Sebuah software Flux dapat menurunkan efek cahaya biru pada monitor dengan lampu LED. Lampu LED menghasilkan cahaya berwarna putih memiliki tambahan dengan intensitas cahaya biru. Tetapi efek cahaya biru kabarnya dapat menganggu kesehatan dari penglihatan mata

Bila sering mengunakan computer pada saat menjelang tidur, dan sering mengalami kesulitan tidur. Mungkin disebabkan cahaya dari lampu LED di monitor.

Dampak bagi mereka yang mengunakan layar computer dengan lampu backlit LED seperti• Gangguan tidur / Insomnia• Menurunkan tubuh dalam menghasilkan Melatonin• Efek cahaya biru terjadi di mata dengan tingkat stres pada retina.• Dampak menurunnya hormon Melatonin sebagai hormon tidur alias memberikan peringatan

kepada tubuh untuk istirahat. Intensitas cahaya lampu biru di LED, berdampak menurunkan hormon Melatonin dari tubuh kita sendiri.

Entah benar atau tidak, intensitas cahaya lampu LED cukup berdampak bagi penguna perangkat. Khususnya pada malam hari dimana tubuh memerlukan istirahat. Sebuah software dinamai Flux. Dapat digunakan pada computer, fungsinya menurunkan intensitas cahaya biru di layar computer. Caranya dengan meningkatkan cahaya kuning atau membuat monitor lebih berwarna kuning.

Software Flux dapat di install di computer dan notebook dengan layar backlit LED.Download F.lux

Dibawah ini beberapa setting software Flux yang dapat membantu menurunkan efek cahaya biru dari lampu LED monitor

AbstractOBJECTIVES:Self-luminous electronic devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression. Melatonin suppression resulting from exposure to light at night has been linked to increased risk for diseases. The impact of luminous cathode ray tube (CRT) computer monitors on melatonin suppression was investigated.DESIGN:Twenty-one participants experienced three test conditions: 1) computer monitor only, 2) computer monitor viewed through goggles providing 40 lux of short-wavelength (blue; peak λ ≈ 470 nm) light at the cornea from light emitting diodes (LEDs), and 3) computer monitor viewed through orange-tinted safety glasses (optical radiation <525 nm ≈ 0). The blue-light goggles were used as a "true-positive" experimental condition to demonstrate protocol effectiveness; the same light treatment had been shown in a previous study to suppress nocturnal melatonin. The orange-tinted glasses served as a "dark" control condition because the short-wavelength radiation necessary for nocturnal melatonin suppression was eliminated. Saliva samples were collected from subjects at 23:00, before starting computer tasks, and again at midnight and 01:00 while performing computer tasks under all three experimental conditions.RESULTS:Melatonin concentrations after exposure to the blue-light goggle experimental condition were significantly reduced compared to the dark control and to the computer monitor only conditions. Although not statistically significant, the mean melatonin concentration after exposure to the computer monitor only was reduced slightly relative to the dark control condition.CONCLUSIONS:Additional empirical data should be collected to test the effectiveness of different, brighter and larger screens on melatonin suppression.

