Laser Accidents (part 2)

----15 WHY SHOULD RECOMMENDATIONS BE MADE?

The most important final step is to come up with a set of well-considered recommendations designed to prevent recurrences of similar accidents. Once you are knowledgeable about the work processes involved and the overall situation in your organization, it should not be too difficult to come up with realistic recommendations. Resist the temptation to make only general recommendations to save time and effort.

For example , you have determined that a beam block that was knocked over contributed to an accident. Rather than just recommending "show more care around beam blocks," it would be better to suggest:

1. Anchor all beam blocks to the optical table.

2. Color beam blocks for easier recognition if out of place or tipped over.

Never make recommendations about disciplining a person or persons who may have been at fault. This would not only be counter to the real purpose of the investigation, but would jeopardize the chances for a free flow of information in future accident investigations.

In the unlikely event that you have not been able to determine the causes of an accident with any certainty, you probably still have uncovered safety weak nesses in the operation. It’s appropriate that recommendations be made to correct these deficiencies.

----16 WHAT SHOULD BE DONE IF THE INVESTIGATION REVEALS HUMAN ERROR?

A difficulty that has bothered many investigators is not wanting to lay blame.

However, when a thorough worksite accident investigation reveals that some person or persons among management, supervisors, or workers were apparently at fault, then this should be pointed out. The intention is to remedy the situation, not to discipline an individual. Failing to point out human failings that contributed to an accident won’t only downgrade the quality of the investigation; it will also allow future accidents to result from similar causes because they have not been addressed.

----17 NOT EVERY LASER ACCIDENT INVOLVES AN EYE OR SKIN INJURY

Having a laser beam or reflection show up where it’s not expected can also be the cause of an accident. The worker who is flashed with a construction laser and is startled may fall off the ladder he or she is standing on. In a laboratory somebody may drop a piece of expensive equipment. In either case the person operating the laser may now be in danger from the individual struck by the laser.

The overwhelming number of accident reports from exposure to laser pointers fall into this group. Rarely has a laser pointer been the cause of a retinal eye injury, but the startle reaction has caused car accidents.

The most common effects from direct exposure to viewing the beam from a laser pointer are afterimage, flash blindness, and glare.

Afterimage is the perception of spots in the field of vision. This can be distracting and annoying, and may last several minutes, although there have been reports of afterimages lasting several days. Flashblindness is temporary vision impairment after viewing a bright light. This is similar to looking directly at a flashbulb when having a picture taken. The impairment may last several minutes.

However, a longer look can cause serious damage to your eyes. It’s worse if the laser beam is being projected through a piece of optical equipment, such as a telescope or a pair of binoculars. In these situations, the laser beam could actually burn a tiny spot, or cut open a blood vessel on the retina at the back of your eye.

In a worst-case scenario, you could go blind.

Glare is a reduction or complete loss of visibility in the central field of vision during exposure to the direct or scattered beam. This is similar to viewing oncoming headlights on a dark night. Once the beam is out of the field of vision, the glare ceases. While this does not pose a hazard to the eye, it be a serious distraction. Glare can be exacerbated when the beam is reflected from a mirror like surface.

----18 TYPICAL LASER POINTER INCIDENTS

1. Law enforcement officers have reportedly drawn their weapons when the light from laser pointers is mistaken for a gun sight.

2. Laser beams projected into airspace to intercept aircraft have caused distractions and temporary vision impairment to pilots.

3. The operator of a roller coaster ride in a Hershey, Pennsylvania , amusement park claimed a laser flash temporarily blinded him.

4. Some sport venues and theaters have banned laser pointers after incidents with laser pointer beams.

5. A high school cheerleader reported being exposed at least three times.

After the last episode, she reported first seeing green, then experiencing partial vision loss, which lasted for several months. An ophthalmic exam found no retinal damage. The cheerleader's vision returned to normal after several months.

