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

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 pm2. 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) ,um. The total number of pores is about 20,000. Calculations show that if all the observed pores exist in vivo, the resistance t o outflow in the paths through the endothelial cells is a small fraction of the total resistance to outflow.

Mechanism of Aqueous Humor Secretion, Its Regulation and Relevance to Glaucoma

“…The inner side of the canal is formed by 3 layers of the trabecular meshwork. The first layer is the uveal meshwork, which is the forward extension of the ciliary muscle inserting in the cornea (Bill and Svedbergh, 1972). The second layer is constituted by several sheets of connective tissue extending between the scleral spur and the peripheral cornea.…”

A model to measure lymphatic drainage from the eye

“…From here, it drains into the lumen of Schlemm"s canal, which serves as a collector channel that leads to the episcleral venous system, allowing for aqueous humor to enter the blood. Fluid movement is via a pressure-dependent transcellular mechanism, frequently associated with paracellular routes such as giant vacuoles and pores acting as one-way valves (Bill and Svedbergh, 1972).…”

Effect of Low Fluence Diode Laser Irradiation on the Hydraulic Conductivity of Perfused Trabecular Meshwork Endothelial Cell Monolayers

“…[52][53][54][55][56][57][58][59][60][61] The question of where the primary resistance to outflow takes place has been studied with various models since 1958. [52][53][54][55]60,[92][93][94][95] In vivo, the aqueous percolates in and around the trabecular beams, driven by the IOP, until it reaches the JCT and IW endothelium that lines the inner wall of Schlemm's canal. The JCT and IW endothelium form the only occlusive structures that fluid must actually flow across as it enters Schlemm's canal.…”