9 ms·

I agree with you that this is probably overblown. But, just to play devil's advocate, it seems plausible that sunlight might activate some kind of defense mech

by NickM 10y ago

I agree with you that this is probably overblown. 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.

jessriedel 10y ago
It's definitely a good point. Dark sunglasses that don't block UV light can actually increase damage to your eyes, because your pupil dilates in response to visible light only. http://healthland.time.com/2009/08/04/can-cheap-sunglasses-be-bad-for-your-eyes/ 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_retinal_ganglion_cells https://en.wikipedia.org/wiki/Intrinsically_photosensitive_r...
- jules 10y ago
  That's interesting, because when working with UV light I could feel pain in my eyes, so the body does have some sort of defense mechanism.
  - throwanem 10y ago
    That's not really a defense per se, just a warning that something is wrong. I had pain in my left eye when I burned my retina with a laser, too, but that didn't reduce the damage.
    - deleted 10y ago
      [deleted]
    - jules 10y ago
      Warning signals do reduce damage though: if you hadn't gotten the warning then maybe you would have continued burning your eye. I certainly would have continued looking at the UV light if I hadn't felt any pain.
      - throwanem 10y ago
        It was a visible-wavelength laser, so I would've known there was a problem as soon as it hit my retina, even without the audible click and the sudden and disquietingly misplaced feeling of having been kicked pretty hard in the nuts. But I take your meaning. (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!)
        a_t48 10y ago
        Laser to the eye causes testicle pain?
        xorxornop 10y ago
        Probably "overwhelming" pain. Where you almost complete loss of rationality, a torrent of sensation that blocks out all other thought and sensation - vision narrows to a point, sound becomes choppy and discordant, limbs feel far away or even absent (no, I don't mean the one that's potentially chopped off or something ;) , the other ones)
        throwanem 10y ago
        Oh, it wasn't anywhere near that threshold! (Although it was well over that for swearing the air blue.) See my sibling comment to yours; I just meant that the nature of the sensation was almost identical to that produced by a shot to the area, just in my head instead of my belly - and, yes, that really does feel as weird as it sounds like it would.
    - jacobush 10y ago
      Don't look into laser with remaining eye.
    - owenversteeg 10y ago
      If you don't mind me asking, what was the damage, and what wavelength/power was it? Laser eye incidents fascinate me since there's not too much information about them. [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 :)
      - throwanem 10y ago
        I don't mind at all! Happy to oblige. It was a 405nm (violet) 5mW diode laser, housed in a pointer of a sort that's sold cheaply on eBay [1]. It was focused through a spherical lens taken from an old scanner and another from a broken magnifying glass. With such a short focal length, it should've been very hard to injure myself, but I had my head quite close to the bench and was also messing with a couple of mirrors. Given such a golden opportunity, Murphy rarely fails to oblige, and in this case he obliged me right in the eye. (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-Purple-Laser-Pointer-Pen-5MW-Light-Beam-DD/252706512339 http://m.ebay.com/itm/Teaching-Powerful-405NM-Blue-N3ioiet-P...
  - hvidgaard 10y ago
    Our eyes are extremely advanced. When I stand near a laser cutter, of course wearing protection glasses, I can feel it in my eyes whenever it is turned on.
  - nommm-nommm 10y ago
    I always found this interesting... 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.
    - pitaj 10y ago
      Do you have blue eyes?
nostromo 10y ago
Two other areas for additional inquiry: 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 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 https://youtu.be/1IDf16R_eJ0?t=13s
- Freestyler_3 10y ago
  Its funny, I replaced 2 spot lights in my kitchen with leds and when I use one certain kitchen device (high speed rotation thing) the leds start flickering visibly.
  - lightedman 10y ago
    One or the other doesn't have proper grounding or the cable for power to your appliances is run too close to your cable for lighting (which should be on separate circuits, mind you!)
    - Freestyler_3 10y ago
      Different rules here. There is proper grounding, but both the device and leds do not use grounding. Grounding is just for the metal cases, the lamp holder for example.
      - lightedman 10y ago
        Proper grounding regardless helps eliminate this. https://www.youtube.com/watch?v=l6bTSJVLCVI https://www.youtube.com/watch?v=l6bTSJVLCVI - I used to build fully-functional hydroponics buildings from the foundation-up. Electrical included.
        10y ago
vmarsy 10y ago
As I mentioned in another comment[1], there is in this paper a 500 lux experiment where LED were found harmful. [1] https://news.ycombinator.com/item?id=13331492 https://news.ycombinator.com/item?id=13331492
Franciscouzo 10y ago
Sun exposure can inhibit the development of myopia (on chicken): http://iovs.arvojournals.org/article.aspx?articleid=2126968 http://iovs.arvojournals.org/article.aspx?articleid=2126968
- rahimnathwani 10y ago
  And humans: https://www.ncbi.nlm.nih.gov/pubmed/23380471 https://www.ncbi.nlm.nih.gov/pubmed/23380471
thecrazyone 10y ago
Occam's razor would say that's an unneeded assumption (that there's a defense mechanism in the eyes) to explain observed results. 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 :)

by NickM 10y ago

jessriedel 10y ago

It's definitely a good point. Dark sunglasses that don't block UV light can actually increase damage to your eyes, because your pupil dilates in response to visible light only. http://healthland.time.com/2009/08/04/can-cheap-sunglasses-be-bad-for-your-eyes/ 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_retinal_ganglion_cells https://en.wikipedia.org/wiki/Intrinsically_photosensitive_r...

