The contributions of near work and outdoor activity to the correlation between siblings in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study

Myopia Management in Daily Routine - A Survey of European Pediatric Ophthalmologists

PURPOSE

Assessment of diagnostic and therapeutic strategies currently used in routine practice for myopia management in Europe.

METHODS

Online survey study including 11 main questions. The questionnaire was sent to members of the European Paediatric Ophthalmology Society (EPOS). The following items and questions were surveyed: I. Profession and workplace of the survey participants. II. Preventive measures and recommendations for myopia management, a) regarding reading distance and near work, b) optical tools, i.e., application of Defocus Incorporated Multiple Segments (DIMS) glasses, near additions, or contact lenses, and c) the application of atropine eye drops. III. Application of additional diagnostic tools.

RESULTS

Forty-eight individuals completed the survey. Of the respondents, 88% (n = 42) affirmed that they generally gave advice on strategies for myopia prevention and management strategies. Almost all study participants (n = 41; 85%) recommend outdoor time as a preventive measure. The recommendation on near distance is given less frequently, with 28 (58%) participants confirming that they do recommend a "safe" reading distance, and 15 (31%) negating this. Eight (17%) survey participants recommend using near addition glasses, while 36 (75%) do not. Similarly, 35 (73%) respondents do not apply DIMS glasses and 8 (17%) apply them. Fourteen (29%) participants recommend myopia-reducing contact lenses while 30 (63%) do not, and 29 (60%) confirmed that they applied atropine eye drops to slow myopia progression while 14 (29%) do not prescribe these eye drops. The majority of respondents (n = 25; 86%) who prescribe atropine eye drops use atropine 0.01% eye drops.

CONCLUSIONS

Prevention and therapeutic management of childhood myopia is an essential part in the daily routine of pediatric ophthalmologists. Substantial agreement was found for the protective role of outdoor time (85%). The only common therapeutic approach is the administration of atropine eye drops (60%).

Ocular biological parameters and prevalence of myopia in vocational high school and general high school in China

Significance

Higher prevalence of myopia is possibly associated with more extended schooling schedules. Therefore, adjustments to high school curricula may aid in reducing the prevalence of myopia among adolescents.

Purpose

To investigate the prevalence of myopia among 15- to 18-year-old adolescents in Tianjin, China, and to evaluate the impact of different educational schedules on the prevalence of myopia among high school students.

Methods

This is a school-based epidemiological study with a cross-sectional design. Ocular biological parameters and noncycloplegic photorefraction were examined using optical biometry devices and photoscreener devices. Each student’s spherical equivalent (SE) and ocular biometry were recorded, and the prevalence of myopia was calculated.

Results

A total of 2,867 participants (1,519 males and 1,348 females) were tested for non-cycloplegic refraction, axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD) and lens thickness (LT). In this research, the overall prevalence of myopia was 81.6%, with high myopia accounting for 11.8%. Myopia prevalence was substantially higher in general high schools than in vocational high schools, with 86.1 and 70.1%, respectively. There were no significant differences in the prevalence of myopia (p = 0.744) or high myopia (p = 0.851) across the three vocational school years. In the general high school, however, there was an increase of 4.6% (p < 0.05) in myopia prevalence between year 10 and year12.

Conclusion

Comparing vocational and standard high school students, there are considerable disparities in prevalence of myopia, spherical equivalent, and ocular biological parameters. The prevalence of myopia and high myopia increased among standard high school students, but remained relatively consistent among students in vocational schools.

Prevalence of Myopia in Children Before, During, and After COVID-19 Restrictions in Hong Kong

Importance

Childhood myopia increased during the COVID-19 pandemic. Limited evidence exists about whether myopia development was reversed or worsened after the lockdown.

Objective

To determine the prevalence of myopia and its associated factors before, during, and after COVID-19 restrictions.

Design, Setting, and Participants

This population-based, repeated cross-sectional study evaluated children aged 6 to 8 years from the Hong Kong Children Eye Study between 2015 and 2021 in 3 cohorts: before COVID-19 (2015-2019), during COVID-19 restrictions (2020), and after COVID-19 restrictions were lifted (2021).

