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ukmla 2026

Central Retinal Vein Occlusion

Occlusion of the central retinal vein causing sudden painless visual loss with "stormy sunset" fundus — flame haemorrhages in all four quadrants, dilated veins, and disc oedema

Review date
reviewed 2026-04-05
Reading time
5 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Ophthalmologyless-commonacute
On this page
Condition details
Ophthalmology
less-common
5 min read
reviewed 2026-04-05
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About This Page

This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.

Key points

  • Sudden painless visual loss — severity depends on ischaemic vs non-ischaemic
  • "Blood and thunder" fundus: flame haemorrhages in ALL FOUR quadrants + dilated veins + disc oedema
  • Ischaemic CRVO: RAPD, poor VA (<6/60), high risk of neovascular glaucoma at ~3 months
  • Macular oedema: intravitreal anti-VEGF is first-line
  • Hypertension is the most important systemic risk factor

Overview

CRVO occurs when thrombosis obstructs the central retinal vein at the lamina cribrosa. Classified as non-ischaemic (better prognosis) or ischaemic (extensive capillary non-perfusion, high risk of neovascularisation). Macular oedema is the main cause of visual loss.

Epidemiology

Second commonest retinal vascular disorder. Incidence ~2–5 per 10,000 per year. Key risk factors: hypertension, glaucoma (raised IOP compresses the vein), diabetes, hyperlipidaemia, smoking. In patients <50, consider thrombophilia.

Clinical Features

Symptoms
Sudden painless unilateral visual loss or blurring
Signs
Flame haemorrhages in ALL FOUR quadrants — "blood and thunder"
Dilated, tortuous retinal veins
Disc oedema and cotton wool spots
Macular oedema on OCT
RAPD in ischaemic CRVO

Investigations

First-line
Dilated fundoscopyDiagnostic — widespread haemorrhages, venous engorgement
VAClassifies ischaemic (<6/60) vs non-ischaemic
OCT maculaQuantifies macular oedema
BP, glucose, HbA1c, lipidsRisk factor assessment
Second-line
Fluorescein angiographyDetermines degree of capillary non-perfusion
IOPGlaucoma is a risk factor
Specialist
Thrombophilia screenIn patients <50 or bilateral/recurrent

Management

RCOphth Retinal Vein Occlusion Guidelines
1
Risk factor management
  • Optimise BP, diabetes, lipids
  • Smoking cessation
  • Treat glaucoma
2
Macular oedema
  • Intravitreal anti-VEGF (ranibizumab/aflibercept) — first-line
  • Intravitreal dexamethasone implant (Ozurdex) as alternative
3
Neovascular monitoring (ischaemic CRVO)
  • Monthly review initially for rubeosis iridis
  • PRP if neovascularisation develops

Complications

  • Macular oedema: Commonest cause of visual loss
  • Neovascular glaucoma: ~20% of ischaemic CRVO at 3 months ("100-day glaucoma")
  • Conversion to ischaemic: ~30% within 3 years
UKMLA Exam Tips
  • 1CRVO = flame haemorrhages in ALL FOUR quadrants + dilated veins + disc oedema
  • 2CRAO vs CRVO: CRAO = pale retina + cherry-red spot. CRVO = red haemorrhagic retina + dilated veins
  • 3Ischaemic CRVO: poor VA + RAPD → "100-day glaucoma"
  • 4Anti-VEGF is first-line for CRVO-related macular oedema
  • 5Always check BP — hypertension is the most important risk factor

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Verified Sources & References

RCOphth — Retinal Vein Occlusion Guidelines
NICE TA283 — Ranibizumab for CRVO
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Ophthalmology · Article 12 of 15