 25.1–40.7) in South-East Asia, the EPP of hyperopia ranged from 23.1% (95% CI: 6.1%–40.2%) in Europe to 38.6% (95% CI: 22.4–54.8) in Africa and 37.2% (95% CI: 25.3–49) in the Americas, and the EPP of astigmatism ranged from 11.4% (95% CI: 2.1–20.7) in Africa to 45.6% (95% CI: 44.1–47.1) in the Americas and 44.8% (95% CI: 36.6–53.1) in South-East Asia. The results of meta-regression showed that the prevalence of myopia increased from 1993 (10.4%) to 2016 (34.2%) (P = 0.097).

Conclusion

This report showed that astigmatism was the most common refractive errors in children and adults followed by hyperopia and myopia. The highest prevalence of myopia and astigmatism was seen in South-East Asian adults. The highest prevalence of hyperopia in children and adults was seen in the Americas.

The epidemics of myopia: Aetiology and prevention

There is an epidemic of myopia in East and Southeast Asia, with the prevalence of myopia in young adults around 80-90%, and an accompanying high prevalence of high myopia in young adults (10-20%). This may foreshadow an increase in low vision and blindness due to pathological myopia. These two epidemics are linked, since the increasingly early onset of myopia, combined with high progression rates, naturally generates an epidemic of high myopia, with high prevalences of "acquired" high myopia appearing around the age of 11-13. The major risk factors identified are intensive education, and limited time outdoors. The localization of the epidemic appears to be due to the high educational pressures and limited time outdoors in the region, rather than to genetically elevated sensitivity to these factors. Causality has been demonstrated in the case of time outdoors through randomized clinical trials in which increased time outdoors in schools has prevented the onset of myopia. In the case of educational pressures, evidence of causality comes from the high prevalence of myopia and high myopia in Jewish boys attending Orthodox schools in Israel compared to their sisters attending religious schools, and boys and girls attending secular schools. Combining increased time outdoors in schools, to slow the onset of myopia, with clinical methods for slowing myopic progression, should lead to the control of this epidemic, which would otherwise pose a major health challenge. Reforms to the organization of school systems to reduce intense early competition for accelerated learning pathways may also be important.

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

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

Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China

BACKGROUND

To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China.

METHODS

A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia.

RESULTS

Longitudinal data were available for 1858 children (60.5%). The cumulative mean change in refractive error was -2.21 (standard deviation [SD], 1.87) diopters (D) for the entire study population, with an annual progression of refraction in a myopic direction of -0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of -0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%-63.5%), with an annual incidence of 10.6% (95% CI, 8.7%-13.1%). Myopia was found more likely to happen in female and older children.

CONCLUSIONS

In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China.

Global variations and time trends in the prevalence of childhood myopia, a systematic review and quantitative meta-analysis: implications for aetiology and early prevention

The aim of this review was to quantify the global variation in childhood myopia prevalence over time taking account of demographic and study design factors. A systematic review identified population-based surveys with estimates of childhood myopia prevalence published by February 2015. Multilevel binomial logistic regression of log odds of myopia was used to examine the association with age, gender, urban versus rural setting and survey year, among populations of different ethnic origins, adjusting for study design factors. 143 published articles (42 countries, 374 349 subjects aged 1–18 years, 74 847 myopia cases) were included. Increase in myopia prevalence with age varied by ethnicity. East Asians showed the highest prevalence, reaching 69% (95% credible intervals (CrI) 61% to 77%) at 15 years of age (86% among Singaporean-Chinese). Blacks in Africa had the lowest prevalence; 5.5% at 15 years (95% CrI 3% to 9%). Time trends in myopia prevalence over the last decade were small in whites, increased by 23% in East Asians, with a weaker increase among South Asians. Children from urban environments have 2.6 times the odds of myopia compared with those from rural environments. In whites and East Asians sex differences emerge at about 9 years of age; by late adolescence girls are twice as likely as boys to be myopic. Marked ethnic differences in age-specific prevalence of myopia exist. Rapid increases in myopia prevalence over time, particularly in East Asians, combined with a universally higher risk of myopia in urban settings, suggest that environmental factors play an important role in myopia development, which may offer scope for prevention.

