Histopathological study of trabecular meshwork after trabeculotomy in monkeys

: Trabeculotomy is a commonly indicated surgical procedure for primary open angle glaucoma and congenital glaucoma. In order to clarify the mechanisms of lowering the intraocular pressure (IOP) following the intervention, we performed this procedure in monkey eyes, and did postoperative histopathological examinations using light microscopy, and scanning and transmission electronmicroscopy for trabecular mesh work specimens incised at various time intervals up to one year after operation. Immediately after the operation, a direct communication was seen between the Schlemm's canal and the anterior chamber. Subsequently, the repairing process of trabecular tissue occurred initially in the corneoscleral and endothelial meshwork and finally in the uveal meshwork. At one year after operation the chamber angle was almost completely repaired by newly-formed trabecular tissue which was identical to the normal trabecular tissue. There was no direct communication between the Schlemm's canal and anterior chamber at that time. These results suggest that the decreased resistance for the aqueous outflow might be caused by direct communication between the Schlemm's canal and anterior chamber at an early postoperative stage, and the repairing process of the endothelial meshwork increases the resistance of aqueous outflow.