Exposures

All the children received ocular examinations, including cycloplegic autorefraction and axial length. Data about the children's lifestyle, including time spent outdoors, near-work time, and screen time, were collected from a standardized questionnaire.

Main Outcomes and Measures

The main outcomes were the prevalence of myopia, mean spherical equivalent refraction, axial length, changes in lifestyle, and the associated factors over 7 years. Data were analyzed using descriptive statistics, logistic regression, and generalized estimating equations.

Results

Of 20 527 children (mean [SD] age, 7.33 [0.89] years; 52.8% boys and 47.2% girls), myopia prevalence was stable from 2015 to 2019 (23.5%-24.9%; P = .90) but increased to 28.8% (P < .001) in 2020 and 36.2% (P < .001) in 2021. The mean (SD) time spent outdoors was much lower in 2020 (0.85 [0.53] h/d; P < .001) and 2021 (1.26 [0.48] h/d; P < .001) compared with pre-COVID-19 levels (1.40 [0.47]-1.46 [0.65] h/d). The trend was reversed for total near-work time and screen time. High myopia prevalence was associated with the COVID-19 pandemic (odds ratio [OR], 1.40; 95% CI, 1.28-1.54; P < .001), younger age (OR, 1.84; 95% CI, 1.76-1.93; P < .001), male sex (OR, 1.11; 95% CI, 1.03-1.21; P = .007), lower family income (OR, 1.05; 95% CI, 1.00-1.09; P = .04), and parental myopia (OR, 1.61; 95% CI, 1.52-1.70; P < .001). During the pandemic, mean (SD) near-work and screen times in children from lower-income families were 5.16 (2.05) h/d and 3.44 (1.97) h/d, more than from higher-income families (4.83 [1.85] and 2.90 [1.61] h/d, respectively).

Conclusions and Relevance

The findings of this cross-sectional study revealed that after COVID-19 restrictions were lifted in Hong Kong, myopia prevalence among children was higher than before the pandemic, and lifestyle did not return to pre-COVID-19 levels. Younger children and those from low-income families were at a higher risk of myopia development during the pandemic, suggesting that collective efforts for myopia control should be advocated for these groups.

Short-Term Exposure to Violet Light Emitted from Eyeglass Frames in Myopic Children: A Randomized Pilot Clinical Trial

Violet light (VL), 360−400 nm wavelength, is contained in the sunlight and is an effective element for myopia suppression. This study is to investigate the safety and efficacy of novel eyeglasses that emit VL from the frames. This is a double-masked, randomized, pilot clinical trial conducted in a clinic in Japan. Forty-three children with myopia were enrolled. Participants were randomly assigned to two groups, wearing VL-emitting eyeglass frames (VLf) that emitted VL of 310 μW/cm2 (VLf group, n = 22) or pseudo-placebo eyeglass frames with a minimal emission of VL (<10 μW/cm2) (control group, n = 21). The exposure time was 3 h per day. The primary outcomes were visual acuity, tear film break-up time, corneal endothelial cell density, and the slit-lamp/fundus examinations. The secondary outcome was the 6-month changes in the axial lengths and cycloplegic refractions. Forty-one (95%) participants were included; twenty-one in the VLf group and twenty in the control group. No significant differences were seen in any safety evaluation. Significant changes were seen in axial elongation, choroidal thickness, and cycloplegic refractions in the subgroup analysis of 8- to 10-year-old children (p < 0.05), but otherwise no significant differences were seen. The VLf showed short-term safety and effectiveness against myopia progression.

Slowing Down Myopia Progression with Contact Lenses - Everyday Cases from the Clinic

BACKGROUND

An estimated 49.8% of the world population will be myopic by 2050. Multifocal contact lenses (MFCLs) and orthokeratology (OK) reduce peripheral retinal hyperopic defocus, which animal studies have shown to positively impact eye growth. MFCLs are expected to slow myopic progression by 20 - 50% and OK by 30 - 60%, making them valuable therapeutic tools. In view of the guidelines for myopia management published by the International Myopia Institute in 2019, the aim of this retrospective data analysis of a tertiary care center was to review past experience with OK and MFCLs for myopia control and gain information to update current practice.

