Aqueous humor exits the anterior chamber via two primary routes: the conventional trabecular pathway and the unconventional (uveoscleral) outflow pathway. Intraocular pressure is primarily determined by resistance to outflow within the trabecular pathway. Most of this resistance is localized to the inner wall region, comprising the juxtacanalicular connective tissue and the inner wall endothelium of Schlemm’s canal. Resistance at this site is dynamically regulated by contractile, myofibroblast-like cells within the trabecular meshwork and the adjacent scleral spur, as well as through tension generated by the ciliary muscle. Additional, albeit lower, resistance also occurs distally along the trabecular outflow tract beyond the inner wall region. In patients with primary open-angle glaucoma and elevated intraocular pressure, trabecular outflow resistance is significantly increased. The pathological changes are spatially confined to within approximately 1 μm of Schlemm’s canal’s inner wall, coinciding with the region of cell–matrix interactions in the cribriform plexus. Experimental studies in genetically engineered mouse models indicate that this elevated resistance is driven by increased activity of the transforming growth factor-beta signaling cascade and its downstream mediators, notably CCN2/CTGF. The molecular alterations likely contribute to extracellular matrix remodeling and increased tissue stiffness, impairing outflow facility.