Which gonioscopic angle classification system is most commonly used to predict the risk of angle closure in primary angle-closure glaucoma?

Explanation

## Gonioscopic Classification Systems for Angle Assessment **Key Point:** The Shaffer classification is the gold standard for predicting angle-closure risk and is universally used in clinical practice and research. ### Shaffer Classification | Grade | Angle Width | Risk of Closure | Clinical Significance | |-------|-------------|-----------------|----------------------| | **4** | ≥ 40° | No risk | Wide open angle, normal | | **3** | 20–40° | Low risk | Gonioscopy recommended | | **2** | 10–20° | High risk | Prophylactic iridotomy indicated | | **1** | < 10° | Very high risk | Imminent closure, urgent iridotomy | | **0** | Closed | Angle closure present | Peripheral anterior synechiae likely | **High-Yield:** Shaffer grades are based on the angle between the iris and cornea at the trabecular meshwork level. A grade of 2 or less warrants prophylactic intervention. ### Why Shaffer Over Other Systems? **Spaeth classification:** - More detailed (includes iris insertion, iris contour, angle recess depth) - Overly complex for routine clinical use - Better for research but not practical for screening **Scheie classification:** - Older system, less precise - Based on visibility of structures (gonioscopic landmarks) - Rarely used in modern practice **Van Herick classification:** - **Anterior segment OCT technique** (not gonioscopy) - Rapid screening tool for angle assessment - Grades based on peripheral anterior chamber depth - Useful for population screening but less detailed than gonioscopy **Clinical Pearl:** Van Herick is a non-contact screening method (useful in primary care), but **gonioscopy with Shaffer grading is mandatory** for definitive angle assessment before diagnosing or ruling out PACG. **Mnemonic:** **SHAFFER = Standard, Handy, Accurate, Functional, Frequently used, Excellent, Reliable** — the most practical and widely adopted system.