But even so, the high energy spectral content of indoor LED lighting is much, much less than what you see from direct sunlight. If LEDs are really a vision risk to the modern office worker, they're significantly less so than the same risk of agricultural or other outdoor workers.

But, just to play devil's advocate, it seems plausible that sunlight might activate some kind of defense mechanism in the eye that protects it from the effects of the higher energy part of the spectrum.

If nothing else, the overall brightness levels would cause your pupil to shrink more in sunlight than under LED lighting.

http://healthland.time.com/2009/08/04/can-cheap-sunglasses-b...

However, the ganglion cells that influence dilation and melatonin happen to be mostly sensitive to blue light (~470 nm), so in theory this would only be a problem for LEDs largely concentrated at even shorter wavelength.

https://en.wikipedia.org/wiki/Intrinsically_photosensitive_r...

I have worn polycarbonate lenses my whole life, well since infancy. Polycarbonate lenses block UV light. If I go outside without my glasses or sunglasses my eyes hurt, even in winter. I don't know if my eyes are super sensitive or they just aren't used to the UV light and the micro-damage it causes.

[edit] My email's in my profile if you'd prefer not to say publicly, although since a few others upvoted my comment it looks like it's a popular question :)

(The idea there, if you're curious, was to build a light collector with a relatively wide incidence angle that'd focus the beam onto a mostly decapsulated violet LED reverse-biased to act as a photodiode and tied to the base of an NPN transistor, so as to switch a GPIO on my entertainment center Raspberry Pi and use the laser pointer as a kind of remote control. The circuit worked quite well when illuminated, but a ~1mm target is hard to hit from ten feet away, hence the messing about with focusing optics.)

I don't have a detailed characterization of the injury because I'm rather overdue for an optometrist's appointment, but later experiments with the same configuration (and goggles!) showed that, so focused, the beam would deform and start to burn black ABS plastic within a few seconds, and took no perceptible time to burn a hole in a sheet of black construction paper, in both cases producing damage in a radius well under a millimeter - I found that, unless placed precisely in the focal plane, the beam was too widely spread even to raise smoke from the paper. The effect on my retina would therefore have had to be the same sort of closely localized heating, a hypothesis borne out by the effects I observed to result.

Beyond the pain already described (which lasted a good couple of hours), those effects included the click sound I mentioned, which I believe to have been produced by the sudden vaporization of a small volume of aqueous humor adjacent to the retina, and a quite noticeable but thankfully non-foveal bright green floater which did not cease to be perceptible until about a month had gone by. Whether this latter is the result of the injury healing, as I gather such minor retinal injuries often do, or rather of my visual cortex having grown a new filter, I won't know until my next slit-lamp exam.

[1] http://m.ebay.com/itm/Teaching-Powerful-405NM-Blue-N3ioiet-P...

(And I own a pair of wavelength-matched laser goggles now, as should you if you're going to do anything at all with a laser and any kind of focusing optics. Carelessly enough handled, even a 5mW pointer beam can pose a real risk. Don't make the same mistake I did!)

Fascinating though it was, I have to say I found the experience with very little to recommend it, not least because it disquiets to realize that the click you've just heard, conducted through the bone and tissue of your head, was produced by a small volume of fluid inside your eyeball suddenly boiling.

1) Flicker: does the LED's high-speed flicker play a role in damage to the eye? (Here's an LED viewed in slow motion: https://www.youtube.com/watch?v=3wdljou1M8Q)

2) Spectrum: LEDs can have very uneven spectrums with spikes at particular frequencies (particularly in applications like street lamps that don't use phosphors). This is something an eye in nature would never experience.

Here's a great video showing LEDs strobing compared to other bulb types: https://youtu.be/1IDf16R_eJ0?t=13s

In the living room or especially the bedroom and bathroom, I prefer dimmer lighting with less blue spectrum. My 29W halogen incandescent on the night table doesn't exactly burn through a lot of electricity and has the most pleasing light in my eyes. Until there's a LED that can perfectly match that, I'll stick with that until these bulbs get banned, too.

