Blue light has saturated the daily flow of our lives long before men and women created jobs or began working in front of digital screens.
This portion of the visible spectrum helps to set our biological clocks to a greater degree than the other colors present in white light, or sunlight, such as turquoise, green, yellow, orange and red. Blue light signals the photoreceptors just in front of the retina that it’s time to start our day and get going. Its presence tells the brain to become alert and active.
“The blues more easily penetrate the surface of the oceans — where life (and photoreceptors) likely first evolved — than do other visible wavelengths,” wrote David C. Holzman in Environmental Health Perspectives. “The color balance of the sky may have helped to preserve blue’s clock-setting role throughout evolutionary history.”
Today, many experts agree that exposure to blue light during the day contributes to focus and boosted learning ability — a straightforward benefit for people on the job. But those who have to work in front of screens in the evening, do overnight shift work, or drive after dark may want to become aware of the facts concerning blue light.
Blue, sometimes called high-energy visible (HEV) light, may also contribute to digital eye strain for staffers working long hours in front of computers at any time of the day. And a considerable number of Americans put in these long hours. The Vision Council estimated in its DigitEYEzed report that 43% of adults have jobs requiring prolonged periods working at a tablet or computer, and it is likely that the number has grown since 2013.
Contact lens manufacturer Acuvue® sponsored a study in 2018, reporting that the average office worker spends 1,700 hours each year in front of a digital screen — about six-and-a-half hours a day, posted CBS Boston.
Let’s take a look at the blue.
About blue light
The visible light spectrum ranges from frequencies of 380 nm–700 nm — representing the rainbow of colors; red, orange, yellow, green, blue, and violet. Blue-violet rays have the shortest wavelength and higher energy, while red light has the longest wavelength and less energy.
“Blue light is visible light with a wavelength between 400 and 450 nanometers (nm),” wrote David Ramsey, M.D. on the Health.Harvard.edu/blog. “As the name suggests, this type of light is perceived as blue in color. However, blue light may be present even when light is perceived as white or another color.”
There are two ranges of blue light — blue-violet light, from 380 nm– 450 nm, and blue-turquoise light from about 450 nm–500 nm, wrote optometrist Gary Heiting on AllAboutVision.com.
Together, blue-violet and blue-turquoise add up to about one-third of the visible spectrum, he added.
Sunlight is the primary source of light, and this includes blue light. Man-made sources of illumination range from incandescent, fluorescent, LED and other lamps, to televisions and lighted displays, to computer monitors, tablets, and smartphones. These sources vary in brightness.
“For example, recent iPhones have a maximum brightness of around 625 candelas per square meter (cd/m2),” Dr. Ramsey wrote. “Brighter still, many retail stores have an ambient illumination twice as great. However, these sources pale in comparison to the sun, which yields an ambient illumination more than 10 times greater.”
While incandescent light bulbs have a warmer, more yellow-toned light, fluorescent and LED lamps may give off a cooler, blue-toned light.
“The screens of modern electronic devices rely on LED technology,” Ramsey added. “Typical screens have individually controlled red, green, and blue LEDs tightly packed together in a full-color device. However, it is the bright white-light LEDs, which backlight the displays in smartphones, tablets, and laptop computers, that produce the greatest amount of blue light.”
Blue light is more energy efficient due to its short wavelength, providing more light for less energy. This has made it a good choice for indoor LED bulbs and digital screens.
“Having a higher amount of emitted blue wavelength light is one of the reasons why these newer screens seem whiter, brighter, more crisp and fresh,” wrote optometrist Cheryl G. Murphy on 2020Mag.com.
Blue light during the day increases attentiveness
Blue light keeps us sharp, clear, and at ease as we experience it during the daylight hours.
“Evidence shows that the use of blue-enriched, white fluorescent lighting (17,000K) in an office setting improves alertness, positive mood, concentration, ability to think clearly, and evening fatigue when compared with white fluorescent lighting (4,000K),” wrote Mark Rosenfield, Ph.D., professor at SUNY College of Optometry.
