# Are modern LED lights harmful to your eyes or health?



## HighlanderNorth (Feb 27, 2018)

**Im not sure whether this is the best place for this thread, or if general lighting would be better. Please move it if necessary. 

I didnt think id ever be discussing anything relating to LED lights and eye damage, except for maybe the possibility of eye damage due to staring directly into a 2000+ lumen flashlight for too long. But just as most of us dont sit on our front porches at high noon, while staring directly at the sun for long periods of time, most of us also know better than to stare at high lumen LED's. 

That being said, i just stumbled upon a bunch of articles and videos that claim that LED lighting is bad for our eyes, due to their excessive blue light spectrum, and lack of red and some IR spectrum wavelengths. Some of these are authored by alleged scientists and doctors. 

Its certainly a possibility that these 'experts' are only aware of the older, cheaper blue tinted LED's, and unaware of the newer, higher quality LED's with warmer, yellow tinted models. But i intentionally watched and read articles and videos from 2017 and newer, and these claims were made at those late dates. Now we have choices of many different LED's, with varying color wavelengths. 

Even so, are these people correct in their claims that even the newest, least blue tinted LED's are still lacking in the "important red spectrum wavelengths", while still emitting "potentially damaging blue spectrum wavelengths"? Or is this just a matter of exaggerated sensationalism, or a lack of knowlege about newer LED's? Are there modern, home and office LED bulbs that offer a safe and healthy spectrum of color wavelengths that include red and some IR?


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## JoakimFlorence (Feb 28, 2018)

My eyes have a bit more trouble focusing under LED as compared to incandescent or natural sunlight. Things just seem slightly less "in focus". Especially when I need a good reading lamp.
But I'm very sensitive to these sort of things.

(This is regardless of the color temperature, if anyone was going to ask)


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## ssanasisredna (Feb 28, 2018)

JoakimFlorence said:


> My eyes have a bit more trouble focusing under LED as compared to incandescent or natural sunlight. Things just seem slightly less "in focus". Especially when I need a good reading lamp.
> But I'm very sensitive to these sort of things.
> 
> (This is regardless of the color temperature, if anyone was going to ask)




I have my doubts to the accuracy of your post. Comparing reading under sunlight and incandescent is a non-starter. The spectrums are vastly different as are the typical light levels. Sunlight is never really the same color temperature as incandescent except perhaps minutes per day and still with a different spectrum, so I don't know how you can make that comment "independent of color temperature"

Technically we do have slightly higher red resolution, but if you want to talk "in-focus", then nothing impacts focus generally as much as pupil diameter. Incandescent does not provide an ideal spectrum for causing pupil restriction, that requires blue, 450-520nm. I have repeatedly shown people how cooler light sources provide higher visual acuity .... I would encourage everyone reading this post to do the same ... try reading with an incandescent and an LED bulb of similar CCT and brightness on the page.


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## ssanasisredna (Feb 28, 2018)

HighlanderNorth said:


> **Im not sure whether this is the best place for this thread, or if general lighting would be better. Please move it if necessary.
> 
> I didnt think id ever be discussing anything relating to LED lights and eye damage, except for maybe the possibility of eye damage due to staring directly into a 2000+ lumen flashlight for too long. But just as most of us dont sit on our front porches at high noon, while staring directly at the sun for long periods of time, most of us also know better than to stare at high lumen LED's.
> 
> ...




For the most part brutally exaggerated but some truth in some claims.

1) Blue does suppress melatonin and impacts sleeping patterns which can cause a whole host of health impacts.
2) Blue keeps you awake and alert. Last time I checked, that is a good thing when driving a car.
3) Blue does damage the eye (over time). Typical lux levels indoors with LEDs, 50-500. Sunlight 10,000+ .... Even with pupil restriction, an hour outdoors every day is comparatively huge, and add is significant UV.
4) Most of us work (or will/did). Fluorescent and Metal halide have significant energy in the blue as well. 
5) Most work lighting is 3500K and 4000K ... where suddenly that blue peak is not nearly as significant looking.
6) "missing" red only causes an issue with color perception, not health. Also note, most fluorescent lighting, the majority of our previous exposure, has holes. 
7) Missing infrared? ... new one. Perhaps they just mean deep red.