Or, do what I did. Just make the rectifier directly out of LEDs itself - https://www.youtube.com/watch?v=jDnCHyF7o5U And from there you can power your devices with the leftover DC power.

LEDs are seriously far more robust than they were a decade ago.

That's not PWM in the video. That's raw mains frequency.

Here's one directly on the mains power. NO CONTROL CIRCUITRY.

https://www.youtube.com/watch?v=AE9QkHmeA-o

Sodium lamps are much less objectionable because their spectral spikes are at much longer wavelength.

The only sodium lamps I'm familiar with are high pressure sodium, which emit a garrish orange hue.

https://www.youtube.com/watch?v=l6bTSJVLCVI - I used to build fully-functional hydroponics buildings from the foundation-up. Electrical included.

Ground is for safety in AC, when there is a short the ground should take the current away resulting in power loss through the earth that in turn makes the breaker flip. Without grounding the wire that is exposed and touching something will (depending on material etc.) not transfer any current because of too high resistance, then as you touch it it will shock you and then the breaker will go off. (A loss power breaker, not a draw power breaker)

Perhaps you mean the neutral?

Same way you complete any other ground - since ground and neutral are literally on the same leg (go look at any installation. You've got TWO wires coming in at the mains, ungrounded.)

So, tell me, how do you ground those ungrounded 240/277V wires??

You don't. Both of them ARE the natural ground dependent upon whether you're at the peak or trough of the waveform. That's kinda how AC works.

Where I am from we have installations differently. phase and neutral come in the box, they go through a loss breaker(RCD) and then split up in to multiple breakers. Then those wires go to the socket. Then near the box there is a metal rod in the ground with a wire going to the box, this wire connects to the ground wires coming from sockets. The ground wire, is not connected to anything but things that are not supposed to have any power flowing through.

Yes Neutral is grounded (outside my house, on the main) But when we say we ground things we mean the third connection.

Sorry, didn't know it was so different over there.

edit: Saw the correct name for the "loss breaker" in other post, it is RCD :)

edit: Question, what happens if you hold the neutral to the ground wire there?

Forgive my ignorance, I'm no electrical expert, but did you just say that the ground wire is connected to the neutral somewhere in the circuit? Or did I misunderstand you?

EDIT: That "always" is assuming the house is modern wiring and not older-style two-prong wiring for the wall outlets. Those systems were just main and neutral at the box and controlled by a fusible link.

If I'm understanding you correctly, in the US the ground wire is functionally identical to the neutral due to the bonding. Therefore (this is my own deduction and I'd appreciate being corrected if I'm wrong) you could, in theory, invert the ground and neutral wires in the plug of an electrical appliance and there would be no change in the behaviour or safety of the appliance?

Generally, no. I've seen backwards wiring jobs cause 48-80VAC to run through the casing of microwaves (they usually use the casing as a floating ground.) Any wiring inversion will usually cause some issue somewhere.

http://ecmweb.com/code-basics/grounding-and-bonding-part-2-3

[1] https://news.ycombinator.com/item?id=13331492

http://iovs.arvojournals.org/article.aspx?articleid=2126968

There are no results which say that our eyes are safer outside.

If you meant: "if we're safer outside then if we've a defense mechanism then we'd be safe "

That's already two "If"s deep and not a reasonable position to take :)

Those outdoor workers probably ought to be wearing UV-blocking sunglasses regularly to avoid increasing their chance of cataracts:

https://en.wikipedia.org/wiki/Cataract#Radiation

My optometrist was quite emphatic about this because she said the damage is thought to be cumulative, so if you're going to have a lifelong outdoor career or avocation, the difference could be significant.

I do think the theory elsewhere in this thread about the different spectral distribution could be significant. This is why apparently non-UV blocking sunglasses can make UV damage worse: the pupils open wider when visible light is blocked and so let even more UV in. If you just skew the spectrum of some light source toward the UV without increasing the overall luminous intensity, presumably it could cause some health risks in a similar way.

