diminshed blue or green in vision (too much 445nm?)

[Ash]

Wicked lasers website states that prolonged exposure to 400nm to 500nm will:
“alter and have a diminishing effect on a person’s perception of the color green.”
Question: besides common sense, how do they know this as fact?

My theory: several laser technicians at their sweatshop (read: factory) in China were possibly complacent with safety eyewear during testing and reported diminished color perception.
Thoughts?
:thanks:

 

[Tech_Junkie]

You freaked me out. I thought you hurt your eye.

Kind of obvious that we dont listen to anything WL says. Its kind of a no brainer.

 

[RA_pierce]

I thought this effect was known.

I can't be the only one who can confirm it. Right?
When I powered up my first 445nm build for the first time at ~800mW, I did notice that even brief exposure to a diffuse reflection from a wall or object some distance away would cause sensitivity to blue and green wavelengths to diminish.
I noticed this because after looking at the blue dot, I had trouble perceiving a 5mW 532nm dot. It looked more like a pale cyan than the bright green I was used to. The effect lasted for maybe 30-45 seconds.

The blue photo-receptors on your retina are much more sensitive than those for green and red since there are fewer of them. Exposure to an intense blue light source will cause these photo-receptors to get "tired." The color perception is due to a chemical inside these cells that responds to light of certain wavelengths. When this chemical is bleached from overexposure, it takes some time for them to recuperate.

 

[Ra1nfade]

I'm colorblind so I have to distinguish beams by grayscale I have read that prolonged exposure to certain wavelengths does leave diminished color vision. (through overuse of the chemicals the cones use to create color vision)

 

[LSRFAQ]

I'm colorblind so I have to distinguish beams by grayscale I have read that prolonged exposure to certain wavelengths does leave diminished color vision. (through overuse of the chemicals the cones use to create color vision)

Its well known and well studied with longer blue wavelengths.. It was first found in eye doctors who used blue argon light in their practice to treat retinas. With 488 to 457 nm light (Argon Ion) it was found that after a few months the color vision comes back.

However since the eye was not designed to work with 440 and shorter, there is not much known about how 440 acts with regard to the eye long term. Its NOT QUITE actinic UV, and its NOT QUITE blue. It does NOT occur in large amounts in nature compared to longer blue wavelengths, so little is known about its effects and it is not well studied. 445 is much more energetic then most common blue sources.

Every time I warned people about 445 lots of people told me I was wrong because there are no studies to cite, so I must be wrong. I'm not wrong.
Be careful around it.

Since most newer light sources use blue to excite yellow to make pseudo white, you will soon see some short term studies.

You might want to eat some carrots to pick up some Vitamen "A" to help regenerate.

Steve

 

[Ash]

Wow. Steve, excellent info. +Rep
I also believe that there are many dangers associated with ~440nm light and that we haven't performed enough studies to determine concisely to what extent.
I am still not certain, however, that an eye with actually "pop" when hit with a ~1W 445, (focused or not, or for any length of time.)
I would gladly conduct the experiment myself, but I don't usually go into butcher shops where they sell fresh pig or cow heads or eyes. To me, those seem to be the closest analogy to a human eye for this test. :evil:
..eta;

You freaked me out. I thought you hurt your eye.

...
You might want to eat some carrots to pick up some Vitamen "A" to help regenerate.

Steve

Oh, thanks, but I don't want you guys to read anything into the title, I didn't have any close calls or anything. I am practically a safety nazi with protective eyewear and laser propagation protection (beam dump, etc.) when it comes to higher powered lasers. I was just wondering.

 

[LSRFAQ]

Unless hit by a very high power laser ie 40-100 watts, or Qswitched lasers, eyes do not "POP"

You get a series of 10-100 micron spots on the back of the eye, unless you get hit by something adsorbed by the cornea or lens. (IR/UV) All that water in the eye is difficult to boil to steam. Very difficult.

The stories of popping come from Q-Switched big lasers, and its the sound of of the pulse blowing holes and vaporizing blood vessels in the back of the eye. The pop sound travels back through tissue to the ears. This is very rare. Very, Very rare. If your messing with a big Qswitched YAG without goggles, you have never seen what one does to soft material before you used it. This has only happened to less then a handful of people. The story has propogated because it is included in many of the standard texts on laser safety. Its very rare.


Steve

 

[mfo]

Isn't this basically the Blue Light Hazard we're speaking of?

 

[Benm]

Its not really a hazard - the mechanism partially works as RA Pierce explained above, and the effects are temporary... your vision should be back to normal within 15 minutes or so.

Another aspect is that the brain performs an 'auto white balance' (for lack of a better term) on whatever you are looking at. So if you partially expose a white room to blue light, and the rest of it to white light, the white part can actually start to look pink/orange. Recovery from this effect is often pretty quick, seconds to a minute after you turn the blue light off.