The black body spectrum (incandescent) is physical property. However, 2700K/3000K black-body radiators do not exist in our natural environment. What evolutionary process would tune to something that does not exist? Sunlight is somewhat black-body at 5000-5500K, but is often at higher and lower CCTs and does not match the black-body curve very well.


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## iamlucky13 (Feb 28, 2018)

Good job covering quite a few related points succinctly ssanasisredna.

A bit of extra commentary I wanted to add about doctors. There is a common tactic when you want to "prove" something (eg, vaccines are bad, we never landed on the moon, the earth if flat, etc), of finding somebody with some expertise, and either asking leading questions to get an answer you can spin the way you want, or partially quoting something they wrote. Thus, a paper about the hazards of prolonged exposure to high intensity light strong in the blue wavelengths, gets purported to be proof that anything with a strong blue component, high intensity or not, will ruin your eyesight.

That said, there's roughly 150,000 doctors in the US, and unfortunately, not all of them are competent, or least, not all of them restrict themselves to commenting on topics they actually have competency on. That includes the doctor behind Mercola.com, who has faced warnings from the FDA of illegally making false or unproven medical claims multiple times. Checking there now, he also has started exaggerating the concerns about blue light, even suggesting (but not claiming, because he's gotten the message he'll get in trouble if completely fabricates concrete claims) that it causes cancer.


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## JoakimFlorence (Feb 28, 2018)

There may be some truth to too much blue light not being good for our eyes indoors, for prolonged periods.
https://www.ncbi.nlm.nih.gov/labs/articles/27751961/

However, whether LEDs are any worse than incandescent at the same color temperature, I have not seen any studies looking at that.


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## JoakimFlorence (Feb 28, 2018)

ssanasisredna said:


> ... nothing impacts focus generally as much as pupil diameter.


It probably isn't the absolute _amount_ of blue light that causes damage the eye, but rather the ratio of different wavelengths in the spectrum. At lower light levels the pupil is going to open more, letting in more of the blue light.




ssanasisredna said:


> Incandescent does not provide an ideal spectrum for causing pupil restriction, that requires blue, 450-520nm.


You are right here. Pupil constriction is mainly triggered by wavelengths between 450-520nm (study on that was done here ). 

Although 450-520nm is really more blue to green colored light.

I don't want to overly read into those graphs, but from the way I'm interpreting them it looks like the pupil response is around twice as high between 470-500nm as it is for the points 450nm and 520nm, respectively. (They are logarithmic graphs, so take a little bit of interpretation to read)

It is, of course, interesting to note that the spectra of incandescent has a higher intensity of 470-500nm than a white LED of the same color temperature. 

Thus, while you were right, it seems you may also be wrong. ​​


ssanasisredna said:


> Incandescent does not provide an ideal spectrum for causing pupil restriction ... I have repeatedly shown people how cooler light sources provide higher visual acuity .... I would encourage everyone reading this post to do the same ... try reading with an incandescent and an LED bulb of similar CCT and brightness on the page.


But it's also true that blue light scatters more in the human eye than longer wavelengths (source here) so it may be creating more glare. As we know, the average blue light from an incandescent bulb has a bit longer wavelength than the blue light from a white LED.

It's also true that the lens in the human eye does not focus shorter wavelengths as well. This is obvious to anyone who's ever played around with a violet laser pointer before.

​


ssanasisredna said:


> I would encourage everyone reading this post to do the same ... try reading with an incandescent and an LED bulb of similar CCT and brightness on the page.


I would encourage you to try looking at a blue-color storefront sign at night and observe how blurry and out of focus it appears, compared to signs of other colors.

(Particularly talking about *royal blue* color, not *lighter blue* color)


​


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## iamlucky13 (Feb 28, 2018)

JoakimFlorence said:


> There may be some truth to too much blue light not being good for our eyes indoors, for prolonged periods.
> https://www.ncbi.nlm.nih.gov/labs/articles/27751961/
> 
> However, whether LEDs are any worse than incandescent at the same color temperature, I have not seen any studies looking at that.



Thanks for linking to some of the actual research. Just to clarify a bit about that study, their test level was 500 lumens per square meter, or the equivalent of having 8 standard 60W equivalent light bulbs in a typical 140 square foot children's bedroom. This is at the high end of realistic light levels anywhere in a home, much less a bedroom, and is more typical of office lighting.

