Outdoor light and the prevention of myopia

The management of myopia is facing an unprecedented challenge, as the prevalence of myopia has ascended rapidly in the last decades. Although there is still no clinically acceptable and satisfactory management available, growing evidence has suggested that outdoor exposure, mediated by outdoor light, is a simple and useful option to prevent the development of myopia. In my thesis, I have investigated the roles of spectral properties of indoor light and of high light intensity on experimental myopia, the dose-effect response and the temporal function of the exposure, and the possible molecular mechanism underlying the light-mediated protective effect against myopia. I found that with the same spectral property (i.e. spectral composition and distribution), high-level light intensity prevented myopia development compared with low-level intensity. However, there was no significant difference in the protection effect between the sunlight-like and fluorescent lighting presented at the same level of intensity, indicating that high level of light intensity is the primary reason for the outdoor light to display a powerful inhibitor against myopia. Furthermore, the dose-effect response of bright light exposure was found to be not linear, but rather saturate at approximately 5 hours of treatment, suggesting that additional protection could not be obtained through simply increasing the exposure duration. By contrast, frequent and short episodes of exposure were found to enhance the protection effect than a single continuous exposure even though the light intensity and total dose of exposure was the same. With regard to the underlying mechanism, I found that wearing diffusers dramatically suppressed dopamine release from the retina and also the expression of ZENK protein in the retinal glucagonergic amacrine cells (GACs). Bright light, no matter presented continuously or intermittently, could significantly reduce the suppression of dopamine release. But no any difference in the rescue effect of dopamine release was detected between these two exposure patterns. Neither continuous nor intermittent bright light could rescue the suppression of ZENK induced by wearing diffusers. As a whole, my doctoral thesis has extended our knowledge of the mechanism underlying outdoor light against myopia: high level of intensity is the major reason for the protective effect of sunlight, which depends not only on the total duration but also the temporal property of the exposure. Findings in the thesis provide further evidence for a role of dopamine in the signaling cascade of the bright-light-mediated protection, but a role of ZENK in glucagon amacrine cells, representing an important element in the retinal circuitry for the detection of the sign of defocus, is unlikely. The reason why intermittent bright light had a more prominent suppressive effect on myopia than continuous bright light exposure is still unclear and needs further investigation

Refractive errors in 3-6 year-old Chinese children: a very low prevalence of myopia?

PURPOSE To examine the prevalence of refractive errors in children aged 3-6 years in China. METHODS Children were recruited for a trial of a home-based amblyopia screening kit in Guangzhou preschools, during which cycloplegic refractions were measured in both eyes of 2480 children. Cycloplegic refraction (from 3 to 4 drops of 1% cyclopentolate to ensure abolition of the light reflex) was measured by both autorefraction and retinoscopy. Refractive errors were defined as followed: myopia (at least -0.50 D in the worse eye), hyperopia (at least +2.00 D in the worse eye) and astigmatism (at least 1.50 D in the worse eye). Different definitions, as specified in the text, were also used to facilitate comparison with other studies. RESULTS The mean spherical equivalent refractive error was at least +1.22 D for all ages and both genders. The prevalence of myopia for any definition at any age was at most 2.5%, and lower in most cases. In contrast, the prevalence of hyperopia was generally over 20%, and declined slightly with age. The prevalence of astigmatism was between 6% and 11%. There was very little change in refractive error with age over this age range. CONCLUSIONS Previous reports of less hyperopic mean spherical equivalent refractive error, and more myopia and less hyperopia in children of this age may be due to problems with achieving adequate cycloplegia in children with dark irises. Using up to 4 drops of 1% cyclopentolate may be necessary to accurately measure refractive error in paediatric studies of such children. Our results suggest that children from all ethnic groups may follow a similar pattern of early refractive development, with little myopia and a hyperopic mean spherical equivalent over +1.00 D up to the age of 5-6 years in most conditions.Supported by the National Natural Science Foundation of China, Beijing, China (grant no.: 81200714;http://www.nsfc.gov.cn/); Foundation for Distinguished Young Talents in Higher Education of Guangdong, Guangdong Province, China (grant no.: LYM 11009;http://www.gdhed.edu.cn/) and the Science and Information Technology Bureau of Guangzhou, Guangdong Province, China (grant no.: 2011Y2-00018-3;http://www.gzsi.gov.cn/)

Reliability of Ocular Aberration Measurements in Children with Moderate and Low Myopia under Scotopic Conditions

