# Retinal Vein Occlusions > Retinal vein occlusion for NEET-PG Ophthalmology: four-quadrant haemorrhages in CRVO, ischaemic versus non-ischaemic, 90-day glaucoma, anti-VEGF and PRP. - Canonical URL: https://prepelephant.com/topics/neet-pg/ophthalmology/retinal-vein-occlusions - Exam / course: NEET-PG · Subject: Ophthalmology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Retinal Vein Occlusions", PrepElephant, https://prepelephant.com/topics/neet-pg/ophthalmology/retinal-vein-occlusions ## 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.