How does being outdoors benefit myopes?

Paper title: How does spending time outdoors protect against myopia? A review 

Authors: Gareth Lingham (1), David A Mackey (1), Robyn Lucas (1,2), Seyhan Yazar (3,4)

1. Centre for Ophthalmology and Visual Science, Lions Eye Institute, University of Western Australia, Perth, Western Australia, Australia.
2. National Centre for Epidemiology and Population Health, Research School of Population Health, Australian National University, Canberra, Australian Capital Territory, Australia.
3. Centre for Ophthalmology and Visual Science, Lions Eye Institute, University of Western Australia, Perth, Western Australia, Australia seyhanyazar@lei.org.au.
4. Single Cell and Computational Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.

Date: May 2020

Reference: Lingham G, Mackey DA, Lucas R, Yazar S. How does spending time outdoors protect against myopia? A review. Br J Ophthalmol. 2020 May;104(5):593-599.

[Link to abstract]

Myopia has become a growing concern worldwide due to associated risks of ocular pathologies, which increase with myopic severity. Research has established that the risk of myopia development in children can be reduced by spending time outdoors.^1,2 It may also be possible that outdoor time could reduce the risk of progression for children already myopic.² If there was evidence to show outdoor time is beneficial to children’s eyesight, then it would be a simple measure to encourage.

This review weighed up the evidence for and against elements of outdoor time such as: bright light, reduced peripheral defocus, higher vitamin D levels, differing chromatic spectrum of light, higher physical activity, entrained circadian rhythms, less near work and greater high spatial frequency (SF) energies.

Exposure to bright light was found to be an aspect of outdoor time which carried evidence for being able to reduce myopia risk.

The brightness of outdoor light may not be the only benefit of outdoor time. The authors state that the spectrum of light, circadian rhythms and higher spatial frequencies are also plausible factors, despite a current lack of evidence of their benefit. As this is an abstract rather than a full paper, there is no detail on the extent of the evidence reviewed or how these factors may have been measured.

So although these aspects of the outdoors require further investigation, eye care practitioners can be aware these may also play a part in myopia onset and progression.

The benefit of reducing the risk of myopic prevalence needs to be balanced against the risk of developing other long-term ocular complications such as pterygium, cataracts and melanomas. Reminding children and parents of the importance of sun protection for the eyes and skin while outdoors to reduce these risks is crucial.

Peripheral defocus was mentioned in the review as an established method of regulating eye growth.

• This theory has been adopted in the design of some myopia control methods such as dual focus soft contact lenses, orthokeratology and some spectacle lens designs.
• What is currently less clear is the exact effect being outdoors might have on peripheral defocus patterns or myopia risk.
• One study investigating time outdoors for children wearing dual focus soft contact lenses found that spending over 4hrs outside every week while wearing the lenses gave the best response.³ However, this study did not assess the influence of outdoor light on myopia risk itself.

Further research into this would explain if outdoor time would give a definite enhancing or worsening effect to treatment options based on peripheral defocus and how this may relate to myopia risk.

Other elements which remain unclear for now are the roles vitamin D, physical activity and near work might play in myopia risk and outdoor time. This review has suggested they are unlikely to contribute to the benefit of time outdoors.

Further studies into these could investigate their influence and explain how much they may contribute to the benefit of time outside for myopes.

Title: How does spending time outdoors protect against myopia? A review 

Authors: Gareth Lingham, David A Mackey, Robyn Lucas, Seyhan Yazar

 Purpose: Myopia is an increasingly common condition that is associated with significant costs to individuals and society. Moreover, myopia is associated with increased risk of glaucoma, retinal detachment and myopic maculopathy, which in turn can lead to blindness. It is now well established that spending more time outdoors during childhood lowers the risk of developing myopia and may delay progression of myopia. There has been great interest in further exploring this relationship and exploiting it as a public health intervention aimed at preventing myopia in children. However, spending more time outdoors can have detrimental effects, such as increased risk of melanoma, cataract and pterygium. Understanding how spending more time outdoors prevents myopia could advance development of more targeted interventions for myopia. 

Methods: We reviewed the evidence for and against eight facets of spending time outdoors that may protect against myopia: brighter light, reduced peripheral defocus, higher vitamin D levels, differing chromatic spectrum of light, higher physical activity, entrained circadian rhythms, less near work and greater high spatial frequency (SF) energies.

Results: There is solid evidence that exposure to brighter light can reduce risk of myopia

Conclusions: Peripheral defocus is able to regulate eye growth but whether spending time outdoors substantially changes peripheral defocus patterns and how this could affect myopia risk is unclear. Spectrum of light, circadian rhythms and SF characteristics are plausible factors, but there is a lack of solid evidence from human studies. Vitamin D, physical activity and near work appear unlikely to mediate the relationship between time spent outdoors and myopia.

[Link to abstract]