IR lasers and application systems for myringotomy

The study examines an Er:YAG laser (2940 nm) and different application syst ems of the CO2 laser (10 600 nm) with regard to their suitability for a one -shot laser myringotomy of an adequate perforation size (similar to 2 mm). The laser-tissue interaction of the Er:YAG laser and the CO2 laser in fresh tympanic membranes of horses (thickness: 80-100 mu m) as well as in formal in-fixed human tympanic membranes (thickness: 100 mu m) is studied correlat ing perforation diameters to the applied power/energy density and the effec ts demonstrated by light and scanning electron microscopy are analysed. Usi ng the Er:YAG laser with a focused laser beam (spot diameter: 400 mu m) or with a maximally defocused laser beam (spot diameter: 1600 mu m) perforatio ns of an adequte size (2 mm) can only be achieved with multiple laser pulse s. Histological studies disclose only minimal thermic side effects in the a djacent tissue in both specimens. If the CO2 laser radiation is transmitted via a silver halide polycrystalline fibre (diameter: 900 mu m) a maximal p erforation diameter of 1300 mu m is achieved with significant thermic side effects such as coagulation. Using an Acuspot(TM) 710 micromanipulator (foc used beam diameter: 180 mu m) combined with a SilkTouch(TM) scanner a maxim al perforation diameters of 1700 mu m can be achieved in horse tympanic mem brane with one laser pulse. A prototype of a hand-held CO2 laser otoscope i n combination with the SilkTouch(TM) scanner is suitable for performing las er myringotomies with a diameter of 2 mm with a single laser pulse in fresh horse tympanic membrane.