Retinal vein occlusion

Referral priority: Moderate or urgent

All patients with signs of ischaemic central retinal vein occlusion (CVRO) must be urgently referred to an ophthalmologist following local guidelines. Patients with the non-ischaemic form of the condition – with or without macular oedema – should be referred to an ophthalmologist semi-urgently.

As there is a conversion rate of non-ischaemic CRVO to ischaemic CRVO within the first three months, it is recommended to review the patient within 4 weeks, regardless of the referral.

Written by
Marko Lukic
Edited by
Svein Tindlund and Jon Gjelle
June 2023


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Clinical signs

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Diagnostic procedures

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Management and Treatment

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Retinal vein occlusion (RVO) is a common retina vascular disorder and the second most common cause of blindness from retinal vascular disease after diabetic retinopathy.(1) It is classified based on the location of the occlusion. The cause of the occlusion differs, and in central retinal vein occlusion (CRVO), the cause is a thrombus which occludes the central retinal vein near the lamina cribrosa.(2) Hemi-retinal vein occlusion (HRVO) is a form of CVRO where the inferior or superior branch of the retinal vein is occluded, and half of the retina affected.

The branch retinal vein occlusion (BRVO) occurs when a thrombus occurs at the arteriovenous crossing point, secondary to atherosclerosis of the retinal artery causing compression of the retinal vein.(3) There are two major subtypes of BRVO: major and macular. The incidence of BRVO is most common in the superior temporal quadrant (58.1-66%), followed by the inferior temporal quadrant (29%), and least common in the nasal quadrants (12.9%).(4,5) Macular BRVO involves the superior macular region in 81% of cases and the inferior macular region in 19% of cases.(6)

The aetiology and risk factors of CRVO and BRVO differ.According to the Eye Case-Control Study Group, the risk factors for CRVO are hypertension, open-angle glaucoma, and diabetes mellitus, while the risk factors for BRVO are hypertension, high body-mass index, open-angle glaucoma, and cardiovascular disease.(7,8)

Further studies proved that other conditions are risk factors for developing central retinal vein occlusion:(8-11)

  • carotid insufficiency
  • hematologic alterations (hyperviscosity syndrome, multiple myeloma, blood dyscrasias (polycythaemia vera, lymphoma, leukaemia, sickle-cell disease or trait), anaemia, elevated plasma homocysteine, factor XII deficiency, antiphospholipid antibody syndrome, activated protein-C resistance, protein-C deficiency, protein-S deficiency)
  • systemic lupus
  • HIV
  • syphilis
  • some medications (oral contraceptives, diuretics)
  • dehydration
  • pregnancy

There is conflicting evidence that hypercoagulable conditions are risk factors for BRVO, while vasculitis is indeed one of the risk factors.(12)

Most patients with CRVO are older than 65 years. Most cases are unilateral, with approximately 6%-14% of the cases bilateral. BRVO is three times more common than CRVO. Men and women are affected equally, mostly between the ages of 60 and 70.(13) A large study from 2010 reported the prevalence of BRVO to be 2.8 per 1,000 in whites, 3.5 in blacks, 5.0 in Asians, and 6.0 in Hispanics, and the prevalence of CRVO to be 0.88 per 1,000 in whites, 0.37 in blacks, 0.74 in Asians, and 1.0 in Hispanics.(14)

The pathogenesis of CRVO is believed to follow the principles of Virchow’s triad for thrombogenesis, involving vessel damage, stasis, and hypercoagulability.(14) The central retinal vein and artery share a common adventitial sheath at arteriovenous crossings, posterior to the lamina cribrosa, so that atherosclerotic changes of the artery may compress the vein and cause CRVO.(15)

The association between BRVO and arteriovenous crossings has been proved in multiple studies. In almost all cases of BRVO (97.6-100%) the thick-walled artery is found anterior to the thin-walled vein.(16-18) The artery and vein also share a common adventitial sheath at these crossings, contributing to the predisposition of vein occlusion at these crossings. Arteriolar sclerosis increases the rigidity of the artery and further supports the mechanical basis of BRVO at arteriovenous crossings.(16,19) Mechanical compression of the vein by the rigid artery results in turbulent blood flow at arteriovenous crossings, resulting in venous intima-media and endothelial damage, which leads to vein occlusion.(5,20)

In addition, both BRVO and CRVO can be divided according to perfusion status, and classified as non-ischaemic and ischaemic. It is essential to be aware of the signs and symptoms of ischaemic form as it risks new vessel development and has a poorer visual prognosis.(21)



Patients with CRVO get a sudden unilateral drop in vision. The level of baseline visual acuity differs in ischaemic and non-ischaemic RVOs. In ischaemic ones, the baseline visual acuity is significantly decreased, while the non-ischaemic cases, it is mild to moderately decreased (20/200 or better). Symptoms of patients with HRVO are similar to those with CRVO.

