The Schlemm canal is a circular tube that closely resembles a lymphatic vessel. It is formed by a continuous monolayer of nonfenestrated endothelium and a thin connective tissue wall. The basement membrane of the endothelium is poorly defined. The lateral walls of the endothelial cells are joined by tight junctions. Micropinocytotic vesicles are present at the apical and basal surfaces of the cells. Larger vesicles (so-called giant vacuoles) have been observed along the internal canal wall (Fig 2-16). These vacuoles are lined by a single membrane, and their size and number are increased by a rise in intraocular pressure. They are thought to contribute to the pressure-dependent outflow of the aqueous humor. In one form of microinvasive glaucoma surgery (MIGS), a microstent is implanted in the Schlemm canal to bypass the trabecular meshwork, the point of greatest outflow resistance, thereby increasing aqueous outflow.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.