Corneal perforation during laser in situ keratomileusis.

Two cases of corneal perforation that occurred during laser ablation but not during flap formation in laser in situ keratomileusis (LASIK) are reported. In the first case, no problem in flap formation occurred, and stromal bed thickness was assumed to be about 239 microns after laser application. However, a stromal bed perforation was found when 608 pulses were applied (theoretical ablation depth was 140 microns). Excessive dehydration due to prolonged exposure to the operating microscope light may change the ablation rate and cause corneal perforation. In the second case, LASIK retreatment was performed using the original flap for correction of regressed myopia (-4.0 diopters). Although the stromal bed thickness was assumed to be about 175 microns after the laser application, a stromal bed perforation was found when 151 pulses were applied (theoretical ablation depth was 37 microns). Unexpected corneal ectasia after the first LASIK treatment may cause a corneal perforation in LASIK retreatment. In conclusion, excessive dehydration of the cornea should be avoided, and careful examination of the corneal shape is necessary to prevent corneal perforation during laser ablation in LASIK.