So, working or studying from morning through afternoon is enhanced with added blue light. Then, taking it away in the evening allows us to become tired and to settle in for some rest.
“’Increasing the blue portion of artificial light may improve performance and learning ability in school kids and employees working indoors, and health will be improved in patients staying at nursing homes or hospitals,’” said Daniel Kripke, emeritus professor of psychiatry at the University of California, San Diego, in Holzman’s article.
Blue light may add to digital eye strain
Many articles written in the past few years have covered the topic of blue light’s impact on our biological clock, as well as its contribution to the sensation of digital eye strain.
“Blue light radiates at a short wavelength and it scatters easily,” Murphy wrote. “This scattering can interfere with visual contrast and increase the feeling of eye fatigue. Again, users of smartphones, computers and tablet devices should be advised to decrease screen brightness, increase the distance between the device and their eyes, take frequent breaks whenever possible and to limit their use of these devices.”
A powerful example of the way that blue light scatters is seen right above us. As sunlight hits water molecules in the atmosphere and blue rays scatter, the sky appears blue.
Yellow-tinted eyeglasses may help those who work long hours in front of a digital screen.
“Research has shown that lenses that block blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly,” Heiting added. “Therefore, computer glasses with yellow-tinted lenses may increase comfort when you’re viewing digital devices for extended periods of time.”
Another outcome of blue light’s short wavelength is visual glare.
Bright blue-toned light from high-intensity discharge headlights increase clarity at night, although they also create glare for oncoming drivers, Holzman wrote. This factor affects professional drivers as well as the general public.
Blue light is under scrutiny regarding macular degeneration
“Blue-violet light (380 nm–455 nm) is very close in wavelength to ultraviolet light (10 nm–380 nm), a well-known hazard to our eyes and our health if we are exposed to it in repeated, large doses,” Murphy wrote.
Ultraviolet (UV) energy is composed of wavelengths that are not visible, and occurs next to the visible light spectrum — between the frequencies of light and X-rays. Its wavelength is shorter than blue light, and UV has more energy; enough to damage cells.
The cornea and crystalline lens at the front of your eye block most of the harmful UV from reaching the retina at the back of your eye, but most blue visible light rays pass through cornea and lens to the retina, Heiting wrote.
A number of eye care providers are concerned that extra blue light exposure from digital screens may lead to the development of macular degeneration, although more research is needed, he added. Other professionals disagree and argue there is no proven risk to the retina when exposed to added blue light.
“Many people ask whether blue light will increase their risk of age-related macular degeneration and blindness,” Dr. Ramsey wrote. “The short answer to this common question is ‘no.’ The amount of blue light from electronic devices, including smartphones, tablets, LCD TVs, and laptop computers is not harmful to the retina or any other part of the eye.”
The American National Standards Institute (ANSI), International Electrotechnical Commission (IEC), and lighting manufacturers rate the safety of LED lamps and devices on a 0–3 scale.
“’0’ means that the light poses no risk to your eyes, and doesn’t require any kind of warning label,” wrote Katherine Ellen Foley on Quartz. “The LED lights present in homes, offices, and your screens, have this kind of a low-risk rating. The eye-health risks posed by lamps increase as the scale goes up; but notably, those that are high-risk, with a rating of 2 or 3, are usually only present in industrial settings. People who work with these types of lights are required to wear protective gear to filter out some of the blue light.”
It is widely known that looking directly, or for long periods of time at the sun can damage the retina. The same caution may be applied to other strong light sources, such as military-strength flashlights or concentrated lasers.
The International Commission on Non-Ionizing Radiation Protection (ICNIRP), based in Germany, provides guidance on safe levels of non-ionizing radiation such as the energy present in electricity, magnetic fields, and visible light. In measuring light energy, candela per square meter (cd/m2) is a unit used to evaluate the strength of a source. The ICNIRP, a non-profit organization, considers negative health impacts unlikely when a light source is less than 104 cd/m2 in brightness, Rosenfield wrote.