They did see a significant effect, at least in rats exposed for 24 hours a day. More details than that are not publicly available. I did find another paper with similar research that I that the full article is available for:
https://ehp.niehs.nih.gov/1307294/

In this study, they used 750 lumens/square meter exposure for 12 hours per day. Compared to rats kept in dark conditions for similar lengths of time, they saw significant effects under both pure blue and 6500K LED's, a moderate effect under 6500K fluorescent lights, and a small effect under 3000K fluorescent lights.

I don't know enough about their measurements to say how severe the effect was in practical terms. I do know that 4000-6500K fluorescent lights at 500 lumens/square meter have been common in office environments for decades, and the paper seems to me to suggest that situation should at least show some of the same effect, so it doesn't appear to me that this is an alarming finding, but something to follow up with additional research, such as with more realistic lighting cycles.

Another critical part of the long term research will be to develop a way of correlating how results with rat studies translate to human effects. Keep in mind, rats are nocturnal animals and may be less well adapted to prolonged exposure to high light levels. I'm loosely familiar with other research that has been done to correlate results from cancer studies in rats to risk levels in humans, and it's rather challenging and somewhat interesting topic.


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## ssanasisredna (Feb 28, 2018)

JoakimFlorence said:


> There may be some truth to too much blue light not being good for our eyes indoors, for prolonged periods.
> https://www.ncbi.nlm.nih.gov/labs/articles/27751961/
> 
> However, whether LEDs are any worse than incandescent at the same color temperature, I have not seen any studies looking at that.




To say this paper is crap, would be unkind to crap. http://hal.upmc.fr/hal-01383394/document Here is it without a paywall.

You will notice there are very little in the way of details for any other the light sources. No spectra for the COOL-White LED (6300K - at best approx), no CRI to know ratios, not even the CCT for the CFL, CCFL light sources. They could be 2700K which is hardly a good comparison.

They build specially "diffused" LED boxes for exposure (but not really CCFL), which put 500 lux directly onto the eyes .... but if you have a large diffuse surface "EVERYWHERE", you are forcing a ridiculously large light level compared to reality.

The paper claims that 500 lux is recommended domestic lighting levels. NO! Maybe in a kitchen or laundry room, maybe workshop, but most domestic (home areas) are 100-200lux. Offices are 500 lux ... but that is surface level. Most environments absorb a significant amount of the blue light so what reaches the eye will be significantly less.

This researcher in my mind is a quack. Previously they claimed that LEDs have "intense blue" not seen in daylight spectra. That is an out and out lie.


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## ssanasisredna (Feb 28, 2018)

JoakimFlorence said:


> It is, of course, interesting to note that the spectra of incandescent has a higher intensity of 470-500nm than a white LED of the same color temperature.
> Thus, while you were right, it seems you may also be wrong.​
> 
> ​



Nope, this comes from a misunderstanding of how comparative graphs are typically shown on the web like this one: http://www.ledsmagazine.com/content/dam/leds/migrated/objects/features/10/2/11/Avnet_Fig2T_22513.jpg

They are not normalized for total energy, but for spectral peak. 

If you compare the spectral energy of the exact same lumen 2700K Incan and 2700K - 80CRI bulb, from 450-520nm, they are pretty close (within 10% for typical LED). If you look at the more critical 450-500, the white 2700K bulb is up about 20-25%. Adjusted for the total ipRGC action spectrum, the LED carries a similar advantage. Of course if you use a 4000K LED, which would be much better for reading under ... you have nothing in the incan world to compare it to.


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## ssanasisredna (Feb 28, 2018)

JoakimFlorence said:


> But it's also true that blue light scatters more in the human eye than longer wavelengths (source here) so it may be creating more glare. As we know, the average blue light from an incandescent bulb has a bit longer wavelength than the blue light from a white LED.
> 
> It's also true that the lens in the human eye does not focus shorter wavelengths as well. This is obvious to anyone who's ever played around with a violet laser pointer before.
> ​



But also true that LED concentrate into a narrower spectrum at lower CRI which enhances focus. 

The blue sign is a bad example as lighting a white page means the relative portion (lumen/lux) of blue is quite low at short wavelengths, unlike the sign which is all blue.


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## jimbo231 (Feb 28, 2018)

Staring into a 2000 lumen light will blind you....


