Relatively Few Laser Injury Reports
The lasers used for many laser displays have energy levels that can exceed the MPE within a few tens of microseconds. Measurement and calculation techniques both show that the beam durations that audience members are routinely subjected would indicate that the MPE is being exceeded, often by a significant factor. Yet reported injuries from medical reports, and even anecdotal reports are rare.
For example, a 1996 study commissioned by a lasershow-related company tried to find worldwide reports of audience scanning injuries at any time during the then-20 years of laser light shows. As reported in a 1997 paper presented at the International Laser Safety Conference, the study found only five accidents (claimed injuries) and two incidents (potential injury). Accounting for an estimated 90% under-reporting factor, the ILSC paper estimated that there were roughly 70 injuries per decade — a relatively small number considering the total number of concert-goers and disco patrons exposed to laser light, some night after night.
(Since 1997, there have been one or two reports of serious accidents involving pulsed lasers being used at discos. Pulsed lasers can be much more dangerous than the continuous-wave lasers used for audience-scanning displays. Because of the danger, they should never be used for audience scanning, or where there is a danger of the beam going into the audience.)
Since reports of laser shows substantially exceeding the MPE are so common, yet reported injuries are so infrequent, this leads to the question of "where are all the injuries?".
Many safety experts are certain that the injuries are occurring, and are going unreported for several reasons. It is also a fact that the eye can often receive several thousand "damage spots" or lesions to the retina without it causing a significant problem to the subject's visual acuity.
The consensus among many respected safety professionals is that the although the study conducted in the mid-nineties had good intentions in trying to establish its goals, the methods in which the study was conducted were somewhat flawed, and could not give a proper indication as to how many injuries were occurring.
Read more about this topic: Audience Scanning
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