How did you become interested in the effects of light on sleep?Brainard: I was interested in the effects of light on animals as a teenager. I never planned to be a scientist—I wanted to be a writer! So I learned more about the topic out of pure curiosity. When I began my career as a journalist, I interviewed researchers on the topic who encouraged me to pursue a career in science. So I returned to school to get my doctorate and studied the effects of different wavelengths and intensities of light on rodents. I have exclusively studied the effects of light on humans for the past 30 years.Chang: As a graduate student, I researched circadian rhythm disorders resulting from different human sleep patterns, particularly those of early and late sleepers. I became interested in the effects of various aspects of light—such as time of day and duration of exposure—on circadian rhythm, sleep and performance.How exactly does light affect our circadian rhythms? And how is melatonin involved?Chang: We have known for quite awhile now that light is the most powerful cue for shifting the phase or resetting the time of the circadian clock. We also know that melatonin is present at low levels during the day, begins being released a few hours before bedtime and peaks in the middle of the night. Past studies have shown that light suppresses melatonin, such that light in the early evening causes a circadian delay, or resets the clock to a later schedule; and light in the early morning causes a circadian advancement, or resets the clock to an earlier schedule.So how did scientists become interested in blue light in particular?Brainard: In the 1990s my team performed more than 700 experiments over seven years to measure how different wavelengths of light regulate acute melatonin production. Unexpectedly, we found that humans display a peak sensitivity to light in the blue wavelength region of the spectrum.Rods and cones [photoreceptors in the eye] could not account for this differential regulation of melatonin production, so we postulated another type of photoreceptor was responsible for mediating such physiological responses. These wavelength-sensitive photoreceptors were identified soon after and are known as melanopsin-containing ganglion cells.What happens in the body when our eyes are exposed to blue light on electronic devices?Chang: Recent studies have shown that short-wavelength [blue] light has a greater effect on phase shifting the circadian clock and on melatonin suppression. In 2014 my colleagues and I examined the effects of reading on a light-emitting device compared with reading a printed book. Participants who read on light-emitting devices took longer to fall asleep, had less REM sleep [the phase when we dream] and had higher alertness before bedtime [than those people who read printed books]. We also found that after an eight-hour sleep episode, those who read on the light-emitting device were sleepier and took longer to wake up. In the study all participants had to stop reading and turn off the lights at exactly 10 P.M., even if they did not feel sleepy. At home, I would expect people do not have the motivation to turn off their devices and go to bed, so they would stay up longer and experience even more circadian delay and shorter sleep times. The effects in the real world could actually be even greater.What about extreme environments in which the body does not experience a normal daily cycle of sunlight and darkness?Brainard: My research into the clinical applications of light got NASA interested in applying these findings to spaceflight scenarios. When an astronaut leaves Earth, his or her body is operating on a 24-hour light/dark cycle, but the space station orbits Earth every 90 minutes, and astronauts see the sun rise and set each time. This shift in the lighting environment, known as slam shifting, can have many health consequences and inspired my work with NASA on creating light-exposure schedules specifically for astronauts. [Editors’ Note: As a result of this work, NASA will begin implementing a new lighting system onboard the International Space Station next year, designed to improve astronauts’ sleep and waking performance.]Can the effects of light on melatonin ever benefit the body?

Brainard: My research in the 1980s showed that the effect of light on melatonin secretion has clinical benefits. Since then, light therapy has been shown to be effective in treating several other conditions, including depression, sleep disorders, eating disorders and age-related dementia.Chang: Short-wavelength light can be applied in different circumstances where you actually want to shift the clock. For example, it could help in the mornings when we need to be at peak alertness or in cases of jet lag when we change time zones abruptly and our circadian clocks get thrown off. People with variable sleep patterns, such as shift workers, could also benefit from using a schedule of short-wavelength light exposure to help realign their circadian clocks.Finally, the question everyone is wondering about: Do you have any suggestions as to what we can do to reduce our blue-light exposure before bed?Chang: For those who just cannot turn off digital devices, here are a few suggestions: You can dim the brightness of your devices or you can make use of programs that filter out short-wavelength light in the evening. I’ve also heard of modern technologies that use different settings, such as reversing the print so the page is dark and the text is light, which, though untested, are probably beneficial if they reduce the amount of emitted light. But the best and least popular answer would be to simply avoid your devices before going to sleep!READ SCIENTIFIC AMERICAN MIND’S SEPTEMBER/OCTOBER ISSUE TO LEARN HOW MODERN LIFESTYLES SCRAMBLE THE BODY’S RHYTHMS.

Visible light is much more complex than you might think.Stepping outdoors into sunlight; flipping on a wall switch indoors; turning on your computer, phone or other digital device — all of these things result in your eyes being exposed to a variety of visible (and sometimes invisible) light rays that can have a range of effects.Most people are aware that sunlight contains visible light rays and also invisible ultraviolet rays that can tan or burn the skin. But what many don't know is that the visible light emitted by the sun comprises a range of different-colored light rays that contain different amounts of energy./relProdLgMobileWhat Is Blue Light?Sunlight contains red, orange, yellow, green and blue light rays and many shades of each of these colors, depending on the energy and wavelength of the individual rays (also called electromagnetic radiation). Combined, this spectrum of colored light rays creates what we call "white light" or sunlight.sidebar Med

THE LIGHT SPECTRUM

/sidebar MedWithout getting into complicated physics, there is an inverse relationship between the wavelength of light rays and the amount of energy they contain. Light rays that have relatively long wavelengths contain less energy, and those with short wavelengths have more energy.Rays on the red end of the visible light spectrum have longer wavelengths and, therefore, less energy. Rays on the blue end of the spectrum have shorter wavelengths and more energy.The electromagnetic rays just beyond the red end of the visible light spectrum are called infrared — they are warming, but invisible. (The "warming lamps" you see keeping food warm at your local

eatery emit infrared radiation. But these lamps also emit visible red light so people know they are on! The same is true for other types of heat lamps.)On the other end of the visible light spectrum, blue light rays with the shortest wavelengths (and highest energy) are sometimes called blue-violet or violet light. This is why the invisible electromagnetic rays just beyond the visible light spectrum are called ultraviolet (UV) radiation.UV rays have higher energy than visible light rays, which makes them capable of producing changes in the skin that create a suntan. In fact, the bulbs in tanning booths emit a controlled amount of UV radiation specifically for this reason.But too much exposure to UV causes a painful sunburn — and even worse, can lead to skin cancer. These rays also can cause sunburned eyes — a condition called photokeratitis or snow blindness.But ultraviolet radiation, in moderation, also has beneficial effects, such as helping the body manufacture adequate amounts of vitamin D.Blue light contributes to digital eye strain; computer glasses that block blue light may increase comfort.

