There is clear evidence from randomized clinical trials that increased outdoor time can delay the onset of myopia, and thus decrease the final amount of myopia a child develops. Increased outdoor time may also have a small protective effect in slowing myopia progression. Greater duration of near work and close working distances have been associated with increased risk of myopia. A recent observational study provides some suggestions that a closer working distance may also be associated with increased progression. Other possible risk factors include use of LED lamps for homework, dim light, fewer hours of sleep and living in an urban environment.
The same factors that are related to onset are likely related to progression, but further research is needed to fully understand the interplay of genetic and environmental factors in both onset and progression. For now, the potential benefit and very low cost and risk associated with outdoor time and breaks from close near work make them ideal goals for pre-myopic and myopic children. This means limiting cell phone and tablet use as much as possible.
Recent evidence, together with changes found during COVID-19 lockdowns demonstrates that behavior changes related to digital devices may indeed worsen myopia in youngsters. Although more high-quality research is needed to prove causation, optometrists caring for children at risk should evaluate the possibility that excessive smart device use could lead to an increase in myopia. The recent global growth in myopia prevalence predates the advent of digital devices. However, this result does not rule out the likelihood that such devices would have an impact on future myopia trends.