A 58-year-old man presents with sudden onset of floaters and flashing lights in the right eye for 2 days, followed by a shadow in the superior temporal field. On examination, visual acuity is 6/9 and intraocular pressure is normal. The anterior segment is unremarkable. Which investigation is most appropriate to confirm the diagnosis?

## Clinical Presentation Analysis The patient presents with classic signs of **rhegmatogenous retinal detachment (RRD)**: - Sudden onset floaters and photopsia (flashing lights) - Progressive shadow in the visual field (superior temporal field → inferior nasal retinal detachment) - Normal IOP and anterior segment ## Investigation of Choice **Key Point:** Dilated fundus examination with indirect ophthalmoscopy is the gold standard investigation for suspected retinal detachment. ### Why This Is the Best Investigation 1. **Direct visualization** of the detached retina, breaks, and extent of detachment 2. **Identifies the primary break** (retinal hole or tear) — essential for surgical planning 3. **Assesses quadrant involvement** and proximity to macula 4. **Evaluates vitreous** for hemorrhage, inflammation, or vitreous traction 5. **Non-invasive, bedside test** — immediate diagnosis without delay 6. **Guides urgency** — macula-on vs. macula-off determines timing of surgery ## Why Indirect Ophthalmoscopy Over Direct? | Feature | Direct Ophthalmoscopy | Indirect Ophthalmoscopy | | --- | --- | --- | | **Field of view** | 5–10° | 40–50° | | **Peripheral retina** | Poor visualization | Excellent | | **Retinal breaks** | May miss | Reliably identified | | **Detachment extent** | Limited assessment | Complete mapping | | **Vitreous view** | Obscured by media** | Clear | **High-Yield:** Indirect ophthalmoscopy with scleral indentation is the standard of care for RRD diagnosis and pre-operative assessment. ## Role of Other Investigations **B-scan ultrasonography** — Used only when media is opaque (dense cataract, vitreous hemorrhage) and fundus cannot be visualized. Not first-line when clear media allows direct visualization. **OCT of macula** — Useful post-operatively to assess macular recovery and detect epiretinal membrane, but cannot visualize the entire detachment or identify breaks. **Gonioscopy** — Assesses angle structures; irrelevant in RRD unless anterior segment involvement is suspected (rare). **Clinical Pearl:** The combination of sudden photopsia + floaters + visual field shadow is pathognomonic for RRD. Dilated fundus examination must be performed urgently (within 24 hours if macula-on, within 48 hours if macula-off) to prevent permanent vision loss.