A 58-year-old man from Delhi presents with sudden onset of painless vision loss in his right eye. He reports seeing a dark shadow that started from the superior temporal field and progressively moved downward over 2 hours. On examination, visual acuity is 6/9 in the right eye. Dilated fundoscopy reveals a pale, edematous optic disc with retinal whitening in the superior half. Intraocular pressure is 16 mmHg bilaterally. What is the most likely diagnosis?

Explanation

## Diagnosis: Branch Retinal Artery Occlusion (BRAO) — Superior Temporal Branch ### Clinical Presentation The patient presents with: - Sudden painless vision loss - **Altitudinal visual field defect** (superior temporal shadow progressing downward) - Pale, edematous retina in the superior half - Normal intraocular pressure - Relatively preserved visual acuity (6/9) ### Pathophysiology **Key Point:** Branch retinal artery occlusion (BRAO) causes a **sectoral or altitudinal visual field defect** corresponding to the territory of the occluded vessel. The superior temporal branch of the central retinal artery supplies the superior temporal quadrant of the retina, producing a field defect that matches the patient's presentation. ### Distinguishing Features | Feature | BRAO | CRAO | Acute Angle-Closure | Optic Neuritis | |---------|------|------|-------------------|----------------| | **VA Loss** | Mild–moderate | Severe (CF/HM) | Severe | Mild–moderate | | **VF Defect** | Sectoral/altitudinal | Central scotoma or diffuse loss | Peripheral constriction | Central scotoma | | **Fundus** | Retinal whitening in sector | Cherry-red spot, widespread pallor | Normal initially | Disc edema, hyperemia | | **IOP** | Normal | Normal | Elevated (>40 mmHg) | Normal | | **Pain** | No | No | Yes (severe) | Yes (eye movement) | **High-Yield:** The **altitudinal/sectoral visual field defect with corresponding retinal whitening** is the hallmark of BRAO. The superior temporal branch BRAO produces a superior temporal field defect. ### Clinical Pearl BRAO is often associated with cardiovascular risk factors (hypertension, diabetes, hyperlipidemia) and may be a harbinger of systemic vascular disease. Amaurosis fugax (transient monocular vision loss) can precede BRAO. ### Management Approach 1. Urgent carotid imaging (ultrasound/CTA) to exclude embolic source 2. Cardiac evaluation (ECG, echocardiography if indicated) 3. Aggressive management of cardiovascular risk factors 4. Consider antiplatelet therapy (aspirin) after ruling out other causes ```mermaid flowchart TD A[Sudden painless vision loss]:::outcome --> B{Visual field pattern?}:::decision B -->|Altitudinal/sectoral| C{Retinal whitening present?}:::decision B -->|Central scotoma| D[CRAO or Optic Neuritis]:::outcome B -->|Peripheral constriction| E[Acute Angle-Closure]:::outcome C -->|Yes, in sector| F[BRAO]:::action C -->|No| G[Optic Neuritis]:::outcome F --> H[Check IOP, carotid imaging, cardiac workup]:::action ``` **Tip:** Remember that BRAO preserves relatively good visual acuity (unlike CRAO), because the macula is often supplied by the temporal branch and may be partially spared.