Histopathological study of trabeculum after excimer laser trabeculectomy ab interno

To study the clinical manifestations and histopathologic changes of trabeculum after excimer laser trabeculectomy ab interno (ELT), and to investigate the mechanisms of ELT in reducing intraocular pressure.

ELT was performed on ten rabbit eyes and postoperative responses were documented. Corneoscleral tissue samples were harvested consecutively each week until the 5th postoperative week and these samples were examined under light and electrical microscopy.

Mild stimulation signs were present postoperatively in nine of ten eyes, but no serious complications were experienced. Obvious inflammation was observed in one rabbit eye as a result of iris damage during the surgical manipulations. Local fractures on the trabecular meshwork and openings into Schlemm's canal were detected in all tissue samples under light microscope. Mitochondria were found to be turgescent and dilated like vacuoles and endoplasmic reticula were found to be dilated under electrical microscope in the early postoperative period. Later, all trabecular cells returned normal and no fibroblast cells were ever detected.

Permanent openings through trabecular meshwork into the inner wall of Schlemm's canal can be created with ELT. The outflow resistance of aqueous humor can be reduced with these openings and intraocular pressure can be controlled thereafter.