Generally, scientists say the visible light spectrum comprises electromagnetic radiation with wavelengths ranging from 380 nanometers (nm) on the blue end of the spectrum to about 700 nm on the red end. (By the way, a nanometer is one billionth of a meter — that's 0.000000001 meter!)Blue light generally is defined as visible light ranging from 380 to 500 nm. Blue light sometimes is further broken down into blue-violet light (roughly 380 to 450 nm) and blue-turquoise light (roughly 450 to 500 nm).

So approximately one-third of all visible light is considered high-energy visible (HEV) or "blue" light.Key Points About Blue Light

Like ultraviolet radiation, visible blue light — the portion of the visible light spectrum with the shortest wavelengths and highest energy — has both benefits and dangers. Here are important things you should know about blue light:1. Blue light is everywhere.Sunlight is the main source of blue light, and being outdoors during daylight is where most of us get most of our exposure to it. But there are also many man-made, indoor sources of blue light, including fluorescent and LED lighting and flat-screen televisions.Most notably, the display screens of computers, electronic notebooks, smartphones and other digital devices emit significant amounts of blue light. The amount of HEV light these devices emit is only a fraction of that emitted by the sun. But the amount of time people spend using these devices and the proximity of these screens to the user's face have many eye doctors and other health care professionals concerned about possible long-term effects of blue light on eye health.2. HEV light rays make the sky look blue.The short-wavelength, high-energy light rays on the blue end of the visible light spectrum scatter more easily than other visible light rays when they strike air and water molecules in the atmosphere. The higher degree of scattering of these rays is what makes a cloudless sky look blue.

Digital electronic devices emit blue light that can cause eye strain and may lead to eye problems over time.3. The eye is not very good at blocking blue light.Anterior structures of the adult human eye (the cornea and lens) are very effective at blocking UV rays from reaching the light-sensitive retina at the back of the eyeball. In fact, less than one percent of UV radiation from the sun reaches the retina, even if you aren't wearing sunglasses.(Keep in mind, though, that sunglasses that block 100 percent of UV are essential to protect these and other parts of the eye from damage that could lead to cataracts, snow blindness, a pinguecula and/or pterygium, and even cancer.)

On the other hand, virtually all visible blue light passes through the cornea and lens and reaches the retina.4. Blue light exposure may increase the risk of macular degeneration.The fact that blue light penetrates all the way to the retina (the inner lining of the back of the eye) is important, because laboratory studies have shown that too much exposure to blue light can damage light-sensitive cells in the retina. This causes changes that resemble those of macular degeneration, which can lead to permanent vision loss.

Although more research is needed to determine how much natural and man-made blue light is "too much blue light" for the retina, many eye care providers are concerned that the added blue light exposure from computer screens, smartphones and other digital devices might increase a person's risk of macular degeneration later in life.

5. Blue light contributes to digital eye strain.Because short-wavelength, high energy blue light scatters more easily than other visible light, it is not as easily focused. When you're looking at computer screens and other digital devices that emit significant amounts of blue light, this unfocused visual "noise" reduces contrast and can contribute to digital eye strain.Research has shown that lenses that block blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly. Therefore, computer glasses with yellow-tinted lenses may increase comfort when you're viewing digital devices for extended periods of time.

6. Blue light protection may be even more important after cataract surgery.The lens in the adult human eye blocks nearly 100 percent of the sun's UV rays. As part of the normal aging process, the eye's natural lens eventually blocks some short-wavelength blue light as well — the type of blue light most likely to cause damage to the retina and lead to macular degeneration and vision loss.If you have cataracts and are about to have cataract surgery, ask your surgeon what type of intraocular lens (IOL) will be used to replace your cloudy natural lens, and how much blue light protection the IOL provides. After cataract surgery you might benefit from eyeglasses that have lenses with a special blue light filter — especially if you spend long hours in front of a computer screen or using other digital devices.

