[Comparative study of ab-externo sclerostomy with the excimer and Er:YAG laser].

The specific ablative effect of pulsed 308 nm XeCl-excimer laser radiation (4 mJ 80 Hz) on the tissue has proved its worth in clinical use in glaucoma patients. However, the cytotoxic and mutagenic photochemical reactions induced by intraocular ultraviolet irradiation could theoretically be cataractogenic and retinotoxic. Unlike the excimer laser technique, ab externo sclerostomy with the Er:YAG laser (2940 nm/11 mJ, 7 Hz) excludes these risks. Histological and scanning electron microscope analysis of pig eyes showed thin, and smoothly limited zones of necrosis and only minimal irritation of the adjacent tissue and a slightly wavy surface. A newly developed handpiece for the Er:YAG laser enables energy transport via zirconium fluoride fiber and coupling to a quartz fiber tip with a core diameter of 320 microns. Er:YAG laser sclerostomy has so far been performed on 16 eyes in which the average preoperative IOP was 29 mmHg. The procedure took only a few minutes and the patients reported feeling no pain although retrobulbar anesthesia was not induced. The postoperative average IOP was less than 20 mmHg after 6 weeks and for the rest of a maximum observation period of 12 weeks. Reoperation was necessary in 2 cases. Er:YAG laser ab externo sclerostomy could be another alternative for the operative therapy of glaucoma.