A 58-year-old man from Delhi presents with sudden-onset painless vision loss in the left eye for 2 days. He reports seeing a dark shadow that started from the superior temporal field and progressively moved downward. On examination, visual acuity is 6/9 in the left eye. Dilated fundoscopy reveals a pale, edematous optic disc with blurred margins and retinal whitening in the distribution of the superior branch of the central retinal artery. The right eye is normal. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Branch Retinal Artery Occlusion (BRAO) ### Key Clinical Features **Key Point:** The patient presents with a sectoral visual field defect (superior temporal shadow progressing downward) corresponding to the territory of a single arterial branch, not the entire central retinal artery distribution. ### Distinguishing Features | Feature | BRAO | CRAO | AION | Retrobulbar ON | |---------|------|------|------|----------------| | **Onset** | Sudden | Sudden | Sudden | Hours to days | | **Visual field defect** | Sectoral (altitudinal or wedge-shaped) | Diffuse ("cherry-red spot") | Altitudinal (superior or inferior) | Central scotoma | | **Fundoscopic findings** | Retinal whitening in one arterial territory | Pale, edematous disc; cherry-red spot | Optic disc swelling; flame hemorrhages | Normal disc initially | | **Optic disc appearance** | May be normal or pale in affected sector | Pale, edematous | Swollen, hyperemic | Normal (retrobulbar = behind disc) | | **Prognosis** | Variable; depends on location | Poor; often NLP | Moderate; often recovers partially | Good; often recovers fully | ### Why This Is BRAO 1. **Sectoral visual field defect**: The superior temporal shadow that progresses downward is pathognomonic for occlusion of the superior temporal branch of the central retinal artery. 2. **Fundoscopic findings**: Retinal whitening and edema confined to the distribution of one arterial branch, not the entire retina. 3. **Preserved central vision**: Visual acuity of 6/9 suggests the macula is spared (which occurs in BRAO when the superior temporal branch is affected). 4. **Optic disc appearance**: Pale, edematous disc with blurred margins in the affected territory is consistent with acute arterial ischemia. ### Pathophysiology **High-Yield:** Branch retinal artery occlusion typically results from: - Thromboembolism (most common) - Atherosclerotic disease - Vasculitis - Hypercoagulable states The visual field defect follows the vascular territory because the ischemic retina in that distribution becomes pale and edematous, blocking light transmission. ### Clinical Pearl **Clinical Pearl:** The pattern of visual field loss in BRAO is **sectoral** (wedge-shaped or altitudinal), whereas CRAO causes a more diffuse visual loss with a characteristic "cherry-red spot" at the macula due to the contrast between the pale, ischemic retina and the perfused choroid visible through the fovea. ### Management Approach **Key Point:** BRAO management focuses on: 1. Urgent systemic evaluation for embolic source (carotid ultrasound, echocardiography, ECG) 2. Assessment for giant cell arteritis in older patients (ESR, CRP, temporal artery biopsy if indicated) 3. Cardiovascular risk factor modification 4. Antiplatelet therapy (aspirin) in most cases 5. Consideration of anticoagulation if cardioembolic source identified [cite:Neuro-Ophthalmology by Burde, Savino, Trobe; Kanski's Clinical Ophthalmology]