Objective: To study the anatomic background of non-penetrating trabecular surgery (NPTS) and to explore the resistant site of aqueous outflow in primary open-angle glaucoma.
Methods: NPTS was performed in 18 eyes of 12 cases (10 males, 2 females) with POAG. The age of these patients ranged from 42 to 65 years old. The deep scleral flap and external trabecular membrane were obtained during the surgical procedure and were examined by light microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM).
Results: The beginning part of the collection canal in the outer wall of the Schlemm's canal were very narrow, and there was electron dense material (so-called plaques) around the outer wall of the Schlemm's canal. The external trabecular membrane consisted of adjacent trabecular meshwork and part of the corneoscleral trabecular meshwork. The number of the trabecular cells was decreased and a large amount of electron dense materials were deposited in the adjacent trabecular meshwork. The holes of the corneoscleral trabecular meshwork was small and irregular. In the corneoscleral trabecular meshwork, the trabecular lamellae was thicken, the amount of elastic-like fibers was increased and the trabecular cells, especially the nucleus, were enlarged. In the advanced stage of POAG, a great amount of electron dense material was deposited in the corneoscleral trabecular meshwork and the inter-trabecular spaces was blocked.
Conclusions: The deep scleral flap of NPTS contains the outer wall of Schlemm's canal and the external trabecular membrane, which consists of the inner wall of the Schlemm's canal, the adjacent trabecular meshwork and part of the corneoscleral trabecular meshwork. The main resistant site of aqueous outflow in POAG lies in the adjacent trabecular meshwork and in part of the corneoscleral trabecular meshwork. The outer wall of the Schlemm's canal is another important resistant site for aqueous outflow.