Purpose. To investigate the reliability of ocular aberration measurement in myopic children under scotopic conditions and to validate the mathematical Zernike pupil scaling-down technique. Methods. Ocular aberrations of 45 myopic children were examined under scotopic conditions via iTrace aberrometer. The intra- and intersession repeatability was evaluated for both the measured values with the true pupil sizes and the estimated ones that were determined by scaling down the pupil sizes to the largest integer value across all measurements. Results. The intra- and intersession difference of clinically measured aberration was generally insignificant, and the ICCs for each aberration component exhibited good to excellent reliability (ICCs > 0.4). Similar results were found for the estimated aberration using the scaling-down technique. Although the majority of the estimated Zernike components were comparable with the corresponding measured one, the estimated values of defocus, coma, and the corresponding total aberrations were found significantly smaller than the measured values (all P<0.01). Conclusions. The ocular aberration measurements in myopic children under the circumstances described are reliable. The scaling-down technique is a useful option for comparing the results obtained from different pupil sizes, but the estimated Zernike coefficients were not always comparable with the corresponding measured values

a practical tool to implement hospital-based syndromic surveillance: SCM

Background: syndromic surveillance has been widely used for the early warning of infectious disease outbreaks, especially in mass gatherings, but the collection of electronic data on symptoms in hospitals is one of the fundamental challenges that must be overcome during operating a syndromic surveillance system. The objective of our study is to describe and evaluate the implementation of a symptom-clicking-module (SCM) as a part of the enhanced hospital-based syndromic surveillance during the 41st World Exposition in Shanghai, China, 2010.Methods: the SCM, including 25 targeted symptoms, was embedded in the sentinels’ Hospital Information Systems (HIS). The clinicians used SCM to record these information of all the visiting patients, and data were collated and transmitted automatically in daily batches. The symptoms were categorized into seven targeted syndromes using pre-defined criteria, and statistical algorithms were applied to detect temporal aberrations in the data series.Results: SCM was deployed successfully in each sentinel hospital and was operated during the 184-day surveillance period. A total of 1,730,797 patient encounters were recorded by SCM, and 6.1 % (105,352 visits) met the criteria of the seven targeted syndromes. Acute respiratory and gastrointestinal syndromes were reported most frequently, accounted for 92.1 % of reports in all syndromes, and the aggregated time-series presented an obvious day-of-week variation over the study period. In total, 191 aberration signals were triggered, and none of them were identified as outbreaks after verification and field investigation.Conclusions: SCM has acted as a practical tool for recording symptoms in the hospital-based enhanced syndromic surveillance system during the 41st World Exposition in Shanghai, in the context of without a preexisting electronic tool to collect syndromic data in the HIS of the sentinel hospitals

IMI risk factors for myopia

Risk factor analysis provides an important basis for developing interventions for any condition. In the case of myopia, evidence for a large number of risk factors has been presented, but they have not been systematically tested for confounding. To be useful for designing preventive interventions, risk factor analysis ideally needs to be carried through to demonstration of a causal connection, with a defined mechanism. Statistical analysis is often complicated by covariation of variables, and demonstration of a causal relationship between a factor and myopia using Mendelian randomization or in a randomized clinical trial should be aimed for. When strict analysis of this kind is applied, associations between various measures of educational pressure and myopia are consistently observed. However, associations between more nearwork and more myopia are generally weak and inconsistent, but have been supported by meta-analysis. Associations between time outdoors and less myopia are stronger and more consistently observed, including by meta-analysis. Measurement of nearwork and time outdoors has traditionally been performed with questionnaires, but is increasingly being pursued with wearable objective devices. A causal link between increased years of education and more myopia has been confirmed by Mendelian randomization, whereas the protective effect of increased time outdoors from the development of myopia has been confirmed in randomized clinical trials. Other proposed risk factors need to be tested to see if they modulate these variables. The evidence linking increased screen time to myopia is weak and inconsistent, although limitations on screen time are increasingly under consideration as interventions to control the epidemic of myopia

IMI : global trends in myopia management attitudes and strategies in clinical practice : 2022 update

PURPOSE. Surveys in 2015 and 2019 identified a high level of eye care practitioner concern/activity about myopia, but the majority still prescribed single vision interventions to young myopes. This research aimed to provide updated information. METHODS. A self-administered, internet-based questionnaire was distributed in 13 languages, through professional bodies to eye care practitioners globally. The questions examined awareness of increasing myopia prevalence, perceived efficacy and adoption of available strategies, and reasons for not adopting specific strategies. RESULTS. Of the 3195 respondents, practitioners’ concern about the increasing frequency of pediatric myopia in their practices differed between continents (P < 0.001), being significantly higher in Asia (9.0 ± 1.5 of 10) than other continents (range 7.7–8.2; P ≤ 0.001). Overall, combination therapy was perceived by practitioners to be the most effective method of myopia control, followed by orthokeratology and pharmaceutical approaches. The least effective perceived methods were single vision distance undercorrection, spectacles and contact lenses, as well as bifocal spectacles. Practitioners rated their activity in myopia control between (6.6 ± 2.9 in South America to 7.9 ± 1.2/2.2 in Australasia and Asia). Single-vision spectacles are still the most prescribed option for progressing young myopia (32.2%), but this has decreased since 2019, and myopia control spectacles (15.2%), myopia control contact lenses (8.7%) and combination therapy (4.0%) are growing in popularity. CONCLUSIONS. More practitioners across the globe are practicing myopia control, but there are still significant differences between and within continents. Practitioners reported that embracing myopia control enhanced patient loyalty, increasing practice revenue and improving job satisfaction