Food for Thought (safety related)

[mixedgas]

From a discussion at LPF. Where with some prodding and help they are developing a small safety culture.. Granted 60 seconds is a huge exposure... But something to think about.. Steve

QUOTE:

Retinopathy From a Green Laser Pointer
A Clinicopathologic Study
Dennis M. Robertson, MD; Jay W. McLaren, PhD; Diva R. Salomao, MD; Thomas P. Link, CRA

Objective: To report retinopathy following exposure to
light from a commercially available class 3A green laser
pointer.
Methods: A 55-year-old woman with a ring melanoma
was scheduled for enucleation. The eye (visual acuity 20/
20) had a healthy-appearing macular retina. The retina
was exposed to light from a commercially available class
3A green laser: 60 seconds to the fovea, 5 minutes to a
site 5° below the fovea, and 15 minutes to a site 5° su-
perior to the fovea. Color photographs were obtained be-
fore and after exposure. The eye was enucleated 20 days
after exposure.
Results: Laser power measurements averaged less than
5 mW. Retinopathy was observed 24 hours after laser ex-
posure. This was characterized by a yellowish discolora-
tion at the level of the retinal pigment epithelium (RPE)
in the subfoveal region and at the site superior to the
macula where the retina received 15 minutes of laser ex-
posure. Each site developed granular changes at the level
of the RPE within 5 days of exposure. Histologic study
showed RPE damage in the exposed subfoveal and para-
foveal regions.
Conclusion: A class 3A green laser pointer caused vis-
ible retinopathy in the human eye with exposures as short
as 60 seconds.
Arch Ophthalmol . 2005;123:629-633

[Jem]

Conclusion: A class 3A green laser pointer caused vis-
ible retinopathy in the human eye with exposures as short
as 60 seconds.
Arch Ophthalmol . 2005;123:629-633

Hi Steve

That's really interesting stuff. However, I would say pretty unrealistic in real life for our interests. Who on earth would stare into a laser pointer for 60 seconds???

They would have been better off using a higher powered laser and shortening the exposure times to something more realistic. Having said that, i'm uncertain as to exactly what they were setting out to acheive or prove, so I guess if they had a particular experiment in mind the results may be exactly what they wanted.

Cheers

Jem

[Doc]

I fail to understand how they could have reached this conclusion with a true to the rule 3a laser.

3a laser <5mW, but the part that I'm doubtful about <2.5mW cm^2.

Did they expand a 5mW laser to (approx) 16mm diameter, I doubt that.

Or did they (as assuming a 2mm diameter beam) reduce the laser power to 0.08mW, I doubt that too.

Or did they just ignore the power density part of the classification and apply 159mW cm^2 to that eye with a 2mm beam 5mW pointer?

[The_Doctor]

Did they say how they measured their 5 mW? Low power greens often have DPSS IR leaks, and more than 5mW. Even experts might sometimes forget that.

Also, the eye is very sensitive to green, so I wonder if that sensitivity aggravated the risk and caused the melanoma and perhaps red light at 5 mW might not do the same. (I suspect shortwave light would, even with less of it possibly).

Edit:
Doc, I don't get it... Assuming it's collimated, that 5 mW could form a near to diffraction limited spot on the retina, though I doubt the woman focussed on it with extreme precision much of the time. But that spot would be small. That text only mentions positions... Then again, if the melanoma were also very tiny they'd not have found it.

[gottaluvlasers]

Steve-

Very interesting find, however very misleading i think. Nothing against you obviously, but i really don't like studies and results like this. It gives a false sense of danger for people who may not know anything about the subject.

I am quite sure that staring into *anything* for 60 seconds straight would cause some sort of damage and pose a hazard. lol. Heck, a 25 Watt Xenon headlight at a few inches away and being stared at for 60 seconds im sure would cause some serious pain/discomfort and possible permenent damage to ones vision. my 3W streamlight flashlight would probably blind me and hurt me if i was a jack ass and stred at it for 60 seconds.

there is enough studies and scientific proof out there to show evidence of the *real* dangers of lasers. I just disagree with the methodology of this particular study. it is misleading and IMO is manipulative as a "scare tactic."

