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<<   作成日時 : 2011/03/07 20:24   >>

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 高性能の緑のレーザーポインタによって遊ぶ間の眼障害を受けたティーンエイジャーが多いことを、世界中の眼科医が警告している。
 また、レーザーが飛行機に向けられる報告が5年間で9倍の増加したが、関係していたポインタは、FDAが決めた限度の10〜20倍も強力なのだが、これまでよりオンラインで注文しやすいという。
 眼障害を起こす可能性があるグリーン・レーザーが市販されていて、FDAの基準値の10倍の50mWのパワーがある。オンラインでは28ドルで100mWのポインタが買える。
 100ワットの白熱電球は約5ワットの可視光を作り出すが、5ミリワットのレーザー光線は1000番も強力である。一般人の使用ではレーザーポインタは1ミリワットより少ないようにするべきだという。パワーが強いと眼障害は1マイクロ秒で起こる可能性がある。

----------------------------------------------------
Lasers Rise as Threat to Retinas
http://www.nytimes.com/2011/03/01/health/01laser.html
By CHRISTINE NEGRONI
Published: February 28, 2011

画像So far, the reports have been scattered and anecdotal. But eye doctors around the world are warning that recent cases of teenagers who suffered eye damage while playing with high-powered green laser pointers are likely to be just the first of many.

“I am certain that this is the beginning of a trend,” said Dr. Martin Schmid, a Swiss ophthalmologist who reported one such case last September in The New England Journal of Medicine.

The pointers, which have also been implicated in a ninefold increase over five years in reports of lasers’ being aimed at airplanes, are easier than ever to order online, doctors say ― even though they are 10 to 20 times as powerful as the legal limit set by the Food and Drug Administration.

At the American Association of Ophthalmologists, a spokeswoman said the group was unaware of any increase in eye injuries caused by lasers. But doctors interviewed for this article said they were shocked by the easy availability of high-powered lasers.

Not long ago a high school student went to see Dr. Robert G. Josephberg, a retina specialist at Westchester Medical Center in Valhalla, N.Y., complaining of a blind spot in his left eye. The boy, who did not want to be identified, said the injury occurred when a friend waved a green laser pointer in front of his face.(Whether it will heal completely is uncertain.)

Dr. Josephberg said that at first he doubted the story. “I didn’t believe that a green laser was out there that could cause the damage,” he said.

But it turned out the laser put out 50 milliwatts of power, 10 times the F.D.A. limit. And as he investigated his patient’s case, Dr. Josephberg went online and bought a 100-milliwatt pointer for $28. He could hardly believe how easy it was.

“I kept waiting for the error message telling me I could not complete the purchase,” he said.

Like household lights, lasers are measured in watts, but the similarity ends there. A 100-watt incandescent bulb produces about five watts of visible light; the five-milliwatt laser is only one-thousandth as powerful. But because the light from a bulb is diffuse and a laser beam is concentrated, the effect of five milliwatts on the eye is 10,000 times as intense, according to Samuel M. Goldwasser, a laser expert and author of the online guide Sam’s Laser FAQ.

Dr. Jerald A. Bovino of the American Retina Foundation says the way the eye focuses can also intensify the laser.

“It is going to the fovea, the center of the retina,” he said. The darker pigment in the fovea absorbs the light as heat, quickly raising the temperature of the retina the same way a black car seat gets hot as it absorbs the sun.

Dr. Kimia Ziahosseini of the St. Paul’s Eye Unit at Royal Liverpool University Hospital in England says the dangers are so acute that even the F.D.A.’s five-milliwatt limit is too high.

“Laser pointers available for sale to general public should be less than one milliwatt,” she said. “Anything more than this puts people at risk by the criminally minded or those who are unaware of the risks.”

In a consumer update in December, the F.D.A. said it was aware that illegal laser pointers were being sold and warned that “a higher-powered laser gives you less time to look away before injury can occur, and as power increases, eye damage may happen in a microsecond.”

Daniel Hewett, a health promotion officer at the agency, said by e-mail, “There are many noncompliant products available for purchase from retailers, importers and, of course, via the Internet.” He noted that the agency had seized products from Wicked Lasers, an online store based in Hong Kong.

Steve Liu, chief executive of Wicked Lasers, said in an interview that its products did not violate the F.D.A. restrictions because those over the five-milliwatt limit were not called pointers.

