Investigations on the vapor bubble formation during

Background: The formation of evaporation bubbles and pressure waves during Erbium:YAG laser vitrectomy might cause intraocular damages. Methods: In water, the formation of the evaporation bubbles was observed by high-speed photography. The output energy of the quartz tip ranges from 5 to 50 mJ and the laser pulse duration from 50 isec to 300 p.tsec. The dynamic ofthe evaporation bubbles were investigated for different diameters, various angles and radii ofthe quartz fiber tip. Furthermore, the spread out ofthe evaporation bubbles was observed for various geometries ofthe microsurgery probe. The induced stress waves were measured with a PVDF-hydrophone. Results: The evaporation bubble size increases semi-logarithmic with the pulse energy and reduces with the increase of the pulse duration. The diameter of the tip has no significant influence on the vapor bubble size. The expansion of the vapor bubble can be controlled by the geometry of the tip. The spread out of the vapor bubble can reduced by a slit geometry of the aspiration hole. The maximum pressure amplitude was found to be < 2 MPa. Conclusions: The evolution of evaporation bubbles and the induced pressure amplitudes from the microsurgery probe can be minimized for Erbium:YAG laser vitrectomy. Key words: Erbium:YAG laser, vitrectomy, vapor bubble, evaporation 1