7. Not all blue light is bad.So, is all blue light bad for you? Why not block all blue light, all the time?Bad idea. It's well documented that some blue light exposure is essential for good health. Research has shown that high-energy visible light boosts alertness, helps memory and cognitive function and elevates mood. In fact, something called light therapy is used to treat seasonal affective disorder (SAD) — a type of depression that's related to changes in seasons, with symptoms usually beginning in the fall and continuing through winter. The light sources for this therapy emit bright white light that contains a significant amount of HEV blue light rays.Also, blue light is very important in regulating circadian rhythm — the body's natural wakefulness and sleep cycle. Exposure to blue light during daytime hours helps maintain a healthful circadian rhythm. But too much blue light late at night (reading a novel on a tablet computer or e-reader at bedtime, for example) can disrupt this cycle, potentially causing sleepless nights and daytime fatigue.Blue Light Filters and Protective EyewearIf you are using your phone constantly — especially if you use it primarily for texting, e-mailing and web browsing — a convenient way to reduce your blue light exposure is to use a blue light filter.Your eye doctor can recommend lenses and filters that protect your eyes from blue light.

These filters are available for smart phones, tablets, and computer screens and prevent significant amounts of blue light emitted from these devices from reaching your eyes without affecting the visibility of the display. Some are made with thin tempered glass that also protects your device's screen from scratches.Examples of blue light filters for digital devices include: Eyesafe (Health-E), iLLumiShield, RetinaShield (Tech Armor), Retina Armor (Tektide), Frabicon and Cyxus.As mentioned above, computer glasses also can be helpful to reduce blue light exposure from computers and other digital devices. These special-purpose glasses are available without an eyeglass prescription if you have no need for vision correction or if you routinely wear contact lenses to correct your eyesight. Or they can be specially prescribed to optimize your vision specifically for the distance from which you view your devices.If you have presbyopia and routinely wear bifocals or progressive lenses, prescription computer glasses give you the additional benefit of a much larger field of view for seeing your entire computer screen clearly. (Keep in mind, though, that this type of computer eyewear is exclusively for seeing objects within arm's length and cannot be worn for driving or other distance vision needs.)Also, a number of lens manufacturers have introduced special glare-reducing anti-reflective coatings that also block blue light from both natural sunlight and digital devices.Ask your eye doctor about which type of vision correction and lens features best suit your needs for viewing your computer and other digital devices and protecting your eyes from blue light.

There’s a lot of evidence that blue light, emitted by smartphones, tablets, laptops, and many other electronic devices, is impacting on the quantity and quality of the sleep we are getting. Darkness is a natural cue to our bodies that it’s time for sleep, but we’re circumventing it by staring at bright screens for hours after the sun has gone down.You can decrease your exposure to blue light in a variety of ways, beyond turning off all the light sources. There are special filters, glasses, light bulbs, and even software you can use. But, before we get into that, let’s delve into the science behind it.

WHAT’S THE PROBLEM WITH BLUE LIGHT?Blue light tells our brain that it isn’t time to sleep, according to the experts.“There are about 30,000 cells inside your eye that are reactive to the wavelength of light which would be considered blue,” explains clinical psychologist and sleep therapist, Dr. Michael J. Breus. “Blue runs in about the 460 nanometer range, in terms of the spectrum of light. That particular spectrum of light hits these cells and makes them send a signal to an area of the brain known as the suprachiasmatic nucleus and tells it to turn off melatonin production. Melatonin is the key that starts the engine for sleep.”

The impact of blue light has been well-known to sleep researchers and scientists for many years now. Our circadian rhythms determine our internal clocks. Someone who routinely stays up late probably has a longer rhythm than an early riser. Daylight traditionally keeps those rhythms aligned with our environments. Blue light therapy is frequently used to shift sleep patterns and tackle sleep disorders.

“In the past 50 years, there has been a decline in average sleep duration and quality.”“In the past 50 years, there has been a decline in average sleep duration and quality, with adverse consequences on general health,” so begins an illuminating paper entitled, Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness, based on research from Harvard Medical School, amongst other places.

The paper assessed two groups; half read a normal printed book for four hours before bedtime for five consecutive nights, while the other group read a light-emitting ebook reader for the same period. The patients using the ebook reader showed suppressed levels of melatonin. On average, they took 10 minutes longer to fall asleep and displayed significantly less rapid eye movement (REM) sleep than the group reading printed books.

Unsurprisingly, the ebook reader group reported feeling less tired in the evening, but they also reported that they felt more tired in the morning, despite having the same duration of sleep as the other group.

