Study of corneal ablation with picosecond laser pulses at 211 nm and 263 nm.

BACKGROUND AND OBJECTIVE

Corneal ablation has been studied by picosecond laser pulses in the far-UV region.

STUDY DESIGN/MATERIALS AND METHODS: Laser pulses of 25 ps duration at 211 nm and 263 nm wavelengths and a 1 kHz repetition rate have been used to ablate human and rabbit corneas. The dependence of the etch rate on laser fluence has been measured at both wavelengths. The collateral tissue damage has been investigated by electron microscopy.

RESULTS

The ablation threshold for human cornea is determined to be about 3.0 mJ/cm2 at 211 nm, while the thresholds for rabbit cornea are about 2.3 mJ/cm2 at 211 nm and 8.0 mJ/cm2 at 263 nm. The slopes of the ablation curves and the dimensions of the damage zones have also been determined.

CONCLUSION

We compare these results to the existing data on corneal ablation by nanosecond UV pulses and discuss the deficiency of the photochemical model. Experimental results are analyzed in terms of a model that features plasma ablation assisted by chromophore absorption.