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## idleprocess (Feb 28, 2018)

ssanasisredna said:


> To say this paper is crap, would be unkind to crap. http://hal.upmc.fr/hal-01383394/document Here is it without a paywall.
> 
> You will notice there are very little in the way of details for any other the light sources. No spectra for the COOL-White LED (6300K - at best approx), no CRI to know ratios, not even the CCT for the CFL, CCFL light sources. They could be 2700K which is hardly a good comparison.
> 
> ...



I want to say another similar study was posted here a few years back. A little more detail on the testing apparatus and exposure protocol, but it was the kind of experiment that makes animal testing look bad since it was pretty horrific.


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## JoakimFlorence (Feb 28, 2018)

iamlucky13 said:


> I don't know enough about their measurements to say how severe the effect was in practical terms. I do know that 4000-6500K fluorescent lights at 500 lumens/square meter have been common in office environments for decades, and the paper seems to me to suggest that situation should at least show some of the same effect, so it doesn't appear to me that this is an alarming finding, but something to follow up with additional research, such as with more realistic lighting cycles.


On the other hand, it may be that office lighting hasn't been that great for people's eyes over the last five decades.
There have been a few studies that showed a measurable increase in the incidence rate of cataracts and carcinoma for people in fluorescent-lighted work settings, although the increase wasn't gigantic.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3222423/


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## iamlucky13 (Mar 1, 2018)

JoakimFlorence said:


> On the other hand, it may be that office lighting hasn't been that great for people's eyes over the last five decades.
> There have been a few studies that showed a measurable increase in the incidence rate of cataracts and carcinoma for people in fluorescent-lighted work settings, although the increase wasn't gigantic.
> 
> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3222423/



The research I've dug up so far on blue light hazards seems to mainly be related to circadian disruption and age-related macular degenaration, which is an effect in the retina. Cataracts are an effect in the lens. I haven't looked for anything cataract related, but my understanding was it is so far only linked to UV-B or shorter wavelength exposure. Fluorescent lamps actually initially produce emissions way out at these short wavelengths, and the phosphors convert them to visible light, but I think there is usually a little bit of leakage. If so, that could explain findings of increasing cataracts and carcinomas.

Teasing all these possibly confounding factors out of various studies is one of the reasons why science often takes decades and countless studies to come up with a clear consensus on a topic.


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## iamlucky13 (Mar 1, 2018)

ssanasisredna said:


> This researcher in my mind is a quack. Previously they claimed that LEDs have "intense blue" not seen in daylight spectra. That is an out and out lie.



I'll have to try to find time to read that paper, but my first instinct is to think that's a bit of a harsh criticism.

A lot of health research starts at the edge of (500 lux qualifies) or even well above normal levels of exposure in order to first establish if there is any effect at all. If so, then followup studies further constrain the findings, and when you're working with very subtle effects, sometimes it is a necessity to help guide future research. I've separately dug very deeply into the research into the possible link between cell phones and cancer, and there are a lot of parallels, but the fact that some (including most journalists, it seems) read a given piece of research as being alarmist does not mean either that it should be interpreted that way, nor that the researches intended for it to be.

But just from the abstract, it does sound like far short of the full picture, and I see very little reason to be seriously concerned about household use of white LED's based on what I've read so far.


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## JoakimFlorence (Mar 1, 2018)

iamlucky13 said:


> The research I've dug up so far on blue light hazards seems to mainly be related to circadian disruption and age-related macular degenaration, which is an effect in the retina.


I don't know, I know my eyes feel kind of sore after staring into the computer screen a couple of hours.


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## JoakimFlorence (Mar 1, 2018)

This article makes a brief mention to blue light possibly being able to contribute towards macular degeneration, though not as much as ultraviolet light:
https://www.macular.org/ultra-violet-and-blue-light



The Effects of Blue Light on Ocular Health 
Elaine Kitchel, M.Ed.

In an early study conducted by Ham, Ruffolo, Mueller and Guerry, (1980) rhesus monkeys were exposed to high‑intensity blue light at 441nm for a duration of 1000 seconds. Two days later lesions were formed in the retinal pigmented epithelium (RPE.) These lesions consisted of an "inflammatory reaction accompanied with clumping of melanosomes and some macrophage invasion with engulfment of melanosomes which produce hypopigmentation of the RPE" (Ham et al., 1980, p.1110). Since melanin, a common pigment component present in the RPE, strongly absorbs blue light, there is reason to be concerned that the retina is subject to actinic injury from blue light. However, the lens strongly absorbs blue light as well but runs a high risk of possible opacification.

