[Experimental laser sclerostomy ab externo with erbium:YAG laser]

A fistula from the anterior chamber of the eye into the subconjunctival space can be created by external laser application (laser sclerostomy). A pulsed (200 microseconds) Erbium-YAG laser was used because of the high scleral absorption. The laser energy was applied via a special fiber, which was inserted into a special application cannula to guide it into the subconjunctival space. A total of 24 rabbit eyes were treated and examined histologically after various postoperative periods. In all cases a functioning fistula and a marked reduction of the IOP (mean value 13 mmHg to 2 mmHg) were detected. On average, 60 mJ was required. The zone of thermal damage was limited to 40 microns. Cornea and lens showed no evidence of damage after 1 day or after 4 weeks. In the rabbit model, the fistulas were closed within 2 weeks, and long-term persistence of the fistula must therefore be verified in a clinical study. The method presented is minimally invasive, requires only a short operation time, causes minimal trauma to the conjunctiva, and may become an alternative to traditional fistulization operations.