21st-century functional outflow system anatomy for surgeons

The intraocular pressure (IOP) abnormality in glaucoma results from dysfunctional outflow system regulation resulting in IOP elevation. Surgical decisions require knowledge of normal functional anatomy and how it becomes abnormal in glaucoma to target the disease process appropriately. A 19th-century model posits that aqueous move passively downs a pressure gradient with outflow regulation in a narrow region of the trabecular meshwork (TM) at Schlemm’s canal inner wall; the model envisions no dynamic outflow tissue motion or pulsatile flow. Accumulating 21st-century evidence requires a fundamentally different conclusion. Aqueous outflow is regulated by the dynamic motion of the TM coupled to Schlemm’s canal inlet (SIV) and outlet (SOV) valves. The unified system can behave functionally like a lymphatic pump-conduit system. The pressure-dependent location and oscillatory motion of the TM control SC dimensions, and through SIV connections to SOV controls distal outflow. Surgical approaches ideally understand and target all components of the system.