## Prophylactic Management of Narrow Angles (Occludable Angles) ### Risk Stratification: Narrow Angle vs. Angle Closure **Key Point:** A narrow angle on gonioscopy does NOT automatically mean the patient has glaucoma or will develop acute angle closure. However, eyes with narrow angles are at **significant risk** for acute angle-closure glaucoma (AACG), especially in hyperopic individuals. ### Pathophysiology of Narrow Angles Hyperopic eyes have: - Shorter axial length - Thicker lens relative to eye size - Shallower anterior chamber - Increased lens-corneal distance - Greater tendency for pupillary block and angle closure **High-Yield:** Narrow angle + hyperopia + positive family history = high-risk patient for AACG. ### Classification of Angle Findings | Gonioscopic Grade (Shaffer) | Description | Risk of AACG | |---|---|---| | **Grade IV** | Wide open angle, ciliary band visible | Minimal | | **Grade III** | Moderately open, scleral spur visible | Low | | **Grade II** | Narrow, scleral spur not visible | **High** | | **Grade I** | Very narrow, only Schwalbe line visible | **Very high** | | **Grade 0** | Appositional or synechial closure | **Acute or chronic AACG** | ### Management Algorithm for Narrow Angles ```mermaid flowchart TD A["Narrow angle on gonioscopy<br/>(Shaffer II-III)"]:::outcome --> B{"Acute angle closure<br/>symptoms or signs?"}:::decision B -->|"Yes: pain, halos,<br/>elevated IOP"| C["Acute AACG<br/>Medical emergency"]:::urgent C --> D["Medical IOP reduction<br/>then laser iridotomy"]:::action B -->|"No: asymptomatic,<br/>normal IOP"| E{"Risk factors present?<br/>Hyperopia, family Hx,<br/>short axial length"}:::decision E -->|"Yes"| F["Prophylactic laser<br/>peripheral iridotomy<br/>BOTH eyes"]:::action E -->|"No"| G["Close observation:<br/>IOP monitoring,<br/>VF annually"]:::action F --> H["Prevents AACG<br/>in ~95% of cases"]:::outcome G --> I["Risk of AACG<br/>~1% per year"]:::outcome ``` ### Why Prophylactic Iridotomy? **Clinical Pearl:** Prophylactic laser peripheral iridotomy (LPI) in narrow angles with risk factors reduces the risk of acute angle-closure glaucoma by ~95%. It is a low-risk procedure (complication rate <5%) with high preventive benefit. **Mnemonic:** **NARROW** — **N**arrow angle on gonioscopy, **A**ge >50, **R**efractive error (hyperopia), **R**isk factors (family history), **O**ccludable angle, **W**arn patient about symptoms. ### Why NOT Prostaglandin Analogs? **Warning:** Prostaglandin analogs (latanoprost, travoprost, bimatoprost) are **contraindicated** in narrow angles and AACG. They can: - Increase iris thickness - Worsen pupillary block - **Precipitate acute angle closure** ### Why NOT Anterior Chamber Deepening Surgery? Anterior chamber reformation is a surgical option reserved for: - Chronic angle-closure glaucoma with peripheral anterior synechiae - Failed LPI - Phthisical eyes It is NOT first-line for asymptomatic narrow angles. ### Follow-up After Prophylactic LPI - Gonioscopy at 1 week to confirm angle opening - IOP measurement at 1 week and 1 month - Annual IOP and visual field monitoring - Educate patient on acute angle-closure symptoms (sudden pain, halos, blurred vision) [cite:Parson's Diseases of the Eye 22e Ch 12; American Academy of Ophthalmology Preferred Practice Pattern on Glaucoma 2023] 
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