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Invisible Infrared Light May Harm Retina, Study Says
By Katrina Woznicki
WebMD Health News
Reviewed By Laura J. Martin, MD
Aug. 6, 2010 -- Green laser pointers may emit high levels of invisible and potentially dangerous infrared light, a new study says.
Researchers report that green laser pointers deliver light that is brighter to the eye than red lasers, but the infrared light emitted by some inexpensive models could damage the retina of the eye.
Charles Clark, PhD, of the National Institute of Standards and Technology (NIST), led a research team measuring the output of several green laser pointers. The researchers bought three low-cost green laser pointers that had been advertised to have a power output of 10 milliwatts.
Researchers say one of the units emitted dim green light, but delivered infrared levels of nearly 20 milliwatts.
That's enough to cause damage to the retina before a person is even aware of the invisible light.
Tests using several other laser pointers found intense infrared emissions in some, but not all, units.
According to a NIST news release, the problem is the result of inadequate procedures in the manufacturing process. The problem could be solved by building on an inexpensive infrared filter at the end of the laser that would substantially reduce infrared emissions.
Such filters exist in modern digital cameras and the more expensive green laser pointers, but they are commonly left out of inexpensive models.
Owners of green laser pointers should never point them at anyone's eyes or aim them at windows, which could reflect infrared light back to the user.
The research is detailed in a publication called NIST Technical Note 1668. The NIST is part of the Department of Commerce.
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Galang, J. NIST Technical Note 1668.
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