Purpose: To investigate the association between objectively measured ambient light exposure and longitudinal axial length changes (and their seasonal variations) over a period of 12 months in young adults. Methods: This prospective longitudinal observational study included 43 healthy young adult university students (21 emmetropes and 22 myopes) aged between 18 and 30 years. Three axial length measurements were collected at 6-month intervals (i.e. at baseline, 6 and 12 months), in summer and winter to determine the axial eye growth. Personal ambient light exposure data were measured in winter and summer months with wearable sensors, from which the mean daily time exposed to bright (outdoor) light levels (>1000 lux) was derived. Results: Greater daily bright light exposure was associated with less axial eye growth (b = À0.002, p = 0.006) over 12 months. In summer, myopes exhibited significantly greater changes in axial length (mean change 0.04 AE 0.05 mm) compared to emmetropes (À0.01 AE 0.05 mm) (p = 0.001), but there was no significant difference between refractive groups in winter. Emmetropes also spent significantly greater time in outdoor light levels in summer compared to winter (p < 0.0001), while myopes spent similar time outdoors during both seasons (p = 0.12). Differences in light exposure between summer and winter were also associated with seasonal differences in axial eye growth (p = 0.026). Conclusion: In young adults, greater time spent in bright light was associated with slower longitudinal axial eye growth. Seasonal light exposure and axial length changes were dependent on refractive error in this population and also exhibited an inverse relationship.

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These findings suggest that a measurement duration of at least 1 week and a measurement frequency of 2 minutes or finer provides the most reliable estimates of personal outdoor light exposure measures in children and young adults.

Purpose The key preventive measures adopted to minimise the spread of the coronavirus disease (COVID-19) had significant health, economic and physical impacts mostly in developing countries. This study evaluated the health, economic and physical impacts of COVID-19 lockdown measures among sub-Saharan African (SSA) population and associated demographic variations. Methods A total of 1970 respondents took part in this web-based cross-sectional survey during the mandatory lockdown period in most SSA. The dependent variables were health (COVID-19 infection, hospitalisation), socioeconomic (lost job, closed down business) and physical impacts (separated from family) of COVID-19. Univariate and bivariate logistic regression analyses were used to explore the factors associated with each of the dependent variables by the four sub-regions (Southern, Western, Central and East Africa). Results The respondents were aged 34.1 ± 11.5 years (range: 18–75 years) and mostly men (1099, 55%). 25.9% (n = 511) reported an impact of COVID-19 pandemic with significant regional variations (p < 0.0005, higher proportion were East 36.2% and Southern Africans 30.3%) but no gender (p = 0.334) and age group variations (p > 0.05). Among Central African respondents, more men than women lost their businesses (45.7% versus 14.3%, p = 0.002) and contracted COVID-19 infections (40.0% versus 18.2%, p = 0.024) during the study period. Multivariable analysis revealed that respondents from East (adjusted odds ratio [AOR] 1.95, 95% confidence interval [CI]: 1.42–2.69), Southern (AOR 1.46, 95% CI: 1.09–1.96) and Central Africa (AOR 1.47, 95% CI: 1.06–2.03) reported significantly higher impact of COVID-19. Those who reported family separation during the lockdown were more likely to be older participants (39–48 years, AOR 2.48, 95% CI: 1.11–5.57). Conclusion One in four SSA respondents, mostly East and Southern Africans, were adversely affected by the COVID-19 pandemic during the lockdown. Interventions in high-risk populations are needed to reduce the health, socioeconomic and gender disparities in the impacts of COVID-19.

Background. Myopia prevalence varies across the country among schoolchildren in China. Recently, environmental factors have been shown to be important in myopia development and progression. Given China’s geographical diversity with variable environmental factors, we investigated whether environmental factors could explain the regional variations in myopia in mainland China. Methods. We searched PubMed, Web of Science, and Chinese Science Periodical Databases for studies with reports of myopia prevalence in schoolchildren in mainland China from the years 1979 to 2019. Data on environmental factors (annual sunshine hours, temperature, and population density) were obtained from past records. A random-effect univariate metaregression analysis was used to investigate the association between the environmental factors and myopia prevalence and to determine the proportion of variation in regional myopia prevalence that can be attributed to each factor. Results. Forty-nine eligible studies were identified that included 666,864 schoolchildren aged 6 to 20 years. The pooled estimate of myopia prevalence was 32.88% (95% confidence interval: 26.69–39.08%). Univariate metaregression analysis indicated that annual sunshine hours (27.97% of variance), annual temperature (24.66%), and population density (7.06%) significantly contributed to regional myopia prevalence variation (each p<0.05), while seasonal variation in sunshine hours (1.54%, p=0.604) was not a significant predictor of myopia prevalence. However, only annual sunshine hours was significantly associated with myopia prevalence in the multivariate metaregression model. Conclusion. Myopia prevalence in children was higher in regions with low sunshine hours, and annual sunshine hours was significantly associated with regional variation in myopia prevalence in mainland China.