PATIENTS AND METHODS

The contact lens (CL) database of the Eye Clinic of the University Hospital of Basel was searched with the label "myopia progression" between January 2012 - 2020. Patients were included if they gave informed consent, were younger than 19 years old at baseline, and had no ocular comorbidities that could potentially compromise vision. Primary outcomes were progression of spherical equivalent refraction for MFCL patients and progression of axial length (AL) for the OK group, comparing with historical data from OK trials. Secondary outcomes were the presence of risk factors for myopia, age, refractive error at baseline, follow-up duration, and adverse effects during therapy.

RESULTS

Twenty-one patients could be included, with a mean age of 12.80 ± 3.32 years (y) at baseline. The majority of patients were older than 12 years and already myopic (- 3.89 ± 2.30 diopters) when control treatment was started. Overall, follow-up ranged from 0.08 to 6.33 years (2.03 ± 1.66 y). In the patients treated with MFCLs, myopia control improved significantly when patients changed from spectacles to MFCLs. In the OK group, 14% dropped out during the first year and 2 patients had multiple AL measurements during therapy, which showed a slower growth of AL when compared to other OK trials and controls with spectacles. There were two cases of non-severe keratitis. Environmental risk factors had not been documented and only 48% of clinical records had a documented family risk assessment.

CONCLUSION

Patients showed a slower myopia progression under MFCLs or OK, which supports their role as a treatment option in myopia management. In this regard, AL measurement is an important additional parameter to be included in the assessment of myopia progression in clinical practice. Identification of children at risk of developing high/pathologic myopia (family history, environmental risk factors) needs to improve so that the first stages of myopic shift can be recognized and targeted. Changes in lifestyle should be actively encouraged, especially when the impact of decreases in outdoor time secondary to COVID-19 is yet to become clear.

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.

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

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

A review on the epidemiology of myopia in school children worldwide

Background

Due to high prevalence myopia has gained importance in epidemiological studies. Children with early onset are at particular risk of complications associated with myopia, as progression over time might result in high myopia and myopic macular degeneration. Both genetic and environmental factors play a role in the increasing prevalence of myopia. The aim of this study is to review the current literature on epidemiology and risk factors for myopia in school children (aged 6–19 years) around the world.

Main body

PubMed and Medline were searched for the following keywords: prevalence, incidence, myopia, refractive error, risk factors, children and visual impairment. English language articles published between Jan 2013 and Mar 2019 were included in the study. Studies were critically reviewed for study methodology and robustness of data. Eighty studies were included in this literature review.

Myopia prevalence remains higher in Asia (60%) compared with Europe (40%) using cycloplegic refraction examinations. Studies reporting on non-cycloplegic measurements show exceptionally high myopia prevalence rates in school children in East Asia (73%), and high rates in North America (42%). Low prevalence under 10% was described in African and South American children. In recent studies, risk factors for myopia in schoolchildren included low outdoor time and near work, dim light exposure, the use of LED lamps for homework, low sleeping hours, reading distance less than 25 cm and living in an urban environment.

Conclusion

Low levels of outdoor activity and near work are well-established risk factors for myopia; this review provides evidence on additional environmental risk factors. New epidemiological studies should be carried out on implementation of public health strategies to tackle and avoid myopia. As the myopia prevalence rates in non-cycloplegic studies are overestimated, we recommend considering only cycloplegic measurements.

Objectively Measured Light Exposure During School and Summer in Children

SIGNIFICANCE

Significant differences in light exposure were observed between school and summer in children, whereas activity and sleep were similar. Associations between parent and child behaviors suggest a potential mechanism for how myopia is transmitted from parents to children through patterns of environmental exposure, in addition to genetic factors.

PURPOSE

Objectively measured time outdoors, light exposure, activity, and sleep were examined in children during school and summer and assessed with eye growth. Associations between parent and child behaviors were evaluated.

METHODS

Children (aged 7.6 ± 1.8 years, n = 60) in Houston, TX, wore an actigraph device for three 2-week sessions (fall school, spring school, summer) to quantify time outdoors, light exposure, activity, and sleep. Cycloplegic autorefraction (WAM-5500; Grand-Seiko, Tokyo, Japan) and axial length (LenStar; Haag-Streit AG, Koeniz, Switzerland) were measured at baseline and 1 year. A subset of parents wore the device during their child's first 2-week session to compare behaviors (n = 33).

