A 62-year-old Indian woman is referred to the eye clinic for routine screening after her sister was diagnosed with acute angle-closure glaucoma. She is asymptomatic. Examination reveals bilateral narrow angles on gonioscopy, intraocular pressures of 18 mmHg (right) and 19 mmHg (left), clear corneas, and normal optic discs. Anterior chamber depth is 2.0 mm bilaterally. What is the most appropriate management?

Explanation

## Primary Angle-Closure Glaucoma: Prophylactic Laser Iridotomy in Asymptomatic Narrow Angles ### Clinical Classification: Narrow Angles vs. Angle-Closure Disease **Key Point:** This patient has **asymptomatic narrow angles with anatomically predisposing features** — not yet acute angle-closure glaucoma. However, the risk of progression to acute attack is substantial, and prophylactic intervention is indicated. ### Risk Stratification in Narrow-Angle Eyes | Category | IOP | Symptoms | Gonioscopy | Management | |----------|-----|----------|-----------|-------------| | **Narrow angles (at risk)** | Normal | None | Narrow/closed | Prophylactic laser iridotomy | | **Acute angle-closure** | >40 mmHg | Severe (pain, halos) | Closed | Emergency medical + laser | | **Chronic angle-closure** | Mildly elevated | Gradual vision loss | Closed | Medical + laser | | **Angle-closure glaucoma** | Elevated | Optic nerve damage present | Closed | Laser + medical | **High-Yield:** The presence of **narrow angles on gonioscopy + shallow anterior chamber (≤2.5 mm) + normal IOP + no symptoms** defines the **narrow-angle suspect** or **anatomically predisposed eye**. These patients have a significant lifetime risk of acute attack (up to 50% in 5–10 years if untreated) and warrant prophylactic laser iridotomy. ### Why Prophylactic YAG Laser Iridotomy? 1. **Mechanism:** Laser creates a small opening in the iris periphery, allowing aqueous humor to flow directly from posterior to anterior chamber, relieving pupillary block and deepening the peripheral angle. 2. **Prevention:** Eliminates the anatomic substrate for acute attack; prevents progression to angle-closure glaucoma. 3. **Timing:** Performed electively when IOP is normal and cornea is clear — safe, effective, and definitive. 4. **Bilateral:** Both eyes are treated because the fellow eye carries equal anatomic risk (as evidenced by bilateral narrow angles in this case). **Clinical Pearl:** The presence of a family history of acute angle-closure (sister's diagnosis) increases urgency, as narrow-angle anatomy is heritable. ### Evidence & Guidelines **Key Point:** Major ophthalmology guidelines (AAO, ESCRS) recommend prophylactic YAG laser peripheral iridotomy for all eyes with narrow angles and no prior acute attack, especially if: - Gonioscopy confirms angle closure (Shaffer Grade 0–1) - Anterior chamber depth is shallow (<2.5 mm) - Fellow eye has history of acute attack or narrow angles ### Why Other Options Are Suboptimal **Reassurance + annual follow-up alone:** Leaves the patient at risk of acute attack, which can occur suddenly and unpredictably. Once acute attack occurs, vision may be permanently lost despite emergency treatment. Prophylaxis is more effective than surveillance. **Prostaglandin analogues:** While these lower IOP, they do NOT address the underlying anatomic problem (pupillary block and narrow angle). They may delay but do not prevent acute attack. **Frequent gonioscopy + treatment only if IOP rises:** Delays intervention until IOP elevation occurs, by which time angle-closure glaucoma (with optic nerve damage) may have already begun. This is a reactive rather than preventive approach and is not standard practice. ### Post-Laser Follow-Up After successful bilateral iridotomy: - Check IOP and gonioscopy at 1 week, 1 month, then annually - Confirm angle opening on gonioscopy - Monitor optic disc for any signs of glaucomatous damage - Patient education on symptoms of acute attack (pain, halos, blurred vision) and when to seek emergency care