LEDs & 'Blue Glare' & Eye damage

There seems to be increasing evidence that blue/violet frequencies of light cause much more damage to the retina than longer frequencies (green/red).

See these two links:
http://www.sunnexbiotech.com/therapist/main.htm
http://www.sunnexbiotech.com/therapist/blue light and amd.html

From the second link:

Age-related Macular Degeneration (AMD) is a condition of advanced degeneration of the macular portion of the retina that leads to progressive blindness in over 35% of persons over the age of 75.1 AMD has been linked to the stress engendered by radical oxygen species in macular photoreceptor cells and proximate retinal pigment epithelium cells (RPE).2 Both of these types of cells are non-replicating (post-mitotic) and must respond to a lifetime of oxidative insult, which includes light-induced oxidative stress.3 While there are numerous mechanisms in the retina for preventing and forestalling oxidative insult, by middle-age many of these anti-oxidative mechanisms have begun to break down, which increases the susceptibility of the retina to accumulated damage with increasing age.4


Visible light absorbed by photoreceptors is a significant factor in the production of reactive oxygen species that induce the molecular damage in retinal tissue which appears to contribute to the formation of AMD.5 To an overwhelming degree, blue wavelengths of light produce the most oxidative stress within the retina and are primarily responsible for exacerbating the extent of oxidative damage that has begun to occur.6 Since blue light wavelengths impart the greatest risk of photochemical damage, the risk of retinal damage from light is termed "the blue light hazard", with the greatest hazard peaking at wavelength of 440 nm.7

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Note the peak wavelength for retinal damage is about ~440nm. This also corresponds to the peak wavelength of the LED in most 'white' LEDs used in flashlights here. The LED produces a lot of blue light, which after passing though a phosphor/scintillator gets converted into other colors to produce white light. What this means, unfortunately, is all of the white LEDs have a lot a blue light in the spectrum (a big spike in the spectrum), at wavelengths that cause the most damage to the retina - especially compared to more traditional light sources such as incandescent lights and candles.

Whether or not these LEDs are really that damaging I don't know, though I think this is something to be aware of. You really want to avoid being dazzled for flash-blinded by a powerful LED, IMO.

Don't get me wrong, I love LED lights. However they may be more damaging than originally thought.

Here's some more info on the danger of blue light, from this thread off LPF:
http://laserpointerforums.com/f65/plea-eye-safety-51464.html

At 700mW to 1 watt, injuries will be all too common, and blue has some unique short and long term PROVEN side effects with respect to color vision. Prolonged exposure to intense blue results in diminished green vision. This has been proven in studies of eye surgeons who used blue lasers to treat patients. The green vision comes back somewhat in 3-6 months. The surgeons were exposed to milliwatts at best for 20-40 minute sessions per patient.

(...)
This blue wavelength has some unique biochemical actions on releasing free radicals, and is strongly adsorbed by red blood cells in capillaries. It causes larger damaged areas in retinal tissue and is far more likely to be adsorbed by the tissue then 532 nm light.

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FYI

I'm not an eye expert, but I thought blue light in general (the color blue) uses the chemicals from light receptors in your eyes faster than other colors. So it takes longer for your eyes to reproduce light receptive chemicals and process what light is coming into your eyes.

Which I thought is why police switched to them on cruisers - to distract/disorient perps (this thought isn't based on any factual knowledge or evidence).

Red and green use them dramatically slower, which is why you don't suffer 'night vision depletion' when using them.

Interesting though.

FloggedSynapse,

The amount of blue light exposure at noon on a sunny day far exceeds the amount of blue light exposure generated from reflected light when using an LED flashlight. At noon on a June day, you can measure 120,000 lux surface illumination from direct sunlight here in the southwest desert. The only place where an LED flashlight can equal this is at the exit aperture of the reflector (or TIR) from a small diameter high power flashlight - typically when exceeding 60 lumens of output. At 1 meter, these lights can only generate a few thousand lux surface illumination. At normal usage distances, you are well below 1000 lux surface illumination.

Most age-related macular degeneration is caused by over exposure to bright sunlight. This is why dark sunglasses are recommended for eye protection.

Medical lasers generate very high spot intensities even though their total beam output is low. For a laser to cauterize or cut, it must put a lot of energy into a very small location. The equivalent lux value would be way higher than the summer sunlight value - more like taking a magnifying glass and focusing all of that energy until you can burn paper.

Henry.