----19 GUIDANCE FOR LASER POINTER USE

Laser pointers are not toys. Use them with caution, and only for their intended purpose:

1. Never point a laser beam at anyone and never look directly into the beam yourself.

2. Never aim a laser pointer at surfaces that would reflect the light back, such as mirrors or mirrored surfaces, including fish tanks and windows.

3. Never leave a laser pointer where children might get their hands on it.

4. Choose a laser pointer that stays on only when you apply pressure with your fingers.

5. When you buy a laser pointer, choose one that has a clear warning on the label about the potential to cause eye damage. Read the instructions carefully and follow them closely.

----20 EXAMPLES OF LASER ACCIDENTS

This section is a collection of documented laser incidents. Some took place in a medical setting and others in research and academic settings. Each, regardless of the nature of the injury, demonstrates that laser accidents happen and the user must be aware.

One of the oldest laser accident databases was originated and kept by Rock well Laser Industries (RLI), a laser-safety consulting firm that collects documented accident accounts. Approximately every 10 years they publish the updated totals of their database. The firm's Web page contains a form where accidents and incidents can be reported, which can be found at http://www.rli.com/.

The Department of Energy (DOE) has an extensive accident-reporting data base, called the Occurrence Reporting and Processing System (ORPS). Many kinds of accidents and incidents are tracked through this system. Over the past 5 years, a number of the national laboratories have reported a laser injury or a break in laser safety procedures. A national laboratory lessons learned Web page can be found at http://tis.eh.doe.gov/paa/oesummary.

The U.S. military keeps databases of incidents and injuries. One is the Laser Accident and Incident Registry, U.S. Army Medical Research Detachment, Walter Reed Army Institute of Research.

----20.1 MEDICAL DEVICE REPORT (MDR) REPORT KEY 397304, REPORT NUMBER 1218402-2002-00019

Event description: The representative of a medical laser manufacturer sent a user an extra pair of laser protective eyewear. The problem was that the extra pair was not for the wavelengths produced by the laser. The eyewear was correctly marked with wavelength OD, but the doctor who received it did not check. He received a reflection that passed through the eyewear and caused an eye injury.

----20.2 ACCESS NUMBER M320116, MDR DATABASE

Event description: After the kit and laser were connected, it was observed that the red HeNe aiming beam was not visible at the laser kit tip. The physician elected to proceed with the procedure. When the laser control foot switch was depressed, no laser energy was emitted from the laser tip. Flames appeared on the sterile drape where the laser fiber had been resting. No one was injured.

Analysis of the returned product pointed to a broken laser fiber, probably caused by mishandling.

----20.3 ACCESS NUMBER M751889, MDR DATABASE

Event description: A male patient was undergoing microlaryngoscope laser surgery to remove a nodule from his vocal cord. The endotracheal tube was in use when an ignition occurred. The patient sustained severe burns to his vocal cords and surrounding tissues, causing obstructive swelling.

----20.4 ACCESS NUMBER M817394, MDR DATABASE

A nurse in the operating room leaned into the laser system at the point where the laser delivery fiber attached to the laser console and caused the fiber to break at the connector. The broken fiber caused a burn in the nurse's clothing, penetrated the clothing, and caused a small nonserious burn on the nurse's abdomen.

----20.4.1 Post Doc Incident

A postdoctoral student was attempting to align an unfocused laser beam when a stray beam from an optic polarizer he was holding glanced into his face. No protective eyewear was worn, and eye pain developed in 24 hours.

----20.5 ORPS REPORT CH-AA-ANLE-ANLEER-1999-0005

A researcher performing welding of 24-inch-long aluminum plates using 4 kWatt of power from a carbon dioxide laser caused a ceiling panel to start burning, which was detected when the room's smoke detector went off.

----20.5.1 Experience is No Guarantee of Safety

The person injured had 15 years experience with lasers. The experiment was running 1 mJ, 500 HZ, and femtosecond pulse length, with a beam size of several centimeters. The beam was aimed in an upward direction toward a periscope.

