Conference Highlights Medical, Entertainment Laser Safety
ORLANDO, Fla. -- A better understanding of the hazards of the surgical laser plume, real-time videos of retinal laser lesions in live animal's eyes and an in-depth examination of endotracheal laser accidents were among the highlights of the Third International Laser Safety Conference (ILSC '97), which was held here in mid-March by the Laser Institute of America.
ILSC '97 attracted more than 200 registrants who sought information from 17 exhibitors and heard 81 technical papers. The following are some highlights of the technical conference:
Wolfgang Wollmer of the University of Hamburg's Institute for Organic Chemistry presented the findings of four German research groups on the roughly 150 chemical compounds present in the plume that occurs when a surgical laser vaporizes intracellular fluid in tissue.
With some variation for different lasers and tissues, the groups found that 70 percent of the plume was water, 13 percent particulate aerosols and 17 percent gas, including carbon dioxide. Only about 3 percent of the gas included volatile organic compounds such as toluene and styrene. The researchers also found viral DNA fragments in the plume, including oncogenes.
They found that using water sprays in laser surgery reduced the release of more dangerous radicals. (The drier the tissue, the higher the plume toxicity.)
They also found that form-fitting face masks reduce hazards and high-flow, low-pressure instruments reduce risk during open surgery, while high-pressure, low-flow instruments work best for endoscopic surgery.
Harry Zwick and a team from the US Army Medical Research Detach ment at Brooks Air Force Base in Texas, showed real-time videos of retinal laser lesions in the eyes of live garter snakes.
The team used a confocal scanning laser opthalmoscope with lasers operating in the visible and near-infrared regions to image the retinas of two types of common snakes. To produce retinal lesions, the team used an air-cooled argon laser at 488 and 514 nm for exposures ranging from 1000 to 152 µJ for 10- to 20-ms pulse widths at a spot size of 35 µm. They found that photoreceptors degenerate within seconds of exposure. It also recorded changes in blood cell flow, suggesting leukocyte responses to neural and vascular injuries caused by the laser.
Wollmer released a study of 10 endotracheal laser accidents reported between 1993 and 1995 to the US Food and Drug Administration. He attributed many accidents to a drop of blood or tissue fragments covering the fiber tip, causing it to heat and rapidly blow up. In other instances, he said, the nozzle dislodged, the fiber tip was missing, the nylon cladding fell off because of insufficient cooling flow or the cladding caught on the fiber during insertion.
He recommended that operating room personnel carefully examine used fibers and check for inert gas flow just before each use by inserting the tip into a beaker of saline.
During a session on laser light show safety, Patrick Murphy of Pangolin Laser Software in Manassas, Va., presented the results of a survey of audience scanning in Europe. There, show operators intentionally direct lasers into the audience and exceed maximum permissible exposure levels. He found that fewer than 10 injuries had been reported in 20 years.
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