Research Review

The Effects of Outdoor Environments, Sunglasses and Hats on Light Levels

By Geetha Sravani

PhD Candidate, Brien Holden Vision Institute

To understand the impact of sun-protective strategies (such as hats, sunglasses and tree shade) on illuminance levels to prevent myopia, Lanca et al. (2019) conducted a study by developing a custom-built, child-sized mannequin head that allowed for recording illuminance levels incident at the eye and testing across a wide range of Singapore outdoor and indoor environments. One head was designed as a control unit and the other as the measurement unit. The researchers used three different types of sunglasses (8-43 percent transmission) and hats as protective eye measures to various outdoor (open field, street and under a tree) and indoor light conditions (with and without a window).

Abstract

Purpose: Lack of outdoor time is a known risk factor for myopia. Knowledge of the light levels reaching the eye and exposure settings, including sun-protective measures, is essential for outdoor programs and myopia. We evaluated the impact of sun-protective strategies (hat and sunglasses) on maintaining high illuminance levels to prevent myopia.

 Methods: A child-sized mannequin head was developed to measure light illuminance levels with and without sun-protective equipment, across a wide range of environments in Singapore, outdoors (open park, under a tree, street) and indoors (under a fluorescent illumination with window, under white LED-based lighting without window). A comparison was made between indoor and outdoor light levels that are experienced while children are involved in day-to-day activities.

 Results: Outdoor light levels were much higher (11,080-18,176 lux) than indoors (112-156 lux). The higher lux levels protective of myopia (>1,000 lux) were measured at the tree shade (5,556-7,876 lux) and with hat (4,112-8,156 lux). Sunglasses showed lux levels between 1,792 and 6,800 lux. Although, with sunglasses, readings were lower than tree shade and hat, light levels were still 11 to 43 times higher than indoors.

 Conclusions: Recommendations on spending time outdoors for myopia prevention with adequate sun protection should be provided while partaking in outdoor activities, including protection under shaded areas, wearing a hat or sunglasses, sunscreen and adequate hydration.

 Translational Relevance: Light levels outdoors were higher than indoors and above the threshold illuminance for myopia prevention even with adequate sun-protective measures.

Lanca, C., Teo, A., Vivagandan, A., Htoon, H. M., Najjar, R. P., Spiegel, D. P., … & Saw, S. M. (2019). The effects of different outdoor environments, sunglasses and hats on light levels: Implications for myopia prevention. Translational vision science & technology, 8(4), 7-7.

DOI:https://doi.org/10.1167/tvst.8.4.7

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