Confined tissue ablation for vitrectomy: a study at FELIX

The Free Electron Laser for Infrared EXperiments (FELIX) Free Electron Laser Facility provides a continuously tunable source ranging continuously through the 4.5 to 200 micron region. The infrared beam consists of short micropulses, which have a nominal duration of 5 ps and are separated by intervals of either 1 ns or 40 ns of zero intensity. The micropulses form a macropulse train with a duration of up to 15 microseconds. The macropulses are repeated every few hundred ms, with a maximum repetition rate of 10 Hz. Previous studies have shown that the combination of this macro / micro pulse structure, coupled with energy output tuned to the vibrational mode of the Amide- band (lambda = 6.45 mum), gives a source well suited to precise tissue ablation. Here the thermal, mechanical and molecular behavior of the ablation was studied. Unlike previous studies, which have concentrated on unconstrained ablation where particles could be ejected from the system at the tissue - air boundary, this experiment simulated the confined ablation necessary during a vitrectomy. It is thought that this is the first study where this has been done, and also the first to study vitreous, which consists of only 2% protein rather than the 20% present in corneal tissue for example