In 1992, Chen, a researcher at St. Erik's Eye Hospital in Sweden, sought to explore the basis to explain why blue light reactions cause retinal degeneration. Drawing on the research of E. L. Paulter, Morika and Beenley (1989), who found that a chemical chemical called cytochrome oxidase is a key enzyme in the respiration of the retina in higher mammals, Chen decided to investigate this phenomenon in rats. Cytochrome oxidase is found in the RPE and in the inner segment of the photoreceptors. Paulter's in vitro studies of bovine REP tissue showed that blue‑light exposure destroyed cytochrome oxidase and inhibited cellular respiration. This inhibition was followed by retinal degeneration. Chen then performed a similar experiment upon rats in which he exposed them to 15 minutes of 404nm blue light which was not strong enough to cause thermal damage. He then killed some rats immediately, and one for each of the next three days. Upon examining their retinas, he found the blue light exposure had indeed inhibited the production of cytochrome oxidase. This was evident in his observation of the photoreceptor cells which had been destroyed. He concluded inhibition of cytochrome oxidase by blue‑light exposure and the consequent suppression of the cellular metabolism is a potential cause of retinal degenation (1993, p. 422).

In light of findings like these, ophthalmologists are beginning to filter the blue light emitted from their ophthalmoscopes through a yellow lens. A study by Bradnam, Montgomery, Moseley and Dutton concluded: "This study has shown that the use of a yellow lens is very effective at reducing the blue‑light hazard and extends the safe operating period by a factor of approximately 20x. . . In the interests of patient safety, it is recommended that yellow lenses are considered for use for routine indirect ophthalmoscopy" (1994, p. 799).​
Nancy Quinn, a registered nurse and an expert on blue light emissions from VDTs wrote:
 Blue light wavelengths and part of the blue spectrum are focused in front of the retina, while green and yellow are focused on the retina, and some red spectrum is focused behind. Thus blue light contributes little to visual acuity and visual perception loses sharpness as the blue light component adds significantly to the eye's energy expenditure for focusing, and if reduced can greatly reduce eyestrain without loss of acuity.
​

http://www.tsbvi.edu/instructional-resources/62-family-engagement/3654-effects-of-blue-light


Several investigations have shown that exposure to light of specific wavelengths or intensity may induce severe damage to the retina. This type of damage is called light-induced damage.

A more common type of retinal/RPE damage is photochemical damage, which occurs when the eyes are exposed to light of high intensity in the visible range (390–600 nm). The current view suggests that there are two distinct types of photochemical damage. The first type is associated with short but intense exposure to light affecting the RPE, and the second type is associated with longer but less intense light exposure, affecting the outer segment of the photoreceptors. Short (up to 12 h) exposure to blue light may induce damage in the RPE of the rhesus monkey, and a clear relationship has been found between the extent of the damage and the oxygen concentration. The fact that many different antioxidants can reduce the damage suggests that this type of damage is associated with oxidative processes. Experimental data suggest that lipofuscin is the chromophore involved in the mediation of light-induced retinal damage following the exposure to blue light.

The second type of light-induced photochemical damage occurs with longer (12–48 h) but less intense light exposure. This type of damage was initially observed in albino rats but has also been observed in other species.
​
 Kuse et al. reported that 661W cells are more sensitive to light-induced damage when exposed to light emitted by blue (464 nm) LEDs than when exposed to green (522 nm) or white LEDs (wavelength peak at 456 and 553 nm) of the same intensity (0.38 mW/cm2​). The exposure to blue light, unlike the exposure to white and green LEDs, also produced a significant increase in ROS and induced cell damage. Similar results were also observed in primary retinal cells. These data support the idea that exposure to blue light in the range of 400–470 nm (even at low levels) may damage photoreceptors and retinal pigment epithelium cells.

Although most studies have focused on the acute effect of light exposure, several have also investigated the cumulative effect of light. For example, Noell [89] reported that a single 5 min exposure to light did not induce significant damage in photoreceptor cells, whereas a series of 5 min exposures led to significant photoreceptor damage. Furthermore, the time between exposures affects the cumulative effect of light [90-92].

