Trabecular Meshwork Movement Controls Distal Valves and Chambers: New Glaucoma Medical and Surgical Targets.

Area of Science:

• Ophthalmology
• Fluid Dynamics
• Biomedical Engineering

Background:

• Aqueous humor outflow regulation is crucial for maintaining intraocular pressure.
• The precise mechanism of human aqueous outflow has been debated.
• Previous models lacked direct observational evidence in humans.

Purpose of the Study:

• To investigate the mechanism of human aqueous humor outflow.
• To identify the role of Schlemm's canal and trabecular meshwork in outflow regulation.
• To compare outflow dynamics in healthy versus glaucomatous eyes.

Main Methods:

• Direct observation of aqueous flow using microscopy and advanced imaging techniques.
• High-resolution swept-source optical coherence tomography (SD-OCT) to quantify valve dynamics.
• Phase-sensitive OCT (PhS-OCT) to measure nanometer-level tissue motion in human subjects.

Main Results:

• Evidence of pulsatile aqueous flow into and out of Schlemm's canal, involving valves.
• The trabecular meshwork acts as a mobile chamber wall, linked to intraocular pressure.
• Glaucomatous tissue exhibits stiffening and reduced motion, with decreased movement in patients.

Conclusions:

• Human aqueous outflow functions via a pump-conduit system, analogous to lymphatic drainage.
• A sensory-motor baroreceptor-like function regulates intraocular pressure homeostasis.
• Impaired outflow dynamics and tissue stiffening in glaucoma are directly observed and quantified.