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Air Pollution
Published in William J. Rea, Kalpana D. Patel, Air Pollution and the Electromagnetic Phenomena as Incitants, 2018
William J. Rea, Kalpana D. Patel
Even for humans, the formal definition of light is quite limiting. The human visual system is very complex and will exhibit a multitude of spectral sensitivity functions depending upon a range of spectral-spatial-temporal factors associated with that optical radiation. For example, the apparent brightness of a small blue disc of light seen by the fovea will appear dimmer than that same disc seen in the periphery.29 Over the last century, a large number of human visual spectral sensitivity functions have been identified. To at least in part address this complexity, a handful of spectral sensitivity functions have been formally accepted as luminous efficiency functions for optical radiation and, perhaps surprisingly, as alternative definitions for light.27,30,31 The currently accepted luminous efficiency functions that underlie alternative, formal definitions of light, which can lead, and have led, to significant confusion among nonspecialists. The modeled spectral sensitivity of the human circadian system to polychromatic white light.
Specializations of the Human Visual System: The Monkey Model Meets Human Reality
Published in Jon H. Kaas, Christine E. Collins, The Primate Visual System, 2003
Given that humans have a relative preponderance of L cones compared to other primates examined, as well as an S-cone-free zone in the central fovea, one might expect human spectral sensitivity be somewhat “red shifted” compared to other primates. Perhaps the most comprehensive comparison of spectral sensitivity in humans and macaques was undertaken by Harwerth and Smith,9 who examined 12 humans and 12 rhesus macaques. Harwerth and Smith found that humans showed greatest sensitivity to light in the red part of the spectrum and lowest sensitivity in the blue; macaques showed the opposite result. Their data also suggest that the interactions between L and M cones differs between humans and macaques. Despite these data, Harwerth and Smith did not conclude that these spectral sensitivity differences between humans and macaques reflect differences in the distribution or characteristics of photoreceptors, but rather that the functional differences are attributable to differences in pre-retinal light loss, possibly due to higher concentrations of macular pigment in humans than in macaques (macular pigment, which is concentrated in the fovea, attenuates short-wavelength light). Such pigment differences have been disputed, however,17 and in any case, the observed differences in spectral sensitivity between humans and macaques are congruent with the observed differences in the distribution of L, M, and S photoreceptors.
Scotopic microperimetry: evolution, applications and future directions
Published in Clinical and Experimental Optometry, 2022
Laura J Taylor, Amandeep S Josan, Maximilian Pfau, Matthew P Simunovic, Jasleen K Jolly
In scotopic microperimetry, threshold is assessed using short-wavelength stimuli (typically 480-500 nm) at various retinal locations. The same locations can then be tested using a long-wavelength stimulus (typically 640-660 nm) while still under scotopic conditions, which is in contrast to conventional two-colour perimetry. Testing this way, with a long-wavelength target under scotopic conditions enables evaluation of dark-adapted spectral sensitivity difference. In healthy subjects, rod dominant responses are isolated using a short-wavelength stimulus and mixed rod/cone responses are probed using a long-wavelength stimulus (except for foveally presented targets). The lack of photopic testing limits its ability to isolate cone function.19,20 The cyan and red stimuli luminosity are calibrated so that in healthy individuals the difference between cyan and red sensitivity should be 0 dB beyond the rod free zone. In patients with retinal disease, the difference between cyan and red sensitivity needs to be elucidated to understand the extent of rod dysfunction.21
Increase in cortisol concentration due to standardized bright and blue light exposure on saliva cortisol in the morning following sleep laboratory
Published in Stress, 2021
Katja Petrowski, Stefan Bührer, Christian Albus, Bjarne Schmalbach
Considering the cortisol reactivity (AUCG and AUCI) after light exposure, there were significant differences in respect to ground between blue light and dim light as well as blue light and red light, but not in respect to increase. When comparing the different measurement points, this result could be explained by higher salivary cortisol levels across most measurement points in the blue light condition compared to dim light and red light. This result is in line with several studies (Hatanaka et al., 2008; Ishida et al., 2005; Niijima et al., 1992) that have shown that exposure to a short-wavelength light might influence the spectral sensitivity pattern (most reactive at ∼460nm, e.g. blue light). Therefore, blue light of this wavelength or bright white light of broader wavelengths may have a greater stimulatory effect on the hypothalamic-pituitary-adrenal (HPA) axis activity.
Decreased daytime light intensity at nonwindow hospital beds: Comparisons with light intensity at window hospital beds and light exposure in nonhospitalized elderly individuals
Published in Chronobiology International, 2018
Junko Iwamoto, Kenji Obayashi, Miwa Kobayashi, Toshimichi Kotsuji, Rie Matsui, Kyoko Ito, Osamu Yoshida, Norio Kurumatani, Keigo Saeki
Data on daytime light exposure in nonhospitalized elderly individuals were collected from the HEIJO-KYO cohort (Obayashi et al. 2012), which included 1113 nonhospitalized elderly participants aged over 60 years (mean age, 71.9 years). Light data were measured for two consecutive days from September to April between 2010 and 2014 at 1-min intervals using a wrist light meter (Actiwatch 2; Philips Respironics Inc., Murrysville, PA, USA) worn on the nondominant wrist. The device has a photodiode with a spectral sensitivity approximating that of the human eye (illuminance sensitivity, 0–150 000 lux). All participants were given special rubber bands to prevent their shirtsleeves from covering the device. Daytime values of <1 lux were considered artifact data (resulting from covering of the sensor) and were not considered in the analyses (Scheuermaier et al. 2010).