In addition, several authors have proposed that the amount of blue light received during an individual’s entire lifespan can be an important factor in the development of age-related macular degeneration (AMD).
The mechanism through which long-term exposure to blue light may induce photoreceptor damage is mostly unknown. Several studies have indicated lipofuscin (absorption peak around 450 nm) is a possible mediator of the risk associated with long-term exposure to blue light–induced retinal damage.

​​​
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/
​


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## ssanasisredna (Mar 2, 2018)

iamlucky13 said:


> I'll have to try to find time to read that paper, but my first instinct is to think that's a bit of a harsh criticism.



I posted the non paywall version link above.


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## ssanasisredna (Mar 2, 2018)

iamlucky13 said:


> A lot of health research starts at the edge of (500 lux qualifies) or even well above normal levels of exposure in order to first establish if there is any effect



500 lux projected onto surfaces qualifies.

500 lux directly into the eyes does not. The light levels from illumination that reach our eyes tend to be much less, especially blue which depending on the environment is reflected less than other colors. 

If one was doing a "proper" research paper, they would note this obvious fact, not to mention detail the other light sources and spectrums of the comparative sources. They did not even show the spectrum of the LED sources. To me, that is unbelievable. I wouldn't accept that from one of my staff for an internal piece of work, let alone a published paper.


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## ssanasisredna (Mar 2, 2018)

JoakimFlorence said:


> I don't know, I know my eyes feel kind of sore after staring into the computer screen a couple of hours.



Work in a brighter room with higher CCT lighting ... and yes I am serious.

I have the same problem if I work in a room that is too dark, especially with lower CCT lighting.

I would also check your computer screen with your cell phone to make sure there is no low frequency PWM dimming. It's not too common anymore, but I understand they are still out there. The effects of flicker/PWM on a direct view screen are worse than when done with environmental lighting.


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## ssanasisredna (Mar 2, 2018)

JoakimFlorence said:


> Kuse et al. reported that 661W cells are more sensitive to light-induced damage when exposed to light emitted by blue (464 nm) LEDs than when exposed to green (522 nm) or white LEDs (wavelength peak at 456 and 553 nm) of the same intensity (0.38 mW/cm2​). The exposure to blue light, unlike the exposure to white and green LEDs, also produced a significant increase in ROS and induced cell damage. Similar results were also observed in primary retinal cells. These data support the idea that exposure to blue light in the range of 400–470 nm (even at low levels) may damage photoreceptors and retinal pigment epithelium cells.
> 
> 
> ​​



I think this section makes my point nicely. You are I both know that that white LED contains a significant portion of light from the exact spectrum of a blue LED. However, they claimed that the blue LED produced a significant increase in ROS and cell damage, while the white did not. Now how much different was that damage? 10x ?? Was it a direct correlation of intensity of light in the damaging portion of the spectrum?

The other issue with these studies is they don't do enough studies at various intensities to determine if the damage level is linear or not. That is pretty critical as it could set far more effectively a "safe" level.

This brings me back to the original study you posted where 500 lux directly at the eyes was used, a value far outside "normal", and perhaps at a level that is not relevant if the level of damage at a realistic levels is not well understood (and proper CCT light was not used, and comparison sources not detailed).

... AND as we both noted, while LED bulbs at 80 CRI do have higher levels of blue, it's not as large as most people think, and LED bulbs have no very short blue, but incandescent does.

Heck, most of these studies do not even look at relative exposure to interior light and being outside for an hour or two. Maybe the people we need to worry about most are garbage collectors?

Really though, I worry most about looking at my computer screen .... one of the reasons I keep my light level high in the room as it forces pupil closure reducing exposure level (and improving focus).


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## seery (Mar 2, 2018)

HighlanderNorth said:


> Are modern LED lights harmful to your eyes or health?



No, only to your _wealth_!


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## JoakimFlorence (Mar 2, 2018)

Ha ha


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## JoakimFlorence (Mar 2, 2018)

My personal opinion on the matter is that exposure over time to excessive amounts of blue light probably is at least somewhat detrimental to the health of the retina, but not as detrimental as violet light. I think the effects get exponentially worse the shorter the wavelength is.

I don't know what the exact comparisons would be, but I'd imagine it would look something like 400nm being 3 times as bad as 450nm, and 490nm only half as bad as 450nm. (And I'm sure the relationship is probably not a smooth function of the wavelength either)​


ssanasisredna said:


> and LED bulbs have no very short blue, but incandescent does.


