Prevalence and Possible Factors of Myopia in Norwegian Adolescents

Abstract

East Asia has experienced an excessive increase in myopia in the past decades with more than 80% of the younger generation now affected. Environmental and genetic factors are both assumed to contribute in the development of refractive errors, but the etiology is unknown. The environmental factor argued to be of greatest importance in preventing myopia is high levels of daylight exposure. If true, myopia prevalence would be higher in adolescents living in high latitude countries with fewer daylight hours in the autumn-winter. We examined the prevalence of refractive errors in a representative sample of 16–19-year-old Norwegian Caucasians (n = 393, 41.2% males) in a representative region of Norway (60° latitude North). At this latitude, autumn-winter is 50 days longer than summer. Using gold-standard methods of cycloplegic autorefraction and ocular biometry, the overall prevalence of myopia [spherical equivalent refraction (SER) ≤−0.50 D] was 13%, considerably lower than in East Asians. Hyperopia (SER ≥ + 0.50 D), astigmatism (≥1.00 DC) and anisometropia (≥1.00 D) were found in 57%, 9% and 4%. Norwegian adolescents seem to defy the world-wide trend of increasing myopia. This suggests that there is a need to explore why daylight exposure during a relatively short summer outweighs that of the longer autumn-winter.

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

“…; Hagen et al. ). The reasons for these differences between European and East Asian populations are not fully understood.…”

A review on the epidemiology of myopia in school children worldwide

“…Interesting results were presented in a recent study on 16-19-year-old Norwegian Caucasians (n = 393) living in 60°latitude North, where autumn-winter is 50 days longer than summer [55]. In their investigation the total time spent doing outdoor was not associated with myopia (3.65 ± 1.5 h in myopes, and 3.81 ± 1.9 in nonmyopes, p = 0.64).…”

“…In their investigation the total time spent doing outdoor was not associated with myopia (3.65 ± 1.5 h in myopes, and 3.81 ± 1.9 in nonmyopes, p = 0.64). Moreover, the prevalence of myopia was quite low (13% for SER lower than ≤ − 0.5 D), despite the few daylight hours in the autumn-winter period (10 h 36 min-11 h 5 min) and high levels of indoor activity and near work [55]. The commonly agreed underlying mechanism of time spent outdoors proposed by researchers is based on the release of retinal dopamine that controls scleral growing and remodeling.…”

Vision status of children aged 7 - 15 years referred from school vision screening in Norway during 2003 - 2013: a retrospective study

“…Furthermore, changes were made to the school vision screening protocol based on preliminary results from this study (e.g., include cycloplegic refraction). Based on the results from a recent study in Norwegian adolescents [27], we think our results would not be significantly different if more recent years were added. Despite not including recent years, our study contributes important knowledge of vision status and problems in schoolchildren that may guide further research, clinical practice and health care policies to include vision in school health care, as this still receives little attention in Norway and in many other countries [52,53].…”

“…The prevalence of visual problems in primary and secondary schoolchildren (6-16 years) in Norway is unknown, but a recent Norwegian study in 16-to 19-year-olds found that more than half were hyperopes [27]. It is known that common vision problems, such as refractive errors, heterophorias and accommodative disorders, may have a profound effect on learning [4,7].…”