There is nothing inherently bluer about LED technology. LEDs are readily available in color temperatures down to 1600K.

The ratio of yellow to blue light determines the colour temperature perceived. Some of that blue light will always get through, so white LEDs (even "warm" ones) will always have a blue light component to them.

http://www.photonstartechnology.com/learn/how_leds_produce_w...

But LEDs get a bad rep because there are so many garish blue-white, flickering, junk ones flooding the market.

Most people today buy the much warmer ones so they don't feel like they're in a mental institution.

Mine were a gift, but I use them as protection from sun as well. Even dim, cloudy days expose you to far more blue light than a PC monitor.

After spending thousands on eye surgery, I'm back wearing glasses to protect them.

Hopefully this turns out not to be a big deal. Having to choose between depression and retina damage would sure suck :/

http://www.sunnexbiotech.com/therapist/blue%20light%20damage...

This article explains some of the tradeoffs at the specific wavelengths.

The last time I went down the list of references I was personally not convinced, but not my field...

I couldn't find the exact brightness specifications, but I can testify that it is very bright on the max level.

https://www.amazon.com/Philips-GoLITE-Energy-Light-Rechargea...

Using the Philips line for an example, something like a blend of the Philips HF3520 Wake-Up light and the goLITE BLU HF34xx models?

Someone else was nice enough to post a link to the paper:

* http://www.sciencedirect.com.sci-hub.ac/science/article/pii/...

Overall, I think the focus should be on light spectrum, not LEDs per se. Warmer LEDs has far less direct emission, with most of the light being re-emitted from the phosphor.

Daylight ranges up to 120,000 lux, so 6000 is several times the lighting in most spaces, but still nowhere near bright sunlight.

That said, from the abstract (I don't have journal access), it sounds like they found a result in both 24H high intensity, and in on/off "domestic levels".

Is the 6000 lux you mentioned their value for high intensity, or is that what they considered as domestic levels?

     On the other hand, by exposing the same animals to a luminous intensity similar to that usually used in dwellings (500 lux) for 24 hours, only the LEDs appeared harmful

We don't usually stare at light sources; we use them to illuminate objects. A 100W incandescent from 1 meter on to reading material or other work is considered fairly brightly lit, and that's not getting the full 100 lux back to your eyes - only what the surface reflects.

Daylight is far brighter, but most of us have been warned from early childhood about the danger of staring at the sun. 100,000 lux may be present, but we're not directing it in to our eyes.

4000K isn't "blue white" or even what's usually called "cool white". It's warmer (that is, more weighted toward the yellow-red end of the spectrum) than sunlight at midday (5000K-ish) and much warmer than LED and fluorescent sources that are noticeably blue (6000K+).

Beyond that, sources with a flatter or fuller spectrum (most commonly measured as color rendering index, or CRI) will have less of a blue peak even at cooler color temperatures.

And yes, 6000 lux is a lot of light. Staring at a 100W incandescent light bulb from 1 meter away will put about 100 lux on your eyes, by way of comparison.

That puts 6000 lux firmly in the "my eyes hurt, this cannot be good" category.

They had also dilated the rats' pupils with atropine, making the acute exposure test equivalent to, or perhaps worse than staring at the midday sun for 24 hours straight.

Even the lower-level chronic exposure test used 500 lux with light from all directions so there's no way to look away. We don't use light that way in reality, and while I'm sure the intent was to accelerate the test, I can't help but suspect it's the equivalent of testing whether bathing in warm water might be harmful by boiling rats alive.

> The data suggest that the blue component of the white-LED may cause retinal toxicity at occupational domestic illuminance and not only in extreme experimental conditions, as previously reported.

The domestic illuminance they used was only 500 lux, which they describe as the "domestic classic light intensity".

It does however, seem much more likely that this is to do with extra energy in the UV end of the spectrum, which IIRC WW LEDs cut a lot more of (as well as the additional, visible blue light that makes CW seem so much brighter).

http://www.sciencedirect.com.sci-hub.ac/science/article/pii/...

