Modeling of erbium: YAG laser-mediated explosive photovaporization: implications for vitreoretinal surgery.

Overview

BACKGROUND AND OBJECTIVE: Motivated by the potential for highly precise tissue removal, investigators are exploring fiberoptic microsurgical maneuvers with the erbium:YAG (Er:YAG) laser. Tissue is disrupted and removed by direct ablation and the acousto-mechanical sequelae of explosive vaporization of the tissue water. The authors investigated the scaling laws for photoablative and photodisruptive interactions and interpreted these results to optimize energy delivery for vitreoretinal surgical maneuvers. MATERIALS AND METHODS: A model for laser-generated-bubble expansion is presented based on energy principles and adiabatic gas expansion. Comparisons are made with the authors' previous studies of ablation rate and thermometry. RESULTS: The authors' modeling studies generated predictions similar to experimental data. The maximum bubble diameter increases as the cube root of the pulse energy. At constant radiant exposure, the maximum bubble diameter increases as the probe tip diameter raised to the two-thirds power. The authors demonstrated that tissue ablation depends on radiant exposure (J/cm2), whereas temperature increases, bubble size, and peak pressure depend on total pulse energy. CONCLUSIONS: Mechanical injury should be minimized and efficient ablation preserved by delivering low-pulse energy through small-diameter probe tips at high repetition rates.