where lack of eyewear, often coupledwith other mistakes, resulted in dra-matic effects not only to the individ-ual, but also to the project — and, insome cases, to the institution wherethe accident happened.

Los Alamos National Laboratory.On July 14, 2004, an undergraduatestudent was injured at the Los Al-amos lab in Albuquerque, N.M., whileworking with two flashlamp-pumped,Q-switched Nd:YAG lasers. She andher mentor were using one of thelasers to generate and suspend par-ticles inside a target chamber, andthe other laser to monitor the sus-

In Laser Safety, Little MistakesCan Have Big ConsequencesEye injuries are an integral part of the history of lasers, but with a cultural change among experimentalists, that need not be the case.

by Kenneth L. Barat, Lawrence Livermore National Laboratory

One cannot help but wonderwhy laser eye accidents havenot diminished in frequency

as laser technology has matured overthe years. Why have these injuriesnot been eradicated, like smallpox?Surely we understand the biologicaland psychological causes by now,yet every year there are dozens of injuries.

The answer, of course, is the sim-ple carelessness that accompanies afamiliarity with medium- and high-power lasers. This is particularly truein academic and high-tech researchand development environments,where experiments are quickly as-sembled and where success dependsmore on ingenuity and inventivenessthan on adherence to safety rules.

Every laser user this author hasencountered has bypassed somecommon safety precaution in an ef-fort to get the work done in what ap-peared as a faster or more efficientmanner. An examination of therecord of laser accidents reveals that,in virtually every case, the injury re-sulted from a shortcut taken bysomeone who should know betterbut who, in the interest of expedi-ency, took an unnecessary, and ul-timately very costly, risk.

The most common involves pro-tective eyewear. Such eyewear is crit-icized for being uncomfortable towear, for interfering with peripheralvision, for reducing visibility and forblocking precisely the wavelengththat the laser user needs to see.

Each of these charges contains agrain of truth, but no more than that.Laser-safe eyewear is available indozens of designs to minimize the

discomfort and peripheral-visionblockage of users with and withoutregular eyeglasses. And although itnecessarily attenuates the wave-length of the experimentalist’s laser,the knowledgeable laser safety officercan recommend controls or eyeweardesigned for laser alignment to pro-vide protection while still allowingvisualization of the beam.

Nonetheless, the failure to use pro-tective eyewear is the common de-nominator of almost all laser eye ac-cidents. Consider the following fivecases at institutions within the USDepartment of Energy complex,

This retinal. burn, caused by an Nd:YAG rangefinder, resulted in nearly completevision loss.

Reprinted from the March 2005 issue of PHOTONICS SPECTRA © Laurin Publishing

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Worldwide Coverage: Optics, Lasers, Imaging, Fiber Optics, Electro-Optics, Photonic Component Manufacturing

Laser Eye Safety

In one incident, a misaligned laser crystal resulted in an eye injury, lost work and a labwide shutdown. The accident could have been prevented with the use ofsafety eyewear or remote monitoring of the experiment. Be aware of the potentialhazards in an experimental setup.

• Challenge co-workers whodo not employ protective eye-wear.

• Treat evaluation for possiblehazards as second nature,not as an afterthought.

• Use safety reports of past ac-cidents (lessons learned) toshow how adhering to goodpractice could have pre-vented injury.

• Reinforce the consequencesof an incident to the user andentire group so that all un-derstand the impact they mayimpose on others as the re-sult of a violation of lasersafety protocols.

Developing aNew Culture ofLaser Safety

pended particles. The two beamswere perpendicular to each other:the particle-generating beam prop-agating vertically and the particle-monitoring beam propagating hori-zontally.

The scientist said that he neededto view the suspended particles inthe chamber, so he disabled the Q-switch of the particle-monitoringlaser but left its lamps flashing to il-luminate the interior of the targetchamber. He peered into the cham-ber off-axis, saw that the first laserwas creating the particles and in-vited the student to look as well.When she viewed at a direct line ofsight, she immediately saw a flashand a reddish-brown spot in her eye.The injury was subsequently diag-nosed as laser-induced: The laserhad vaporized a 400- � 250-µm holethrough her fovea — the critical vi-sion area on the retina — and intothe underlying choroid layer.

Beyond the physical injury to thestudent, this accident helped pre-cipitate a multiweek shutdown of allscientific work at the lab.

Neither the scientist nor the stu-dent was wearing protective eyewearat the time of the accident. Appar-ently, they assumed that the particle-monitoring laser was disabled andthat the vertically propagating par-ticle-generating laser posed no threat.Although the exact condition of theparticle-monitoring laser at the timeof the accident is unclear, it obvi-ously was not disabled. Nor was itsperceived safe mode confirmed priorto viewing.

The student’s retinal cells will notregenerate, and she has suffered apermanent loss of approximately one-third of the fovea of her left eye. Al-though her brain probably will com-pensate partially by filling in with vi-sion from her right eye (her dominanteye), this will never be as good as herundamaged vision.

It would appear that two mistakesled to this accident. First, the inves-tigators were not wearing the ap-propriate eyewear, probably becausethey felt that it hindered their per-formance of the experiment. Second,they incorrectly assumed that the

laser was not lasing. Like an un-loaded gun, a nonlasing laser is prob-ably the most dangerous kind. Theaccident easily could have beenavoided if the researchers had set upa CCD camera to observe the cham-ber, rather than putting their eyesat risk.

