A 62-year-old Indian woman is referred to the glaucoma clinic after routine eye examination reveals narrow angles bilaterally with normal intraocular pressures (IOP 14 mmHg OU). She is asymptomatic and denies any history of eye pain or visual symptoms. Gonioscopy confirms Shaffer grade II angles. What is the most appropriate management?

Explanation

## Prophylactic Management of Narrow Angles (Occludable Angles) ### Classification of Angle-Closure Risk **Key Point:** Narrow angles are classified into **anatomically occludable** (high risk) and **physiologically occludable** (symptomatic). Management depends on gonioscopic grade and symptoms. | Gonioscopic Grade | Angle Width | Risk Category | Management | |---|---|---|---| | **Shaffer IV** | >35° | Wide open | Observe | | **Shaffer III** | 20–35° | Moderately narrow | Observe with follow-up | | **Shaffer II** | 10–20° | Narrow/Occludable | **Prophylactic iridotomy** | | **Shaffer I** | <10° | Very narrow/Occludable | **Urgent iridotomy** | ### Why Prophylactic Iridotomy for Shaffer Grade II? **High-Yield:** Shaffer grade II angles are **anatomically occludable** — the peripheral iris can physically block the trabecular meshwork. Even with normal IOP, these eyes carry a **5–10% annual risk of acute angle-closure** if left untreated. ### Risk Factors for Angle-Closure in Narrow Angles 1. **Anatomical factors** - Hyperopia (short axial length, thick lens) - Anterior lens position - Thick iris - Pupillary block mechanism 2. **Precipitating factors** - Pupillary dilation (dim lighting, mydriatic drugs, stress) - Accommodation (near work) - Increased episcleral venous pressure 3. **Demographic factors** - Age >50 years (lens swells with age) - Female gender (higher prevalence) - **Asian ethnicity** (anatomically predisposed) **Clinical Pearl:** This patient is a 62-year-old Indian woman — **triple risk** for angle-closure: age, female, and Asian ethnicity. Prophylactic iridotomy is standard of care. ### Mechanism of YAG Laser Peripheral Iridotomy ```mermaid flowchart TD A[Narrow angle with pupillary block]:::outcome --> B[YAG laser creates hole in iris]:::action B --> C[Aqueous bypasses lens-iris contact]:::action C --> D[Pressure gradient eliminated]:::action D --> E[Iris pulled away from angle]:::action E --> F[Angle opens, trabecular meshwork accessible]:::outcome F --> G[Prevents angle-closure crisis]:::outcome ``` ### Why Observation Alone Is Inadequate **Warning:** Observing a Shaffer grade II angle without iridotomy carries significant risk: - 5–10% annual incidence of acute angle-closure - Once acute closure occurs, **irreversible angle synechiae** may form within hours - Chronic angle-closure glaucoma can develop silently, causing permanent vision loss - Patient may not seek care during prodromal symptoms (halos, blurred vision) **Mnemonic: NARROW angles = Need Aggressive Removal Of Relative pupillary block (iridotomy)** ### Bilateral Iridotomy Rationale **Key Point:** Bilateral prophylactic iridotomy is standard because: 1. **Fellow eye risk** — if one eye has occludable angles, the other almost always does 2. **Anatomical symmetry** — hyperopia and anterior lens position are bilateral traits 3. **Prevention** — eliminates risk of angle-closure in second eye 4. **Safety** — YAG iridotomy is minimally invasive, outpatient procedure with <1% complication rate ### Why Prostaglandin Analogs Are Insufficient Prostaglandin analogs (latanoprost, travoprost) reduce IOP but do **NOT** prevent angle-closure because: - They do not address the underlying **anatomical block** (pupillary block) - They reduce aqueous production, not iris-lens contact - In acute angle-closure, IOP may still rise despite prostaglandins - Medical therapy is adjunctive, not definitive [cite:Khurana Ophthalmology Ch 8; American Academy of Ophthalmology Glaucoma Preferred Practice Pattern 2021]