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. Which investigation is most appropriate to confirm the diagnosis of primary open-angle glaucoma (POAG)?

## Role of Automated Perimetry in POAG Diagnosis **Key Point:** Automated perimetry (visual field testing) is the gold standard confirmatory investigation for POAG because it documents functional loss — the hallmark of glaucomatous damage. IOP elevation alone does not confirm glaucoma; structural and functional evidence are required. ### Diagnostic Triad of POAG | Feature | Finding | |---------|----------| | **Elevated IOP** | ≥21 mmHg (though normal-tension glaucoma exists) | | **Optic nerve damage** | Cupping, rim thinning, disc hemorrhage | | **Visual field defect** | Arcuate, nasal step, or generalized depression | **High-Yield:** A diagnosis of POAG requires ALL THREE components. IOP alone is insufficient; functional loss (visual field defect) must be demonstrated. ### Why Automated Perimetry? 1. **Objective documentation** of visual field loss patterns typical of glaucoma (arcuate defects, nasal steps, generalized depression) 2. **Baseline for monitoring** disease progression and treatment efficacy 3. **Reproducibility** — standard 24-2 or 30-2 programs allow longitudinal comparison 4. **Sensitivity** — detects functional loss before obvious structural changes **Clinical Pearl:** Early POAG may show normal optic discs on clinical examination but abnormal visual fields on perimetry — this is why perimetry is the confirmatory test. ### Diagnostic Algorithm for Suspected POAG ```mermaid flowchart TD A[Elevated IOP or optic disc changes]:::outcome --> B[Gonioscopy to rule out secondary glaucoma]:::action B --> C{Open angles confirmed?}:::decision C -->|Yes| D[Perform automated perimetry]:::action C -->|No| E[Secondary glaucoma workup]:::urgent D --> F{Visual field defect present?}:::decision F -->|Yes| G[POAG diagnosed]:::outcome F -->|No| H[Ocular hypertension or normal-tension glaucoma]:::outcome G --> I[OCT and fundus photography for baseline documentation]:::action ``` **Mnemonic:** **VOP** = **V**isual field + **O**ptic disc + **P**ressure (all three needed for POAG diagnosis).