Product Code: ILSC2007_204
A Proposal How to Deal with Low Power Laser in the New European Directive on Artificial Optical Radiation
Hans-Dieter Reidenbach, Cologne University of Applied Sciences; Koeln Germany
Joachim Hofmann, Research Laboratory Medical Technology; Koeln Germany
Klaus Dollinger, Cologne University of Applied Sciences; Koeln Germany
Presented at ILSC 2007
Laser safety philosophy for low power laser is based on aversion responses including the blink reflex since many years and former the description of laser class 2 and 2M in the international laser product standard IEC 60825-1 implied this approach for the case of short intrabeam viewing. By contrast we have found in a total of 2,250 volunteers that the blink reflex occured in not more than 20 % of all cases if an irradiation is performed under class-2 conditions either with a laser or LED. In addition it has been shown with about 1,200 volunteers that aversion responses in terms of head movements and eye closure, which protect the eyes, occur in less than 10 % i.e. even less frequent compared to the blink reflex. The aversion response investigations were done with volunteers in lab and field trials where the head was unrestrained. In particular lasers have been applied in an adjustment system with an optical bench or with a special eye-tracker. Although the findings do not state that class 2 or 2M lasers are no longer safe, but the safety factor is decreased due to the lack of a confident inherent physiological protection reaction. This is especially discerning according to the fact that the new European Directive on artificial optical radiation 2006/25/EC demands that the employer shall devise and implement an action plan comprising technical and/or organisational measures designed to prevent the exposure exceeding the limit values. For all cases where it is not possible to choose equipment emitting less optical radiation - like class 1 laser - and personal protective equipment is certainly some kind of inexpedient regulation for class 2 laser and therefore might not solve the real problems, other solutions are required in order to fulfil the requirements. We will report the results of field trials with 200 persons who got an instruction to perform active protective reactions, which incorporate immediate closure of the eyes and deliberate head movement, in the case they became irradiated unexpectedly by a laser beam. Up to 80 % of the exposed volunteers carried out active protective reactions within about 1,5 seconds in an eye-tracking procedure, compared to only about 10 %, which showed a blink reflex and belonged to the non-instructed persons. The new concept of active protective reactions is included in the description of the laser classes and potentially associated hazards in the new edition of the international standard IEC 60825-1 and states inter alia that users are instructed by labelling not to stare into the beam, i.e. to perform active protective reactions by moving the head or closing the eyes and to avoid continued intentional intrabeam viewing. Adequate instruction to perform active protective might be a valuable contribution in order to prevent against any potentially hazardous laser radiation and thus fulfils the requirements of the EC directive and in addition actually increases the safety against laser radiation arising from wrong labeled class 2 laser products and true class 3R lasers in the visible spectrum.
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