Exposure to light from self-luminous displays may be linked to increased risk for sleep disorders because these devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression. Thirteen participants experienced three experimental conditions in a within-subjects design to investigate the impact of self-luminous tablet displays on nocturnal melatonin suppression: 1) tablets-only set to the highest brightness, 2) tablets viewed through clear-lens goggles equipped with blue light-emitting diodes that provided 40 lux of 470-nm light at the cornea, and 3) tablets viewed through orange-tinted glasses (dark control; optical radiation <525 nm ≈ 0). Melatonin suppressions after 1-h and 2-h exposures to tablets viewed with the blue light were significantly greater than zero. Suppression levels after 1-h exposure to the tablets-only were not statistically different than zero; however, this difference reached significance after 2 h. Based on these results, display manufacturers can determine how their products will affect melatonin levels and use model predictions to tune the spectral power distribution of self-luminous devices to increase or to decrease stimulation to the circadian system. 

 The pattern of waking during the day when it is light and sleeping at night when it is dark is a natural part of human life. Only recently have scientists begun to understand the alternating cycle of sleep and waking, and how it is related to daylight and darkness. 
 
 A key factor in how human sleep is regulated is exposure to light or to darkness. Exposure to light stimulates a nerve pathway from the retina in the eye to an area in the brain called the hypothalamus. There, a special center called the suprachiasmatic nucleus (SCN) initiates signals to other parts of the brain that control hormones, body temperature and other functions that play a role in making us feel sleepy or wide awake. 
 
 The SCN works like a clock that sets off a regulated pattern of activities that affect the entire body. Once exposed to the first light each day, the clock in the SCN begins performing functions like raising body temperature and releasing stimulating hormones like cortisol. The SCN also delays the release of other hormones like melatonin, which is associated with sleep onset, until many hours later when darkness arrives. 
 
 What is Melatonin? 
 
 Melatonin is a natural hormone made by your body's pineal (pih-knee-uhl) gland. This is a pea-sized gland located just above the middle of the brain. During the day the pineal is inactive. When the sun goes down and darkness occurs, the pineal is "turned on" by the SCN and begins to actively produce melatonin, which is released into the blood. Usually, this occurs around 9 pm. As a result, melatonin levels in the blood rise sharply and you begin to feel less alert. Sleep becomes more inviting. Melatonin levels in the blood stay elevated for about 12 hours - all through the night - before the light of a new day when they fall back to low daytime levels by about 9 am. Daytime levels of melatonin are barely detectable. 
 
 Video production in partnership with 
 
 Besides adjusting the timing of the clock, bright light has another effect. It directly inhibits the release of melatonin. 

 All light is not equal: blue wavelengths are the most potent portion of the visible electromagnetic spectrum for circadian regulation. Therefore, blocking blue light could create a form of physiologic darkness. Because the timing and quantity of light and darkness both affect sleep, evening use of amber lenses to block blue light might affect sleep quality. Mood is also affected by light and sleep; therefore, mood might be affected by blue light blockade. In this study, 20 adult volunteers were randomized to wear either blue-blocking (amber) or yellow-tinted (blocking ultraviolet only) safety glasses for 3 h prior to sleep. Participants completed sleep diaries during a one-week baseline assessment and two weeks' use of glasses. Outcome measures were subjective: change in overall sleep quality and positive/negative affect. Results demonstrated that sleep quality at study outset was poorer in the amber lens than the control group. Two- by three-way ANOVA revealed significant (p < .001) interaction between quality of sleep over the three weeks and experimental condition. At the end of the study, the amber lens group experienced significant (p < .001) improvement in sleep quality relative to the control group and positive affect (p = .005). Mood also improved significantly relative to controls. A replication with more detailed data on the subjects' circadian baseline and objective outcome measures is warranted.
– You may be tempted to stay up to check out all the new late-night TV hosts, but make sure you've got your orange glasses on first. Various studies and expert opinion suggest that special filters, light bulbs, and the aforementioned orange-tinted eyewear can help block melatonin-disrupting blue light emitted by electronic devices such as smartphones, tablets, and computer screens, the New York Times reports. Melatonin is a naturally occurring hormone tied to sleep onset, and blue light has been shown in some studies to suppress its production. The most recent research comes out of a Swiss study published in the Journal of Adolescent Health, in which 13 teen boys were outfitted in these glasses, known as blue blockers, during the evening while they used devices with LED screens. The result, per the Times: The boys experienced "significantly more" sleepiness with the orange-tinted glasses than when they were sporting clear ones. A 2009 study of 20 adults came to similar conclusions, showing that subjects who wore amber-tinted eyeglasses enjoyed better sleep than those in yellow-tinted glasses (blocking UV light only). Orange shades aren't the only solution being bandied about: Bulbs that emit less blue light, filters to cover devices, and apps that change devices' blue-light emissions are also available, per the Times. Or, one could simply cut down on the gadgets once night comes. While experts tell the paper that being exposed to blue light is preferable during the day, it makes sense in the evening to block whatever blue light you can, either via smaller LED screens, dimmer light, or a cutdown on usage. "If you can look at the iPhone for 10 minutes rather than three hours, that makes a lot of difference," a neuroendocrinology professor tells the Times. (Thank these three for inventing blue light.)