[Current status of infrared photoablation of the cornea]

Abstract

Background: IR-photothermal ablation has, for some time, been described as an alternative to UV photoablation with Excimer lasers. Both procedures are based on different laser-tissue-interactions. IR solid state lasers have cost advantages over UV laser technology and allow a broader clinical use. New beam shaping principals had to be developed. IN-VITRO: Systematic biophysical investigations, recently using tunable Free Electron Lasers, have described the ablation efficiency, the collateral thermal adverse effects, the surface properties and particle size, and the dynamic behaviour of the particle ejection, all as a function of wavelengths (and thus of different absorbers in the corneal tissue), of energy and of different pulselengths. The free running Er:YAG laser is suitable and well investigated, the optic parametrical oscillator (OPO) with supershort pulses a more recent alternative.

In vivo: First in vivo photoablation with different Er:YAG lasers has proved the principle feasibility of IR photoablation. Histology of enucleated human eyes indicates that the wound healing and repair after IR photoablation is not principally different from UV-PRK. The evaluation of the achievable optical quality of the cornea in vivo as well as data on the stability resp. regression of the ablation profiles are still pending.