-Marc

[Laserman532]

Hi Steve

That's really interesting stuff. However, I would say pretty unrealistic in real life for our interests. Who on earth would stare into a laser pointer for 60 seconds???

They would have been better off using a higher powered laser and shortening the exposure times to something more realistic. Having said that, i'm uncertain as to exactly what they were setting out to acheive or prove, so I guess if they had a particular experiment in mind the results may be exactly what they wanted.

Cheers

Jem

in response to your specific question...

http://linkinghub.elsevier.com/retri...02939498002542

Abstract

PURPOSE: To report a patient with a macular injury caused by a laser pointing device.
METHODS: Case report. A healthy 34-year-old man was examined 2 days after he deliberately gazed into the beam of a laser-pointing device with his left eye for an estimated 30 to 60 seconds. His uncorrected visual acuity in each eye was 20/20. He reported a transient central scotoma in the left eye and headache after laser exposure.
RESULTS: Both eyes were unremarkable except for a focal retinal pigment epithelial disturbance at the nasal edge of the fovea in the left eye. Fundus fluorescein angiography demonstrated window- defect type hyperfluoresence in the same location.
CONCLUSIONS: Laser-pointing devices may cause macular injury when used inappropriately. Conformance with consumer safety recommendations should minimize potential hazards.

[mixedgas]

Actually I think the study sucks, but the description of crystallization and tissue color change instead of disrupted blood vessels is what is interesting. Traditional blue green damage is popped blood vessels followed by tissue charing.

Steve

[frothychimp]

The problem with the excerpt is we don't know why the study was commissioned. I'm sure it wasn't done for the protection of hobbyists. Perhaps the study was done to evaluate the use of class IIIa 532nm systems in targeting other medical systems and the time frames would be used in the adjustment of said systems to target a specific spot. We just don't know. So we cannot blame the researchers for an alarmist position.

I think the safety side of LPF is strictly based on hearsay and anecdotal evidence. Most know they need eye protection but the things that constitute eye protection for many of the members is highly questionable. Safety is clearly driven by cost. The "I want a broadband pair of glasses that gives me OD4 across the entire visible spectrum plus 808nm and 1064nm with a 75% VLT for less than $10" mentality is rampant particularly after stating how many hundreds of dollars they just spent on their toy. I used to post primarily in the safety section over there with what I thought was good, solid safety information only to have someone post something dismissing the info as overkill and then watch everyone jump on the bandwagon. It seems any Chinese vendor claiming OD4 without CE EN207 or ANSI Z136 compliance trumps anyone with the mathematics and background. It just gets old banging your head against the wall.

[ElektroFreak]

There's too many young people on LPF.. it's asking far too much to expect a large group of teenagers (who already have everything in life completely figured out) to listen to reason, no matter how good the advice. The mindset is always "This guy is just talking nonsense.. he's like my mom. This stuff won't actually hurt you, he just wants to rain on our parade." Since that's an easy way out, all the other little kids (and quite a few less-than-brilliant adults) will jump on the bandwagon, as Frothy said.

All we can do is try to continue promoting safety facts. I believe that there are still some people there who can recognize those facts as worthwhile and act accordingly. The stupid ones are the ones who will have to live with spots in their vision or worse, not us... I'm mainly concerned for those who interact with the stupid ones.. those who might catch a beam to the eye as an innocent bystander.

[mixedgas]

ill and then watch everyone jump on the bandwagon. It seems any Chinese vendor claiming OD4 without CE EN207 or ANSI Z136 compliance trumps anyone with the mathematics and background. It just gets old banging your head against the wall.[/QUOTE]

END QUOTE...

What is equally amazing is the number of "fake" safety goggles appearing because of LPF "DEMAND", with remarkably good mold quality.

My company tried to dump about 16 pairs of Argon and Yag goggles on ebay, CE/ANZI approved and med grade, and we cant GIVE them away. Of course we're not going to sell a 400$ pair of goggles for 15$, we were looking for 30-35$ to recover some of our costs. Two years ago they would have been worth 99$ on ebay...

Its becoming Clark's Third law, but the technology is NOT so advanced:

"Any sufficiently advanced technology is indistinguishable from magic."

Whats next, Chinese discount reactor shielding? Chinese discount jet fighters???

Steve