Biological effects of high-energy visible light: Difference between revisions

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&nbsp;nm this greatly increases the potential for oxidative damage.<ref>{{cite journal|vauthors= Grimm C, Wenzel A, Williams T, Rol P, Hafezi F, Remy C |title= Rhodopsin-mediated blue-light damage to the rat retina: effect of photoreversal of bleaching |journal= Invest. Ophthalmol. Vis. Sci. |volume= 42 |issue= 2 |pages= 497–505 |date= February 2001 |pmid= 11157889 |url= http://www.iovs.org/cgi/pmidlookup?view=long&pmid=11157889 |archive-url= https://archive.today/20120525164413/http://www.iovs.org/cgi/pmidlookup?view=long&pmid=11157889 |url-status= dead |archive-date= 2012-05-25 }}</ref> 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."<ref>{{cite journal|author= Remy C|title= Blue Light and the Retina: Good and Bad?|journal= Soc Light Treatment Biol Rhythms|volume= Abstracts 2005, 17:46}}</ref>

{{cite news|last1= Magistroni| first1= Mara|title= Ecco perché la luce blu di smartphone e computer causa danni alla vista|trans-title= This is why blue light from smartphones and computers damages vision|url= https://www.wired.it/scienza/medicina/2018/08/09/luce-blu-danni-vista/?refresh_ce=| department = Scienza| work= Wired.it| location= Milan| publisher= Edizioni Condé Nast s.p.a. | date= 9 August 2018| access-date= 19 June 2019| quote = Un team dell'Università di Toledo, infatti, afferma dalle pagine di Scientific Reports di aver scoperto il meccanismo che conduce alla morte dei fotorecettori della retina che ci consentono di vedere: la luce blu trasformerebbe una molecola chiamata retinale, indispensabile per la vista, in un killer cellulare. [...] 'E i fotorecettori non si rigenerano nell'occhio', fa notare Kasun Ratnayake, uno degli autori della ricerca. 'Una volta morti, non ce ne saranno di nuovi a sostituirli'.}}</ref>

 

 

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]] V(λ). The peak efficiency of light perception is defined at 555&nbsp; nm, having a value of V(λ)=1. Blue LEDs, particularly those used in white LEDs, operate at around 450&nbsp; nm, where V(λ)=0.038.<ref name="Cree">{{cite web|url=https://www.cree.com/led-components/media/documents/XLampXML-11E.pdf|title=Product family datasheet:Cree® XLamp® XM-L LEDs|page=4|publisher=Cree}}</ref><ref>{{cite web|url=http://www.seoulsemicon.com/upload2/X42182(0).pdf |title=Technical Data Sheet X42182(Z-power LEDs) |pages=12–13}}</ref> This means that blue light at 450&nbsp;nm requires more than 26 times the radiometric energy for one to perceive the same luminous flux as green light at 555&nbsp;nm. For comparison, UV-A at 380&nbsp; 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.<ref>{{cite web |url=https://www.iso.org/standard/74164.html |title=Colorimetry -- Part 1: CIE standard colorimetric observers|access-date=December 9, 2018|publisher=International Organization for Standardization}}</ref><ref>{{cite web|url=http://www.kayelaby.npl.co.uk/general_physics/2_5/2_5_3.html|title=Kay & Laby;tables of physical & chemical constants;General physics;SubSection: 2.5.3 Photometry|publisher=National Physical Laboratory; UK|access-date=December 9, 2018}}</ref> 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.<ref>{{cite web|url=https://hal.sorbonne-universite.fr/hal-01383394/file/Krigel_Light-induced.pdf |title=Light-induced retinal damage using different light sources, protocols and rat strains reveals LED phototoxicity|first1=Arthur|last1=Krigel|publisher= Centre de Recherches des Cordeliers. Université Paris Descartes, France.(Sorbonne University Faculty of Medicine, Physiology Department)|date=2016|access-date=December 9, 2018}}</ref><ref>{{cite web|title=Light-emitting-diode induced retinal damage and its wavelength dependency in vivo|url=http://www.ijo.cn/en_publish/2017/2/20170203.pdf|publisher=International Journal of Ophthalmology, Vol. 10, No. 2|date=Feb 18, 2017 }}</ref> 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.<ref>{{cite web|url=http://www.symmetron.ru/suppliers/lighting/files/lighting/led/lighting_led/mid_power_led/1212/LM131A.pdf|page=12|title=LM131A - Middle Power LED|publisher=SAMSUNG ELECTRONICS}}</ref><ref>{{cite web|url=https://www.electronicsweekly.com/news/products/led/lb-samsungs-flip-chip-leds-modules-2014-04/|title=L+B: Samsung's flip-chip LEDs and modules|first=Steve|last=Bush|date=April 7, 2014}}{{cite web|url=http://led.lginnotek.com/|title=PRODUCT FAMILY DATA SHEET: 3535 G6 LEMWA33X Family|page=12}}<!--direct link unavailable, download datasheet --></ref><ref name="Cree" /> White LEDs are designed to emulate natural [[Sunlight#Spectral composition of sunlight at Earth's surface|sunlight]] as closely as is economically and technologically possible. [[Sunlight#Spectral composition of sunlight at Earth's surface|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.