Analytical evolution of measurement methods for light's non-visual effects
Mahya Cheshmeh Noor, Fatemeh Mehdizadeh Saradj, Seyed-Abbas Yazdanfar
Abstract
Recently, considerable literature has grown up around the theme of the non-visual effect of light in interior spaces, and researchers propose different methods and indices for quantifying this effect. Due to the vital role of light in human health, it is recommended that these methods be used along with photometric calculations of indoor lighting for visual functions. However, unlike visual measurement techniques of light, little review has been undertaken on the measurement methods for non-visual qualities of light. A lack of perspective on these methods impedes the assessment of their limitations and capacities and, consequently, the selection of the most appropriate one. This study aims to identify these approaches and their evolutions through a chronological review. As these methods are upgraded with medical achievements, their developments, gaps, needs, and then their future trajectory, are discussed by conducting a parallel bibliometric study across multiple disciplines. The findings are classified into the spectrum, intensity, timing, duration, and light direction. A large number of calculating techniques devised in medical disciplines take into account the spectral properties and intensity of light, but less considered the timing, duration, and light direction as influential factors in the architectural context. Additionally, many of these methods are focused on quantifying light's effect on circadian sleep-wake rhythm, melatonin suppression, and, on a lesser scale, subjective alertness. The other light's non-visual effects required further evaluations. Moreover, recent methods modified to account for maximal melanopsin spectral response, while further research is required to determine its applicability for other timeframes and other non-visual effects of light.