“The emission of blue light from digital displays barely reaches four percent of this limit,” he added. “Thus, clinicians may conclude that the magnitude of exposure from digital devices does not approach dangerous levels.”
Blue light can impact our health indirectly, by disrupting our biological clock. Most scientists agree that blue light can alter circadian rhythms — the body’s cycle of wakefulness and sleepiness.
“Melatonin is a hormone that makes our bodies drowsy and ready for sleep,” Murphy wrote. “In the absence of blue light, specialized cells in our retina called intrinsically photosensitive retinal ganglion cells (ipRGCs) become switched on. When they are activated, they send a signal to the brain telling the pineal gland to start the process of melatonin production. When melatonin is produced in our bodies, it lets us know it’s time for rest.”
Blue light has a greater impact on disrupting melatonin production than other colors of light.
“Although most visible wavelengths can reset the (biological) clock, the blues do the job with the greatest efficiency,” Holzman wrote.
So, working at a laptop long into the evening may impair the quality of one’s sleep.
“That is why Dr. Khurana (spokesperson for the American Academy of Ophthalmology) recommends that you try to limit your screen time in the two to three hours before you go to bed,” wrote Celia Vimont on AAO.org. “Many devices have nighttime settings that minimize blue light exposure in the evenings.”
The setting may be called night mode, night setting, or dark mode. In night mode, the screen will appear yellower and more like the light from ambient incandescent bulbs. Since most of us have become used to the crisp and sharp appearance of blue-toned light from digital displays, the screen on night mode may appear dull and old until viewers are acclimated to the change in color.
Shift workers are affected by blue light and biorhythm disruption
One group of working people may be especially affected by exposure to blue light at night.
Dieter Kunz is director of the Sleep Research and Clinical Chronobiology Research Group at the Charité–Universitätsmedizin, in Berlin, Germany.
“Shift workers, whom Kunz calls ‘a model for internal desynchronization,’ are known to experience increased morbidity and mortality for a number of diseases, including cardiovascular disorders and cancer,” Holzman wrote. “In fact, in 2007, the World Health Organization decreed that shift work is a risk factor for breast cancer, and on that basis, in 2009, the Danish government began compensating some female shift workers with breast cancer.”
Samer Hattar is an assistant professor at the Solomon H. Snyder Department of Neuroscience, studying circadian rhythms and light’s effects on activity, sleep patterns, and hormone regulation.
“Hattar says no previous experiment has determined whether the ill effects of shift work are due to light stimulation at the wrong time of day, to the circadian clock’s being out of phase, or to a combination of the two,” Holzman added. “However, he adds, even as activating melanopsin photopigment during the day is believed to be beneficial, it could be bad to activate it at night.”
There are strategies to lessen the negative impacts, though.
“On the other hand, he (Kunz) adds, a reduction of the blue portion in artificial light during nighttime hours could protect shift workers against disorders such as cancer and cardiovascular disorders as well as reduce sleep disturbances and their consequences among the general population,” Holzman wrote.
Look for more blue in the day, and less in the evening
Research confirms the substantial effect blue light has on our comfort, mood, and sleep patterns.
Ophthalmologists contend that there is no need to be fearful of these wavelengths, simply to manage them effectively; using blue light to boost alertness at work and school during the day, and reducing these wavelengths in the evening hours to prepare for rest.
“According to the National Center on Sleep Disorders Research, sleep-related problems affect 50–70 million U.S. men and women of all ages,” Holzman wrote.
A number of sleep disorders may be related to man-made light, and the impact of this factor is kind of “blue.”
But, by managing our exposure to high-energy blue light — better matching natural biorhythms and reducing eye strain — perhaps working people can finish up the day simply … “golden.”