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 ≤À0.50 D in right eye. Results: We included 1443 participants (45% boys) with a median age (AEIQR) of 16.6 years (AE0.3). 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.

Background: The purpose of the study was to examine 5-year changes in eyes with optic disc drusen at baseline on optical coherence tomography (OCT) scans and the relation of incident drusen to hyperreflective prelaminar lines. Methods: The study included children who presented at baseline, when participants were aged 11–12 years, and again 5 years later. Grading for optic disc drusen was made in all. Grading for prelaminar lines was made in all children at follow-up and in eyes with optic disc drusen at baseline. Analyses included associations with scleral canal diameter at baseline in all children with optic disc drusen and a nested control group of 115 children without optic disc drusen. Data are reported as the number of children having at least one drusen or at least one hyperreflective line per person. Results: The analysis included 724 children who attended both rounds of the study. Of these, 11 (1.5%) had optic disc drusen at baseline. Five additional children had developed optic disc drusen at follow-up, whereas optic disc drusen had disappeared in none, so that 16 (2.2%) children had optic disc drusen in one or both eyes at follow-up. Children with optic disc drusen at the 5-year follow-up had had a mean scleral canal diameter of 1,364 µm (interquartile range [IQR] 81 µm), compared with 1,457 µm (IQR 197) µm in 115 nested controls without optic disc drusen (P < 0.001). Optic disc drusen at follow-up were associated with more hypermetropic refraction. All children who had optic disc drusen at follow-up also had prelaminar hyperreflective lines. In addition, such lines were found at follow-up in 24 of the remaining 708 children without optic disc drusen (P < 0.001). Prelaminar hyperreflective lines with or without optic disc drusen were associated with a narrower scleral canal (diameter 1,364 µm, IQR 119 µm) compared with absence of prelaminar lines (1,486 µm, IQR 206 µm; P < 0.0001). Conclusion: This study provides the first evidence from a prospective study that small optic discs and prelaminar hyperreflective lines on OCT are risk factors for the development of optic disc drusen. The association between prelaminar hyperreflective lines, hypermetropia, and a narrow scleral canal supports that a crowded disc is an essential predisposing factor for the development of optic disc drusen.

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