1Kampmeier J., 2Stock K., 2Hibst R., 1Lang G. E., 2Steiner R., 1Lang G. K.

1Department of Ophthalmology, University of Ulm, Germany; 2Institut für Lasertechnologien in der Medizin und Meßtechnik, Ulm, Germany

Purpose: To develop a new ab-externo technique for glaucoma trabecular surgery using the infrared Er:YAG laser radiation (2.9 µm) guided into Schlemm's canal by an optical fiber.
Material and methods: In order to perform a draining canal to the anterior chamber a quartz fiber (core diameter: 100 µm), coupled to an Er:YAG laser, was shielded by a metal canula (diameter: 280 µm) bent in accordance with the Schlemm's canal curvature. A 45°-mirror enabled the laser radiation to exit the canula perpendicular to the fiber axis. The complete surgery device was tested on agar medium and enucleated human eyes including gonioscopy.
Results: Using the unshielded quartz fiber eight pulses of 8 mJ (frequency: 7 Hz, pulse duration: 150 µs) were sufficient to perforate the trabecular meshwork of the human eye. Histology showed a rippled canal with 50 µm average diameter and a surrounding necrosis zone of 15-35 µm. The complete device could be easily inserted into Schlemm's canal similar to the classic trabeculostomy probe and a conical shaped canal with a length of 2-3 mm could be created in agar medium within a few seconds.
Conclusions: First experiences in an experimental setup show the ab externo creation of a draining canal between Schlemm's canal and the anterior chamber with only minimal irritation of the surrounding tissue. Further refinements of the laser parameters and the biomechanical setup lead to a new handheld device of improved function. The Er:YAG laser intracanalicular trabeculostomy might become a new "ab externo" technique for minimal invasive therapy of open angle glaucoma.
DFG - KA 1584/1-1

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