Retinal Vein Occlusions
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Direct answer
Retinal vein occlusion presents as sudden, painless, unilateral visual loss over a haemorrhagic fundus. Central retinal vein occlusion (CRVO) floods all four quadrants with dot-blot and flame haemorrhages along dilated, tortuous veins and a swollen disc; branch retinal vein occlusion (BRVO) confines bleeding to one quadrant at an arteriovenous crossing, most often superotemporally. Splitting CRVO into ischaemic and non-ischaemic types decides prognosis: the ischaemic eye carries an afferent pupillary defect, vision often below 6/60 and a high risk of anterior segment neovascularisation with neovascular glaucoma — classically around three months, the "90-day" or thrombotic glaucoma — demanding panretinal photocoagulation. Macular oedema, the main cause of persistent poor vision, is treated with intravitreal anti-VEGF injections.
What you must remember
- Risk factors: hypertension, diabetes, hyperlipidaemia, glaucoma and advancing age; in the young, consider oral contraceptives, antiphospholipid syndrome, hyperviscosity and dehydration.
- Non-ischaemic CRVO: mild vision reduction, no afferent pupillary defect, few cotton-wool spots; many stabilise, though macular oedema can still reduce reading vision.
- Ischaemic CRVO: vision commonly below 6/60, a relative afferent pupillary defect, more than ten cotton-wool spots and deep dark haemorrhages; fluorescein angiography shows widespread capillary non-perfusion.
- Neovascular risk: iris and angle new vessels appear within about three months in a large share of ischaemic eyes — neovascular glaucoma, historically the "90-day glaucoma"; monthly review with gonioscopy for the first three to six months is mandatory.
- Treatment forks: panretinal photocoagulation when new vessels appear or the angle is threatened (prophylactic scatter laser before neovascularisation did not help in the Central Vein Occlusion Study); intravitreal anti-VEGF for macular oedema; vitrectomy for persistent vitreous haemorrhage.
- BRVO: occurs at an arteriovenous crossing where a sclerotic artery compresses the vein; quadrant of haemorrhages follows the occluded branch; anti-VEGF is first line for macular oedema, with grid laser an older option and sector scatter laser for new vessels.
- Young adults with periphlebitis and vitreous haemorrhage belong to Eales disease rather than simple vein occlusion.
- Differentiating CRVO from papilloedema: papilloedema is bilateral with relatively preserved early vision, while CRVO is overwhelmingly unilateral with haemorrhages in all four quadrants; diabetic retinopathy is bilateral with hard exudates and microaneurysms at the posterior pole.
- Systemic workup: blood pressure, fasting glucose, lipids; in the under-fifties add thrombophilia screening and carotid evaluation where indicated.
Ischaemic or not — the branching that matters
A 65-year-old hypertensive man wakes to find the right eye blurred; acuity is 6/36, there is a right afferent pupillary defect, and the fundus shows dilated tortuous veins with dot-blot haemorrhages in all four quadrants and a dozen cotton-wool spots. Each element of that sentence is a decision node. The four-quadrant pattern makes it a central occlusion; the poor acuity, the pupillary defect and the cotton-wool count push it towards the ischaemic type, which fluorescein angiography will confirm by showing large areas of capillary non-perfusion. Plan the follow-up now: gonioscopy and iris examination monthly for at least three to six months, because rubeosis is silent until the pressure climbs; the moment new vessels appear, panretinal photocoagulation blunts the drive toward neovascular glaucoma. His central vision depends on macular oedema management — monthly anti-VEGF injections with optical coherence tomography monitoring — and on how much foveal perfusion survived. Had the acuity been 6/12 with no pupillary defect and scant cotton-wool spots, the label would be non-ischaemic, the outlook far kinder, and the job mainly observation with treatment of oedema.
Where students slip
Two slips cost marks. The first is recommending prophylactic panretinal photocoagulation for every ischaemic CRVO: the evidence reserves laser for established or imminent neovascularisation. The second is mislabelling a fundus photograph of CRVO as papilloedema or diabetic retinopathy; the exam expects the reasoning — unilateral versus bilateral, four-quadrant haemorrhages, dilated veins, and the state of vision and pupil. The "90-day glaucoma" one-liner is asked verbatim in Indian postgraduate examinations.
Frequently asked questions
What are the fundus findings of central retinal vein occlusion?
Dilated tortuous veins with dot-blot and flame-shaped haemorrhages scattered across all four quadrants, cotton-wool spots, optic disc swelling and often macular oedema — the "blood-and-thunder" fundus.
What is 90-day (thrombotic) glaucoma?
Neovascular glaucoma following ischaemic central retinal vein occlusion, with iris and angle new vessels typically arising within about three months of the occlusion.
Which features classify a CRVO as ischaemic?
Vision commonly below 6/60, a relative afferent pupillary defect, numerous cotton-wool spots and extensive capillary non-perfusion on fluorescein angiography.
How is macular oedema in vein occlusion treated?
Intravitreal anti-VEGF injections (ranibizumab, aflibercept or bevacizumab) are first line, monitored by optical coherence tomography; grid laser retains a role in some branch occlusions.
Where does a branch retinal vein occlusion most often occur?
At an arteriovenous crossing — typically superotemporal, where a thickened arteriole compresses the shared adventitia of the crossing vein.
How is CRVO differentiated from papilloedema on a photograph?
Papilloedema is bilateral with preserved early vision and haemorrhages near the disc; CRVO is unilateral with four-quadrant haemorrhages, dilated veins and visual loss proportional to ischaemia.