When it comes to lasers, green means ‘stop’

Laser pointers are light, accurate and precise – attributes that make them very useful for those of us of who give a lot of presentations.

And when used properly, laser pointers, especially the ubiquitous, red-beamed variety, are very safe. But any laser pointer can injure the eye, which is why they should never be used unsupervised by children, who may be tempted to shine them into the eye of a friend or sibling, tease a pet with them, or point them at airplanes (which can not only injure the pilot, but is also a federal crime).

The output of laser pointers is measured in milliwatts. The U.S. Food and Drug Administration sets 5 milliwatts as a standard, and requires special permission for manufacturers wanting to make more powerful pointers. But is that 5-milliwatt limit low enough? Some experts think not:

“Laser pointers available for sale to general public should be less than one milliwatt,” Dr. Kimia Ziahosseini of the St. Paul’s Eye Unit at Royal Liverpool University Hospital, told the New York Times. “Anything more than this puts people at risk by the criminally minded or those who are unaware of the risks.”

The Times article details what appears to be a growing prevalence and risk of high-powered green laser pointers, which pose a more potent threat to eye health than the more familiar, low-powered pointers that emit a red beam. Green laser pointers are gaining in popularity among aficionados because the green beam, unlike a red one, is visible along the length of its path.

Despite being banned in this country, these high-powered laser pointers are easily purchased online. The Times article describes the experience of an ophthalmologist who, for $28, was able to obtain via the Internet a laser pointer that outputs 100 milliwatts—that’s 20 times more power than the FDA allows. These are very dangerous, indeed. Their improper use has been linked to cause corneal flash burns, which are often accompanied by temporary blindness, or more severe injuries, such as those to the retina, that can cause permanent vision loss

For more safety information about laser pointers – of both the green and red variety – I suggest you visit this FDA page, which has a lot of great information.

And you may wonder, as I have, about the safety of “laser tag,” a popular recreational activity during which you and your opponents are equipped with “phasers” (but not eye protection) and encouraged to fire them at each other. Well, it turns out that the “laser” in “laser tag” is a marketing gimmick. The devices used in laser tag emit light, but they are generally not lasers. That being said, I recommend checking out the technology before you let your kids engage in this activity (chances are the biggest risk to their safety will be tripping and falling in the darkened play area).

In the meantime, here’s a great rule of thumb to keep in mind: Don’t let anyone other than an ophthalmologist ever point a laser at your eye.

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