Effects of blue light technology
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Current academic and medical consensus suggests there are no known health effects of day-to-day exposure to blue light (visible light with wavelengths 400-450 nm), and it is not regarded as a cause of eye disease, eye strain, or disruptions to circadian rhythm, as distinct from any other frequency band of visible light. Despite the lack of scientific basis, numerous products and software claim to filter out blue light to prevent eye strain and sleep disruptions. It is illegal in the UK for a health practitioner to indicate to a patient that 400-450 nm blue light causes health effects or affects sleep.[failed verification] Harvard Health continues to support claims that exposing to blue light at night has a stronger negative effect on sleep.
Blue light is a range of the visible light spectrum, defined as having a wavelength between 400−495 nm. This short wavelength means that blue light is a type of high-energy visible light, defined as having a wavelength between 400 and 450 nm.
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. 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). This is often considered “the next generation of illumination” as SSL technology dramatically reduces energy resource requirements.
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. 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. Moreover, 93% of teens owned a computer or had access to one at home. In contrast, computer ownership rates are lower for older Americans.
Alleged 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 450 nm. 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 555 nm, having a value of V(λ)=1 at 450 nm, 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 555 nm. For comparison, UV-A at 380 nm(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. 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. 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. 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 making exposure to relatively high levels of blue light not a new or unique phenomenon despite the relatively recent emergence of LED display technologies.
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.
IOLs (Intraocular lenses) 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. A particular study claimed a large difference in observed fluorescein angiography examinations concluding they observed markedly less "progression of abnormal fundus autofluorescence"  however the authors failed to discuss the fact that the excitation beam is filtered light between 465-490 nm, is largely blocked by blue light filtering IOLs but not clear IOLs present in the control patients.
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 segued into the amoral nature of upselling unnecessary lenses, finishing by arguing that patients will go blind without blue-filtering lenses. 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. The Essilor website claims that one may experience vision loss without their special filtering lenses, whether one requires prescription glasses or not. Zeiss offers a similar product yet does not make nearly as extreme claims.
The UK's General Optical Council has criticised Boots Opticians for their unsubstantiated claims regarding their line of blue-light filtering lenses; and the Advertising Standards Authority fined them £40,000. Boots Opticians sold the lenses for a £20 markup. Trevor Warburton, speaking on behalf of the UK Association of Optometrists stated: "...current evidence does not support making claims that they prevent eye disease." Harvard University suggests - without revealing its original research or having any listed authors, suggesting a paid advertisement and not a scholarly reference - that blue light adversely affects the circadian rhythm. They appear to have partially attempted to retract their previous health claims from 2012, "Light at night is bad for your health, and exposure to blue light emitted by electronics and energy-efficient lightbulbs may be especially so." The main article is not supported by any references or authorship but states that blue light could "potentially cause disease".
Despite the lack of evidence for the effect of blue light on circadian rhythm, Apple's and Microsoft's operating systems include options to reduce blue-light emissions by adjusting color temperature to a warmer gamut. These settings dramatically reduce the color gamut of the display, sacrificing usability of devices without providing any of the alleged benefits of reducing eye-strain or preventing circadian-rhythm disruption.
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