"Prior to the advent of artificial lighting, the sun was the primary source of light. When the sun sets today, however, one is hard-pressed to find darkness—illumination from light-emitting diodes (LEDs), and incandescent, fluorescent, and xenon-arc sources (among others) provide indoor and outdoor illumination. The effects of exposure to this seemingly unnatural technological adaptation are starting to become evident, with several studies indicating undesirable associations between exposure to artificial light at night and both reduced sleep quality and diminished alertness during the day. A relatively recent concern is the excessive near-field exposure to handheld and other electronic light-emitting devices. Estimates from large population surveys in developed countries indicate that 35% of people born between the years of 1965 and 1996 spend at least 9 h/day on digital devices, such as smartphones, tablets, or computers, and a recent report indicates that the average American spends 10 h and 39 min viewing screens. Such intense use of these devices has been found to have undesirable effects not only on sleep quality and alertness during waking hours, but also on parameters of physical health (e.g., neck and eye strain, eye fatigue, headache;) and cognitive performance (e.g., poor inhibitory control;). The prevalence of complaints associated with excessive use of computers and other digital devices is so great that the common ocular and physical effects have been collectively termed “Computer Vision Syndrome” (CVS)."