Erbium : YAG laser vitrectomy - temperature measurements in different replacement materials

Background:The erbium:YAG laser has the potential of being used routinely f or vitrectomy because of the excellent quality of liquefying vitreous struc tures and the low vacuum forces required. However, the use of silicone oil and perfluorocarbon may lead to unwanted temperature increases in the micro surgery probe. The aim of this work was to investigate this side effect. Materials and methods: Different replacement materials such as water, metho cel, silicone oil and perfluorocarbone were used in a simple eye model. The temperature increase during laser application was measured by means of the rmocouples. The maximum temperature increase and time decay were derived wi th and without aspiration from these time-resolved measurements. The averag e power at the distal end of the microsurgery probe was chosen to be 1 W. Results: The temperature increase with aspiration in water was found to be significantly smaller than all other replacement materials. Interruption of aspiration leads to a critical temperature increase of approximately 14 K; however, this increase occurred very slowly (decay time 200 s). A comparab le result could be observed for methocel, which was used to simulate conden sed vitreous structures. In perfluorocarbon and silicone oil we measured a far higher increase in temperature of up to 130 K within a few seconds. Fur thermore, small remnants of carbonizd materials can be seen in the microsur gery probe after laser application. Conclusions: The temperature increase during erbium:YAG laser vitrectomy in water can be considered to be harmless for other intraocular structures. H owever, insufficient aspiration or increased vitreous condensation leads to increased temperature in the microsurgery probe. Our results demonstrate t hat the use of erbium:YAG laser vitrectomy in materials such as silicone oi l or perfluorocarbons is contraindicated.