Mid‐Infrared laser ablation of the cornea: A comparative study

The ablation thresholds and patterns of collateral damage in cornea produced by Er:YAG (2.94 μm) and Er:YSGG (2.79 μm) lasers were measured. Two different pulse durations, 200 μs (normal spiking mode) and 100 ns (Q–switched mode), were used at both wavelengths. In the normal spiking mode, damage zones of 16 ± 2 μm and 39 ± 7 μm and ablation thresholds of 250 ± 20 mJ/cm 2 and 420 ± 35 mJ/cm 2 were measured at 2.94 μm and 2.79 μm, respectively. In the Q–switched mode, damage zones of 4 ± 2 μm and ablation thresholds of 150 ± 10 mJ/cm 2 were found irrespective of the laser used. The similarity between the results using the Er:YAG and Er:YSGG lasers in the Q–switched mode suggest that either laser can be used with equal effectiveness for corneal trephination. © 1992 Wiley‐Liss, Inc.