Variation of Ambient Illumination Across Different Locations: An Impact on Antimyopia Strategy.

Abstract

Purpose: To evaluate whether the level of ambient illumination in winter at different locations, time of a day, sun protection, and source position remains optimum (≥1000 lux) for controlling myopia progression.

Methods: Illuminance level was recorded for 6 outdoor and 5 indoor locations using factory calibrated digital lux meter and under different measurement conditions. Outdoor locations included "open playground," "between two buildings," "between three buildings," "under a porch facing east," "under a big tree," and "under a porch facing west." Similarly, indoor locations included "rooms with multiple large windows," "rooms with a combination of light sources," "room with single artificial light," "room with multiple artificial lights," and "canopy covering the buildings."

Results: The overall median illumination level across 6 outdoor locations and 5 indoor locations were 1900 lux (803-4300 lux) and 227 lux (82-556 lux) respectively. Indoor locations showed an overall low median illuminance level (<1000 lux) irrespective of the locations and source positions. However, the illuminance level >1000 lux was recorded for "Room with multiple large windows" for specific points of time (10:00-11:00 and 13:00-14:00) in both sunny and foggy weather. The highest illumination level was recorded only in the "open playground" irrespective of various conditions such as time of the day, weather of the day, relative source position, and sun protection.

Conclusion: The ambient illumination level was optimum (≥1000 lux) for antimyopia strategy in winter for maximum outdoor locations. However, children should be motivated to spend their outdoor time during the afternoon (13:00-14:00 h) so that light intensities reaching the eye should be optimum in winter.