[Cavitation bubble formation during Erbium:YAG laser vitrectomy].
BACKGROUND
Clinical and experimental studies demonstrated the potential advantages of Erbium:YAG laser vitrectomy for posterior segment surgery. However, a detailed knowledge on the laser-tissue interaction is needed for an optimization of new ophthalmic applications. The aim of this experimental work was to investigate the cavitation bubble formation during Erbium:YAG laser vitrectomy and to find optimized laser parameters and the best geometry of the aspiration port of the microsurgical probe.


METHODS
We investigated the formation of cavitation bubbles in water by high-speed photography. The output energy at the quartz tip reached up to 50 mJ and the laser pulse duration ranged from 50 to 300 microseconds. Various commercially available microsurgery probes were investigated regarding the extent of the cavitation bubbles.


RESULTS
The threshold for laser-induced cavitation bubble formation was found to be 0.32 +/- 0.1 mJ for a laser pulse duration of 130 microseconds and a core diameter of 320 microns of the quartz fiber tip. The length of the cavitation bubbles increases with the laser pulse energy up to a length of 1.6 mm at a pulse energy of 10 mJ. In contrast, the size of the vapor bubbles decreases with an increase of the laser pulse duration. A slit-shaped aspiration port led to a 50% smaller volume of the cavitation bubble exiting the port compared with a circular aspiration port.


CONCLUSIONS
The optimized laser parameters and microsurgery probe geometry may significantly decrease the risk of intraoperative ocular damages during Erbium:YAG laser vitrectomy.
Universitäts-Spital Zürich, Augenklinik, Frauenklinikstrasse 24, CH-8091 Zürich. michael.mrochen@aug.usz.ch
M
M
Mrochen
P
P
Riedel
C
C
Donitzky
T
T
Seiler
D000818:Animals; D004871:Erbium; D006801:Humans; D053685:Laser Therapy / Q000379:methods*; D010781:Photography / Q000379:methods; D014821:Vitrectomy / Q000379:methods*; D015019:Yttrium
D015019:Yttrium; D004871:Erbium