Office work has so far been carried out in company buildings and was largely based on the use of paper on a horizontal surface. Due to multiple reasons, more workers are working in their homes with electronic devices. As a result, both the working environment and personal tools are changing. Since the discovery about 20 years ago of the non-visual ways of light absorption, it was known that apart from the image forming effects (IF) of light from which the criteria for correct lighting have been developed, non-image forming effects (NIF) of light exist. The discovery of NIF has enhanced researcher belief in the importance of daylighting and has raised new criteria to be taken into account for proper interior lighting. Due to all the factors mentioned above, the parameters to be met by a luminaire and its environment for proper lighting of the workstation have been modified and expanded. The rapid advance in the development of new light-emitting diode (LED) luminaires with which the spectral power distribution (SPD) can be practically created opens the door to a genuine technological revolution comparable to the invention of electric lighting around 150 years ago. The authors of this study will review the latest published studies on the importance of light in our lives, IF and NIF effects of light, the parameters which from these effects are suggested to be taken into account for a correct indoor lighting, the regulations in force on indoor lighting workplaces, and proposals to improve indoor lighting and therefore the quality of life of workers.
TopThe Effects Of The Light
Humans are diurnal hunting mammals so their visual system is genetically designed to look and focus preferably at distant distances and their biorhythms are synchronized to live day and night.
Because the sun has been our source of natural light and for millions of years has shaped mammals endogenous circadian rhythms including when to wake up, body temperature, metabolism, oscillations of gene expression and hormone production throughout our bodies. (Edwards & Torcellini, 2002)
This change was radical since it was invented about 150 years ago electric light to be from that time much of our time indoors where the intensity of the lighting does not correspond to that of the outside and due to the characteristics of the luminaires, the spectral distribution we receive from such indoor lighting sources does not reproduce incompletely that of the sun. (Edwards & Torcellini, 2002)
Endogenous timekeepers are present in human beings. The suprachiasmatic nucleus (SCN) of the anterior hypothalamus is our master clock which coordinates individual oscillators in multicellular organisms. SCN is capable of maintaining rhythmicity in the absence of environmental inputs, but cues like sunrise increase its temporal fidelity. (Dibner et al., 2010) The expression of various genes and associated protein products vary throughout the day in the SCN and these variations are associated with changes in the synthesis, sensitivity, efficacy, and concentrations of various neurotransmitters, neuropeptides, and hormones throughout the brain and body. (Hirota & Fukada, 2004) The SCN exhibits cyclical patterns of electrical activity and responsiveness to input over an approximate 24 h cycle. (Edwards & Torcellini, 2002) The internal period of the human circadian rhythm can range between 23.5 and 24.7 h, with an average of 24.2 h among healthy adults and relies on a resetting response driven by light received at the retina to maintain entrainment with the local 24-h light/dark cycle. (Konis, 2017) These rhythmic patterns of activity, are called circadian oscillations (from Latin: “circa” = approximately and “diem” = day). Of the inputs received by the SCN, light, arriving at the SCN via the retino hypothalamic tract (RHT) from intrinsically photosensitive melanopsin expressing intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) elicits the most robust effects within the SCN. When combined, these multimodal inputs inform daily cycles of SCN activity which then feed into the transcriptional and translational machinery of each neuron. Photic stimulation is an example of an environmental input that targets the core region of the SCN. Thus, the neurons within the core can be described as environmentally responsive, particularly to photic inputs. (Zelinski et al., 2014)
Melatonin circulates in the blood stream and is easily absorbed by individual cells, serving as a coordinating time-of-day (specifically, night time) signal throughout the body. At night, light absorbed by retinal photopigments signal the biological clock in the SCN of the hypothalamus to suppress nocturnal melatonin production by the pineal gland. (Rea & Figueiro, 2016)
Light is a powerful stimulus for the regulation of circadian, hormonal and behavioral systems. Retinal exposure to light stimulates three types of photoreceptors: rods, cones, and the melanopsin containing (ipRGC). Rods and cones transduce light into neural signals that carry IF information through ganglion cells. These are sent to the thalamus and the visual cortex in the brain where images are being processed. (Lucas et al., 2014)