High-energy visible light (HEV light) is high-frequency, high-
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
light in the
violet
Violet may refer to:
Common meanings
* Violet (color), a spectral color with wavelengths shorter than blue
* One of a list of plants known as violet, particularly:
** ''Viola'' (plant), a genus of flowering plants
Places United States
* Viol ...
/
blue
Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when obs ...
band from 400 to 450
nm in the
visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...
,
[
] which has a number of biological effects, including those on the
eye
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
.
HEV light may be a cause of
age-related macular degeneration
Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...
. Some
sunglasses
Sunglasses or sun glasses (informally called shades or sunnies; more names below) are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can s ...
and beauty creams specifically block HEV, for added marketing value.
Currently, a 2019 report by France's Agency for Food, Environmental and Occupational Health & Safety (ANSES) supports the 2010 result on the adverse effect of blue LED light (400-450 nm spike) on the eye, which can lead to impaired vision. It highlights short-term effects on the retina linked to intense exposure to blue LED light, and long-term effects linked to the onset of age-related macular degeneration. Although few studies have examined occupational causes of macular degeneration, they show that long-term sunlight exposure, specifically its blue-light component, is associated with macular degeneration in outdoor workers.
Harvard Health Publishing additionally asserts that exposure to blue light (especially blue LED light, but also broad-spectrum blue light) at night has a stronger negative effect on sleep.
A June 14, 2016 press release by the
American Medical Association
The American Medical Association (AMA) is a professional association and lobbying group of physicians and medical students. Founded in 1847, it is headquartered in Chicago, Illinois. Membership was approximately 240,000 in 2016.
The AMA's state ...
concludes that there are negative health impacts from the unrestrained use of LED
street light
A street light, light pole, lamp pole, lamppost, street lamp, light standard, or lamp standard is a raised source of light on the edge of a road or path. Similar lights may be found on a railway platform. When urban electric power distribution ...
ing in general. Lenses that block blue light may be particularly useful for people with insomnia, bipolar disorder, delayed sleep phase disorder, or ADHD, though less beneficial for healthy sleepers.
Background
Blue light is a range of the
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
spectrum, defined as having a
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
between 400 and 525 nm. This includes wavelengths between violet and cyan in the spectrum. ''Narrow-spectrum'' blue light (also called blue LED light or short-wavelength LED light) is a type of
high-energy visible light
High-energy visible light (HEV light) is high-frequency, high-energy light in the violet/blue band from 400 to 450 nm in the visible spectrum,
which has a number of biological effects, including those on the eye.
HEV light may be a cause o ...
, defined as having a wavelength between 400 and 450 nm. This light is common in LEDs (even when used in illumination products) as a carry-over from computer-screen technology.
Blue light is an essential component of white light. White can be made from either narrow-spectrum or broad-spectrum blue. For example, LED technology tends to combine narrow-spectrum blue and yellow, while other technologies include more cyan and red. Fluorescent coatings generate violet and cyan spikes, in addition to having a smaller narrow-spectrum blue component. Natural light has a much more even distribution of blue wavelengths than most artificial light.
Blue LED light
![Light spectrum (precise colors)](https://upload.wikimedia.org/wikipedia/commons/0/0a/Light_spectrum_%28precise_colors%29.svg)
Blue LED 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 harmful 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 LED light via everyday technology. The 2015
Pew Research Center
The Pew Research Center is a nonpartisan American think tank (referring to itself as a "fact tank") based in Washington, D.C.
It provides information on social issues, public opinion, and demographic trends shaping the United States and the w ...
study found that 68% of U.S. adults own a
smartphone
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
and 45% own a
tablet
Tablet may refer to:
Medicine
* Tablet (pharmacy), a mixture of pharmacological substances pressed into a small cake or bar, colloquially called a "pill"
Computing
* Tablet computer, a mobile computer that is primarily operated by touching the s ...
. 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
Common Sense Media (CSM) is an organization that reviews and provides ratings for media and technology with the goal of providing information on their suitability for children. 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.
Concerns regarding prolonged exposure to blue LED light
On eye health
Blue-light hazard is the potential for
photochemical
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–7 ...
ly-induced
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
l injury resulting from electromagnetic
radiation-exposure at wavelengths primarily between 400 and Researchers have not studied the phenomenon in humans, but only (and inconclusively) in some rodent, primate, and ''in vitro'' studies. Photochemically-induced retinal injury is caused by the absorption of light by
photoreceptors in the eye. Under normal conditions, when light hits a photoreceptor, the cell bleaches and becomes useless until it has recovered through a metabolic process called the
visual cycle
The visual cycle is a process in the retina that replenishes the molecule retinal for its use in vision. Retinal is the chromophore of most visual opsins, meaning it captures the photons to begin the phototransduction cascade. When the proton is ...
.
Absorption of blue light, however, has been shown in rats and in a susceptible strain of mice to cause a problem in the process so that cells become unbleached and responsive again to light before they are ready. At wavelengths of blue light below 430 nm this greatly increases the potential for oxidative damage. For blue-light circadian therapy, harm is minimized by employing blue light at the near-green end of the blue spectrum. "1-2 min of 408 nm and 25 minutes of 430 nm are sufficient to cause irreversible death of photoreceptors and lesions of the retinal pigment epithelium.
