AG Schwentner, FB Physik, Freie Universität Berlin

NRL Chemist Has Eye Damaged by Dye Laser

The following text was printed in "Laser Focus", november 1981.

A Naval Research Laboratory chemist who was struck in the eye with a laser beam this summer is still suffering from the injury. The victim, who requested his name not be printed, was hit by 585-nanometer dye laser light that had reflected off an angle-tuned frequency doubler when he bent over to adjust a stepper-motor drive. Although his vision has gradually improved, he told Laser Focus he lost much of the high-resolution capability in the eye.

The chemist, who's worked with lasers for five years and considers himself a "laser jock", was "amazed" by how little laser energy it took to do so much harm. Measurements made after the accident showed that the pulse back-reflected of the frequency doubler carried only about 25 microjoules. But that was enough to punch a hole through multiple layers of eye tissue and to cause hemorrhaging. The result was a blood blister over the macula lutea, the part of the eye that provides visual acuity and which is necessary for tasks such as reading. The pulse energy would have been much higher - close to two millijoules - if the NRL group had not earlier taken steps to suppress amplified spontaneous emission in the dye amplifier chain, the victim said.

A surprising - and unsettling - discovery after the accident was how little the doctors knew about laser eye injufies. According to the injured, even retinal specialists were often reduced to guessing during treatment.

The NRL researcher said he never saw a flash when the laser beam struck the eye. "I bent over and all of a sudden I couldn't see" he recalled. He wasn't wearing safety glasses at the time, which he said was common practice in the lab. One reason was that the laser - a YAG-pumped dye system - was run by computer and seldom needed adjustments which required close eye proximity to the beam. Also, he pointed out, laser systems that simultaneously produce numerous beams at wavelengths from the ultraviolet to the infrared are fifficult to guard against. Since no single pair of goggles will block out all the beams, many lab workers choose to wear none at all. And in a darkened laser room, gasses that protect the wearer from laser light also obscure vision enough to raise the possibility of other hazards, such as hitting your head or tripping over cable.

The injured chemist critized laser manufacturers for their method of compliance with Bureau of Radiological Health safety rules. Lasers are built in such a way "that to use one you've usually got to partly disassemble it", he said. "Laser companies should design their product so that it can actually be adjusted and used while complying with BRH rules." He also had harsh words for the maker of the frequency doubler that reflected the light into his eye. "A $10 beam-stop on that doubler could have prevented this whole thing from happening," he said.

... so YOU might add the beam-stop in time!

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