Macular Pigment Optical Density and Ocular Pulse Amplitude in Subjects with Different Axial Lengths and Refractive Errors

BACKGROUND

The purpose of our study was to: (1) investigate the macular pigment optical density (MPOD) and ocular pulse amplitude (OPA) in subjects with different axial lengths (AL) and refractive errors (RE); (2) determine if there is a correlation between MPOD and OPA; and (3) evaluate whether MPOD and OPA depend on intraocular pressure (IOP).

MATERIAL AND METHODS

This study included 140 eyes of 70 subjects - 17 men and 53 women, aged 18 to 29 years (mean: 22.5 years; SD=2.8). Every examined person underwent a thorough eye examination including: visual acuity, anterior segment and fundus examination, keratometry, auto-refractometry, and MPOD, OPA, AL, and IOP measurements. The obtained results were analyzed statistically using Statistica 10 software. P values of <0.05 were considered statistically significant.

RESULTS

The following refractive errors were selected: emmetropia (34 eyes), hyperopia (18 eyes), low myopia (60 eyes), medium myopia (19 eyes), and high myopia (9 eyes). It has been established that the OPA increases with the rise in the spherical equivalents (SE) (Rs=+0.38, P<0.001), while the increase in AL correlates with the decrease of OPA (Rs=-0.40, P<0.001). The increase in IOP correlates with the rise in the OPA (Rs=+0.20, P<0.05). There were no significant correlations between IOP and SE or AL.

CONCLUSIONS

(1) MPOD is not correlated with the OPA in subjects with different AL and RE; (2) OPA decreases with the rise of AL; (3) OPA decreases with the fall of the SE; and (4) OPA increases with the rise in IOP.

The prevalence and causes of visual impairment and blindness among older adults in the city of Lodz, Poland

To investigate the prevalence and causes of visual impairment and blindness in a sample of Polish older adults. The study was designed in a cross-sectional and observational manner. Data concerning the vision status were assessed in 2214 eyes from 1107 subjects of European Caucasian origin; most of whom live in the city of Lodz, in central Poland. Visual impairment was defined as distance visual acuity <20/40 in the worse-seeing eye. Low vision was defined as best-corrected visual acuity (BCVA) <20/40 but >20/200 in better-seeing eye, and blindness was defined as BCVA ≤20/200 in both eyes (United States criteria). Visual impairment was found in 27.5% subjects in the worse-seeing eye. Multiple regression analysis showed that increasing age (OR 0.98, 95% CI 0.97-0.99) and female gender (OR 1.47, 95% CI 1.11-1.93) were independent risk factors. No association was found between visual impairment and socioeconomic status of subjects. Noncorrectable visual impairment was found in 7.0% of subjects, including 5.2% of subjects with unilateral and 1.8% of subjects with bilateral visual impairment. Low vision and blindness accounted for 1.3% and 0.5%, respectively, and were only associated with older age (OR 1.05, 95% CI 1.02-1.10). Retinal diseases represented the major cause of noncorrectable visual impairment and accounted for more than half of causes of blindness. Provision of appropriate refractive correction improves visual acuity in 75% subjects presenting with visual impairment. Retinal diseases are a major cause of noncorrectable visual impairment and blindness in this older population.

Refractive error, visual acuity and causes of vision loss in children in Shandong, China. The Shandong Children Eye Study

PURPOSE

To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China.

METHODS

Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA) and best corrected visual acuity (BCVA) and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤-0.5 diopters (D), high myopia as ≤ -6.0D, and amblyopia as BCVA ≤ 20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons.

