Physics:High-energy visible light

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In ophthalmology, 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.[1] Despite a lack of concurring scientific evidence, HEV light has sometimes been claimed to be a cause of age-related macular degeneration.[2][3] Some sunglasses and beauty creams specifically block HEV, for added marketing value.[1]

Blue-light hazard

Blue-light hazard is the potential for photochemically-induced retinal injury resulting from electromagnetic radiation-exposure at wavelengths primarily between 400 and 450 nm. Researchers have not studied the phenomenon in humans, but only ( and inconclusively) in some rodent, primate, and in vitro studies.[4] 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.[5][6]

Absorption of blue light, however, has been shown in rats and in a susceptible strain of mice to cause a reversal of the process where 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.[7] 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."[8] A 2014 study found that LEDs cause retinal damage even in settings where they are used indirectly, such as in household light-bulbs.[9]

An unpublished and non peer-reviewed 2013 in vitro study, financed by skin-care company Lipo Chemicals, used shorter blue-band spectrum LED lights and claimed that prolonged exposure may permanently damage the pigment epithelial cells of the retina.[10] However, according to a specialist, the test conditions were the equivalent of staring at a blue light equivalent to a 100 watt incandescent source from 20 cm (8 in) for 12 hours, which is not deemed to be a realistic light exposure.[11][12].

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[13] especially for children, who are big users of LED screens (smartphones, tablets...).[citation needed]

The CIE published its position on the low risk of blue-light hazard resulting from the use LED technology in general lighting bulbs in April 2019 [14]

Blue-light therapy

Blue light within the range 400-450 nm has been reported in a number of studies to be effective as local treatment of eczema and psoriasis, as it purportedly helps dampen the immune response.[15][16][17] Recent studies have also shown improvement of facial acne upon exposure to a LED emitting at 414 nm.[18][19] A combination of exposure to red and blue lights is used more and more in clinical dermatologic therapies.[20][21] Constructors such as Philips currently develop devices and techniques emitting in the blue visible spectrum to be used in dermatologic therapy.[22][23]

See also

References

  1. ↑ 1.0 1.1 Dykas, Carol (June 2004). "How to Protect Patients from Harmful Sunlight". www.2020mag.com. http://www.2020mag.com/CE/TabViewTest/tabid/92/LessonId/3127/Default.aspx. 
  2. ↑ "Could blue light-blocking lenses decrease the risk of age-related macular degeneration?". Retina (Philadelphia, Pa.) 26 (1): 1–4. January 2006. doi:10.1097/00006982-200601000-00001. PMID 16395131. 
  3. ↑ "Do blue light filters confer protection against age-related macular degeneration?". Prog Retin Eye Res 23 (5): 523–31. September 2004. doi:10.1016/j.preteyeres.2004.05.001. PMID 15302349. 
  4. ↑ ANSI/IESNA RP-27.1-05: Recommended Practice for Photobiological Safety for Lamp and Lamp Systems – General Requirements. American National Standard Institute/ Illuminating Engineering Society of North America. 10 June 2007. https://www.iesna.org/shop/. 
  5. ↑ "Action spectrum of retinal light-damage in albino rats". Invest. Ophthalmol. Vis. Sci. 24 (3): 285–7. March 1983. PMID 6832904. http://www.iovs.org/cgi/pmidlookup?view=long&pmid=6832904. 
  6. ↑ "Hemoprotein(s) mediate blue light damage in the retinal pigment epithelium". Photochem. Photobiol. 51 (5): 599–605. May 1990. doi:10.1111/j.1751-1097.1990.tb01972.x. PMID 2367557. 
  7. ↑ "Rhodopsin-mediated blue-light damage to the rat retina: effect of photoreversal of bleaching". Invest. Ophthalmol. Vis. Sci. 42 (2): 497–505. February 2001. PMID 11157889. http://www.iovs.org/cgi/pmidlookup?view=long&pmid=11157889. 
  8. ↑ Remy C. "Blue Light and the Retina: Good and Bad?". Soc Light Treatment Biol Rhythms Abstracts 2005, 17:46. 
  9. ↑ Lougheed, Tim (March 2014). "Hidden Blue Hazard? LED Lighting and Retinal Damage in Rats". Environmental Health Perspectives 122 (3): A81. doi:10.1289/ehp.122-A81. PMID 24583823. 
  10. ↑ [1]
  11. ↑ LED lighting damages eyes, says Spanish investigator. thinkSPAIN (10 May 2013).
  12. ↑ Specialists question validity of LED eye damage study. ozgled.com (27 Oct 2015)
  13. ↑ Magistroni, Mara (9 August 2018). "Ecco perché la luce blu di smartphone e computer causa danni alla vista". Wired.it (Milan: Edizioni Condé Nast s.p.a.). https://www.wired.it/scienza/medicina/2018/08/09/luce-blu-danni-vista/?refresh_ce=. "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'." 
  14. ↑ "Position Statement on the Blue Light Hazard (April 23, 2019) | CIE" (in en). http://www.cie.co.at/publications/position-statement-blue-light-hazard-april-23-2019. 
  15. ↑ [2]
  16. ↑ "Prospective randomized study on the efficacy of blue light in the treatment of psoriasis vulgaris". Dermatology 223 (3): 251–9. 2011. doi:10.1159/000333364. PMID 22105015. 
  17. ↑ "Prospective Randomized Long-Term Study on the Efficacy and Safety of UV-Free Blue Light for Treating Mild Psoriasis Vulgaris". Dermatology 231 (1): 24–34. 2015. doi:10.1159/000430495. PMID 26044167. 
  18. ↑ "Clinical Efficacy of Self-applied Blue Light Therapy for Mild-to-Moderate Facial Acne". J Clin Aesthet Dermatol 2 (3): 44–50. 2009. PMID 20729943. 
  19. ↑ "An open study to determine the efficacy of blue light in the treatment of mild to moderate acne". J Dermatolog Treat 16 (4): 219–23. 2005. doi:10.1080/09546630500283664. PMID 16249142. 
  20. ↑ "Current evidence and applications of photodynamic therapy in dermatology". Clin Cosmet Investig Dermatol 7: 145–63. 2014. doi:10.2147/CCID.S35334. PMID 24899818. 
  21. ↑ "Efficacy and Tolerability of a Combined 445nm and 630nm Over-the-counter Light Therapy Mask with and without Topical Salicylic Acid versus Topical Benzoyl Peroxide for the Treatment of Mild-to-moderate Acne Vulgaris". J Clin Aesthet Dermatol 9 (3): 25–35. 2016. PMID 27354885. 
  22. ↑ [3]
  23. ↑ [4]

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