During screening for angle-closure risk in a 52-year-old Indian woman with hyperopia, you identify several anatomical features. Which is the most common site of angle closure in primary angle-closure glaucoma?

Explanation

## Site of Angle Closure in Primary Angle-Closure Glaucoma **Key Point:** The **superior angle** is the most common site of initial angle closure in primary angle-closure glaucoma (PACG). This is well-established in standard ophthalmology texts and is attributable to specific anatomical features of the superior quadrant. ### Anatomical Basis for Superior Angle Closure 1. **Thicker peripheral iris superiorly** — The superior iris is anatomically thicker and more convex, predisposing it to apposition against the trabecular meshwork 2. **More anterior ciliary body insertion** — The ciliary body inserts more anteriorly in the superior quadrant, narrowing the angle recess 3. **Lens vault effect** — The superior lens equator is closer to the iris, augmenting pupillary block superiorly 4. **Gravity-independent mechanism** — Unlike inferior pooling of aqueous, superior closure is driven by structural crowding rather than positional factors ### Quadrant-Specific Angle Characteristics | Quadrant | Typical Width | Closure Sequence | Clinical Significance | |----------|--------------|-----------------|----------------------| | Superior | Narrowest | **First to close** | **Most common site** | | Inferior | Intermediate | Second to close | Follows superior closure | | Nasal | Intermediate | Third to close | Less frequent initial site | | Temporal | Widest | Last to close | Often remains open | **Mnemonic:** **SINT** — Superior closes first, Inferior second, Nasal third, Temporal last. ### Clinical Implications **High-Yield:** On gonioscopy in PACG, the superior angle typically shows the most advanced closure. Because the superior angle is partially obscured by the upper lid during routine gonioscopy, it requires deliberate indentation or dynamic gonioscopy to assess fully — making it both the most commonly affected and the most commonly missed quadrant. **Clinical Pearl:** According to Parsons' Diseases of the Eye and Kanski's Clinical Ophthalmology, progressive angle closure in PACG follows the pattern: superior → inferior → nasal → temporal. Recognizing this sequence guides the clinician in prioritizing gonioscopic examination of the superior quadrant and in planning laser peripheral iridotomy placement. ### Why Other Quadrants Are Not the Primary Site - **Nasal angle** — While relatively narrow, it is not the first to close; closure here follows superior involvement - **Temporal angle** — Widest quadrant; last to close; often spared even in advanced PACG - **Inferior angle** — Intermediate; closes after the superior quadrant [cite: Kanski's Clinical Ophthalmology 9e; Parsons' Diseases of the Eye 22e Ch 8]