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Retinal vein occlusion (CRVO and BRVO)
Retinal vein occlusion causes haemorrhage, oedema and ischaemia in the area the vein drains; vision is lost from macular oedema — treated with anti-VEGF — and from neovascular complications, while vascular risk factors and intraocular pressure are investigated and treated in parallel.
Why it matters in the exam
CRVO presents as sudden painless loss of vision in an older adult with hypertension, and the fundus shows "blood and thunder" — haemorrhages in all quadrants, dilated tortuous veins, cotton-wool spots and disc swelling. BRVO occurs at an arteriovenous crossing, usually superotemporal, with wedge-shaped haemorrhages in the vein's territory. Risk factors: age, hypertension (the commonest), diabetes, dyslipidaemia, glaucoma and raised intraocular pressure; in a patient under 50 hyperviscosity, thrombophilia and vasculitis are also tested.
The key distinction in CRVO is between non-ischaemic and ischaemic forms: CVOS defined ischaemia as non-perfusion of 10 disc areas or more on angiography, and poor acuity and an RAPD also point to it. In the ischaemic form the risk of iris new vessels is high, mainly in the first 3 months (the "100-day glaucoma"), so the iris and angle are examined monthly for the first half year. PRP is given when new vessels appear, not prophylactically.
Macular oedema in both types is treated with anti-VEGF injections (ranibizumab, aflibercept, bevacizumab) as first line, with a dexamethasone implant as an alternative. In BRVO with retinal new vessels — sector laser. The outcome depends mainly on the starting acuity and the degree of ischaemia. There is no routine role for anticoagulation just because of the occlusion. The patient also needs work-up and follow-up with the family physician: a vein occlusion is a marker of overall cardiovascular risk, and treating hypertension, diabetes and lipids is part of treating the eye. In the fellow eye pressure and the disc should be checked, because undiagnosed glaucoma is often found only after the occlusion.
Key points
- CRVO: "blood and thunder"; BRVO: wedge haemorrhage at a crossing.
- Hypertension is the commonest risk factor; glaucoma too.
- Macular oedema → anti-VEGF.
- Ischaemic CRVO → monthly iris and angle follow-up.
- PRP when new vessels appear, not beforehand.
Summary table
| Type | Finding | Main risk | Treatment |
|---|---|---|---|
| Non-ischaemic CRVO | Haemorrhages in all quadrants, fair acuity | Macular oedema; conversion to ischaemic | Anti-VEGF for oedema, follow-up |
| Ischaemic CRVO | Non-perfusion of 10 disc areas or more, RAPD | Neovascular glaucoma | Monthly follow-up; PRP and anti-VEGF for NVI |
| BRVO | Wedge haemorrhages at a crossing | Macular oedema, NVE | Anti-VEGF; sector laser for NVE |
| Hemi-RVO | Half the retina involved | As BRVO | As BRVO |
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Sources
- AAO Preferred Practice Pattern: Retinal Vein Occlusions, 2019 — Systemic evaluation and treatment
- Royal College of Ophthalmologists: Clinical Guidelines — Retinal Vein Occlusion, 2022 — Management
- AAO Basic and Clinical Science Course, Section 12: Retina and Vitreous, 2024-2025 — Retinal venous occlusive disease
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.