In POAG, which anatomical structures are involved in aqueous humor outflow that may be impaired?

• A. Iris and cornea
• B. Retina and optic nerve
• C. Trabecular meshwork and Canal of Schlemm
• D. Lens and ciliary body

Answer: (C)

Aqueous humor outflow in primary open-angle glaucoma mainly occurs through the conventional drainage pathway, which includes the trabecular meshwork and Schlemm’s canal. The trabecular meshwork acts like a filter at the junction where the aqueous humor leaves the anterior chamber, guiding it into Schlemm’s canal, and from there into the episcleral veins. If this pathway develops increased resistance or dysfunction, outflow diminishes and intraocular pressure rises, which is central to POAG. The iris and cornea are anterior segment structures involved in light entry and refraction, not the drainage channels. The retina and optic nerve are the tissues affected by elevated pressure, not the outflow route itself. The lens and ciliary body relate more to accommodation and aqueous production rather than drainage, though they are part of the overall anterior segment anatomy. The uveoscleral route exists as a secondary outflow pathway, but POAG predominantly involves the trabecular meshwork–Schlemm’s canal route.