A possible evidence-based model of myopia development (Photo credit: Harb & Wildsoet 2019)
Human myopia
The concept that the more common form of human myopia might be visually-driven is not new. At the turn of the century, special management strategies to include hygiene desk and sea voyages were being used to counter the presumed harmful effects of near work. There also is much anecdotal evidence linking near work and myopia and recent studies provide more direct evidence of links between visual activities and myopia.
Does near work cause myopia?
Of the many theories that abound, two fit well with evidence from animal studies. One theory argues that printed text, as most commonly encountered in near work activities, acts as a form deprivation stimulus for all but the central retina. On the other hand that human myopia could be a response to hyperopic defocus is consistent with observations of increased lags of accommodation in developing and progressing myopes. However, the picture is by no means clear-cut in terms of causality. Also, that eyes may progress at different rates leading to significant anisometropia is not easily covered by this hypothesis. Currently in this area, there are more questions than answers.
The concept that the more common form of human myopia might be visually-driven is not new. At the turn of the century, special management strategies to include hygiene desk and sea voyages were being used to counter the presumed harmful effects of near work. There also is much anecdotal evidence linking near work and myopia and recent studies provide more direct evidence of links between visual activities and myopia.
Does near work cause myopia?
Of the many theories that abound, two fit well with evidence from animal studies. One theory argues that printed text, as most commonly encountered in near work activities, acts as a form deprivation stimulus for all but the central retina. On the other hand that human myopia could be a response to hyperopic defocus is consistent with observations of increased lags of accommodation in developing and progressing myopes. However, the picture is by no means clear-cut in terms of causality. Also, that eyes may progress at different rates leading to significant anisometropia is not easily covered by this hypothesis. Currently in this area, there are more questions than answers.
 Wu 2013 (green), He 2015 (blue), Wu 2018 (orange), Jin 2015 (yellow) (Photo credit: Harb & Wildsoet 2019)
Outdoor activity and myopia
Randomized controlled trials were conducted for 1-3 years investigating the effects of increased outdoor recess time compared to a traditional school day in Asian schoolchildren. The studies found varied relative reductions in myopia incidence during the trial periods. Myopia progression in children with baseline myopia was controlled by less than a quarter of a diopter. Outdoor activity may be protective against myopia development and progression, but we do not know what aspect of outdoor activity may be responsible for this delay. Using child-friendly wearable technologies to capture physical activity, lighting characteristics, indoor-outdoor activity, and object nearness may help us better understand the role of the visual environment in the development of myopia. |
Wearable technologies like the Actiwatch may help with myopia research (Photo credit: Harb & Wildsoet 2019)
|
