Question: Is blue light bad for eyes?

Effects of blue light technology


Background
Blue Light is a range of the visible light spectrum, defined as having a wavelength between 400−495nm.[1] This short wavelength means that blue light is a type of high-energy visible light, defined as having a wavelength between 400 and 450nm.  Violet, indigo, and some blue-green light are other types of high-energy visible light.[2]

Blue light sources are becoming increasingly common in today’s environment. Exposure to blue light comes from a variety of technologies including computers, televisions, and lights.[1][3]  Much of the exposure arises from light emitting diodes (LEDs). Today, many white LEDs are produced by pairing a blue LED with a lower-energy phosphor, thereby creating solid-state light (SSL).[3] This is often considered “the next generation of illumination”[3] as SSL technology dramatically reduces energy resource requirements.[4]
Increasingly, people are exposed to blue light via everyday technology. The 2015 Pew Research Center study found that 68% of U.S. adults own a smartphone and 45% own a tablet. The study also found that levels of technology ownership vary by age; 86% of Americans 18-29 and 83% of those 30-49 own smartphones.[5]  Younger Americans also use high rates of blue light technologies. The survey of Common Sense Media in 2013 also demonstrated that 72% of children age 0–8 years old used mobile devices for watching videos and playing games.[6]  Moreover, 93% of teens owned a computer or had access to one at home.[7] In contrast, computer ownership rates are lower for older Americans.[5]
Effects of blue light on sleep and circadian rhythm
It is claimed the timing people receive light should be taken into consideration, as light can prevent sleep when absorbed at night from devices. A 93 page European Commission report concluded that, "exposure to light in the late evening, including that from LED lighting and/or screens, may have an impact on the circadian rhythm...At the moment, it is not yet clear if this disturbance of the circadian system leads to adverse health effects." The comissions findings were not specific to digital devices, LEDs or blue light but to light exposure in general.[8]
Blue light exposure has been shown to impact the circadian rhythm. Natural exposure to blue light during the daylight hours boosts people's energy, alertness and mood.[9] However, elongated exposure to the waves transmitted through screen devices during the evening can disrupt normal sleep schedules.[10] Scientists believe this is caused by blue-light-sensitive intrinsically photosensitive retinal ganglion cells suppressing the production of melatonin and/or stimulating the suprachiasmatic nucleus of the hypothalamus.[11]
The average sleep time has significantly decreased over the last two decades. Teens typically need to receive nine hours of sleep a night, but statistics reveal that less than twenty percent actually do receive enough sleep each night. People who do not get enough sleep each night tend to become more depressed, exercise less, and eat more because a hormone stimulates their appetite. Not getting enough sleep severely affects cognitive performance and overall health, and long-term sleep deprivation eventually leads to death. A study has discovered teenagers are more likely to exhibit behavior problems and have trouble paying attention during the day if they spend time on blue light screens at night.[12]
Lack of sleep has consequences for teenagers. A study found that over seventy percent of teenagers get less than eight hours of sleep each night, and less than ten percent receive the recommended nine hours of sleep. Just one night of irregular sleep can drastically cause an imbalance in our bodies. Because blue light is the color of the sky, this may be the reason it is extremely sensitive to our eyes. Blue light has been found to delay sleepiness and can affect our circadian rhythm. Wearing yellow tinted sunglasses at night to avoid the blue wavelengths can ensure that you will become naturally tired and may help induce sleep quicker.[13]
A research study measured the effect of iPads at full brightness. It was found that after one hour of use, there was no notable change in melatonin. However, after two hours of light exposure through the iPad, melatonin was drastically inhibited. Blue light has been found to affect teenagers more than adults. Teenagers were more alert and awake compared to adults, even when the teenagers were only exposed to a tenth of the blue light adults were exposed to. In another study, a group of people spent a week outdoor camping without any blue light devices. At the end of the week, the circadian rhythm of the entire group locked into the sunrise and sunset.[14]
A Harvard research study indicated that blood sugar levels and leptin production become altered when the subjects’ schedules were shifted, changing their circadian rhythms. Two additional studies focused on the power of blue light’s powerful suppression of melatonin compared to other light wavelengths.[11]
Many people who are convinced they have sleep disorders average over six hours of sleep each night, and our bodies need significantly less sleep than that to remain functional. In fact, one study found that the risk of a stroke was doubled in middle-aged people and older who received more than eight hours of sleep a night. Dr. Irshaad Ebrahim, a director of the Sleep Centre in London believes most people are actually receiving sufficient sleep. Research has showed that the primitive age of ancestral humans actually received only about six hours of sleep each night without any negative impact on their health.[15]
Use of computers with blue-lit screens in the hours immediately before bedtime can lead to fewer hours of deep sleep. Staying up late to study for a test may seem prudent, but research has found the practice can actually impede memory retention. A clinical psychological study found that students who were able to fall asleep earlier and sleep more received better grades than students who slept less. Additionally, as technology continues to grow, the sleep time for students decreases. It has been found that the average American sleeps an hour and a half less than the average sleep time half a century ago.[16]
Alzheimer's disease affects the sleep of people who carry this disease by making it more difficult to fall and stay asleep. An experiment measured the effect of sleep on patients who had Alzheimer's by seeing how well they slept after being exposed to blue light in the evening compared to red light (which is believed not to impact our sleep cycle). In this study, when the patients were exposed to blue light, they were able to sleep better throughout the night. In addition, the patients were more active during the day and had more energy when they were exposed to blue light.[17]
Blue light vs other forms of light on sleep
An experiment in this article was performed to test this idea using three variables, blue light, yellow light, and darkness. Each group was exposed to light or in the case of the control group, darkness, for before bed. The results concluded that blue light inhibited signs of sleepiness while the control group showed expected signs of tiredness and the yellow light showed no significant effect on sleep.[18] Overall, absorbing light during the day, as opposed to night, may make a difference in falling and staying asleep.[19]