RESULTS

Children spent 94.4 ± 30.6 minutes per day outdoors in spring, 110.6 ± 45.7 minutes in summer, and 72.2 ± 31.0 minutes in fall, with significant differences between sessions (P < .0001). Daily activity and sleep duration were similar across sessions (P = .73 and .06, respectively). Axial growth rate decreased with light exposure, but did not reach significance after adjusting for baseline axial length, age, sex, activity, and parental myopia (P = .073). Parent and child time outdoors and sleep duration were significantly correlated (P = .0002 and 0.026, respectively).

CONCLUSIONS

Significant differences in light exposure were observed between school and summer, whereas activity and sleep were constant throughout the year. Children's behaviors were associated with their parent's behaviors, which may represent a modifiable component to potential environmental influences on eye growth. However, light exposure was not a significant environmental influence on axial growth in this study.

Higher order aberrations, refractive error development and myopia control: a review

Evidence from animal and human studies suggests that ocular growth is influenced by visual experience. Reduced retinal image quality and imposed optical defocus result in predictable changes in axial eye growth. Higher order aberrations are optical imperfections of the eye that alter retinal image quality despite optimal correction of spherical defocus and astigmatism. Since higher order aberrations reduce retinal image quality and produce variations in optical vergence across the entrance pupil of the eye, they may provide optical signals that contribute to the regulation and modulation of eye growth and refractive error development. The magnitude and type of higher order aberrations vary with age, refractive error, and during near work and accommodation. Furthermore, distinctive changes in higher order aberrations occur with various myopia control treatments, including atropine, near addition spectacle lenses, orthokeratology and soft multifocal and dual-focus contact lenses. Several plausible mechanisms have been proposed by which higher order aberrations may influence axial eye growth, the development of refractive error, and the treatment effect of myopia control interventions. Future studies of higher order aberrations, particularly during childhood, accommodation, and treatment with myopia control interventions are required to further our understanding of their potential role in refractive error development and eye growth.

IMI - Clinical Management Guidelines Report

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

The visual status of adolescents in Riyadh, Saudi Arabia: a population study

Purpose

The visual status of adolescents in Saudi Arabia (SA) has not been well reported. To date, the prevalence and types of refractive errors (REs), amblyopia, strabismus, and correctable visual impairments have not been quantified. The aim of the study was to investigate the visual status in adolescents in Riyadh, SA.

Methods

This study was based on a population cross-sectional and random cluster design. After design and the sample calculations, 1,007 participants, 12–20 years of age, were screened during the study. Nine participants were excluded due to ocular disorders. The participants were assessed for REs, distance visual acuity logarithm of the minimum angle of resolution, contrast sensitivity, stereoacuity, pinhole test findings, and cover–uncover test findings.

Results

The results showed that 55.5% of the participants had some form of REs, while correctable visual impairment was found in one-fifth of the screened participants. Myopia was the dominant type (53.3%, ranged from −0.50 DS to −14.00 DS), whereas hyperopia was found in 2.2% (+2.00 DS to +5.50 DS) and astigmatism was present in 15% (−0.75 DC to −5.25 DC). Only 43% of the participants had corrected REs; however, the noncompliance for spectacle use was 20.25%.

Conclusion

This study was the first attempt to investigate the visual status in adolescents in SA. It provided estimations of the REs, amblyopia, and strabismus. The high prevalence of REs emphasizes the need to identify the best proactive strategies to detect and manage REs to reduce the incidence of visual impairment in SA. Increasing awareness about eye health and employing efficient screening programs could help to address the need for REs corrections.

Investigating the Visual Status Of Preschool Children in Riyadh, Saudi Arabia

PURPOSE:

The purpose of the study was to explore the vision status of preschool children aged 3–6 years in Al Riyadh and to identify children at risk of amblyopia.