Related: Does staring at screens all day really damage your eyes?There are more serious health issues to consider if you aren’t getting enough sleep. When our circadian rhythms are thrown off researchers believe we are put at more risk of all sorts of things including heart attacks, obesity and type-2 diabetes, and various cancers. Those examples are mostly related to long term night shift, or severe sleep disorders, but any disruption to your circadian rhythm can cause problems. Lack of sleep has also been linked with mood problems, anxiety and depression, and increased risk of accidents.

CAN BLUE LIGHT DAMAGE OUR EYES?There are also some scientists linking blue light to age-related macular degeneration, though the evidence doesn’t seem to be conclusive. Over exposure could be playing a role in the rise of cataracts and even blindness.“We are seeing a much greater number of age-related macular degeneration patients, even back correcting for the aging population, so the risk factors are clearly changing,” explains Professor John Marshall, Frost Professor of Ophthalmology at the Institute of Ophthalmology in London, “If you look at cataracts there’s a very good correlation between the age of onset of cataracts and the degree of ultraviolet where you live in the world, that’s why people close to the equator tend to get their cataracts 5 to 10 years earlier.”

We know ultraviolet (UV) is damaging and the blue range is closest to it. For damage to the eye, the peak wavelength for blue light is around 440nm, but the suppression of melatonin is higher, at around 460nm.

“By far and away the biggest exposure you’re going to get is from the sun – that is the biggest blue light hazard that you will meet in your lifetime,” says Professor Marshall. “The big red herring here is smartphones. If you actually do the calculations from the spectral emission of those things – it’s tiny.”The risk of damage has a great deal to do with power and brightness.“Light bulbs are much brighter sources,” explains Prof. Marshall. “When was the last time you got an after image from looking at your iPad? When you look at a light source, especially an LED, you’ve got that multicolored image on your retina which takes a long time to fade.”

LED LIGHT BULBS MAY BE WORSE THAN YOUR PHONEThe electric lights in our homes may be having a bigger impact than our devices. The paper Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans, found that exposure to room light before bedtime suppressed melatonin in 99 percent of individuals and shortened melatonin duration by about 90 minutes.“Until recently, we lit our homes with incandescent bulbs and they were relatively biologically friendly, in that there was very little blue,” says Prof. Marshall, “More commonly now they’re LEDs and these light sources have a lot of the potentially damaging blue, to the extent that I don’t use

them.”Turning everything off and sitting in a dark room is not something many of us will do.There’s a Florida company called Lighting Science Group which offers a line of “biological” lighting. You might opt for a warm light bulb that emits lower levels of blue light for your bedroom, and use an Awake & Alert bulb in the kitchen to get you going in the morning along with your first cup of coffee. There is evidence that the bulbs we use can also impact on our circadian rhythms, and worse, affect our skin the way that the sun does, but this usually requires close, prolonged proximity.A lot of bright lighting is obviously going to be an issue, that’s often a problem for night shift workers, depending on their environment. For most of us, subdued lighting towards bedtime is going to be enough to make a difference. But, what about the blue light coming from our devices?If you’re really concerned about blue light exposure, then there are bigger fish to fry than smartphones and tablets.“Wear a big hat, appropriate sun glasses, and consider the lighting in your home,” says Professor Marshall. “If it’s iPads and iPhones, I wouldn’t worry.”

THE RIGHT BALANCE OF BLUE LIGHT“There’s nothing wrong with blue light for most of the day,” says Dr. Breus. “You just don’t want to have it about 90 minutes or so before bed.”Sunlight has a tremendous amount of blue light in it. The worrying negative effects are connected with the melatonin deficit and disruption of circadian rhythms that leads to less sleep and poorer quality sleep. But, we need blue light to get us going in the morning, and it has been linked with higher levels of alertness.“When we wake up in the morning our circadian rhythm is a little off, our internal biological clock runs on a slightly longer schedule in many cases than 24 hours, and so to reset that clock every morning we need sunlight,” says Dr. Breus. “One of my biggest recommendations for patients is every morning go outside and get 15 minutes of sunlight.”

At the other end of the day we need to be more mindful of our blue light exposure. Proximity is an important factor. That’s why smartphones, tablets, and laptops are perceived as a bigger risk than light bulbs or TV screens. Though, it’s worth remembering that the impact on sleep is about more than just the blue light exposure.“I think there’s a second factor that people aren’t really talking about that much, and that is the level of engagement in whatever the device is,” explains Dr. Breus. “If you’re playing your favorite game, or whatever it is you like to do before you go to bed, you’re mentally engaged in that act.”Let’s be honest, turning everything off and sitting in a dark room is not something many of us will do. Thankfully, there are alternatives.

