Laser-grid trabeculectomy in rabbits: an experimental in-vivo study

Background: Laser-grid trabeculectomy (TE) is a modification of micro-TE designed to enhance the intra- and postoperative safety of filtering surgery by creating several small oval fistulas (max. diameter <200 mu m) beneath a scleral flap without peripheral iridectomy. Methods: After dissecting the conjunctiva and a conventional scleral flap, 10 small perforating fistulas were created in five pigmented rabbits in the region of the gray-white border using an erbium:YAG laser with a beveled side-firing 200 pm endoprobe; conventional TE with iridectomy was performed in another five animals. Anterior chamber inspection and IOP measurements of both eyes were conducted on days 1, 4, and 14 after operation. After the last inspection eyes were saved for morphological analysis. Results: Both procedures (laser-grid and conventional TE) led to a reduction of intraocular pressure in the treated eye compared to the control eye. Differences between the outcomes for the two procedures were not statistically significant. Morphology of the eyes treated by laser-grid TE revealed dense scarring of perforations around the center of the ligamenta pectinata and loose tissue refilling of the more peripheral openings. Conclusions: The functional outcome of laser-grid TE in rabbits was similar to that of conventional TE in the short term. Histological examination of microperforations in the area of the trabecular meshwork after 2 weeks indicated that tissue repair was less pronounced than in the more anterior perforations. This morphologic finding may be of importance for non-penetrating glaucoma surgery.