The beam output was not lowered, because it burned through the neutral density filters. The two researchers decided that if they were careful, it would be all right to insert a mirror into the full-power beam path. This activity was a violation of written procedures for the experiment. An IR viewer was not used. One researcher was placing the mirror into the beam path and was struck by reflection from the corner of the mirror. The person heard a popping sound from his eye, followed by swelling of the eye. The result was a 100-micron spot injury. Vision went from 20/50 to near blindness; the researcher still cannot read large print.

The chemistry division, where this incident occurred, houses nearly 50% of all lasers at Argonne . All laser work stopped for a month while all groups were required to review laser use procedures or generate them if they had none. The chemistry division halted all laser work for more than 30 days. The researcher involved was banned from laser work for 30 days.

----20.6 FROM THE MILITARY DATABASE

----20.6.1 GLIN 4

The subject experienced a large flash of light and described seeing black circles and experiencing an almost complete loss of vision. The vision slowly cleared in the next 48 hours, but many dark brown spots continued to form a "curtain" in front of the eye. Assuming the pupil diameter was about 7 mm (dark environment), the retina was exposed to about 4.3 mJ of total beam energy. The resulting pressure wave damaged all the structures in the image area. The bruch's membrane was ruptured posteriorly, the sensory retina and nerve fiber layer were disrupted anteriorly, and at the retinal level, the photoreceptors sustained severe damage peripherally.

----20.6.2 Q-Switched Nd:YAG Injury ( Israel )

The injury involved a paramacular burn, later puckering, and permanent loss of visual acuity. The laser had a 1064-nm wavelength with a 20-nsec pulse duration, 20-mJ/cm squared beam energy, and a 4.3-mJ/pulse duration exposure (assuming a 7-mm pupil). The distance to the laser was 0.03 m.

----20.6.3 Military Range Finder

A civilian in Germany purchased a British military range finder at a local flea market. He then accidentally exposed his right eye, causing a central cub and intraretinal hemorrhage. Vision was 20/100. At 4 weeks the eye was clear with a pigmented spot 200 mm from the fovea. Aggressive treatment consisted of intraocular pressure control and medications and staying face down for 5 days.

The Nd:YAG laser was 1060 nm, with 10 mJ at 10-nsec pulses.

----20.6.4 Airline Pilot

The pilot of a United Airlines 737 aircraft was tracked for 3 sec with a green light thought to be an argon laser. The aircraft was flying at 13,000 feet at 21:10 hours.

The event occurred April 16, 1997 . The pilot landed the aircraft safely. The beam seemed to come from a residential area. An afterimage persisted for some time.

----20.6.5 Airline Pilot

In October 1996, a Southwest Airlines flight was taking off from Las Vegas , Nevada . At an altitude of 17,000 feet, the beam from a nearby hotel-based laser light show entered the cockpit and caused the pilot to be temporarily blinded in the right eye. The pilot turned control of the plane over to the copilot. An argon laser is assumed to be the laser radiation source.

----20.6.6 Student Sues

The following example provides a major argument supporting "real" laser safety policies and practices and why these should be a significant part of all laser programs. A research assistant received exposure in both eyes while working unsupervised in the lab. She was in the lab reportedly having an argument with her boyfriend, who was not authorized to be there. The assistant was not wearing laser protective eyewear, although it was available. She claimed that the professor never wore the eyewear and that it was just a "paper policy." Following the event, the student sued the university for $39 million and reportedly settled for $1 million out-of-court. She claimed the protective eyewear and laser safety policy was only on paper and was not practiced. She ignored a policy that no guests were allowed in the labs and that supervision was required to operate the laser. Nonetheless, she collected on the claim. Such a settlement clearly indicates that the courts tend to favor the injured party. Obviously laser safety programs that are viewed only as "paper policies" can ultimately be very expensive.