HOW TO FILTER BLUE LIGHT WITH SPECIAL GLASSESThere have been protective glasses on the market for a while, but they tend to have colored lenses. Now, we’re beginning to see alternatives that aren’t so strongly tinted, such as the Jins Screen range of glasses, which have been specifically developed to address the blue light problem.“They reduce the transmission of light in the 460 nm range by 25 percent via two pathways: coating and substrate,” explained Lilian Wouters, PR Manager at Jins. “Certain wavelengths of blue light are reflected by the patented coating on the lenses, while others are absorbed by the substrate, which is made of a compound that absorbs certain wavelengths of blue light.”

You can pick them up as standalone non-prescription specs, but the special coating will also be available on prescription glasses.There’s also a newcomer on the scene, called Gauss, which recently smashed its Kickstarter target.Related: Jins Screen Glasses block blue light from your phone for better sleep

“Gauss glasses come with lenses that have multiple layers of coating applied to them. Each layer has different properties and all this combined results in our Blueguard coating,” developer Jay Uhdinger told us. “It reflects light peaking with the wavelengths of 400 to 440 nanometers, while still letting other wavelengths pass through, to enable people to still see blue as blue with minimal impact on normal color vision. Studies show that these frequencies can cause most damage to the retinal pigment cells of the eyes.”Blue light is just one of the factors that determines your sleeping pattern, but it’s clearly very important.With self-tinting lenses and UV blocking, Gauss glasses are intended to serve as sunglasses and offer indoor protection. They are designed primarily to protect your eyes against the potentially harmful 440nm peak blue light, but they do also filter 460nm light that might impact on your melatonin production.“Our goal was to create the perfect sunglasses for the digital age because it is simply easier for people to carry around one pair of glasses that they can use to protect their eyes while they are outside or when sitting in front of a computer or other digital device screen,” says Uhdinger.The science behind these glasses appears to be sound. There is a lot of research on lenses that block blue light and they do seem to have a positive impact on sleep quality. Jins was also a sponsor of the recent New York Blue Light Symposium which had various academics presenting research on blue light and its negative impacts.WHY NOT USE SOFTWARE?One of the most popular options right now is F.lux. It tweaks the color of your computer’s display according to the time of day, so it gets warmer at night and has more blue throughout the day. It’s completely free and you can use it on Windows, Mac, Linux, and jailbroken iOS devices. There’s an app called Twilight on Android that does the same thing.

We asked Uhdinger why people would use glasses over software and here’s what he said,“We think apps like F.lux or Twilight are great and everyone should use them. In fact, they should be part of future operating systems. Gauss glasses just add another layer of protection because unless you completely turn off the blue color channel in your monitor it still emits blue light. Plus many other sources of blue light like light bulbs with cold color temperatures still emit blue light that interferes with your melatonin production and as a result, with your circadian rhythm.”WHAT WORKS TO REDUCE BLUE LIGHT?I’ve been using Twilight and F.lux for a couple of weeks and it does feel like it’s made a difference. Just like millions of other people, I tend to read on a screen in bed, with no other light source, and since using the apps I have felt tired earlier and fallen asleep more easily than before. Judging by the reviews and discussion online, a lot of people feel the same way.I’ll be getting a hands-on look at the Gauss glasses very soon, so stay tuned for more on that.In the meantime, think about your exposure, and if you’re having trouble sleeping, try modifying your lighting and device use. Blue light is just one of the factors that determines your sleeping pattern, but it’s clearly very important. Some experts recommend staying away from devices for a half hour before sleeping.“Would I say we have a health problem because of phones and tablets shining light in our faces? I would say, yes we do,” Dr. Breus told us. “But, they’re not the only factor.”You can find more advice on getting healthy sleep at his Secrets to Sleep Success website.

The pervasive glow of electronic devices may be an impediment to a good night’s sleep. That’s particularly noticeable now, when families are adjusting to early wake-up times for school. Teenagers can find it especially hard to get started in the morning. For nocturnal animals, it spurs activity. For daytime species such as humans, melatonin signals that it’s time to sleep.