..The action spectrum of light-sensitive retinal ganglion cells was found to peak at approximately 450 nm, a range with lower damage potential, yet not completely outside the damaging range."
One study has given more insight into the blue-light hazard: permanent damage to the eye cells, as reported by a research-team from Toledo University.
The
CIE published its position on the low risk of blue-light hazard resulting from the use of LED technology in general lighting bulbs in April 2019.
Concerns regarding blue LEDs are related to the difference between the photopic luminous flux and radiometric radiance. Photometry is concerned with the study of human perception of visible light, while 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 perception of the brightness of different frequencies of light is defined according to the CIE
luminosity function
A luminous efficiency function or luminosity function represents the average spectral sensitivity of human visual perception of light. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to descri ...
V(λ). The peak efficiency of light perception is defined at 555 nm, having a value of V(λ)=1. Blue LEDs, particularly those used in white LEDs, operate at around 450 nm, where V(λ)=0.038.
This means that blue light at 450 nm requires more than 26 times the radiometric energy for one to perceive the same luminous flux as green light 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
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
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.
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 as well as a recent systematic review found no evidence of any effect in IOLs filtering blue light.
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 and 490 nm, is largely blocked by blue light filtering IOLs but not clear IOLs present in the control patients.
The international standard IEC 62471 assesses the safety of light sources, including blue light.
Aggressive marketing
Aggressive advertisements may contribute to the incorrect public perception of the purported dangers of blue light. Even when research has shown no evidence to support the use of blue-blocking filters as a clinical treatment for digital eye strain, ophthalmic lens manufacturers continue to market them as lenses that reduce digital eye strain. 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
The General Optical Council (GOC) is an organisation in the United Kingdom which maintains a register of opticians and regulates the services provided by dispensing opticians and optometrists. The stated function of the GOC is "''to protect the pu ...
has criticised
Boots Opticians
Boots Opticians Ltd. operates a chain of ophthalmic and dispensing optician stores in the United Kingdom. The company is a subsidiary of Walgreens Boots Alliance (58%) and De Rigo (42%).
History
The company began trading in the British optical ...
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."
Despite the problem of deceptive marketing practices, the aforementioned ANSES report, from 2019, " highlights
hedisruptive effects to biological rhythms and sleep, linked to exposure to even very low levels of blue light in the evening or at night, particularly via screens", thus there are legitimate concerns as to the unconstrained use of LED lighting.
Apple's and Microsoft's operating systems and even the preset settings of standalone computer monitors include options to reduce blue-light emissions by adjusting color temperature to a warmer gamut.
These settings dramatically reduce the
color gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain ''complete subset'' of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circ ...
of the display, sacrificing the usability of devices without providing any of the alleged benefits of reducing
eye strain
Eye strain, also known as asthenopia (from Greek ''a-sthen-opia'', grc, ἀσθενωπία, ), is a common eye condition that manifests through non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and ...
or preventing
circadian rhythm
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
disruption.
Much of this marketing fails to distinguish between the sharp, 400-450 nm blue spike in mainstream LED bulbs, versus the broad-spectrum blue (up to 525 nm cyan) present in other lighting technologies (including pre-LED technologies, and very new, cyan-rich LED technologies that go beyond the older CRI metrics), and natural light.
Benefits of broad-spectrum blue light
Broad-spectrum blue light (for example, including cyan wavelengths, such as in natural light or most fluorescent lights) is essential to wakefulness, because it stimulates
melanopsin
Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene ''Opn4''. In the mammalian retina, there are two additional categories of opsins, both involved in the for ...
receptors in the eye. This suppresses daytime melatonin, enabling wakefulness. Working in blue-free light (aka yellow light) for long periods of time disrupts circadian patterns because there is no melatonin suppression during the day, and reduced melatonin rebound at night.
Dermatology
Blue light within the range 400-450 nm has been reported in a number of studies to be effective as local treatment of
eczema
Dermatitis is inflammation of the Human skin, skin, typically characterized by itchiness, erythema, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become lichenification, thick ...
and
psoriasis
Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by raised areas of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete ...
, as it purportedly helps dampen the immune response. Recent studies have also shown improvement of facial acne upon exposure to a LED emitting at 414 nm. A combination of exposure to red and blue lights is used more and more in clinical dermatologic therapies. Constructors such as
Philips
Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
currently develop devices and techniques emitting in the blue visible spectrum to be used in dermatologic therapy.
See also
*
Fluorescent lamps and health
Fluorescent lamps have been suggested to affect human health in various ways.
Flicker effects
New lighting systems have not used magnetic ballasts since the turn of the century, however some older installations still remain. Fluorescent lamps with ...
*
Phase response curve#Light
*
Ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
References
External links
*
*
*{{cite journal , vauthors=Koide R, Ueda TN, Dawson WW, etal , title=
etinal hazard from blue light emitting diode, language=Japanese , journal=Nippon Ganka Gakkai Zasshi , volume=105 , issue=10 , pages=687–95 , date=October 2001 , pmid=11692615
Ophthalmology
Optical spectrum
Technology hazards
Circadian rhythm
Sleeplessness and sleep deprivation