----20.7 DATA FROM THE NASA AVIATION SAFETY REPORTING SYSTEM DATABASE

There are many examples of commercial flights in which the pilots suffered eye damage from lasers. These include aircraft landings at Honolulu , Las Vegas , Miami , New York , Los Angeles , and Phoenix . In Phoenix , one crew member was flash-blinded, with resulting afterimages and loss of night vision for about 1½ hours. Takeoffs have also been affected: in a 737 outbound from Los Angeles , two pilots were struck by a blinding flash that lasted 5 to 10 sec. The first officer had burns on the outer eye and broken blood vessels. In a flight from Cleveland , one crew member received a bright blue light in his right eye and experienced vision impairment for the next 1½ hours. Data from the National Air Intelligence Center indicate that, in the United States alone, commercial lasers have caused over 50 blinding incidents. Lasers have also injured a number of air force personnel. For example, the Palace Casino's laser show laser-illuminated a C-130 landing at Keesler Air Force Base. The flight engineer, who was looking straight ahead, was blinded for 3 to 5 sec and then experienced blurred vision. The next day, he experienced eye pain requiring eye drops. In April 2005 two Royal Canadian Air Force helicopter pilots were laser-illuminated from a Russian trawler during a routine mission.

----20.7.1 Severe Skin Exposure from a Xenon Chloride Excimer Laser

A male research technician was working on a class I XeCl excimer laser operating at a wavelength of 308 nm when the protective enclosure was opened near the pre-ionization discharge. He was exposed with several reflected laser pulses while the laser was operating in the pulsed mode at approximately one pulse per second.

The technician had removed a portion of the protective housing that covered a beam splitter and was watching for an abnormal electrical discharge inside the laser chamber. About 15 mJ per pulse reflected off the beam splitter and produced four distinct burns on his neck. As this wavelength, no heat was detected and the burns were not evident until several hours after the exposure. The beam reflections from the beam splitter that exposed the technician's neck area were unfocused.

He felt nothing at the time, but several hours later, four burns (probably photo chemical in origin) appeared on his neck. These areas required nearly three weeks to heal. The technician was using eye protection.

----20.7.2 9-mm Murphy Style Cuffed Endotracheal Tube

The patient was in the intensive care unit with multiple medical problems including uncontrollable tracheal hemorrhage. On December 10, 1991 , the patient was taken to the operating room for a rigid bronchoscopy with a laser. The endotracheal tube that was in place was removed and a number 9 PVC tube was placed.

The procedure was then changed to a fiberoptic bronchoscopy with a YAG laser.

The fiberoptic bronchoscope was positioned approximately 1 cm distal to the endotracheal tube, and the laser was situated about 1 cm distal to the tip of the fiberoptic bronchoscope. The power was set at 30 W with 1-sec pulses. After four or five doses of the laser coagulation therapy, the tip of the endotracheal tube ignited and a tracheal fire occurred. The patient suffered thermal burns of the trachea, left main stem bronchus, left upper lobe bronchus, and left lower lobe bronchus. This patient was gravely ill. It was necessary during the procedure to deliver 100% oxygen. When the normal procedure is performed, the amount of oxygen is approximately 30%. The patient died 9 days following the incident.

No sample was returned to the company from the hospital. The hospital's director of risk management explained that the hospital does not blame the endotracheal tube for the trachea fire; it was a risk they had to take to attempt to prolong the life of a gravely ill patient. Labeling instructions warn against using a laser or electrosurgical device in conjunction with the endotracheal tube because contact with the tube could result in its rapid combustion.

----20.7.3 Gastroenterology-Urology

As the device was being used with a CO2-cooled laser fiber in the intra-abdominal area, the patient underwent cardiac arrest. It was alleged that an air embolism occurred. The patient was resuscitated and no permanent injury occurred. A laparoscopy was performed on a 32-year-old woman. The procedure went smoothly, was successful, and nothing unusual was noticed. At the completion of the procedure, the anesthesiologist noticed that the patient had an electrocardiogram pattern but no pulse. It was determined that the patient had a CO2 gas embolism in the heart. The intra-abdominal pressure was 30 mm Hg. The surgeon immediately released CO2 gas from the abdomen.