As lamps switch off in teens’ bedrooms across America, the lights from their computer screens, smartphones and tablets often stay on throughout the night. These devices emit light of all colors, but it’s the blues in particular that pose a danger to sleep. Blue light is especially good at preventing the release of melatonin, a hormone associated with nighttime.Ordinarily, the pineal gland, a pea-size organ in the brain, begins to release melatonin a couple of hours before your regular bedtime. The hormone is no sleeping pill, but it does reduce alertness and make sleep more inviting.However, light — particularly of the blue variety — can keep the pineal gland from releasing melatonin, thus warding off sleepiness. You don’t have to be staring directly at a television or computer screen: If enough blue light hits the eye, the gland can stop releasing melatonin. So easing into bed with a tablet or a laptop makes it harder to take a long snooze, especially for sleep-deprived teenagers who are more vulnerable to the effects of light than adults.During adolescence, the circadian rhythm shifts, and teens feel more awake later at night. Switching on a TV show or video game just before bedtime will push off sleepiness even later even if they have to be up by 6 a.m. to get to school on time. Blue light prevents the release of melatonin, a hormone associated with nighttime and sleep. (BIGSTOCK)The result? Drowsy students struggling to stay awake, despite the caffeinated drinks many kids now consume.“Teenagers have all the same risks of light exposure, but they are systematically sleep-deprived because of how society works against their natural clocks,” said sleep researcher Steven Lockley of Harvard Medical School. “Asking a teenager to get up at 7 a.m. is like asking me to get up at 4 a.m.”In a 2014 poll, the National Sleep Foundation, an advocacy organization, polled parents, asking them to estimate their children’s sleep. More than half said their 15-to-17-year-olds routinely get seven hours or fewer hours of sleep. (The recommended amount for teens is 81 / 2 to 10 hours.) In addition, 68 percent of these teens were also said to keep an electronic device on all night — a television, computer, video game or something similar.Based on what parents reported, sleep quality was better among children age 6 to 17 who always turned their devices off: 45 percent of them were described as having excellent sleep quality vs. 25 percent of those who sometimes left devices on.“It is known that teenagers have trouble falling asleep early, and every teenager goes through that,” said light researcher Mariana Figueiro of the Rensselaer Polytechnic Institute in Troy, N.Y.Figueiro investigates how light affects human health, and her recent research focused on finding out which electronics emit blue light intense enough to affect sleep. When comparing melatonin levels of adults and teenagers looking at computer screens, she was astonished by the younger group’s light sensitivity. Even when exposed to just one-tenth as much light as adults were, the teens actually suppressed more melatonin than the older people.In another experiment, she had adults use iPads at full brightness for two hours and measured their melatonin levels with saliva samples. One hour of use didn’t significantly curtail melatonin release, but two hours’ did.

So although teenagers may be particularly susceptible, we all should be aware that artificial light can affect our circadian rhythms.“The premise to remember is [that] all light after dusk is unnatural,” Lockley said. “All of us push our sleep later than we actually would if we didn’t have electric light.”A study from 2013 found that people who spent a week camping in the Rocky Mountains, exposed to only natural light and no electronic devices, had their circadian clocks synchronized with the rise and fall of the sun. Although there were only eight campers, they all reacted in the same way, whether they considered themselves early birds or night owls.So light serves as a cue, but how? It has long been known that the retina contains two types of photoreceptors, or light sensors: rods and cones. The cones allow us to see colors, while the ultra-

sensitive rods are used for night vision, motion detection and peripheral vision. But surprisingly, neither of them is the body’s primary tool for detecting light and darkness and synchronizing our circadian clocks.There’s a third kind of sensor in our eyes, officially discovered in 2002. Called intrinsically photosensitive retinal ganglion cells, or ipRGCs, these relatively crude sensors are unable to pick up on low levels of light — from a dim night light, for example — but sluggishly signal light changes.They are the body’s way of sending ambient light information to the master circadian clock, a huddle of nerve cells in the brain. This clock makes the pineal gland start and stop the secretion of melatonin. The ipRGCs are most sensitive to blue light — that’s why blue light is bad for your sleep.To counteract the effects of tablets’ blue light, Figueiro and Lockley recommend a free app, F.lux, that automatically warms up the colors on your various screens — more reds and yellows — at sunset and returns them to normal at sunrise.“The amount of light you need [in order] to see is lower than the amount of light you need to affect your melatonin,” Figueiro said, which means that light-emitting screens can be used at night without disrupting sleep cycles if you put some distance between your eyes and the device. In other words, place the tablet farther away from your face than usual, or watch TV instead. Also, turning the brightness setting down on laptops, tablets and phones should help.But for teenagers, this doesn’t completely remedy the problem of early school start times. Lockley also blames the early-morning sluggishness of many students on school start times that ignore their changing body clock.High schools in a handful of cities have shifted their start times to 8:30 a.m. or later. In a University of Minnesota study whose final report was issued in February, researchers who surveyed about 9,000 students at eight high schools found that such a shift correlated with improvements in grades, achievement tests, attendance rates and car accident rates.In Virginia, Fairfax County has been considering delaying its high school start time until after 8 a.m. In Maryland, Montgomery County has discussed a change but has not decided on one yet.

