A 52-year-old man presents with progressive loss of central vision and metamorphopsia. Fundoscopy reveals drusen and retinal pigment epithelium changes in the macula. Which investigation is most appropriate to confirm the diagnosis and assess disease severity?

Explanation

## Clinical Context The patient presents with classic signs of age-related macular degeneration (AMD): central vision loss, metamorphopsia (distorted vision), drusen, and RPE changes. The investigation of choice must confirm the diagnosis and assess structural changes. ## Why OCT is the Investigation of Choice **Key Point:** Optical coherence tomography (OCT) is the gold standard for imaging the retinal microstructure and detecting both dry and wet AMD. ### Advantages of OCT in AMD - **Cross-sectional imaging:** Provides detailed layer-by-layer visualization of the retina and choroid - **Detects subretinal fluid:** Essential for identifying wet AMD (neovascular AMD) - **Quantifies drusen:** Measures drusen size and distribution - **Assesses RPE integrity:** Shows photoreceptor-RPE-Bruch's membrane complex changes - **Non-invasive:** No dye injection required; safe for all patients - **Reproducible:** Allows longitudinal monitoring of disease progression **High-Yield:** OCT has replaced fluorescein angiography as the first-line imaging modality for AMD diagnosis and monitoring in modern practice. ## Comparison of Investigations | Investigation | Role in AMD | Timing | Limitations | |---|---|---|---| | **OCT** | Gold standard for structural assessment | First-line | Cannot assess retinal perfusion | | **Fluorescein angiography** | Assesses choroidal neovascularization and retinal perfusion | Confirmatory/supplementary | Dye allergy risk, delayed imaging | | **Goldmann perimetry** | Assesses visual field defects | Not specific for AMD | Detects functional loss, not diagnosis | | **ERG** | Assesses photoreceptor function globally | Diffuse retinal disease | Abnormal in advanced AMD only | **Clinical Pearl:** In wet AMD, OCT can detect subretinal and intraretinal fluid before fluorescein angiography becomes abnormal, making it superior for early detection and treatment monitoring. ## When to Use Supplementary Tests - **Fluorescein angiography:** When OCT shows signs of neovascularization and you need to assess retinal perfusion or plan anti-VEGF therapy timing - **Indocyanine green angiography:** For polypoidal choroidal vasculopathy (a subtype of wet AMD) - **Fundus autofluorescence:** To assess RPE health and predict progression in dry AMD