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While the international lighting community does not yet know enough to prescribe a certain type of electric lighting to meet the specific needs of specific individuals, enough has been learned in the past few years “to make a difference in people’s lives.” So said Mariana G. Figueiro, Ph.D., Director of the Lighting Research Center, a professor of architecture at Rensselaer Polytechnic Institute, and a member of the “Prescription Lighting” discussion panel convened at the National Lighting Bureau’s 7th Annual Lighting Forum. Robert Soler, vice president of human biological technologies and research with BIOS Lighting, was the other panelist. Randy Reid of the EdisonReport moderated the discussion.
Although the focus of the panel was prescription lighting, both panelists agreed that no widely accepted definition of the term exists. And, in fact, as Figueiro emphasized, no widely accepted definition of “circadian lighting” exists either; different people mean it to signify different things, especially spectral distribution of light. But spectral distribution is only one aspect of light that needs understanding if light is to be prescribed: Others are intensity of the light, the amount of light, how the light is distributed, and when the exposure occurs. “Optic history” is also a factor, as Soler remarked, noting that someone who routinely works outdoors all day is affected far less by “blue light” – light that, undetectable to the human eye, emphasizes the blue portion of the spectrum – than an individual who spends all or most of the day indoors, such as hospital and nursing-home patients, Alzheimer’s victims, and prisoners, among others.
Although far more must be learned to have what could be termed “full-blown” prescription lighting, Dr. Figueiro and her Lighting Research Center team are already thinking about a wearable instrument dubbed a personal lighting device (PLD). It would know a person’s lighting prescription and, as the person moved about an office or similar area, it would adjust the overhead, ambient lighting to maintain the individual’s prescribed exposure. We are far from that situation right now, because more research is needed. Nonetheless, we do know that lighting affects people’s health. In the case of Alzheimer’s patients, for example, a population that stays indoors all day, circadian-effective lighting has been shown to improve patients’ sleep, lessen their agitation, and reduce their depression.
