In primary angle-closure glaucoma (PACG), peripheral iridotomy (PI) relieves pupillary block by:

• A Reducing aqueous humour production from the ciliary body
• B Creating an alternate pathway for aqueous to flow from posterior to anterior chamber, bypassing the pupillary block and equalizing pressure across the iris ✓
• C Widening the trabecular meshwork to improve conventional outflow
• D Shrinking the peripheral iris to mechanically deepen the drainage angle

Explanation

Pupillary block — resistance to aqueous flow through the narrow pupil from the posterior to anterior chamber — causes the iris to bow forward (iris bombe), occluding the trabecular meshwork. Peripheral iridotomy creates a full-thickness hole in the peripheral iris through which aqueous can directly pass from the posterior to anterior chamber, bypassing the pupil. This equalizes pressure on both sides of the iris, allowing the iris to fall back and the angle to open. PI is the definitive treatment for all forms of pupillary-block angle closure. It does not affect aqueous production or trabecular function directly.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.