Its quite interesting how this matter keeps popping up, since its been around for ages. Back in the day of the green computer terminal screen, users would complain that the world looked pink after extensive use. Afaik it has never been proven that this had a lasting effect, although the sort term effect is very real... just try reading green text on a black background for 20 minutes in a dim environment and look around.

 

[InfinitusEquitas]

Fascinating thread...

Personally I experience yellow flashspots after viewing the dot of a 445nm laser, even when it is at a blatantly safe distance. I find the effect quite disconcerting.

Actually just had an eye exam two weeks ago, and had it compared to pictures of my retina from 2007 (long before I got involved with lasers). Aside from some minor discolorations "equivalent of sun tan on skin" there were no other abnormalities. I have noticed a marked increase in floaters, but again according to doc... it's normal.

I was wondering if one you could touch upon another topic though.

The dangers of visible wavelengths vs IR... specifically dealing with specular reflections.

Or for example the danger of a 650nm laser vs a 532nm laser. Is there a greater danger due to better perception of 532nm, or in any way decreased danger from the less visible 650nm wavelength.

Clearly there are differences... If anyone could point me in the right direction I'd be happy to do some reading on the subject myself, although I'm looking for just basic information.

 

[Benm]

There are differences indeed. When comparing 650 and 532 nm, the damage from exposure is fairly comparable since they are both far from ionizing and such. Since the apparent brightness of 532 is about 10 times higher, the blink reflex is also stronger for the green light. This reflex is not a reflex like the one from tapping your knee, its mediated by the lower brain and therefor inherently slow already (0.25 seconds or so).

Under most circumstances you will blink at exposure levels far below damaging, but some circumstances may change that... like when you are already in an extremely bright environment.

As a rule of thumb you could state that more visible wavelengths are inherently safer, or at least not more dangerous than ones that are less visible. Bluray would probably top the list of dangerous visible lasers as its barely visible yet borders on UV and can start to do some damage due to its high photon energy.

 

[InfinitusEquitas]

^^^First thank you for answering.

Taking away the blink reflex though, isn't 532nm more dangerous than say 650nm or 405nm since we are that much more sensitive to it?

For example, watching the dot of a 50mW green laser from 10 feet on an off white wall is quite unpleasant imho. At the same time the dot of a 50mW 405nm is not bright at all.

Both are at a safe distance in terms of specular reflection right? But one is almost painful to look at, while the other... is not.

Not sure if my questions make sense:tinfoil:

 

[Benm]

I can see why you would think so, but the damage is done by heat, regardless of how bright the light appears to you. 50 mW of red heats up the retina just as fast as 50 mW of green does, though the latter would appear 10 times brighter.

The 'painful to look at' part IS determined by how visible the color is. Although the sensation is painful, its not created by pain receptors at all. This is also why near-IR lasers are very dangerous: the optics of the eye will focus the beam on the retina, but you don't experience this at all until it is too late.

 

[InfinitusEquitas]

^^^Ok, I see what you're saying.

I guess one last question on the subject then... given that we are most sensitive to green light, if the displeasure from viewing a green dot an overall safety indicator?

So the treatment of viewing a green dot (not beam or obviously looking into beam) should be extended to treating the dots of all wavelengths?

 

[Benm]

Looking at the dot is rarely dangerous at all, unless you do it up -very- close and with a high powered laser. The dot of a 200 mW 532 nm on a matte surface may look uncomfortably bright to you, but as long as you keep it at arms length or further it poses to threat to your vision.

Our eyes are highly adaptive to different lighting levels, but the response is not all that fast - the pupil will dilate or contract in a split second, but the rest of the adjustmen is chemical and takes several minutes at least.

Consider walking out of a dark room into a summers noon. The light level will probably be very painful on your eyes, but that same lighting condition is 'pleasant' when you have adjusted to the lighting level by spending some time outdoors that day.

The pupil can adjust to something in the order of 50 fold differences very rapidly, but combined with the chemistry of the retina they human eye can produce a usable image in lighting levels a factor of 1 million to 1 billion apart. Rapidly switching between such environments doesnt occur in nature though, so if we do it through technology the result is temporary night blindness or temporary overload depending on which way you go.

 

[InfinitusEquitas]

I know it's not exactly scientific, but while back I did a test on specular reflections off of various object lying around with a 1.1W 445nm laser.

Despite making sure that the maximum amount of light possible would be falling on the thermopile, at distances of over 12" I wasn't able to get any readings. The exceptions were the really glossy things.

Once again thank you for the responses, cleared up a bit of confusion for me:beer:

Edit, system won't let me yet, but I owe you a +1