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Light Sources
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
The human eye is not equally sensitive to all the wavelengths of light. The eye is most sensitive to green–yellow light, the wavelength range where the sun has its peak energy density emission, and the eye sensitivity curve falls off at higher and lower wavelengths. The eye response to light and color depends also on light conditions and is determined by the anatomical construction of the human eye, described in detail in Encyclopedia Britannica, 1994. The retina includes rod and cone light receptors. Cone cells are responsible for the color perception of the eye and define the light-adapted vision, that is, the photopic vision. The cones exhibit high resolution in the central part of the retina, the foveal region (fovea centralis), which is the region of greatest visual acuity. There are three types of cone cells, which are sensitive to red, green, and blue light. The second type of cells, the rods, are more sensitive to light than cone cells. In addition, they are sensitive over the entire visible range and play an important role in night vision. They define the scotopic vision, which is the human vision at low luminance. They have lower resolution ability than the foveal cones. Rods are located outside the foveal region, and therefore, are responsible for the peripheral vision. The response of the rods at high-ambient-light levels is saturated and the vision is determined entirely by the cone cells (see also Refs. [5,15]). Photometry is based on the eye’s photopic response, and therefore, photometric measurements will not accurately indicate the perceived brightness of sources in dim lighting conditions.
The Evolving and Aging Eye
Published in Lisa Heschong, Visual Delight in Architecture, 2021
In contrast, cones completely dominate at the very center of our focal vision. The fovea centralis is the formal name for this unusual visual structure where, within 1–2 degrees of the center of our visual field, our retina is packed with nothing but cones. (This visual area is about the width of one finger held at arm’s length from your face.) Other cones are scattered lightly through the rest of the retina, connected to groups of rods via the receptive fields and providing color information throughout our peripheral view.
Obstructive sleep apnea risk and hearing impairment among occupational noise-exposed male workers
Published in Archives of Environmental & Occupational Health, 2023
Seunghyeon Cho, Won-Ju Park, Ji-Sung Ahn, Dae-Young Lim, Su-Hwan Kim, Jai-Dong Moon
Previous studies have been conducted to examine the association of OSA and hearing impairment primarily in patients who visited a hospital with snoring, sleep apnea, or sleep disorder.6,7,13–18 These studies have suggested that OSA, especially severe OSA, is associated with hearing impairment. In a study by Chopra et al., increased OSA severity was associated with hearing loss at both high and low frequencies in Hispanic population.6 Similarly, in our study, the hearing thresholds of the high-risk OSA group at a frequency of 1, 2, 3 and 4 kHz in each ear were higher than those of the low-risk OSA group. The high OSA risk elevated the risk of hearing impairment in all models. However, in the analysis performed by reclassifying hearing impairment into high- and low-frequency, high-risk OSA group showed a significant association only with high-frequency hearing impairment compared with the low-risk OSA group. These results are consistent with those of studies reporting hearing loss only at higher frequencies.13,14 It is also consistent with the results of a study by Yu Li et al. that evaluated OSA using STOP-Bang questionnaire in middle-aged men.45 This can be explained by the following. Inner and outer hair cells of the organ of Corti respond to sound frequencies according to their tonotopic arrangement; high-frequency sounds localize to the base of the cochlea. The base of the organ of Corti is supplied by end arterioles without anastomoses, and thus, it may be more vulnerable to hypoxemia and fluctuations in oxygen than areas of the retina remote from the fovea centralis.46,47