Correction of Myopia With Er:YAG Laser Fundamental Mode Photorefractive Keratectomy

Abstract

ABSTRACT BACKGROUND: Photorefractive keratectomy (PRK) has been performed with the ultraviolet 193 run radiation of the excimer laser. Due to its high absorption in water (3 µm water absorption band), the Er:YAG's 2.94 µm wavelength in the mid-infrared also qualifies for photoablation. METHODS: A new laser source, providing an output energy of 2.6 J (multimode) and 380 mJ in the fundamental mode, was used to perform corneal areal ablation (large) in two blind human eyes eccentrically. The fundamental 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 about 5 mm. Its effective ablation diameter was 4.85 ± 0.2 mm. The maximal ablation depth was 155 ± 5 µm. Surface roughness was 0.73 ± 0.06 µm, as assessed by a corneal silicone replica and subsequent confocal laser topometry. Intraoperatively, the ablation site turned opaque, clearing after a couple of minutes. The resultant surface was rough; 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 persisted in case 1, while a clear ablation site was seen in case 2. CONCLUSION: Areal corneal ablation with an Er:YAG laser that emits mid-infrared wavelengths seems possible. Although the thermally induced collateral damage is more pronounced, the wound healing pattern is comparable to 193 am PRK. This preliminary result has to be confirmed in normal eyes. [J Refract Surg. 1995;11:392-396.]