Aqueous Humor Production and Drainage: Physiology
Authors: Natalie Arnold, Graeme Prosperi-Porta Reviewers: Paige Shelemey, Crystal Liu, Bill Stell* * MD at time of publication
Blood plasma passes through fenestrated capillary walls in the ciliary body
Anterior ciliary body produce aqueous humor (AH) through combined hydrostatic pressure + active transport
AH enters the posterior chamber
AH flows around the lens through the pupil into the anterior chamber
Temperature gradient cause aqueous humor to flow convectively: downwards at the cornea (colder, fluid denser); upwards at lens (warmer)
Abbreviations:
• AH – Aqueous Humor
• TM – Trabecular Meshwork
Provides nutrition, removes wastes, and transports neurotransmitters to the avascular lens and cornea.
Circulates inflammatory cells to avascular structures
Maintains structural integrity of ocular structures via intraocular pressure (10-21 mmHg)
AH leaves the anterior chamber via two pathways located near the limbus
Limbus
Trabecular Meshwork Pathway (~60-80 % of flow)
AH passes through the TM layers: Uveal, corneoscleral, and juxtacanalicular
Flows into Schlemm’s Canal
Flows through internal outflow channels into the external outflow channels, aqueous veins, intrascleral venous plexus, and the deep scleral venous plexus
Drains into the episcleral and conjunctival veins
Uveoscleral Pathway (~20-40 % of flow)
AH enters uveal meshwork and anterior ciliary body
Flows in suprachoroidal space
Passes outward through the sclera
Enters the scleral, and conjunctival veins
Drains back into systemic venous circulation
Inflow
Trabecular Outflow
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published January 19, 2020 on www.thecalgaryguide.com