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Ask the Experts


Are the less intense, blue and green light therapy boxes as effective as using a 10,000 lux white light box?

Answered by: Michael Terman

1. "Intensity" has several definitions, and the conventional lux measure cannot be used to compare white with colored sources. In addition to lamp output power, the light received at the eyes are joint functions of the color spectrum, distance from the source, shielding, angle of incidence, and field of illumination. 2. Clinical trials of colored sources have thus far not been definitive, either in terms of effectiveness or long-term safety. The most recent literature indicates that all wavelengths (or colors) participate. White light presents the full mix.