Last week, the American Academy of Pediatrics issued a recommendation that middle and high schools delay the start of classes to 8:30 a.m. or later. Pediatrician Judith Owens, the lead author of this policy statement, said that later start times will help adolescents get the sleep they need and lower their risks of obesity and depression.“Sleep is important for learning, memory, brain development, health,” Lockley said. “We’re systematically sleep-depriving kids when their brains are still developing, and you couldn’t design a worse system for learning.”Many Americans may believe early risers are more successful and that people can learn to live on little sleep, Lockley said, but that notion is neither true nor healthy.“There’s no training people to live without sleep,” Lockley said. “It’s like trying to train people to live without food.”

Kim is a freelance science journalist in Philadelphia.

Light at night is bad for your health, and exposure to blue light emitted by electronics and energy-efficient lightbulbs may be especially so.Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. Now, in much of the world, evenings are illuminated, and we take our easy access to all those lumens pretty much for granted.But we may be paying a price for basking in all that light. At night, light throws the body’s biological clock—the circadian rhythm—out of whack. Sleep suffers. Worse, research shows that it may contribute to the causation of cancer, diabetes, heart disease, and obesity.

But not all colors of light have the same effect. Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown.Daily rhythms influenced by lightEveryone has slightly different circadian rhythms, but the average length is 24 and one-quarter hours. The circadian rhythm of people who stay up late is slightly longer, while the rhythms of earlier birds fall short of 24 hours. Dr. Charles Czeisler of Harvard Medical School showed, in 1981, that daylight keeps a person’s internal clock aligned with the environment.The health risks of night time lightStudy after study has linked working the night shift and exposure to light at night to several types of cancer (breast, prostate), diabetes, heart disease, and obesity. It’s not exactly clear why nighttime light exposure seems to be so bad for us. But we do know that exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms, and there’s some experimental evidence (it’s very preliminary) that lower melatonin levels might explain the association with cancer.A Harvard study shed a little bit of light on the possible connection to diabetes and possibly obesity. The researchers put 10 people on a schedule that gradually shifted the timing of their circadian rhythms. Their blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down.Even dim light can interfere with a person’s circadian rhythm and melatonin secretion. A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect, notes Stephen Lockley, a Harvard sleep researcher. Light at night is part of the reason so many people don’t get enough sleep, says Lockley, and researchers have linked short sleep to increased risk for depression, as well as diabetes and cardiovascular problems.The power of the bluesWhile light of any kind can suppress the secretion of melatonin, blue light does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).In another study of blue light, researchers at the University of Toronto compared the melatonin levels of people exposed to bright indoor light who were wearing blue-light–blocking goggles to people exposed to regular dim light without wearing goggles. The fact that the levels of the hormone were about the same in the two groups strengthens the hypothesis that blue light is a potent suppressor of melatonin. It also suggests that shift workers and night owls could perhaps protect themselves if they wore eyewear that blocks blue light. Inexpensive sunglasses with orange-tinted lenses block blue light, but they also block other colors, so they’re not suitable for use indoors at night. Glasses that block out only blue light can cost up to $80.Less-blue lightIf blue light does have adverse health effects, then environmental concerns, and the quest for energy-efficient lighting, could be at odds with personal health. Those curlicue compact fluorescent lightbulbs and LED lights are much more energy-efficient than the old-fashioned incandescent lightbulbs we grew up with. But they also tend to produce more blue light.The physics of fluorescent lights can’t be changed, but coatings inside the bulbs can be so they produce a warmer, less blue light. LED lights are more efficient than fluorescent lights, but they also produce a fair amount of light in the blue spectrum. Richard Hansler, a light researcher at John Carroll University in Cleveland, notes that ordinary incandescent lights also produce some blue light, although less than most fluorescent lightbulbs.What you can do

IntroIn the modern age of technology it is not uncommon to come home after a long day at work or school and blow off steam by reading an e-book or watching television. Lately, however, scientists have been cautioning against using light-emitting devices before bed. Why? The light from our devices is “short-wavelength-enriched,” meaning it has a higher concentration of blue light than natural light—and blue light affects levels of the sleep-inducing hormone melatonin more than any other wavelength.Changes in sleep patterns can in turn shift the body’s natural clock, known as its circadian rhythm. Recent studies have shown that shifts in this clock can have devastating health effects because it controls not only our wakefulness but also individual clocks that dictate function in the body’s organs. In other words, stressors that affect our circadian clocks, such as blue-light exposure, can have much more serious consequences than originally thought.