MATERIALS AND METHODS:

This was a cross-sectional population-based study. Visual acuity (VA) was measured using 15-line Lea symbols, refractive error was assessed using the Mohindra near retinoscopy technique, and peak contrast sensitivity (CS) was measured with the aid of the numerical CS test. We recruited 335 children, with their parents' written consent, from 14 kindergartens.

RESULTS:

A total of 335 children were recruited; 42 children (13%) exhibited reduced VA (Median [interquartile ranges (IQRs)], 0.00 [0.01]); most were emmetropic (87.7%). Myopia (4.2%), hyperopia (8.1%), and astigmatism (20%) were also observed. Most children had normal CSs. About 14% of children were at risk of amblyopia. It has been observed that 26% of families have some kind of refractive error.

CONCLUSIONS:

It is important to perform vision screening of preschoolers. Early detection of abnormalities in refractive errors could help to minimize the effect of visual impairment.

Violet Light Transmission is Related to Myopia Progression in Adult High Myopia

Myopia is increasing worldwide. Although the exact etiology of myopia is unknown, outdoor activity is one of the most important environmental factors for myopia control. We previously reported that violet light (VL, 360-400 nm wavelength), which is abundant in the outdoor environment, suppressed myopia progression for individuals under 20 years of age. However, whether VL is also effective for adult high myopia, which can be sight-threatening, has remained unknown. To investigate the influence of VL for adult myopia, we retrospectively compared the myopic progression and the axial length elongation over five years in adult high myopic patients over 25 years of age after two types (non-VL transmitting and VL transmitting) of phakic intraocular lens (pIOL) implantation. We found that high myopic patients with the non-VL transmitting pIOLs implanted are almost two times more myopic in the change of refraction and four times longer in the change of axial length, compared to those implanted with the VL transmitting pIOLs. This result indicated that the VL transmitting pIOL suppressed myopia progression and axial length elongation compared with the non-VL transmitting one. In conclusion, our study showed the VL possibly has an anti-myopia effect for human adults with high myopia.

[Epidemiology of refractive errors]

Refractive errors are very common and can lead to severe pathological changes in the eye. This article analyzes the epidemiology of refractive errors in the general population in Germany and worldwide and describes common definitions for refractive errors and clinical characteristics for pathologicaal changes. Refractive errors differ between age groups due to refractive changes during the life time and also due to generation-specific factors. Current research about the etiology of refractive errors has strengthened the influence of environmental factors, which led to new strategies for the prevention of refractive pathologies.

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.

Violet Light Exposure Can Be a Preventive Strategy Against Myopia Progression

Prevalence of myopia is increasing worldwide. Outdoor activity is one of the most important environmental factors for myopia control. Here we show that violet light (VL, 360–400 nm wavelength) suppresses myopia progression. First, we confirmed that VL suppressed the axial length (AL) elongation in the chick myopia model. Expression microarray analyses revealed that myopia suppressive gene EGR1 was upregulated by VL exposure. VL exposure induced significantly higher upregulation of EGR1 in chick chorioretinal tissues than blue light under the same conditions. Next, we conducted clinical research retrospectively to compare the AL elongation among myopic children who wore eyeglasses (VL blocked) and two types of contact lenses (partially VL blocked and VL transmitting). The data showed the VL transmitting contact lenses suppressed myopia progression most. These results suggest that VL is one of the important outdoor environmental factors for myopia control. Since VL is apt to be excluded from our modern society due to the excessive UV protection, VL exposure can be a preventive strategy against myopia progression.

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Violet light (360–400 nm wavelengths) suppressed the axial length elongation both in a chick myopia model and in human.

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The myopia suppressive gene EGR1 was upregulated by the violet light exposure.

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Violet light, one of the myopia suppressive factors in the outdoor environment, is deficient from our modern society.

Short-sightedness (myopia) has been increasing worldwide especially over the past 50 years. Our studies on chicks and humans revealed that violet light (360–400 nm wavelength) suppressed myopia progression. At a molecular level we found that violet light increased the expression of the gene EGR1 known to prevent myopia. Interestingly, violet light is deficient in our modern society because various ultraviolet-protected products are not transmitting violet light, and light sources such as LED irradiate no violet light. Ultraviolet protection is important for ocular health, but excessive ultraviolet protection, including violet light, should be reconsidered from the aspect of myopia control.

