Anterior and posterior parts of human trabecular meshwork.

From gonioscopic observations, the trabecular meshwork was tentatively divided into anterior and posterior parts. The anterior part was defined as the zone from the Schwalbe's line to the anterior edge of the Schlemm's canal, and the posterior part was from the anterior edge of the Schlemm's canal to the angle recess. The patients' own blood cells were injected into the anterior chamber of two eyes about to be enucleated due to malignant tumors, and cell distribution in the trabecular meshwork was examined histologically. Blood cells in the posterior part of the trabecular meshwork were numerous, particularly in the area adjacent to the Schlemm's canal and anterior to the ciliary muscle at the angle recess, yet only a few cells were seen in the anterior part. At the angle recess, the blood cells accumulated in the perivascular connective tissue of the major arterial circle of the iris. These observations suggest that the posterior part of the trabecular meshwork is the most important for aqueous humor drainage in the human eye, both with regard to the conventional and unconventional routes, while the anterior part plays a lesser role in the aqueous outflow. It is also suggested that some proportion of the aqueous humor entering the tissues at the angle recess may flow through the perivascular tissue of the major arterial circle of the iris.