A 58-year-old man presents to the ophthalmology clinic with a family history of glaucoma. On examination, intraocular pressure (IOP) is 22 mmHg in both eyes, optic disc appears normal, and visual fields are intact. Gonioscopy shows open angles. Which investigation is most appropriate to confirm the diagnosis of primary open-angle glaucoma (POAG)?

Explanation

## Investigation of Choice for POAG Confirmation **Key Point:** Automated perimetry (visual field testing) is the gold standard and most appropriate investigation to confirm POAG in a patient with elevated IOP and open angles on gonioscopy. ### Why Automated Perimetry? Automated perimetry detects functional damage to the retinal nerve fiber layer and ganglion cells, which is the hallmark of glaucomatous optic neuropathy. It: 1. Quantifies visual field defects objectively 2. Detects early glaucomatous damage (arcuate defects, nasal steps, paracentral scotomas) 3. Allows serial monitoring to assess disease progression 4. Is reproducible and standardized (24-2 or 30-2 programs) **High-Yield:** The diagnosis of POAG requires: - Elevated IOP (>21 mmHg, though not always) - Open angles on gonioscopy - **Evidence of optic nerve damage** (cup-to-disc ratio >0.5, vertical cup asymmetry, neuroretinal rim thinning) - **Visual field defect** on automated perimetry (most important confirmatory test) ### Diagnostic Sequence for POAG ```mermaid flowchart TD A[Elevated IOP + Family History]:::outcome --> B[Gonioscopy]:::action B --> C{Open angles?}:::decision C -->|Yes| D[Optic disc assessment]:::action D --> E{Disc damage signs?}:::decision E -->|Yes| F[Automated Perimetry]:::action E -->|No| G[Repeat monitoring]:::action F --> H{VF defect present?}:::decision H -->|Yes| I[POAG Confirmed]:::outcome H -->|No| J[Suspect glaucoma/Monitor]:::outcome ``` **Clinical Pearl:** In early POAG, IOP may be normal (<21 mmHg) in some patients (normal-tension glaucoma). The presence of optic nerve damage and visual field defect on perimetry is diagnostic regardless of IOP level. **Mnemonic: POAG Diagnosis = OAD-VF** - **O**pen angles (gonioscopy) - **A**cute/Absent symptoms - **D**isc damage (structural) - **V**isual **F**ield defect (functional) ### Role of Other Investigations | Investigation | Role in POAG | Timing | | --- | --- | --- | | **Automated Perimetry** | Confirms functional damage; gold standard | Initial diagnosis + monitoring | | **OCT (Optic Nerve/RNFL)** | Detects structural damage; early detection | Baseline + follow-up | | **Gonioscopy** | Confirms open angles; rules out secondary glaucoma | Initial assessment | | **Tonometry** | Measures IOP; risk factor assessment | Every visit | | **AS-OCT** | Assesses anterior segment anatomy; rules out angle closure | If angle closure suspected | | **FFA** | Evaluates retinal perfusion; not diagnostic for POAG | Only if vascular pathology suspected | [cite:Khurana Comprehensive Ophthalmology Ch 12]