RESULTS

Out of 6364 eligible children, 6026 (94.7%) children participated. Prevalence of myopia (overall: 36.9 ± 0.6%;95% confidence interval (CI):36.0,38.0) increased (P<0.001) from 1.7 ± 1.2% (95%CI:0.0,4.0) in the 4-years olds to 84.6 ± 3.2% (95%CI:78.0,91.0) in 17-years olds. Myopia was associated with older age (OR:1.56;95%CI:1.52,1.60;P<0.001), female gender (OR:1.22;95%CI:1.08,1.39;P = 0.002) and urban region (OR:2.88;95%CI:2.53,3.29;P<0.001). Prevalence of high myopia (2.0 ± 0.2%) increased from 0.7 ± 0.3% (95%CI:0.1,1.3) in 10-years olds to 13.9 ± 3.0 (95%CI:7.8,19.9) in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;P<0.001) and urban region (OR:3.11;95%CI:2.08,4.66);P<0.001). Astigmatism (≥ 0.75D) (36.3 ± 0.6%;95%CI:35.0,38.0) was associated with older age (P<0.001;OR:1.06;95%CI:1.04,1.09), more myopic refractive error (P<0.001;OR:0.94;95%CI:0.91,0.97) and urban region (P<0.001;OR:1.47;95%CI:1.31,1.64). BCVA was ≤ 20/40 in the better eye in 19 (0.32%) children. UCVA ≤ 20/40 in at least one eye was found in 2046 (34.05%) children, with undercorrected refractive error as cause in 1975 (32.9%) children. Amblyopia (BCVA ≤ 20/32) was detected in 44 (0.7%) children (11 children with bilateral amblyopia).

CONCLUSIONS

In coastal East China, about 14% of the 17-years olds were highly myopic, and 80% were myopic. Prevalence of myopia increased with older age, female gender and urban region. About 0.7% of pre-school children and school children were amblyopic.

Myopia and international educational performance

PURPOSE

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

METHODS

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

RESULTS

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

DISCUSSION

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

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

PURPOSE

To determine the prevalence, incidence, and change in refractive errors for Australian schoolchildren and examine the impact of ethnicity and sex.

DESIGN

Population-based cohort study.

PARTICIPANTS

The Sydney Adolescent Vascular and Eye Study, a 5- to 6-year follow-up of the Sydney Myopia Study, examined 2760 children in 2 age cohorts, 12 and 17 years. Longitudinal data were available for 870 and 1202 children in the younger and older cohorts, respectively.

METHODS

Children completed a comprehensive examination, including cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1). Myopia was defined as ≤-0.50 diopters (D) and hyperopia as ≥+2.00 D right eye spherical equivalent refraction.

MAIN OUTCOME MEASURES

Baseline and follow-up refraction.

RESULTS

Prevalence of myopia increased between baseline and follow-up for both the younger (1.4%-14.4%; P<0.0001) and older cohorts (13.0%-29.6%; P<0.0001). The annual incidence of myopia was 2.2% in the younger cohort and 4.1% in the older. Children of East Asian ethnicity had a higher annual incidence of myopia (younger 6.9%, older 7.3%) than European Caucasian children (younger 1.3%, older 2.9%; all P<0.0001). The prevalence of myopia in European Caucasian children almost doubled between the older (4.4%; 95% confidence interval [CI], 3.0-5.8) and younger samples (8.6%; 95% CI, 6.7-10.6) when both were aged 12 years. Children with ametropia at baseline were more likely to have a significant shift in refraction (hyperopia: odds ratio [OR], 3.4 [95% CI, 1.2-9.8]; myopia: OR, 6.3 [95% CI, 3.7-10.8]) compared with children with no refractive error. There was no significant difference in myopia progression between children of European Caucasian and East Asian ethnicity (P = 0.7).

CONCLUSIONS

In Sydney, myopia prevalence (14.4%, 29.6%) and incidence (2.2%, 4.1%) was low for both age cohorts, compared with other locations. However, in European Caucasian children at age 12, the significantly higher prevalence of myopia in the younger sample suggests a rise in prevalence, consistent with international trends. Progression of myopia was similar for children of East Asian and European Caucasian ethnicity, but lower than reported in children of East Asian ethnicity in East Asia, suggesting that environmental differences may have some impact on progression.