jules 10y ago
That's interesting, because when working with UV light I could feel pain in my eyes, so the body does have some sort of defense mechanism.
- throwanem 10y ago
  That's not really a defense per se, just a warning that something is wrong. I had pain in my left eye when I burned my retina with a laser, too, but that didn't reduce the damage.
  - deleted 10y ago
    [deleted]
  - jules 10y ago
    Warning signals do reduce damage though: if you hadn't gotten the warning then maybe you would have continued burning your eye. I certainly would have continued looking at the UV light if I hadn't felt any pain.
    - throwanem 10y ago
      It was a visible-wavelength laser, so I would've known there was a problem as soon as it hit my retina, even without the audible click and the sudden and disquietingly misplaced feeling of having been kicked pretty hard in the nuts. But I take your meaning. (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!)
      - a_t48 10y ago
        Laser to the eye causes testicle pain?
        xorxornop 10y ago
        Probably "overwhelming" pain. Where you almost complete loss of rationality, a torrent of sensation that blocks out all other thought and sensation - vision narrows to a point, sound becomes choppy and discordant, limbs feel far away or even absent (no, I don't mean the one that's potentially chopped off or something ;) , the other ones)
        throwanem 10y ago
        Oh, it wasn't anywhere near that threshold! (Although it was well over that for swearing the air blue.) See my sibling comment to yours; I just meant that the nature of the sensation was almost identical to that produced by a shot to the area, just in my head instead of my belly - and, yes, that really does feel as weird as it sounds like it would.
  - jacobush 10y ago
    Don't look into laser with remaining eye.
  - owenversteeg 10y ago
    If you don't mind me asking, what was the damage, and what wavelength/power was it? Laser eye incidents fascinate me since there's not too much information about them. [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 :)
    - throwanem 10y ago
      I don't mind at all! Happy to oblige. It was a 405nm (violet) 5mW diode laser, housed in a pointer of a sort that's sold cheaply on eBay [1]. It was focused through a spherical lens taken from an old scanner and another from a broken magnifying glass. With such a short focal length, it should've been very hard to injure myself, but I had my head quite close to the bench and was also messing with a couple of mirrors. Given such a golden opportunity, Murphy rarely fails to oblige, and in this case he obliged me right in the eye. (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-Purple-Laser-Pointer-Pen-5MW-Light-Beam-DD/252706512339 http://m.ebay.com/itm/Teaching-Powerful-405NM-Blue-N3ioiet-P...
- hvidgaard 10y ago
  Our eyes are extremely advanced. When I stand near a laser cutter, of course wearing protection glasses, I can feel it in my eyes whenever it is turned on.
- nommm-nommm 10y ago
  I always found this interesting... 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.
  - pitaj 10y ago
    Do you have blue eyes?

nostromo 10y ago

Two other areas for additional inquiry: 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 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 https://youtu.be/1IDf16R_eJ0?t=13s

Freestyler_3 10y ago
Its funny, I replaced 2 spot lights in my kitchen with leds and when I use one certain kitchen device (high speed rotation thing) the leds start flickering visibly.
- lightedman 10y ago
  One or the other doesn't have proper grounding or the cable for power to your appliances is run too close to your cable for lighting (which should be on separate circuits, mind you!)
  - Freestyler_3 10y ago
    Different rules here. There is proper grounding, but both the device and leds do not use grounding. Grounding is just for the metal cases, the lamp holder for example.
    - lightedman 10y ago
      Proper grounding regardless helps eliminate this. https://www.youtube.com/watch?v=l6bTSJVLCVI https://www.youtube.com/watch?v=l6bTSJVLCVI - I used to build fully-functional hydroponics buildings from the foundation-up. Electrical included.
      - 10y ago

vmarsy 10y ago

As I mentioned in another comment[1], there is in this paper a 500 lux experiment where LED were found harmful. [1] https://news.ycombinator.com/item?id=13331492 https://news.ycombinator.com/item?id=13331492

Franciscouzo 10y ago

Sun exposure can inhibit the development of myopia (on chicken): http://iovs.arvojournals.org/article.aspx?articleid=2126968 http://iovs.arvojournals.org/article.aspx?articleid=2126968

rahimnathwani 10y ago
And humans: https://www.ncbi.nlm.nih.gov/pubmed/23380471 https://www.ncbi.nlm.nih.gov/pubmed/23380471

thecrazyone 10y ago

Occam's razor would say that's an unneeded assumption (that there's a defense mechanism in the eyes) to explain observed results. 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 :)