Moreover, he added, “we make it extremely clear on our Web pages that these lasers are not only eye hazards but fire hazards.” And he said the company would begin offering laser safety lessons to its customers before online checkout.

Several laser experts say the enforcement of regulations is already insufficient and ineffective. “It’s a whole can of worms,” Dr. Goldwasser said, recalling that he recently received a 100-milliwatt laser as a gift from Wicked Lasers. To rein in all the hazardous products out there ― from virtual stores to flea markets ― would be impossible, he said.

And any talk of restricting availability is certain to meet resistance from the large community of laser enthusiasts, including those who use them professionally (like contractors and astronomers) and hobbyists like 18-year-old Alex Triano of Staten Island.

Since middle school, with his parents’ permission, Mr. Triano has been building lasers in his home, wearing safety goggles. “You learn so much in a hobby like this: electronics, soldering, physics,” he said. “And you learn about light, you learn about optics. You also learn a lot of mechanical things.”

The laser injuries Dr. Shepard Bryan has seen at his practice in Mesa, Ariz., involved red lasers, which laser fans like Mr. Triano consider passe'. Green is more easily perceived by the eye and the beam is visible along its path.

But green lasers are also more dangerous. Green is more easily absorbed by the retina than red, so it requires less exposure to cause damage. (Dr. Bryan’s cases involved an 11-year-old girl who focused on the light as part of an endurance game and a young man who also looked directly into the pointer.)

“Right now I haven’t seen an epidemic of injuries,” Dr. Bryan said, but he added that the potential was there. “In the hands of children it’s a very scary proposition.”

This article has been revised to reflect the following correction:

----------------------------------------------------
Retinal Injuries from a Handheld Laser Pointer

N Engl J Med 2010; 363:1089-1091September 9, 2010

Article
To the Editor:

Handheld laser pointers are commonly used in lecture halls and are considered to be harmless and safe.1 However, laser pointers can cause severe eye injury, as demonstrated by the case of a 15-year-old boy. The boy had ordered a handheld laser pointer with green light on the Internet to use as a toy for popping balloons from a distance and burning holes into paper cards and his sister's sneakers. The boy's life changed when he was playing with his laser pointer in front of a mirror to create a “laser show,” during which the laser beam hit his eyes several times. He noticed immediate blurred vision in both of his eyes. Hoping that the visual loss would be transient and afraid of telling his parents, he waited 2 weeks before seeking an ophthalmic assessment, when he could no longer disguise his bad vision. His visual acuity was so poor in his left eye that he was only able to count fingers at a distance of 3 ft, and it was 20/50 in his right eye. A funduscopic examination revealed a dense subretinal hemorrhage in his left macula (Figure 1AFigure 1Retinal Injury in a Teenage Boy and Laser Pointers.) and several tiny round scars in the pigment epithelium of the foveolar region of his right eye (Figure 1B). The clinical findings were consistent with severe bilateral retinal laser injury.1 After 4 months, the boy's visual function remained impaired but improved to 20/32 in the right eye spontaneously and to 20/25 with a remaining scar just beside the center of the fovea in the left eye after one intravitreal injection of ranibizumab (Figure 1C).

In the past, laser pointers sold to the public had a maximal output of 5 mW, which is regarded as harmless because the human eye protects itself with blink reflexes.2 The measured output of the laser in this case was 150 mW. The use of lasers that are threatening to the eye is normally restricted to occupational and military environments; laser accidents outside these fields are very rare.3 However, powerful laser devices, with a power of up to 700 mW, are now easily obtainable through the Internet, despite government restrictions.4 These high-power lasers are advertised as “laser pointers” and look identical to low-power pointers (Figure 1D). The much higher power of such devices may produce immediate, severe retinal injury. Despite their potential to cause blinding, such lasers are advertised as fun toys and seem to be popular with teenagers.5 In addition, Web sites now offer laser swords and other gadgets that use high-power lasers.

Neither the owners nor the potential victims of such dangerous “toys” can distinguish harmless laser pointers from hazardous ones, and we may see more such eye injuries in the near future.

Stefan Wyrsch, M.D.
Philipp B. Baenninger, M.D.
Martin K. Schmid, M.D.
Lucerne Cantonal Hospital, Lucerne, Switzerland
martin.schmid@ksl.ch

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