Product Code: ILSC2009_703

Eye Safety Devices – Problems with Multi Wavelength Laser Systems
Authors:
Wolfgang Woellmer, University Medical Center Hamburg-Eppendorf; Hamburg Germany
Reinhardt Thyzel, A.R.C. Laser Gmbh; Nuremberg Germany
Andreas Fiedler, Laservision GmbH; F�Rth Germany
Presented at ILSC 2009

Medical laser systems with more than one laser wavelength were introduced in the market already decades ago. Recently, these advanced devices become a standard in medical care, since with the use of inexpensive diodes multi-wavelength systems can be realized at affordable prices. If the different laser wavelengths can be activated either simultaneously or only at single lines, and in addition use a common beam delivery system or have independent outputs, the challenges for eye safety increase significantly. Modern laser filters are required with high optical densities for wider bands or for various single wavelengths. Problems may arise especially, if the wavelengths are far apart, like in the visible and in the infrared. Those filters only achieve sufficient optical densities by using very dark filters, not complying for minimum transparency with EN 207. Once this issue is solved, the respective laser system can be used with bare fibers or focussing handpieces. More advanced solutions are required for endoscopic or microscopic medical laser applications with more than one wavelength. These applicators usually have built-in eye-protection filters for the surgeon, which are activated, once the footswitch is pressed. With several filters, these attachments become bulky and may reduce safety, if one of the filters is removable. This problem can arise with filters of the KG type for infrared radiation, which look like a clear glass. Once removed, the user’s eyes are no longer protected against infrared laser radiation. Another interesting question arises with modern illumination systems for endoscopy, which use filtered light, among others in the visible wavelength band of the frequency doubled Nd:YAG laser. Does the appropriate laser filter interfere with this endoscopic illumination? This presentation discusses these topics and points out different control mechanisms for the safe use of a multi-wavelength laser systems.