IR-A and Eyes

[Andrea B.]

Eye Safety Related to Near Infrared Radiation Exposure to Biometric Devices

by N. Kourkoumelis and M. Tzaphlidou

Dept. of Medical Physics, Medical School, U. of Ioannina, Greece

Special Issue: Biometrics Applications: Technology, Ethics, and Health Hazards

TheScientificWorldJOURNAL (2011) 11, 520–528

ISSN 1537-744X; DOI 10.1100/tsw.2011.52

 

LINKIE to PDF: http://downloads.hin...2011/902610.pdf

 

Excerpts

 

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Specifically, intense IR-A exposure of the eye may cause retinal burns and cataractogenesis[3,4].

 

^{3. Sliney, D.H. and Wolbarsht, M.L. (1980) Safety with Lasers and Other Optical Sources: A Comprehensive Handbook. Plenum Press, New York.}

^{4. Driscoll, C.M.H. and Whillock, M.J. (1990) The measurement and hazard assessment of sources of incoherent optical radiation. J. Radiol. Prot. 10, 271–278.}

 

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Generally, wavelengths between 760 and 1400 nm are invisible to the cornea by 96%; they are transmitted through the ocular media and focus on the retina (Fig. 1). As noted, in this spectral region, thermal effects dominate and extreme exposure of the retina and the choroid causes enzyme denaturation due to critical temperature rise. Regenerative capabilities of the retina are very limited and, therefore, any damage results in severe loss of visual acuteness.

 

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The International Commission of Non-Ionizing Radiation Protection (ICNIRP) takes for granted that infrared radiation poses a risk to the human eye under certain conditions[41].

 

^{41. International Commission on Non-Ionizing Radiation Protection (1997) Guidelines of limits of exposure to broadband incoherent optical radiation (0.38 to 3 μm). Health Phys. 73, 539–554.}

 

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Although infrared radiation raises the overall temperature of the aqueous eye, affecting mostly the cornea and the aqueous humor[36], IR-A radiation specifically is absorbed by the retina and is very ineffective in producing retinal injuries[42].

 

^{42. Ham, W.T., Mueller, H.A., and Sliney, D.H. (1976) Retinal sensitivity to damage from short wavelength light. Nature 260, 153–155.}

 

 

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Andrea's Comment: This was a little confusing. The paper had me convinced that IR was bad for the eyes. Then at the end of the paper is the statement about IR-A being "very ineffective" in producing retinal injuries. So, which is it, bad or ineffective?

 

Clearly it is risky to stare at IR lasers.

[Cadmium]

Andrea, Good work , thanks for that!

[Andy Perrin]

Heh, it's bad to stare at anything that can significantly heat your eye, whether it is visible or infrared! That is what they are saying. I imagine torches are also pretty bad, but I doubt typical home lightbulbs are! But it's not dangerous for the same reason ultraviolet is dangerous, with DNA damage and so forth as well as heating.

 

(The paper makes it pretty clear that the duration of the exposure matters quite a bit, as does the paper I linked in the other thread. They mention 1000 seconds as being a threshold in this one? Also apparently the shorter wavelengths are more damaging, even in infrared. See that graph in figure 3.)

[Bill De Jager]

Clearly it is risky to stare at IR lasers.

 

Warning: graphic content

 

I heard of one case where a technician got an IR laser in the eye and the small affected portion of the retina basically exploded. He reported that the effect afterwards was like looking through a fish tank full of floating debris. Sorry, no link.

 

You can get goggles that filter out specific IR wavelength regions for safety while using IR lasers. Also, I've since heard that one common practice is to put a visible laser beam parallel to the IR laser beam so workers know it's there.

 

On another topic, I just scored eight enlarger lenses and four projection lenses (all used and most old) nice and cheaply at a going-out-of-business sale at Adolph Gasser Camera in San Francisco. However, with Keeble and Shuchat having gone out of business last fall I think we'll soon have lost the last full service camera store (full range of used + new equipment) in the San Francisco Bay Area.

[Hornblende]

I found this : Solar retinopathy after the 1999 solar eclipse in East Sussex

Very interesting article, we get to know a little more about actual eye damage from the sun.

 

She said she had watched the eclipse for 30 min under the influence of ‘speed’.

Wow, aïe aïe aïe

[OlDoinyo]

The extent of potential damage is related both to maximum incident intensity (often expressed in KW/cm²) and to the duration of the exposure. At very low intensities, heat is transported away from the retina at the same rate it is delivered, and an equilibrium is established. At higher intensities, no equilibrium is established and the heating becomes roughly the product of the exposure time and the power density. Note that an extremely powerful but extremely brief pulse might not necessarily deliver a damaging dose of thermal energy. Some laser pulses are as brief as 10^-15 second, though most are much longer than that.

[Andy Perrin]

If you wait long enough, a steady state is always established. It just might be at a temperature that's fairly high!

[enricosavazzi]

My take: considering that IRA levels in both sunlight and incandescent bulb illumination exceed VIS levels, if incoherent-IRA eye damage by normal exposure to these sources were a significant risk, this damage should be widespread and well documented. When it comes to collimated high-intensity sources or coherent (=laser) radiation, or people staring directly into the sun, these are not normally occurring situations, and all bets are off. In some cultures, there are historical or anecdotal records (sorry, no references at hand, just things I read many years ago) of forced staring into the sun used as a torture method and as a way of causing permanent blindness in a subject, so these effects are indeed well known.