Ambient light level varies with different locations and environmental conditions: Potential to impact myopia

Abstract

Purpose Considering that time spent outdoors is protective for myopia, we investigated how ambient light levels reaching the eye varies across 9 outdoor and 4 indoor locations in 5 different environmental conditions. Methods Illuminance (lux) was recorded using a lux meter under conditions of weather (sunny/cloudy), time of a day (7:00,10:00,13:00, and 16:00 hours), seasons (summer/winter), and sun protection (hat and cap) in outdoor and indoor locations. Nine outdoor locations were “open playground”, “under a translucent artificial-shade”, “under a porch facing east”, “under a porch facing south”, “under a big tree”, “between three buildings”, “within 4 buildings”, and “canopy”. As a ninth outdoor location, “Under a glass bowl” in the outdoor location was used as a simulation for “glass classroom model” and measurement was taken at the floor level only to determine in overall the illuminance conditions with glass covered on all sides. The 4 indoor locations included “room with multiple large windows”, “room with combination light source”, “room with multiple artificial lights”, and “room with single artificial light”. Results The overall median illuminance level (median; Q1-Q3) recorded in 9 outdoor locations was 8 times higher than that of all indoor locations (1175;197–5400 lux vs. 179;50–333 lux). Highest illuminance in outdoor locations was recorded in “open playground” (9300;4100–16825 lux), followed by “under a translucent artificial shade (8180;4200–13300 lux) and the lowest in “within 4 buildings” (11;6–20 lux). Illuminance under ‘Canopy’, ‘between three buildings’ and ‘within four buildings’ was similar to that of indoor locations (<1000 lux). Time of the day, weather, season, sensor position and using sun protection did not alter illuminance to change from high to low level (>1000 to <1000 lux). Among indoor locations, illuminance in “room with multiple large windows” crossed 1000 lux at a specific time points on both sunny and cloudy days. Conclusions Illuminance levels in outdoors and indoors varied with location type, but not with other conditions. Given the variation in illuminance in different locations, and the impact it may have on myopia control, appropriate detailed recommendations seems necessary while suggesting time outdoors as an anti-myopia strategy to ensure desired outcomes.

Effects of mild‐ and moderate‐intensity illumination on short‐term axial length and choroidal thickness changes in young adults

“…In comparison, the irradiance or energy of 1000 lux of illumination used in our study was almost 3× greater (284 μW/cm 2 ) and so the ocular changes clearly reflected the effect of light exposure (and not diurnal rhythms). However, 500 lux of illumination, which is also a typical indoor light level, 62 was closer to the illumination levels used by Lou and Ostrin. Despite low illuminance, the ocular changes with 500 lux in this study may not represent the normal diurnal changes in the eye.…”

“…With regards to indoor lighting, the illuminance levels can vary significantly at different locations. 62 Therefore, despite being under 500 lux indoors, the eye may not constantly receive the same illuminance at all times, which is different to a close and continuous exposure of 500 lux for 2 h. Thirdly, the spectral composition of white light used in the current study (Figure 1c) was slightly different from Lou and Ostrin, and had relatively less energy in the higher wavelength region. Given the evidence of small increases in AL and choroidal thinning under red light in humans, 49 it is possible that reduced energy in the red spectrum can induce small reductions in AL and choroidal thickening.…”

“…Secondly, because light levels vary significantly depending on the position of the source and viewing direction, 63 wall‐mounted LED panels in Lou and Ostrin study (with light reflecting from walls and other surfaces in the laboratory) can produce a very different ocular effect compared to direct light from a closer distance via light‐emitting glasses. With regards to indoor lighting, the illuminance levels can vary significantly at different locations 62 . Therefore, despite being under 500 lux indoors, the eye may not constantly receive the same illuminance at all times, which is different to a close and continuous exposure of 500 lux for 2 h. Thirdly, the spectral composition of white light used in the current study (Figure 1c) was slightly different from Lou and Ostrin, and had relatively less energy in the higher wavelength region.…”

Prevalence of refractive errors and risk factors for myopia among schoolchildren of Almaty, Kazakhstan: A cross-sectional study

“…The prevalence of myopia in Russia also varies widely from 5.1% to 50.7%, depending on the region and age of the subjects [ 26 – 28 ]. Inconsistent data from the countries across the former Soviet Union may result from varying geographical and climatic conditions in addition to differences in ethnic and cultural composition of the peoples living in these countries [ 29 , 30 ].…”

Blue-Light Therapy for Seasonal and Non-Seasonal Depression: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

“…For comparison, indoor social lighting is rated as less than 100 lux, bright office lighting at 500 lux, outdoors on a cloudy day at 5,000 lux, and outdoors on a sunny day at 50,000 lux or higher. 7 Light therapy is generally well-tolerated with few or mild side effects. 8 Although the precise mechanism of action of light therapy remains unclear, it is hypothesized that alterations in circadian rhythm, suppression of melatonin secretion, and modulation of serotonin may be important contributory factors.…”