Public health concerns regarding prolonged exposure to blue light
On eye health
Concerns regarding blue LEDs are related to the difference between the photopic luminous flux and radiometric radiance. Blue LEDs, particularly those used in white LEDs, operate at around 450nm.[20][21]the perception of the brightness of different frequencies of light is defined according to the CIE luminosity function. Photometry is concerned with the study of the perception of visible light. Radiometry is concerned with the measurement of energy. At the outer edges of the range of light perception, the amount of energy as light required to register as a perception increases. The peak efficiency of light perception is defined at 555nm, having a value of V(λ)=1. at 450nm, V(λ)=0.038 or to put it another way, it requires more than 26 times the radiometric energy to perceive the same luminous flux as green at 555nm. For comparison, UV-A at 380nm(V(λ)=0.000 039) requires 25 641 times the amount of radiometric energy to be perceived at the same intensity as green, three orders of magnitude greater than blue LEDs.[22] [23] Studies often compare animal trials using identical luminous flux rather than radiance meaning comparative levels of perceived light at different frequencies rather than total emitted energy.[24][25] As interest in LED backlighting has increased, so has the technology developed. studies often select low quality generic LEDs from little-known brands with a high proportion of blue light, especially selecting low CRI LEDs which are not suitable for either lighting or backlight technologies. LCD screens and LED lighting generally use much higher CRI LEDs as consumers demand accurate color reproduction. [26][27][20] white LEDs are designed to emulate natural sunlight as closely as is economically and technologically possible. Natural sunlight has a relatively high spectral density of blue light, similar to LEDs, making exposure to relatively high levels of blue light not a new or unique phenomenon. 
Light is transmitted to the retina through the lens. In humans, the amount of light transmitted by the lens is age-dependent. In young children, more than 65% of blue light is transmitted. This transmission rate decreases over time; at age 25, only 20% of blue light is transmitted to the retina. The decreased transmission of blue light occurs as our eyes’ lens naturally yellows and absorbs more blue light over time, thus preventing blue light from reaching the retina. As a result of this natural process, younger people are more susceptible to the effects of blue light.[28]
One public health concern regarding exposure to blue light is based on the fact that children may be more susceptible to its effects. The concern is that not only are children the most vulnerable to the effects of blue light exposure but are also more likely to frequently use devices that emit blue light and will likely be exposed to more blue light sources over the course of their lifetime. The physicist Sébastien Point discusses the validity of blue light exposure values for newborn infants and concludes that "because of focal length and pupil diameter differences, limit for effective blue radiance for newborn infants could be around 2.8 times lower than for adults", what calls for particular caution with luminous toys. However, this author suggests that the higher transparency of the crystalline lens of newborn infants could increase risk from technologies such as halogen lamps and fluorescent lamps, which are rich in violet light, but not from LEDs, which are free from violet light.[29][30] Point also worried about the consequences for public health of using blue-rich lamps in pseudomedecines like chromotherapy, and asked for more regulation of pseudomedicines using lamps.
Although older adults absorb less blue light, possible eye damage from prolonged exposure may occur. The relative newness of blue light technology and its ubiquitous use in society creates questions for which there are no known answers yet. Continued research into the cause and effect of the dose-relationship of exposure to blue light and its negative health effects should be studied, and reasonable policy recommendations (such as limited screen time for young children) should be considered as prudent measures until more information is available.
IOLs are the ideal test model in-vivo on human models. They cannot be removed and are persistently active 24/7 owing to the fact that they are permanently implanted into the eye. A Cochrane Review found no evidence of any effect in 51 trials with yellow tinted intraocular implants. None of the studies reviewed provided any reliable statistical evidence to suggest any effect regarding contrast sensitivity, macular degeneration, vision, color-discrimination or sleep disturbances.[31] A particular study claimed a large difference in observed fluorescein angiography examinations concluding they observed markedly less "progression of abnormal fundus autofluorescence" [32] however the authors failed to discuss the fact that the excitation beam is filtered light between 465-490nm,[33] is largely blocked by blue light filtering IOLs[34] but not clear IOLs present in the control patients.
Aggressive Marketing
Aggressive advertisements may contribute to the public perception of the dangers of blue light. A sponsored post on NewGradOptometry promoted sales training from Essilor and their product range including the moral benefits, then a segue into the amoral nature of upselling unnecessary lenses, finishing by arguing that patients will go blind without blue filtering lenses.[35] Essilor provided a pair of free glasses to a fashion blogger who did not need prescription glasses but nonetheless quoted a large number of Essilor marketing pitches including the blindness preventing promises of their blue light filtering technology.[36] The Essilor website claims that you may experience vision loss without their special filtering lenses, whether you require prescription glasses or not.[37] Zeiss offers a similar product yet does not make nearly as extreme claims.[38]
Boots Opticians was criticised by the General Optical Council for their unsubstantiated claims regarding their line of blue light filtering lenses and fined £40,000 by the Advertising Standards Authority. Boots Opticians sold the lenses for a £20 markup.[39]Trevor Warburton, speaking on behalf of the UK Association of Optometrists stated, "...current evidence does not support making claims that they prevent eye disease."[40]
Mitigation
Harvard University suggests (without revealing its original research or having any listed authors, possibly suggesting it is a paid advertisement and not a scholarly reference): [11]
using red lights in the nighttime and evening
not looking at bright screens for 2 to 3 hours prior to sleeping
using blue-light filtering apps or devices


Additional articles
Sébastien Point and Annick Barlier-Salsi, LED lighting and retinal damage, technical information sheets, SFRP