Photoreceptor Enhanced Light Therapy (PELT): A Framework for Implementing BiologicallyDirected Integrative Lighting

We introduce a lighting technology designed to produce photoreceptor-directed lights (PrD). This photoreceptor-enhanced light therapy (PELT) differs from conventional supplemental lighting by using multiple limited-bandwidth primaries to generate spectra that appear white, and that are tailored to produce circadian equivalent (CE) lights for selectively increasing or decreasing the relative activation levels of specific photoreceptor classes in the human eye. Rather than designing a device to match a spectrum’s shape, we optimize the available hardware, so it best matches the biological effects of that spectrum. It goes beyond three and four dimensions (three cones plus melanopsin) to consider the biological responses mediated via all five photoreceptor classes (including rhodopsin); the inclusion of a fifth photoreceptor class is non-trivial both in implementation and biological effect. Here, we describe the technical specifications of the PELT device and its calibration procedures. Photoreceptor-directed lights with variable melanopsin and rhodopsin excitations and equal photometric luminance are presented. Device application examples are provided that include personalized supplemental light spectra for patients with photoreceptor sensitivity loss, for healthy people exposed to extreme seasonal or work-related variation in their ambient lighting patterns, and as a stimulus generator to evaluate the effects of light on human health and behavior mediated via the melanopsin expressing intrinsically photosensitive retinal ganglion cells (ipRGCs). In integrative lighting practice, the PELT method extends to dynamic control of the biological potency of the melanopsin and rhodopsin excitations over a large range, independent of perceived changes in correlated color temperature (CCT).