The hospital has not conclusively determined what caused the embolism. The laser fiber continuously emits CO2 gas to cool the tip. There was some bleeding at the treatment site, but it was not excessive. The laser was used for ablation and coagulation. The hospital is not sure if the laser fiber may have directly injected CO2 into an open blood vessel. The high intra-abdominal pressure may have forced gas into the open circulatory system. The hospital reports that the laser has no gas shut-off or pressure-sensing features. The insulator has a red light, which comes on when the abdominal pressure exceeds the preset pressure by 4 mm Hg. The insulator interrupts CO2 gas flow at this pressure. In addition, an alarm sounds at sustained pressures over 20 mm Hg. No one heard an alarm, but it was reported that the laser was "very noisy." The insulator was returned to the manufacturer for inspection. The manufacturer concluded after testing the instrument that the device did not malfunction and that the incident is the result of an oversight on the part of the surgical team and the fact that the CO2 gas feeding the laser fiber had no feedback system to control the CO2 flow.

In another incident the laser appears to have continued to work after the footswitch was released. The affected laser system was returned to the manufacturer for investigation, but they could not duplicate the claimed malfunction. The manufacturer found that the laser system performed to specifications. There is triple redundancy in the design. Three failures would need to occur simultaneously: (a) the laser would fail to turn off, (b) the shutter would fail to close, and (c) the mechanism and software that detect shutter failures would fail. The manufacturer believed that the reported malfunction did not relate in any way to the malfunction that led to the recall of the device (recall number z-164-3). This recall was based on the possibility of a shutter coming loose and causing an unintentional radiation exposure during power-up or power seeks. The reported malfunction here is that the laser continued lasing after the release of the foot pedal. The shutter becoming loose would lead to the laser malfunctioning. In addition, release of the foot pedal would signal the laser to stop lasing. The manufacturer made a follow-up phone call to the doctor's office. The doctor reported continuing to hear a noise from the laser system after releasing the foot pedal. The company representative explained that the air pump in the laser system operates for approximately 2 sec after the foot pedal is released. This is normal operation. The doctor now believes that he confused the air pump with the continued lasing. The doctor also used thermal paper to verify that the laser was not continuing to emit energy. He said there were no burn spots on the tissue.

Another complaint was that a laser system continued to lase for approximately 1 sec after the foot switch was released. The affected laser system was returned to the manufacturer for investigation. The claimed malfunction could not be duplicated. The laser system performed to specifications (radiation ceased within 100 msec). There is triple redundancy in the design. Three failures would need to occur simultaneously as in the previous example. The manufacturer believes that the malfunction does not relate in any way to the malfunction which led to the recall of the device (recall number z-164-3). The recall was based on the possibility of a shutter coming loose and causing an unintentional radiation exposure during power-up or power seek. The reported malfunction here is that the laser continues lasing after release of the foot pedal. The shutter becoming loose would lead to the laser faulting. In addition, release of the foot pedal would signal the laser to stop lasing. The manufacturer made a follow-up phone call to ask the doctor what the indications of continued lasing were. The doctor responded that there was charring, not just bubbles or the sound of the air pump.

Lasing did not occur for more than half a second. The laser was being operated in mode 7, 2 to 3 W (pulse mode).

----20.7.4 Iris Medical Slit Lamp, Product Safety Failure

A sales representative demonstrated an iris medical occu-light glass laser system with a slit lamp adapter delivery device to three doctors at a hospital. While making practice burns on a business card, doctor 2 commented on the brightness through the oculars after test firing the laser. Doctors 2 and 3 said they saw spots after test firing; doctor 1 and the sales representative noticed no unusual brightness. Upon further inspection of the slit lamp adapter delivery device, it was noticed that the safety filter frame was labeled 810 nm. The wavelength of the laser being demonstrated was 532 nm. On May 6, 1999 , it was verbally reported by the hospital risk management department to the sales representative that doctor 3 was found to have 20/50 vision and three suspected laser burns on his retina.