That's a somewhat complicated comparison to try to make. While it's true that the average wavelength of the blue light coming from an LED is a shorter wavelength than the blue light from an incandescent spectrum, it's also true that incandescent has some level of very far blue-violet light, whereas LED essentially doesn't. Nevertheless, the amount of violet light compared to the amount of blue light is not so big. (There's about a 4:1 ratio of light between 450-490nm compared to light between 400-450nm, although that ratio is going to be different with a halogen bulb at 3000K) The blue light from an LED is, for practical purposes, almost all composed of a single peak between 450-455nm. 
(That's an oversimplification, but it's relevant for making this comparison here)

Then there's also that effect I mentioned. With the spectral profile from incandescent having a larger ratio of the longer wavelengths of blue light, and 480-490nm having a stronger effect on pupil constriction than 450nm (by about a factor of 2) , it may be that incandescent light results in less blue light overall from being able to enter into the retina. (if we are comparing incandescent to an LED of the same correlated color temperature)


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## ssanasisredna (Mar 4, 2018)

JoakimFlorence said:


> I don't know what the exact comparisons would be, but I'd imagine it would look something like 400nm being 3 times as bad as 450nm, and 490nm only half as bad as 450nm. (And I'm sure the relationship is probably not a smooth function of the wavelength either)
> 
> Then there's also that effect I mentioned. With the spectral profile from incandescent having a larger ratio of the longer wavelengths of blue light, and 480-490nm having a stronger effect on pupil constriction than 450nm (by about a factor of 2) , it may be that incandescent light results in less blue light overall from being able to enter into the retina. (if we are comparing incandescent to an LED of the same correlated color temperature)



You have written something essentially like the second part twice now. It was not accurate the first time, nor the second.

"If you compare the spectral energy of the exact same lumen 2700"K Incan and 2700K - 80CRI bulb, from 450-520nm, they are pretty close (within 10% for typical LED). If you look at the more critical 450-500, the white 2700K bulb is up about 20-25%. Adjusted for the total ipRGC action spectrum, the LED carries a similar advantage. Of course if you use a 4000K LED, which would be much better for reading under ... you have nothing in the incan world to compare it to."

When I add in the first part of the comment, I could extrapolate that the Incan will do more damage ...


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## HighlanderNorth (Mar 8, 2018)

ssanasisredna said:


> You have written something essentially like the second part twice now. It was not accurate the first time, nor the second.
> 
> "If you compare the spectral energy of the exact same lumen 2700"K Incan and 2700K - 80CRI bulb, from 450-520nm, they are pretty close (within 10% for typical LED). If you look at the more critical 450-500, the white 2700K bulb is up about 20-25%. Adjusted for the total ipRGC action spectrum, the LED carries a similar advantage. Of course if you use a 4000K LED, which would be much better for reading under ... you have nothing in the incan world to compare it to."
> 
> When I add in the first part of the comment, I could extrapolate that the Incan will do more damage ...


So, does all the current data show that modern, indoor a/c LED's aren't any more harmful to your eyes, as long as you choose the right bulbs with an ideal color temperature? What would that ideal color temperature be, and/or which particular bulbs?


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## JoakimFlorence (Mar 14, 2018)

HighlanderNorth said:


> So, does all the current data show that modern, indoor a/c LED's aren't any more harmful to your eyes, as long as you choose the right bulbs with an ideal color temperature? What would that ideal color temperature be, and/or which particular bulbs?


There's probably not a definitive cut-off.

I would imagine 4000K and less would be better than 5000K and higher, but that's not based on any particular research studies.

To make matters more complicated, it may not be entirely just dependent on the color temperature. I would imagine very high (>94) CRI LEDs might be a bit less damaging than normal LEDs (maybe by 20-30%, but that's just a complete guess) because of their slightly different shaped spectral distribution.

Anyway, it's not like LEDs are _insanely_ more damaging to your eyes than any other light source. There's no way a 2700K LED could be more than twice as damaging as old-style incandescent lighting, if that helps put things into a little perspective. If we're talking about 3000K LED versus 3000K halogen, that difference is going to narrow even more, or it's possible they may be about the same (I don't know).

If we're talking about Metal Halide discharge lamps, it's very likely LEDs are _less_ damaging.

Some of the early LED streetlamps that appeared were 8000K, which corresponds to 45% blue light. These caused a lot of glare.


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