A 67-year-old hypertensive man presents with painless blurring of vision in the inferior half of his left visual field. On fundoscopy, the structure marked **A** in the diagram shows a characteristic sectoral distribution of flame-shaped and dot-blot haemorrhages. Which of the following best explains the pathophysiology underlying this specific pattern of haemorrhage distribution?

Question

Accepted Answer

A. Occlusion of a second-order retinal venule at an arteriovenous crossing, causing retrograde venous congestion and rupture of capillaries within the affected sector. ## Why option 1 is correct

The sectoral wedge pattern of haemorrhages marked **A** is pathognomonic for branch retinal vein occlusion (BRVO) at an arteriovenous crossing. At these crossing sites, the arteriole compresses the venule; in the setting of hypertension, atherosclerosis, and endothelial dysfunction, thrombosis occurs within the second-order venule. This causes retrograde venous congestion, increased hydrostatic pressure, and rupture of fragile capillaries within the drainage territory of that venule—producing the characteristic sectoral distribution that respects vascular boundaries. The flame-shaped haemorrhages (superficial, nerve fibre layer) and dot-blot haemorrhages (deeper, retinal layers) reflect the depth of capillary rupture. The sparing of other quadrants (structure **D**) confirms the localized nature of the occlusion. (AAO BCSC Section 12, 2023-2024)

## Why each distractor is wrong

- **Option 2**: Central retinal artery occlusion (CRAO) produces diffuse "cherry-red spot" appearance and whitening of the entire posterior pole, not a sectoral wedge of haemorrhages. Cilioretinal artery sparing would not explain the haemorrhagic pattern shown.
- **Option 3**: Superior ophthalmic vein thrombosis is rare, causes orbital signs (proptosis, chemosis, ophthalmoplegia), and produces diffuse retinal haemorrhages and venous engorgement across all quadrants, not a sectoral wedge.
- **Option 4**: Acute intracranial hypertension causes bilateral papilloedema, Roth spots (white-centred haemorrhages), and diffuse retinal haemorrhages, not a unilateral sectoral pattern. This patient has no headache or papilloedema.

**High-Yield:** BRVO at arteriovenous crossings = sectoral haemorrhages respecting vascular territories; CRAO = diffuse whitening + cherry-red spot; CVT = bilateral + orbital signs.

[cite: AAO Basic and Clinical Science Course, Section 12: Retina and Vitreous, 2023-2024]

Answer

B. Occlusion of the central retinal artery with sparing of cilioretinal artery branches supplying the unaffected quadrants

Answer

C. Thrombosis of the superior ophthalmic vein leading to diffuse retinal haemorrhages across all four quadrants

Answer

D. Rupture of the optic nerve head microvasculature secondary to acute elevation of intracranial pressure

Explanation

Why option 1 is correct

Why each distractor is wrong

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