A 45-year-old man presents with sudden painless visual loss in the right eye. Fundoscopy shows optic disc oedema, dilated tortuous retinal veins in all quadrants, multiple flame-shaped haemorrhages, and cotton wool spots. The most likely diagnosis is central retinal vein occlusion (CRVO). Which investigation differentiates ischaemic from non-ischaemic CRVO with the most clinical relevance for neovascularisation risk?

• A OCT showing cystoid macular oedema depth > 500 µm
• B Electroretinography (ERG) showing b/a ratio < 1 (reduced b-wave relative to a-wave)
• C Visual field showing central scotoma on Humphrey 24-2
• D Fluorescein angiography showing >10 disc areas of capillary non-perfusion ✓

Explanation

FFA demonstrating ≥10 disc areas of retinal capillary non-perfusion defines ischaemic CRVO and is the gold standard parameter predicting risk of anterior/posterior segment neovascularisation. Ischaemic CRVO has ~50% risk of developing neovascular glaucoma. ERG b/a ratio <1 (indicating inner retinal ischaemia) is an ancillary marker but FFA quantification is the standard clinical decision-making tool. OCT macular oedema depth and visual field scotoma indicate macular function but not ischaemia.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.