A 62-year-old Indian woman is referred to the ophthalmology clinic for evaluation of narrow angles detected on routine screening. She is asymptomatic with normal intraocular pressures (16 mmHg OU), clear media, and normal optic discs. Gonioscopy confirms Shaffer grade II angles bilaterally. She has no family history of glaucoma. What is the most appropriate next step in management?

Explanation

## Prophylactic Management of Narrow Angles (Asymptomatic) ### Risk Stratification in Narrow-Angle Disease **Key Point:** The distinction between anatomically narrow angles and acute angle-closure glaucoma is critical. This patient has asymptomatic narrow angles (Shaffer grade II) with normal IOP and no signs of angle closure — yet she is at significant risk of acute closure. ### Shaffer Angle Grading System | Grade | Angle Width | Risk of Closure | Clinical Significance | |-------|-------------|-----------------|----------------------| | IV | >35° | Minimal | Wide open, safe | | III | 20–35° | Low | Moderate, monitor | | II | 10–20° | **High** | **Narrow, prophylaxis indicated** | | I | <10° | Very high | Very narrow, high risk | | 0 | Slit or closed | Imminent/present | Acute or chronic closure | **High-Yield:** Shaffer grade II angles are considered **narrow enough to warrant prophylactic iridotomy** in most guidelines, especially in patients with additional risk factors (age >50, female, hyperopia, short axial length, thick lens). ### Why Prophylactic Iridotomy? ```mermaid flowchart TD A[Asymptomatic narrow angles]:::outcome --> B{Risk factors present?}:::decision B -->|Yes: age, female, hyperopia| C[Prophylactic laser iridotomy]:::action B -->|No clear risk| D[Observe with regular gonioscopy]:::decision C --> E[Prevents acute closure]:::outcome D --> F[Monitor for angle narrowing]:::action F --> G{Angle closes or IOP rises?}:::decision G -->|Yes| H[Perform iridotomy]:::action G -->|No| I[Continue surveillance]:::action ``` **Clinical Pearl:** This patient has multiple risk factors for angle closure: - Female sex (2–4× higher risk than males) - Age >60 years (age-related lens thickening narrows angle) - Shaffer grade II (narrow but not yet closed) - Indian ethnicity (higher prevalence of angle-closure anatomy) **Key Point:** Prophylactic laser peripheral iridotomy is safe, minimally invasive, and definitively prevents acute angle-closure glaucoma in susceptible individuals. The risk of acute closure (which can cause permanent blindness) far outweighs the small risks of iridotomy (transient inflammation, rare corneal abrasion, minimal refractive shift). ### Mechanism of Iridotomy Laser peripheral iridotomy creates a patent communication between the posterior and anterior chambers, bypassing the pupillary block mechanism that drives angle closure. This equalizes pressure and allows the iris to relax posteriorly, opening the angle. ### Prophylaxis vs. Observation **High-Yield:** Current evidence and guidelines (American Academy of Ophthalmology, Indian Glaucoma Society) recommend **prophylactic iridotomy for asymptomatic narrow angles**, particularly in older patients and those with high-risk anatomy. Observation-only strategies carry a 5–10% annual risk of acute closure in untreated narrow angles. [cite:Khurana Ophthalmology 7e Ch 12; American Academy of Ophthalmology Glaucoma Preferred Practice Pattern]