It was 1958, when J. Woodland Hasting and Beatrice M. Sweeney wrote the paper entitled "A persistent diurnal rhythm of luminescence in gonyaulax polydra". Paper concluded on how lights of different wavelength have the ability to change flow of a hormone named melatonin and hence affecting human body clock, also known as circadian rhythm.
When we have a look to our eye: buy led high bay lamps are two main sensors in our eye, namely cones and rods which showcase colour and greyness respectively to brain The peak sensitivity of cones came around to be 555nm and that of rods came around to be 507nm. which is towards greenish region of electromagnetic spectrum. Even though with such a higher sensitivity to green light, the blue light was having higher ability to exert powerful effects on eye. Through experiments it was concluded that blue wavelength suppressed melatonin twice as long as compared to green!
Well this source could be from many forms ranging from sun light, arc coming out of arc welding and plasma cutting, molten iron, steel and glass. Other sources being discharge of fluorescent lamps, filament of incandescent lamps and of course LED lamps.
One of the main constituents of eye is retina (as shown in Fig 3) which is bounded by a tissue named retinal pigmented epithelium (RPE). Since melanin being the most common pigment in RPE and its property to strongly absorb blue light, puts retina subject to actinic injury. This photochemical reaction is also known as photo retinitis.
In 1992, Chen a researcher at St. Erik's Eye hospital in Sweden came to conclusion about retinal degeneration with his experiments with rats. He concluded that an important enzyme named cytochrome oxidase, responsible for respiration of retina gets destroyed on the exposure of blue light by inhibiting cellular respiration leading to retinal degeneration.
To make experiments more relevant to human beings, similar experiments were conducted on baboons which have very similar characteristics of eye as that of human beings The results were similar -. Extensive damage in the RPE due to absorption of energy by melanin granules The damage mainly. constituted of macrophagic activity, disrupted cells and plaque formation which is also termed as photochemical lesion.
Illustration of an eye, focusing of two main entities wherein damage can take place due to direct exposure to blue light: ie Retina and Lens. (Image courtesy: Wikimedia.org)
Recent studies by Okuno T et al. Suggested that direct exposure to blue part of light coming from sun, arc welding, plasma cutting and arc discharge lamp with exposure time of 0.6s to 40s suggests damage to retina because of its extremely higher effective radiance.
One way to resolve such damage is to place a yellow lens covering the blue light source. Young people under the age of 20 or very young children who are yet to develop yellowing of their lens are less equipped to protect themselves from direct exposure to blue light .
There are basically three types of white LED's majorly available in market. First being red, green and blue led high bay light for sale together to produce white light. Second UV (ultra violet) LED covered by a particular phosphor giving white light. But the major stake in market as of now is of the third variant - blue LED covered by yellow phosphor to give a white light.
A recent study were conducted by the group of Lilla Knels (2010), where they in vitro experimented blue LEDs with wavelength 411nm and 470nm (near to blue region) with a defined irradiances of 0.6, 1.5 and 4.5 W/m2 on retinal neuronal cells of ocular region.
They observed reduction in metabolism activity and production of mitochondrial superoxide radical's increase. The formation of superoxide creates stress in mitochondria and contributes to its declining functioning. Mitochondria's major role in every cell is to convert glucose to ATP and hence giving energy to the cell.
Lot said about the downside, but blue also have an upside of biological effects. Many studies have gone to work upon the upside of blue light and how it affects tissue.
Daniel Kripke worked on this aspect and believes from his research that bright blue light helps in treating psychological disorders such as premenstrual depression, bulmia (over eating disorder) and anxiety. Moreover researchers at Caser Western Reserve University led by Prof. Patricia Higgins are testing bright blue light to treat patient with mental illness such as dementia (brain disease that cause loss of thinking and reasoning). The results looked promising and showed raised activity levels in daytime and increasing sleep at night time.
Coming back to eye:. In addition to the rod and cone cells present in eye, the researchers in 2001 discovered a new entity named ganglion cell coated with chemical named melanopsin This melanopsin like rods and cones can be activated by light, but only within the boundaries of wavelength between 446nm and 477nm, that is blue light!
Moreover this melanopsin, when activated sends signal to hypothalamus which reduces the level of melatonin and eventually shifting our circadian rhythm and hence our mood.
Also the newborn babies facing jaundice (hyper bili rubinemia) which at higher level may result in damage to brain are treated with blue light therapy (420 - 470 nm) which converts bilirubin so that be excreted through urine and feces as shown in Fig 6.
Also it is agreed that blue light surrounds us day in and day out, inside or outside our house. Whether it might be fatal to living organism crawling on earth is yet to be full proofed, but it does effects our daily life, minutely but as daily dose.
Moreover, the upside of blue light was discussed, how it helps human being to help work out on the mood through a hormone known as melatonin. It helps in treating mental illness and psychological disorders such as dementia and bulimia respectively.
Considering both upside and downside of blue light, it's better for our body to be aware of such effects and till then we have to wait for right time to come, for the researchers to come to a concrete conclusion, wherein a bold decision could be taken to change the whole marketing strategies of technologies surrounding us.
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