CORRECTION OF MYOPIA WITH ER-YAG LASER FUNDAMENTAL MODE PHOTOREFRACTIVE KERATECTOMY

BACKGROUND: Photorefractive keratectomy (PRE) has been performed with the ultraviolet 193 nm radiation of the excimer laser. Due to its high absorption in water (3 mu m water absorption band), the Er:YAG's 2.94 mu m wavelength in the midinfrared also qualifies for photoablation. METHODS: A new laser source, providing an output energy of 2.6 J (mult imode) and 380 mJ in the fundamental mode, was used to perform corneal areal ablation (large) in two blind human eyes eccentrically. The fun damental mode provided a Gaussian-shaped beam profile, able to ablate more tissue centrally, depending on the fluence applied. RESULTS: The visible ablation diameter (opaque area) at the corneal surface was abo ut 5 mm. Its effective ablation diameter was 4.85 +/- 0.2 mm. The maxi mal ablation depth was 155 +/- 5 mu m. Surface roughness was 0.73 +/- 0.06 mu m, as assessed by a corneal silicone replica and subsequent co nfocal laser topometry. Intraoperatively, the ablation site turned opa que, clearing after a couple of minutes. The resultant surface was rou gh; epithelization was uneven but not delayed. Postoperative pain was reported to be minimal. Subepithelial reactions were comparable to a 3 + haze and showed bubble-like inclusions, which slowly disappeared. By week 4, the corneal surface was even; a 1+ subepithelium haze persist ed in case 1, while a clear ablation site was seen in ease 2. CONCLUSI ON: Areal corneal ablation with an Er:YAG laser that emits mid-infrare d wavelengths seems possible. Although the thermally induced collatera l damage is more pronounced, the wound healing pattern is comparable t o 193 nm PRK. This preliminary result has to be confirmed in normal ey es.