Brookhaven National Laboratory.In September 2003, two scientists atBrookhaven National Lab in Upton,N.Y., were aligning an alexandritelaser to excite fluorescence from acrystal in a target chamber when oneof them sustained a permanent eyeinjury.

One scientist was observing thefluorescence as the other adjustedthe laser, but the protective eyewearthey were using made it difficult tosee the fluorescence clearly, so theobserver removed his eyewear. Aslight misalignment of the lasercaused its beam to miss the crystaland to emerge through the observa-tion port. Unfortunately, the scientistwas using a mirror to observe thefluorescence, and he unwittinglyswept the beam across both his eyes.

He suffered hemorrhaging and per-manent vision impairment in bothof his eyes.

The injured scientist was unableto work for a month, and although hehas recovered some of his vision, hestill is able to read only with diffi-culty. Besides the personal injury,the accident resulted in a multiweekhalt of all laser-related work in thescientists’ division while an investi-gation was conducted.

The most obvious error in this in-cident was the lack of protective eye-wear. Although eyewear that blocks

infrared alexandrite radiation whilepassing most of the visible spectrumis available, an even safer alterna-tive would have been to use a CCDcamera to monitor the fluorescence.

Argonne National Laboratory.Observing fluorescence is just oneof many reasons why experimental-ists remove their protective eyewear.Last September, an experienced laserscientist at the Argonne lab’s Ad-vanced Photon Source in Argonne,Ill., who was suffering from a slighteye infection, momentarily raised hiseyewear to rub his eye.

Laser Eye Safety

The failure to wear protective eyewear is the common denominator in most lasereye accidents. Do not assume that an experimental setup is safe. Be sure to blockall potential stray reflections from an optical bench, especially those leaving thehorizontal plane of the setup.

A student suffered permanent vision loss bylooking directly into the target chamber of a laserexperiment without safetyeyewear (recreated here).The injury resulted in amultiweek shutdown of allscientific work at the lab.Be conscientious that violating laser safety protocols poses not only a risk to the individual, butalso a severe imposition to one’s colleagues.

At that moment, the experimen-talist experienced what looked likea bright flash. Afterward, the visionin his left eye became cloudy. An examination revealed that he hadsuffered a laser burn of the retinawhen a polarizer on his optical benchreflected the beam of a Ti:sapphirelaser into his eye.

Although the researcher’s visionhas returned nearly to normal, alllaser operations at the AdvancedPhoton Source were suspended forseveral weeks, and an extensive in-vestigation was conducted of the en-tire laser safety program.

A second error was involved in thisaccident. A careful experimentalistblocks all stray reflections from hisoptical bench, especially those thatleave the horizontal plane of the ex-periment. In this case, it was an un-blocked beam angling up from theoptical table that caused the injury.

University of California, Berke-ley. An unfortunate habit adoptedby some laser users is to strictly ad-here to safety rules when setting upan experiment, but to relax their vig-ilance once it is running and “safe.”

Such was the case in March 2004,when a graduate student at the uni-versity sustained an eye injury froman Nd:YAG laser. He had carefullyworn eyewear in the afternoon whenhe set up the experiment, but whenhe returned to take some data afterdinner, he didn’t bother with eyewearbecause, he felt, there were no ex-posed beams that posed any danger.As he made a slight adjustment to apower meter, he saw a flash and hearda loud popping sound. He had sus-tained a serious injury to his left eye.

The student experienced some vi-sion impairment months after theaccident. Moreover, the incident ledto a prolonged investigation and asignificant decline in funding for theresearch group.

Argonne II. Although carelessworkers can sometimes emerge fromlaser accidents with little or no long-term vision impairment, they are notalways so lucky.

While manipulating the 800-nmbeam from a Ti:sapphire laser with amirror in October 2001, an Argonnescientist with more than 15 years’laser experience suffered a seriouseye injury. The beam had hit his un-

protected eye.Before the accident, his vision was

20/50. After the exposure, he wasnearly blind. Even years later, hecannot read large print.

Ending injuryHow can we prevent such laser ac-

cidents? Nothing short of a funda-mental cultural change among laserexperimentalists is required.

Such a cultural change would notbe unprecedented. Forty years ago,seat belts were almost universallydismissed as an unwanted intrusioninto the traveling experience, despite

the fact that many cars cameequipped with them. Today, nation-wide safety belt use is 80 percent.

The use of laser eyewear has notfared as well during the same 40years, but a similar modification inbehavior and sentiment is essential.Some of the day-to-day activities thatcan lead to such a change and re-sult in much greater safety in laserlaboratories include:

• Co-workers challenging thosewho do not use protective eyewear.

• Treating evaluation for possiblehazards as second nature, not as anafterthought.

• Safety professionals using reportsof past accidents (lessons learned)to show how adhering to good prac-tice could have prevented the injury.

• Reinforcing the consequences ofan incident to the user and entiregroup so that users understand theimpact they may impose on othersas the result of a violation of lasersafety protocols. G

Meet the authorKenneth L. Barat is the laser safety offi-cer at Lawrence Livermore National Lab-oratory in Livermore, Calif.; e-mail: barat1@@llnl.gov.

A cultural change among experimentalists is required to make laser eye accidents, such as this retinal burn from an Nd:YAG,a thing of the past.

Laser Eye Safety