IMI Risk Factors for Myopia

Abstract

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.

Normative data and percentile curves for axial length and axial length/corneal curvature in Chinese children and adolescents aged 4–18 years

“…Education and time outdoors have been identified as two major causal risk factors for myopia. 5 In Chinese children from the Shanghai region, myopia prevalence markedly increased from 6 years of age, 6 with increased educational workload cited as an important risk factor for the high prevalence. 5 Interestingly, for a given AL/CR ratio; female eyes tended to have more myopia than their male counterparts with the difference manifesting especially at the onset of myopia.…”

“…5 In Chinese children from the Shanghai region, myopia prevalence markedly increased from 6 years of age, 6 with increased educational workload cited as an important risk factor for the high prevalence. 5 Interestingly, for a given AL/CR ratio; female eyes tended to have more myopia than their male counterparts with the difference manifesting especially at the onset of myopia. An AL/CR cut-off criterion of >3.0 still applies for detection of myopia across both genders, 19 but at AL/CR values of ≥3.0, the female eye is more myopic.…”

Is myopia prevalence related to outdoor green space?

“…7 This is attributed to urbanised lifestyles being associated with reduced time outdoors, increased near work activities and higher levels of education; all strong risk factors for myopia. 3 Increased time outdoors has been shown to be protective against myopia. 17,46,47 The risk of developing myopia is greatest in school-aged children, and this period represents the critical time to target them with preventative measures such as greater time outdoors (perhaps encouraging this through green space); in particular, a stronger protective effect was observed for 6-year old children compared with those aged 11-12 years.…”

“…some parts of the world, for example in East and South East Asia, 3 but studies are reporting that myopia is on the rise in Australia, 4 the United States and some parts of Europe. Myopia currently (2020) affects 30% of the world and is estimated to affect 50% of the world by 2050.…”

Reappraisal of the historical myopia epidemic in native Arctic communities

“…One of these regulations, mandatory schooling, triggered a well‐documented myopia epidemic 3 in the Inuit during the 1950s and 1960s, which is often cited as cautionary proof that education is strongly associated with myopia development. However, with the scientific progress that has occurred since the original reports were first published, it became clear that education is only one, albeit a key, co‐factor in myopia 4 …”