The ophthalmologist who examined doctor 3 indicated that it could take several months for the vision to recover and stabilize. Doctors 1 and 2, as well as the sales representative, reported no effects. The exact laser powers and exposure durations used during these exposures have not been determined, but it appears that the laser power did not exceed 300 mW and the duration was set to 50 msec.

----20.7.5 Ophthalmic Excimer Laser An ophthalmologist arranged for his patients to travel for the purpose of eye surgery by excimer laser. With two doctors operating the laser, the patient's right eye was contacted by the laser beam 1 cm off center. The procedure was terminated at that point, but the patient's vision was changed from -5.50 to -8.50.

The doctor stated that this had happened previously with another patient. The doctor added that it had something to do with the gears in the control mechanism, but that no one knew why it happened. The manufacturer's representative asked the doctor why he would use such an unreliable machine for this work, and the doctor said that it was a rare occurrence that he likened to driving his car. The doctor added that it would not be high on his list of things to worry about. Today, over a year later, the patient's vision is -7.50 in the right eye.

----20.7.6 Holmium:Yttrium Aluminum Garnet (YAG) Laser System

When the doctor had finished lasing, the laser continued to lase, even though the foot switch was deactivated (released). Lasing was terminated via the emergency off button. No deaths or serious injuries occurred. The laser was thoroughly checked out a short while later. The problem could not be reproduced. At the time of the problem, a large amount of liquid was noted around the foot switch.

Preliminary investigation into the event and simulated lab testing tentatively identified the event as being attributable to shorted connections in the foot switch caused by excessive liquid in the foot switch assembly.

----20.8 FIRE CASE #1

After the kit and laser were connected, it was observed that the red HeNe aiming beam was not visible at the laser kit tip. The physician elected to proceed with the procedure. When the laser control foot switch was depressed, no laser energy was emitted from the laser tip. Flames appeared on the sterile drape where the laser fiber had been resting, but they were quickly extinguished. No one was injured. Analysis of the returned product pointed to a broken laser fiber, probably caused by mishandling.

----20.9 FIRE CASE #2

A nurse was readjusting the laser system for the next patient. During the verification of the energy, she heard an unusual noise. The nurse put the system in "standby" mode and sought assistance from her supervisor. When the supervisor took the system from "standby" mode to "ready" mode, she heard a loud bang and subsequently smelled smoke. Hospital personnel extinguished a small fire, which was contained within the laser system. An internal high voltage arc ignited the component's supporting plastic material, resulting in the internal fire. In order to prevent this from recurring, a design change that increased the high-voltage clearances and changes in associated materials was made.

----20.10 FIRE CASE #3

An incident occurred as a result of a laser-assisted turp procedure. Fiber from one manufacturer was utilized with another manufacturer's laser system. The physician had initiated the procedure and had lased three times for approximately 60 sec each time when the laser nurse smelled smoke and reported that her clothing was in flames. A hole in the clothing approximately 3 × 2" was created by the burn. No injuries occurred to the patient, surgeon, or nurse. The manufacturer's engineers visually examined the fiber. The failure occurred in the center of the small connector, and the proximal aperture was not damaged. Since all fibers are thoroughly tested prior to shipping and the hospital reported that this fiber worked initially, the manufacturer's conclusion was that the beam output from the laser system was not compatible with the other manufacturer's fiber.

This resulted in a hot spot inside the fiber that caused the fiber to fracture and fail. The fiber was not intended for use with lasers producing a beam divergence from the laser system's aperture greater than 17° full angle.

----20.11 LUBRICANT FIRE

USP recently received a report regarding the use of a petroleum-based eye lubricant, Lacri-Lube® S.O.P.®, manufactured by Allergan. In the reported incident, the lubricant was applied to the eyelid and periorbital area of a 4-year-old patient undergoing laser surgery to remove warts around the eye. When a laser was directed to the area, the eyelashes and eyelid ignited, injuring the patient's left eye.

