How does spending time outdoors protect against myopia? A review

Area of Science:

• Ophthalmology
• Public Health
• Environmental Science

Background:

• Myopia is a growing global health concern with significant societal costs.
• It increases the risk of serious eye conditions like glaucoma, retinal detachment, and myopic maculopathy, potentially leading to blindness.
• While outdoor time is known to reduce myopia risk, potential detrimental effects also exist.

Purpose of the Study:

• To investigate the mechanisms by which spending time outdoors may prevent myopia.
• To evaluate the evidence supporting various proposed protective factors associated with outdoor exposure.
• To inform the development of targeted myopia prevention strategies.

Main Methods:

• A comprehensive review of existing scientific literature was conducted.
• Evidence for and against eight proposed factors were analyzed: brighter light, peripheral defocus, vitamin D, light spectrum, physical activity, circadian rhythms, near work, and spatial frequency (SF) energies.
• Studies focusing on human subjects were prioritized.

Main Results:

• Solid evidence supports that brighter light exposure significantly reduces myopia risk.
• The role of peripheral defocus in mediating myopia risk from outdoor time remains unclear.
• While plausible, evidence from human studies is lacking for the roles of light spectrum, circadian rhythms, and SF energies.
• Vitamin D, physical activity, and near work appear unlikely to be the primary mediators.

Conclusions:

• Brighter light exposure is the most strongly supported mechanism by which outdoor time prevents myopia.
• Further research is needed to clarify the roles of other environmental factors.
• Understanding these mechanisms is crucial for developing effective public health interventions against myopia.