A new study from the LRC (Lighting Research Center) at Rensselaer Polytechnic Institute takes a practical, quantitative approach to evaluating light sources for blue-light hazard.
Researchers John Bullough, Andrew Bierman, and Mark Rea evaluate the spectral radiant power characteristics of incandescent, fluorescent, LED, and daylight sources in terms of up-to-date blue-light hazard calculation procedures from the Illuminating Engineering Society and the CIE. The study results suggest that in most use cases, LEDs do not present a risk of blue-light hazard greater than that from other light sources. This, the researchers say, is because our human photophobic (light-avoiding) responses, such as squinting and averting the gaze, limit exposure to bright light. Special precautions are warranted where photophobic responses might not occur, such as during eye surgery or with premature infants.
Organisation such as the American Medical Association have advised against using LEDs with CCT greater than 3000K, but the LRC study found that avoiding blue-light hazard is primarily related to controlling the radiance of light sources, and spectral distribution is much less relevant—particularly when expressed in terms of CCT.
The LRC study authors note that CCT should not be used as a metric for characterising the potential for blue-light hazard, noting that an incandescent filament at 2856K within a clear bulb presents a greater risk for blue-light hazard than any white LED source, including one of 6500K. The spectral radiance distribution must be known to estimate blue-light hazard, particularly for those cases where photophobic responses might not occur. In these cases, and for general lighting applications, the researchers recommend the use of lenses, baffles, and diffusers to mitigate glare as the primary methods for reducing the risk of blue-light hazard. This does leave open the question of whether headlight glare—which cannot be mitigated with diffusers or baffles—might now be of greater concern.
