Ablation rate of human corneal epithelium and Bowman's layer with the excimer laser (193 nm)

Laser keratomileusis is a laser-specific procedure whereby a layer of corneal tissue as thin as 10 microns or more is removed from the anterior surface. In most cases, the laser ablates not only Bowman's layer but also portions of the anterior stroma. The histologic evaluation presented shows that the ablation behavior of these two layers is not uniform: at a fluence of 205 mJ/cm2 in Bowman's layer, the ablation rate was 0.38 +/- 0.05 microns per pulse, whereas in stroma it amounted to 0.55 +/- 0.1 microns per pulse. In epithelium, the ablation rate was 0.68 +/- 0.15 microns per pulse, but decreased with deeper excisions. We discuss the consequences of these different ablation rates on the procedure of laser keratomileusis.