What is the role of the trabecular meshwork and Schlemm's canal in intraocular pressure regulation?

• A. Aqueous humor drains from the posterior chamber through the retina.
• B. Aqueous humor drains from the anterior chamber via the trabecular meshwork into Schlemm's canal; resistance to outflow regulates intraocular pressure, and impaired drainage can cause glaucoma.
• C. The choroid drains aqueous humor via the scleral venous network.
• D. Aqueous humor is produced by Schlemm's canal.

Answer: (B)

Understanding intraocular pressure relies on how the eye drains aqueous humor. Aqueous humor is produced by the ciliary body into the posterior chamber, then flows into the anterior chamber and exits mainly through the trabecular meshwork into Schlemm's canal, finally reaching the venous system. The resistance to outflow that occurs at the trabecular meshwork and the inner wall of Schlemm's canal sets how easily fluid leaves the eye; higher resistance lowers outflow and raises intraocular pressure. If drainage is impaired, IOP increases and optic nerve risk glaucoma. (The alternative uveoscleral route exists but is less significant for regulation, and Schlemm's canal is a drainage vessel, not a producer of aqueous humor.)