Lacri-Lube S.O.P. consists primarily of white petrolatum and mineral oil, with small amounts of chlorobutanol and lanolin alcohols. According to the reporter, the hospital where this incident took place is replacing oil-based ocular lubricants with water-based products for procedures in which a laser or other heat source is used in close proximity to the lubricant.

----20.12 RANGE FINDER

A 24-year-old male patient visited an emergency department with a history of decreased vision in his right eye after looking into the laser beam of a range finder one hour previously. The findings were as follows: visual acuity OD sc=0,2 on the anterior segment without damage. Biomicroscopy revealed a retinal lesion located 200 µm parafoveal, with subsequent submacular bleeding. This hemorrhage had spread below the fovea and was subretinal as well as intraretinal. Infrared laser scanning ophthalmoscopy showed a stretched outer vitreous membrane. A technical examination of the range finder revealed a pulsed Nd:YAG laser of 1064-nm wavelength, 10-nsec pulse duration, 10-mJ pulse energy, and a beam diameter of 2.5 cm. Treatment consisted of 100 mg prednisolone for 9 days systemically, and 50 µg rTPA was injected into the vitreous under local anesthesia. Furthermore, 0.5 ml pure C2F6 was injected via pars plana 24 hours later.

Postoperative follow-up will be demonstrated.

Macular injuries caused by range finders cause substantial impairment. There is a gray market for military laser equipment that is not only illegal but prevents any safety instruction on apparent dangers.

----20.13 BYSTANDER OBSERVES DIFFUSE BEAM DURING LASER OPERATION

An employee returning from a break heard and investigated a hissing sound coming from an equipment area outside a research facility that contained a liquid nitrogen tank. Upon further investigation of this sound, the employee observed a green flashing light through a 12" exterior wall opening. The employee reported the incident and sought medical evaluation 2 hours later.

The incident was caused by a research scientist who had used two class IV Nd:YAG lasers to visualize airflow in a test chamber and removed an interior metal cover from this opening for compressed air relief from the test chamber.

A second metal cover, attached to the building outside this opening, was observed lying on the ground. Based on the laser operating parameters, the diffuse reflection did not exceed the MPE at the employee viewing location, and a retinal examination of the employee confirmed no injury. However, the NHZ from this diffuse reflection did extend several feet beyond the exterior wall and could have resulted in a retinal injury to the employee or a bystander if the reflection was observed at a smaller viewing distance.

----20.14 OTHER LASER ACCIDENTS

1. An Nd:YAG laser beam of 1060 nm and 1.2 kW peak power, at 1 psec and 100 MZ, was directed across a room to a table where a sample bottle was located. The beam was larger than the bottle, and about 10% of the beam went into a nearby area where a graduate student was working. The student heard a popping sound when the beam struck his retina. A white macular damage zone was confirmed by examination.

2. A technician inserted a polished test slide into a Ti:Sapphire laser beam (806 nm, 10 to 50 uJ/pulse at 10 Hz) to determine whether the beam would harm a detector surface. The beam reflected form the test slide into his eye. A flash was observed and was followed by an ocular hemorrhage, and blood filled his eye. He experienced no pain or shock.

At 3 weeks postexposure, there was no vision restoration in the eye.

3. Viewing a laser at a distance of 3 km with a 7× telescope, a soldier experienced a bright orange-red flash, which caused a hemorrhage in the left eye. The source was a ruby laser at 694 nm. At 10 days postexposure, the retinal burn measured 150 µm size with a 1- to 2-mm hemorrhage zone. Acuity was measured at 10/400. After 6 months the retina showed a 7° degree central scotoma with a 2° surrounding scotoma.

4. An engineer received third-degree burns on his back and upper right arm when a carbon dioxide beam from a 1-kW carbon dioxide laser was accidentally turned on. The improper restoration of circuit wires open to the laser control system was deemed to be the cause of the accidental discharge.

