Central retinal vein occlusion

Overview

•Sudden painless unilateral vision loss - onset over hours

•Classic fundoscopy: 'stormy sunset' - flame-shaped haemorrhages in all four quadrants, dilated and tortuous retinal veins, disc oedema, cotton wool spots, macular oedema

•RAPD - present in ischaemic CRVO

🎯
CRVO: haemorrhages in ALL four quadrants. Branch retinal vein occlusion (BRVO): identical changes confined to ONE quadrant only - key differentiating feature on fundoscopy.

Investigations

🥇 First-line

•fundoscopy, visual acuity (Snellen), fluorescein angiography (distinguishes ischaemic from non-ischaemic), BP, fasting glucose/HbA1c, fasting lipids, FBC, ESR/CRP, clotting screen

🏆 Gold standard

•optical coherence tomography (OCT) - quantifies macular oedema; monitors treatment response

Differential diagnosis

Key differentials for sudden painless vision loss with fundoscopy changes
FeatureCRVODiabetic retinopathyHypertensive retinopathy
LateralityUnilateralBilateralBilateral
HaemorrhagesFlame, all 4 quadrantsDot/blot + flame; not quadrant-confinedFlame; not quadrant-confined
Other featuresTortuous veins, disc oedemaHard exudates, neovascularisation, cotton wool spotsAV nicking, severely elevated BP
Vitreous haemorrhageNOT a common causeMost common cause in adults (proliferative DR)Not a common cause

Feature	CRVO	Diabetic retinopathy	Hypertensive retinopathy
Laterality	Unilateral	Bilateral	Bilateral
Haemorrhages	Flame, all 4 quadrants	Dot/blot + flame; not quadrant-confined	Flame; not quadrant-confined
Other features	Tortuous veins, disc oedema	Hard exudates, neovascularisation, cotton wool spots	AV nicking, severely elevated BP
Vitreous haemorrhage	NOT a common cause	Most common cause in adults (proliferative DR)	Not a common cause

⚠️
CRVO is NOT a common cause of vitreous haemorrhage. In adults, the most common cause is proliferative diabetic retinopathy. Neovascularisation + hard exudates + cotton wool spots bilaterally = diabetic retinopathy.

Management

•First-line (macular oedema): intravitreal ranibizumab or aflibercept (anti-VEGF) - monthly injections

🥈 Second-line

•intravitreal dexamethasone implant (Ozurdex) - if anti-VEGF insufficient; risk of raised IOP and cataract

•Neovascularisation: pan-retinal photocoagulation (laser) - destroys ischaemic retina to reduce VEGF; prevents neovascular glaucoma, does not improve VA

•Systemic: BP control, optimise diabetes and lipids, smoking cessation

⚠️
Anticoagulation (warfarin, heparin) is NOT recommended for acute CRVO - the thrombus is already organised at presentation and anticoagulation carries bleeding risk without evidence of benefit.

Complications

•Persistent macular oedema - most common complication; primary cause of chronic visual impairment

•Neovascular glaucoma - up to 50% of ischaemic CRVO; rubeosis iridis precedes angle closure

•Vitreous haemorrhage - from fragile neovascular vessels (not a common cause; contrast with proliferative diabetic retinopathy)

•Conversion from non-ischaemic to ischaemic CRVO - ~15% over 3 years