I didn't know about this mysterious sci-hub, but now I do.

More info on sci-hub: http://bitesizebio.com/28268/access-science-free/

Compared to these, I can conclude that my home LED lights likely strobe in kHz range or above, or maybe not at all.

I can't speak for you but I find the full-wave rectified ones not to be a problem. Of course the difference isn't just the doubled frequency, it's also a much higher duty cycle.

Not terribly scientific, but pretty relevant when transferring this knowledge to humans.

So 6000 lux of blue is approximately 30x as many green photons. For blue LED plus yellow phosphor that 30x "yellow" will be the signal that you will use to decide "that's enough light to perform work."

The rat's eyes were definitely cooked by all of the blue. Imagine if they had used near UV or near infrared LEDs and the same meter to calibrate the intensity. Cooked rats.

From the article:

we investigate, in albinos and pigmented rats, the effects of different exposure protocols

It's much too soon to rip out the lights in any event.

> We used two types of lighting devices. For exposure to white LED, commercial cold white LED panel generating 2300 lumens during 24 h was used. The LED panel was placed above 8 transparent cages, placed on white surfaces, leaving enough space for air circulation and constant temperature maintenance at 21 °C. The illuminance measured at the rats’ eyes position was 6000 lux (Photometre DT-8809A, CEM, China).

> For long-term exposure, specific devices were built and characterized by Statice, France (Fig. 1A). Metallic boxes contained rows of LED with a diffuser in order to improve the directional uniformity of the radiation and avoid punctate sources. Alternatively, CCFL or CFL were uniformly distributed around the metal cages. Each cage was placed in a metallic device that was then placed in a ventilated cupboard allowing for a constant 21 °C temperature control (Fig. 1A). The light intensity was controllable and the distribution of light in the cage was homogenous whatever the rat position. Different types of LEDs were used: cold-white LED (pure white 6300 K), blue LED (royal blue 455–465 nm), and green LED (520–35 nm) (Z-power LED, Seoul Semiconductor, Korea). Exposure intensity was spectrophotometrically measured by Statice.

> Exposure protocols

> Acute exposure: LE and W rats were maintained in a cyclic light/dark (250 lux, 12 h/12 h) environment for 21 days. The day before light exposure, rats were dark-adapted for 16 h. The next day, pupils were dilated with 1% atropine (Alcon, Norvartis, Rueil Malmaison, France) under dim light, and rats were isolated in separate cages containing enough food for one day. After 24 h of exposure, rats were placed again in a cyclic light/dark (250 lux, 12 h/12 h) environment for 7 days and sacrificed for histology and immunofluorescence analysis. Control rats were submitted to the same pre conditioning protocol but not exposed to light. Different types of light sources and light intensities were used as detailed in Fig. 1B. For cold-white LED, different light intensities were tested from 6000 lux, to 1500, 1000 and 500 lux. Blue and green LEDs were used at 500 lux which is the domestic classic light intensity. CFL was used at 6000 lux and 500 lux, CCFL at 6000 lux. Illuminance was measured at the level of the rat eye.

> Long-term exposures: Rats (LE and W) were maintained in a cyclic light/dark (250 lux, 12 h/12 h) environment for 21 days, then placed in specific cages for chronic cyclic exposure to different types of light at 500 lux: CFL, white, green and blue LEDs. Animals were sacrificed right after 8 or 28 days of exposure. For the long-term protocol and in order to be as close to domestic light as possible, rat pupils were not dilated.

http://dx.doi.org/10.1016/j.neuroscience.2016.10.015

This sort of thing should have had 2 control groups. One kept in the dark, the other exposed to the light protocol they used for artificial lighting, using natural sunlight as the light source.

Its not clear from the wording above exactly how the control group was exposed in pre conditioning, and what the nature of their post exposure protocol was.

500 lux in cyclic test is not outside the realm of reason for representative real world exposure.

Personally, I'd like to see a control under natural sunlight, and one under a man-made filtered blackbody radiator.