----21 LASER ACCIDENT ACTION PLAN

While our efforts are directed toward preventing laser accidents, one needs to a have a plan to follow in case an accident happens. More importantly, laser users need to know what that plan is. One solution is to place in every laser work area a poster that provides the names and current phone numbers of emergency personnel and steps to be followed until help arrives. A posted page or section in a laser procedure manual is recommended. The sample poster shown in Figure 9.2 could also be prepared as a Web page. The Web page approach has the advantage of quick updates, such as phone numbers and personnel changes. The disadvantage is that it may not be thought of during the excitement of the moment.

----21.1 GENERAL GUIDANCE FOR SUSPECTED EYE INJURY

1. Keep the individual calm, preferably seated or lying down; avoiding panic or shock is the main goal.

2. Call for assistance.

3. If your institution has a central help number for emergencies, call that number. Otherwise have the number of the local trauma center avail able. Don’t count on using or finding the phone book.

4. If you have a medical clinic on site, they can be called or notified by your response office. If medical or security is called first, they should have standing instructions to contact the LSO.

5. It’s important that the medical facility have some understanding of laser eye injuries as well as the laser mechanism.

6. Transport the person to medical.

7. Many large facilities have a fire department or security force that can transport the individual; they should be instructed on how to handle a person with an eye injury.

8. Notify the individual's or the area supervisor, along with the LSO and others working in the same area or on the same equipment.

This information that can be included on a poster or Web page. Additional examples from three universities can be seen at the following Web pages:

Above: Fig. 2 Action poster for suspected laser eye injury.

1. http://blink.ucsd.edu/Blink

2. http://radsafe.berkeley.edu/lsr-appg.html

3. http://ehs.unc.edu/radiation/manual/laser/I0-1.html

4. http://www.safety.duke.edu/Radsafety/laser%5Fpolicy/#8_1

In case of laser accident with suspected eye injury:

1. Determine if any local assistance is available, such as a coworker.

a. If yes, this person follows steps 2 and 3.

b. If no, call for assistance. Don’t go by yourself.

2. Keep the person as calm as possible.

3. Call the medical or fire department.

a. Regular hours: you can transport the person to medical.

b. Off hours: fire department to provide transportation.

4. Notify the individual's or the area supervisor.

5. Notify the LSO.

6. Work needs to stop until an evaluation is conducted to see if a systematic error exists.

In case of a suspected skin injury:

1. Keep the person calm.

2. Call the medical or fire department.

3. Follow the same steps as for an eye injury.

4. If the injury is a hand burn with no active bleeding, you can transport yourself to medical.

5. At the scene, reassurance is the most important thing to provide.

6. Not all laser injuries have an immediate affect on vision, so initial and follow-up eye examinations are critical.

7. Let others know what happened.

8. Work needs to stop until an evaluation is conducted to see if a systematic error exists.

----22 MEDICAL FACILITY

Depending on your community, you may have limited choices on where to send an individual with a suspected laser eye injury. It’s important that the facility have some understanding of laser eye injuries as well as the laser mechanism.

Usually, once the injured individual informs the medical staff that he or she works with or around lasers, any injury, particularly retinal, will be assumed to be laser related. Medical personnel may overlook the fact that many other optical causes or diseases could be the reason for visual problems or defects. Provide the name of a retinal specialist to the injured individual for further evaluation or follow-up in cases involving visible or near-infrared laser radiation. Not all laser injuries have an immediate effect on vision; consequently, initial and follow-up eye examinations are critical ( Figure 9.2).

----23 CAN LASER ACCIDENTS BE PREVENTED?

Laser accidents and near misses happen all the time. Some are caused by user error and some by equipment failure, and most can be prevented. It really comes down to the desire of the laser users to prevent accidents, their technique and basic laser safety training, and an appreciation of how quickly an accident scenario can develop. The laser use community needs a cultural change. It’s no longer acceptable for people to think that if they are injured it only affects them. We’re all affected. We must be responsible for each other as well as ourselves.