In primary angle-closure glaucoma, which anatomical feature is MOST significant in predisposing to angle closure?

Explanation

## Anatomical Risk Factors in Primary Angle-Closure Glaucoma **Key Point:** Short axial length, shallow anterior chamber, and thick lens are the HALLMARK anatomical features predisposing to PACG. These create a crowded anterior segment with narrow angles. ### Predisposing Anatomical Features | Feature | Role in PACG | Clinical Significance | |---------|--------------|----------------------| | **Short axial length** | Crowded anterior segment | Reduces space for aqueous flow | | **Shallow anterior chamber** | Iris-lens contact closer to trabeculum | Increases pupillary block risk | | **Thick lens** | Increased lens-iris contact | Exacerbates relative pupillary block | | **Narrow angles** | Reduced trabecular meshwork access | Angle closure occurs with iris bowing | | **Small corneal diameter** | Crowded anterior segment | Associated with short eyes | ### Why These Features Matter 1. **Anatomical crowding** = iris and lens are in close proximity 2. **Shallow AC** = less space for aqueous to flow around the lens 3. **Thick lens** = greater iris-lens contact area 4. **Narrow angles** = trabecular meshwork is already positioned posteriorly; minimal iris bowing needed to cause closure **High-Yield:** PACG is a disease of **SHORT, HYPEROPIC eyes** with **SHALLOW anterior chambers**. The angle is narrow even at baseline (gonioscopy shows Shaffer Grade I–II angles). **Mnemonic:** **SHARP** = **S**hort axial length, **H**yperopia, **A**nterior chamber shallow, **R**ounded iris, **P**redisposed to closure. **Clinical Pearl:** Gonioscopy reveals narrow angles (Shaffer Grade I–II) in the fellow eye of PACG patients — this is why prophylactic peripheral iridotomy is offered to the contralateral eye to prevent acute attack.