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%).

Controlling myopia progression in children and adolescents

Myopia is a common disorder, affecting approximately one-third of the US population and over 90% of the population in some East Asian countries. High amounts of myopia are associated with an increased risk of sight-threatening problems, such as retinal detachment, choroidal degeneration, cataracts, and glaucoma. Slowing the progression of myopia could potentially benefit millions of children in the USA. To date, few strategies used for myopia control have proven to be effective. Treatment options such as undercorrection of myopia, gas permeable contact lenses, and bifocal or multifocal spectacles have all been proven to be ineffective for myopia control, although one recent randomized clinical trial using executive top bifocal spectacles on children with progressive myopia has shown to decrease the progression to nearly half of the control subjects. The most effective methods are the use of orthokeratology contact lenses, soft bifocal contact lenses, and topical pharmaceutical agents such as atropine or pirenzepine. Although none of these modalities are US Food and Drug Administration-approved to slow myopia progression, they have been shown to slow the progression by approximately 50% with few risks. Both orthokeratology and soft bifocal contact lenses have shown to slow myopia progression by slightly less than 50% in most studies. Parents and eye care practitioners should work together to determine which modality may be best suited for a particular child. Topical pharmaceutical agents such as anti-muscarinic eye drops typically lead to light sensitivity and poor near vision. The most effective myopia control is provided by atropine, but is rarely prescribed due to the side effects. Pirenzepine provides myopia control with little light sensitivity and few near-vision problems, but it is not yet commercially available as an eye drop or ointment. Several studies have shown that lower concentrations of atropine slow the progression of myopia control with fewer side effects than 1% atropine. While the progression of myopic refractive error is slowed with lower concentration of atropine, the growth of the eye is not, indicating a potentially reversible form of myopia control that may diminish after discontinuation of the eye drops. This review provides an overview of the myopia control information available in the literature and raises questions that remain unanswered, so that eye care practitioners and parents can potentially learn the methods that may ultimately improve a child’s quality of life or lower the risk of sight-threatening complications.

Assumption-free estimation of the genetic contribution to refractive error across childhood

PURPOSE

Studies in relatives have generally yielded high heritability estimates for refractive error: twins 75-90%, families 15-70%. However, because related individuals often share a common environment, these estimates are inflated (via misallocation of unique/common environment variance). We calculated a lower-bound heritability estimate for refractive error free from such bias.

METHODS

Between the ages 7 and 15 years, participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) underwent non-cycloplegic autorefraction at regular research clinics. At each age, an estimate of the variance in refractive error explained by single nucleotide polymorphism (SNP) genetic variants was calculated using genome-wide complex trait analysis (GCTA) using high-density genome-wide SNP genotype information (minimum N at each age=3,404).

RESULTS

The variance in refractive error explained by the SNPs ("SNP heritability") was stable over childhood: Across age 7-15 years, SNP heritability averaged 0.28 (SE=0.08, p<0.001). The genetic correlation for refractive error between visits varied from 0.77 to 1.00 (all p<0.001) demonstrating that a common set of SNPs was responsible for the genetic contribution to refractive error across this period of childhood. Simulations suggested lack of cycloplegia during autorefraction led to a small underestimation of SNP heritability (adjusted SNP heritability=0.35; SE=0.09). To put these results in context, the variance in refractive error explained (or predicted) by the time participants spent outdoors was <0.005 and by the time spent reading was <0.01, based on a parental questionnaire completed when the child was aged 8-9 years old.

CONCLUSIONS

Genetic variation captured by common SNPs explained approximately 35% of the variation in refractive error between unrelated subjects. This value sets an upper limit for predicting refractive error using existing SNP genotyping arrays, although higher-density genotyping in larger samples and inclusion of interaction effects is expected to raise this figure toward twin- and family-based heritability estimates. The same SNPs influenced refractive error across much of childhood. Notwithstanding the strong evidence of association between time outdoors and myopia, and time reading and myopia, less than 1% of the variance in myopia at age 15 was explained by crude measures of these two risk factors, indicating that their effects may be limited, at least when averaged over the whole population.