In primary angle-closure glaucoma, which of the following mechanisms is responsible for the relative pupillary block leading to iris bombe?
- A Increased aqueous production by ciliary epithelium
- B Resistance to aqueous flow at the pupillary margin between lens and posterior iris ✓
- C Obstruction of episcleral venous drainage
- D Trabecular meshwork collapse from zonular laxity
Correct answer: B. Resistance to aqueous flow at the pupillary margin between lens and posterior iris
Explanation
In relative pupillary block, aqueous accumulates in the posterior chamber because the posterior iris surface contacts the anterior lens surface, creating resistance to forward flow through the pupil. This pressure differential bows the peripheral iris anteriorly (iris bombe), appositionally closing the angle. Increased aqueous production and episcleral venous obstruction do not explain the angular closure mechanism.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.