[Photo-ablation of the cornea with the erbium:YAG laser].

BACKGROUND

Ablation experiments and preclinical studies have shown increased thermal damage and surface roughness after photorefractive keratectomy (PRK) with the erbium: YAG laser.

MATERIALS AND METHODS

In this study, the thermal damage was investigated on enucleated pig corneas for various laser pulse durations (80 ns to 1 ms) and radiant exposures (0.2-5 J/cm2). The "scanning-spot" method and the fundamental mode photo-ablation were used for spherical corrections. SEM pictures and surface roughness measurements enabled comparison with the morphology after ArF-excimer laser treatment. The surface roughness is one order of magnitude higher compared to the ArF-excimer laser ablation. The surface of the tissue after ablation looks melted.

RESULTS

The thermal damage reduces with increased intensity, and at high intensities the thermal damage results in a constant thickness of > 5 microns.

CONCLUSIONS

Laser-induced melting processes might be the main reason for the high thermal damage and the increased surface roughness after erbium: YAG laser treatment. This leads to the conclusion that the erbium: YAG laser is not a real alternative to the ArF-excimer laser in PRK.