SCANNING ELECTRON MICROSCOPIC STUDIES OF THE TRABECULAR MESHWORK AND THE CANAL OF SCHLEMM ‐ AN ATTEMPT TO LOCALIZE THE MAIN RESISTANCE TO OUTFLOW OF AQUEOUS HUMOR IN MAN

TLDR

Scanning electron microscopy of human trabecular meshwork and Schlemm’s canal revealed that the inner‑wall endothelial cells are long, slender, oriented along the lumen, cover about 480 µm² each, number roughly 23,000, and possess around 20,000 pores up to 3–5 µm in diameter. Calculations indicate that the resistance to aqueous humor outflow through the endothelial cell pores is only a small fraction of the overall outflow resistance.

Abstract

Chamber angle tissue from human eyes was investigated with scanning electron microscopy. The uveal and corneoscleral parts of the trabecular meshwork are described. The endothelial cells of the inner wall of Schlemm's canal arc long and slender and, at most places, are oriented along the lumen of the canal. The average projected surface of a cell towards the canal is about 480 μm 2 . The total number of endothelial cells in the inner wall of the canal is about 23,000. The cells have pores with diameters up to 3(5) μm. The total number of pores is about 20,000. Calculations show that if all the observed pores exist in vivo , the resistance to outflow in the paths through the endothelial cells is a small fraction of the total resistance to outflow.