A 58-year-old hypertensive woman notices blurring of vision affecting the upper visual field of her left eye over two days. Fundoscopy shows flame-shaped haemorrhages and cotton-wool spots confined to the inferonasal quadrant, with dilated tortuous veins in that quadrant only. At which anatomical site does the underlying vascular event occur?

• A Thrombosis of the central retinal vein at the lamina cribrosa
• B Occlusion of a branch retinal vein at an arteriovenous crossing ✓
• C Embolisation of a branch retinal artery at the optic disc margin
• D Inflammation of a ciliary vessel at the posterior pole

Explanation

Branch retinal vein occlusion almost always occurs at an arteriovenous crossing, where the artery and vein share a common adventitial sheath. Arteriolar sclerosis from hypertension compresses the vein within this sheath, producing turbulent flow and thrombosis. Haemorrhages are confined to the drainage territory of the occluded vein, hence one quadrant here. Central retinal vein occlusion at the lamina cribrosa would involve all four quadrants, which excludes option A.

Reference: Khurana's Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.