| Abstract [eng] |
Femtosecond laser in situ keratomileusis (LASIK) is performed using two laser sources: a femtosecond solid-state laser (wavelength ~1000 nm) for flap creation and a nanosecond ultraviolet (UV), usually excimer, laser (~200 nm) for stromal ablation. The Pharos femtosecond solid-state system (Light Conversion Ltd., Vilnius, Lithuania) with a fifth harmonic generator allows both flap cutting and stromal ablation. The purpose of the study was to optimize and characterize a novel method of corneal stromal ablation based on high repetition rate femtosecond UV pulses at a wavelength of 206 nm using in vivo model. Surgery was performed in 81 rabbit. The quality of ablation and healing outcomes were evaluated for different repetition rates (20 and 50 kHz), power levels (200 and 400 mW), spot sizes (280 and 130 μm) and ablation depths. In comparison, ablation with nanosecond excimer UV pulses was performed. Despite huge difference in peak intensity, the healing outcomes were comparable. When applying maximal power (400 mW), the ablation speed comparable to the fastest reported ablation speed in human corneas using only high-fidelity regime was achieved. Smaller spots and high repetition rates support finer ablation profiles for custom treatment. Longer wavelength used in our study (206 nm) is less absorbed by BSS than the 193 nm excimer laser radiation, thus, the hydration level of the stroma has less influence on the ablation rate. |
