Blue Light is Not More Efficient than White Light
for Light Therapy
Harvard Confirms Lack of Benefit from Blue Light
A Harvard university study* published in a Science journal confirms that increasing the
proportion of blue light wavelengths emitted from a light therapy lamp has no benefit and does not improve
effectiveness or efficiency.
"The editorial comment accompanying the article proposes that blue light now often used for therapy in depression or shift work should perhaps be replaced by green or white illumination."
* J. J. Gooley, S. M. W. Rajaratnam, G. C. Brainard, R. E. Kronauer, C. A. Czeisler, S. W. Lockley, Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light. Sci. Transl. Med. 2, 31ra33 (2010).
"Our results indicate that short-duration (<90 min) retinal exposure to narrow-bandwidth 555-nm [yellow-green] light may be as effective, if not more effective, than an equivalent photon dose of 460-nm [blue] light."
Since light therapy is generally used for less than 90 minutes, and since green light with wavelengths around 555 nm are not very effective for light therapy, there is no benefit in increasing the proportion of blue light wavelengths in a light source used for light therapy.
The subjects used in this study were under 30 years of age, which is meaningful because studies have shown there is a substantial decrease in the efficacy of blue light therapy in people over 40 years old. This results from the age-related yellowing of the lens which increasingly and substantially limits the amount of blue light reaching the retina after age 40.
Although several studies have previously found that blue light wavelengths are not particularly effecive for light therapy, this study is particularly important because the authors of this study include many of the researchers whose earlier publications are used to justify the use of blue light to improve the efficiency of light therapy lamps. (GC Brainard, CA Czeisler, SW Lockley).
Blue light and light therapy.
The theoretical understanding used to justify blue light therapy, that the absorption spectrum of melanopsin in intrinsically photosensitive ganglion cells in the mammalian retina would determine the spectral sensitivity light therapy, was ill-conceived.
As Altimus et al found:
"At low light intensity, ipRGCs lack sensitivity, whereas rods are known to respond to increasing light levels and thus reliably relay this information to higher centers. Rods will continue to signal persistent light exposure through the rod-cone pathway even under conditions where their photocurrent is saturated. Finally, at high light intensities and for prolonged light exposures, melanopsin phototransduction in ipRGCs will extend the range of light intensities that allow circadian photoentrainment."
Rod Photoreceptors Drive Circadian Photoentrainment across a Wide Range of Light Intensities. Nature Neuroscience 13, pages 1107–1112; Altimus, Hatar et al
Lall et al. explained
"Our data suggest a relatively simple segregation of photoreceptor inputs to NIF [nonimage forming] vision under field conditions. They predict that rods play the predominant role in driving responses at night and around dawn/dusk with melanopsin taking over throughout most daylight."
Neuron 66:417-428. GS Lall, VL Revell, H Momiji, JA Enezi, CM Altimus, AD Güler, C Aguilar, MA Cameron, S Allender, MW Hankins, RJ Lucas.
See research demonstrating the superiority of GreenLIGHT to blue light for light therapy Here
Lo-LIGHT Most Efficient LIGHT Therapy
It is now apparent that the wavelength sensitivity of human physiology to light exposure does not simply correspond to the spectral excitation sensitivity of melanopsin. These finding support Sunnex Biotechnologies earlier studies on the spectral sensitivity of the non-visual light response in humans, and help explain the effectiveness of the patented low intensity GreenLIGHT technology used in Lo-LIGHT lamps.
The risk to vision from blue light therapy
Since blue light wavelengths do not contribute to the effectiveness of light therapy, and blue light promotes the development of Age-related Macular Degeneration (AMD), the use of blue or blue-enhanced light therapy lamps can only increase the risk of retinal damage and vision loss without providing any benefit.
Unlike bright light or blue light therapy lamps, the Lo-LIGHT therapy lamp poses no risk to the user's vision.
While the green light wavelengths near 555 nm used in the Harvard study referenced above are not very effective for light therapy, Lo-LIGHT lamps emit a narrow range of green light peaking in the visible light spectral region of 500 to 505 nm, which researchers at Harvard confirmed is the most sensitive region of the spectrum for regulating human circadian rhythms.
The finding that blue light wavelengths do not increase the effectiveness of light therapy, contrast with studies using Lo-LIGHT lamps for the treatment of depression, regulating circadian phase, and on light induced melatonin suppression, which show that GreenLIGHT from a Lo-LIGHT therapy lamp is as effective as "bright" white light therapy that provides more than 20 times the intensity or brightness.
Link to light therapy and retinal damage