Free running erbium:YAG laser for nonmechanical trephination in penetrating keratoplasty: First results of experimental trephination of human donor corneas

Background: A study was carried out to evaluate the potential suitability of a free-running erbium:YAG 2.94-μm laser for trephina tion of human corneas in penetrating keratoplasty. Methods: Two human donor corneas were placed in an artificial anterior chamber and moved with an automated rotation device (one rotation per minute). An erbium:YAG laser beam (pulse duration 400 μs, repetition rate 2/s, energy density 2.5 and 15.0 J/cm²) was focused on the outer edge of a round ceramic mask placed on the human donor corneas for ablation of tissue. Results: With a fluence of 15.0 J/cm², perforation was achieved after 500 pulses. Perpendicular central cut edges with mild stromal ridges and, by light microscopy, a 12 to 45-μm area of stromal thermal effects and focal endothelial changes up to 200 μm central to trephination were observed. Conclusions: The erbium:YAG laser could be a promising 'low-cost alternative' to the excimer laser for nonmechanical trephination in penetrating keratoplasty. Further studies will have to focus on reduction of thermal damage and on wound healing.