Patients with BRVO complain of a sudden and painless decrease in vision or visual-field defect. In rare cases, patients may initially present with new floaters (secondary to vitreous haemorrhage), and in non-recognised cases, they develop new vessels and vitreous haemorrhage. Sometimes, patients may be asymptomatic, especially if BRVO is in nasal quadrants.


Clinical signs

Non-ischaemic central retinal vein occlusion (CRVO)

  • Scattered dot/blot and flame-shaped haemorrhages in all quadrants.
  • Tortuosity and dilatation of all branches of retinal veins (in HRVO, only superior or inferior branches).
  • Optic disc and macular oedema.
  • Cotton-wool spots.

Ischaemic central retinal vein occlusion (CRVO)

  • Relative afferent pupillary defect.
  • Profound blot and flame-shaped haemorrhages affecting the posterior pole.
  • Optic disc and macular oedema.
  • Tortuosity and engorgement of all branches of retinal veins.
Image 1. Ischaemic central retinal vein occlusion of the left eye. Tortuosity and dilatation of retinal veins is obvious.
Image 2. Inferior hemi-retinal vein occlusion. Note scattered haemorrhages in the inferior quadrants respecting horizontal raphe.

Branch retinal vein occlusion (BRVO)

  • Wedge-shaped distribution of intraretinal dot, blot, and flame-shaped haemorrhages (more intensive in ischaemic BRVO).
  • Lipid exudates and microaneurysms.
  • Tortuosity and dilatation of the retinal vein branch.
Image 3. Ischaemic HRVO. Note venous sheathing and new vessels.

Diagnostic procedures

Slit lamp examination and colour fundus photography – those two modalities are a classical method of recognising classic signs of retinal vein occlusion. The colour fundus photos are useful in monitoring the progression/recovery of clinical findings.

Optical coherence tomography – useful in detecting macular oedema and monitoring during treatment. Macular oedema appears as cystoid macular oedema with or without subfoveal neuroretinal detachment. Disruption of the sub-foveal ellipsoid zone (EZ) has prognostic value; patients with disrupted EZ have a poorer visual prognosis.(22)

Optical coherence tomography angiography – a novel diagnostic tool for determining macular and/or retinal perfusion.

Image 4. Mild cystoid macular oedema in a case of macular BRVO. Note the intraretinal cysts (black) and intraretinal hyperreflective material representing intraretinal haemorrhage.
Image 5. Old BRVO case. Note the subfoveal disruption of the ellipsoid zone, which is a poor visual-acuity prognostic factor.

Management and Treatment

All patients should have a systemic workup, and the following laboratory tests are recommended:(23)

  • Blood pressure measurement
  • Full blood count (FBC)
  • Erythrocyte sedimentation rate (ESR)
  • Blood glucose
  • Blood cholesterol
  • Urea
  • Creatinine
  • Plasma electrophoresis
  • Electrocardiogram (ECG)
  • Thyroid gland tests

Patients under the age of 50, who have a clinical picture of bilateral RVO, and a personal history of thrombus should have additional tests:(23)

  • Chest X-rays
  • C-reactive protein (CRP)
  • Thrombophilia screen
  • Angiotensin-converting enzyme (ACE)
  • Rheumatoid factor
  • Anti-nuclear antibody
  • Anti-DNA antibody
  • Treponema (syphilis) screening
  • Plasma homocysteine level
  • Carotid colour doppler

Patients with CRVO are at risk of developing new vessels of the iris and/or angle within the first 90 days. Patients with initially non-ischaemic signs of CRVO are also at risk of progressing to ischaemic form and require close monitoring. It is recommended that patients with ischaemic CRVO are reviewed every four weeks and those with non-ischaemic CRVO every 4-6 weeks for a period of 6 months. Furthermore, gonioscopy is strongly recommended in patients with features of ischaemic CRVO.

The Central Vein Occlusion Study (CVOS) Group-N report compared the efficacy of prophylactic panretinal photocoagulation (PRP) at the time of study entry in eyes with non-perfused CRVO that did not have evidence of iris neovascularisation (IVN) or angle neovascularisation (ANV) with delayed, but prompt, PRP application only when IVN/ANV was detected. The CVOS recommends that PRP should be delivered promptly after developing NVI/ANC but not prophylactically in eyes with nonperfused CRVO.(24)

Patients with BRVO may also develop new vessels of the retina. The Branch Vein Occlusion Study (BVOS) recommends that patients with ischaemic BRVO should undergo scatter laser photocoagulation only once neovascularisation has developed. BVOS data showed that scatter photocoagulation after neovascularisation develops, is as effective as performing it before neovascularisation develops, in preventing vitreous haemorrhage.(25)

Remember that patients with ischaemic RVO may experience vitreous haemorrhage due to the presence of new vessels. Those patients require a fundus fluorescein angiogram to assess retinal perfusion.

Retinal vein occlusion may be complicated with macular oedema. In CRVO and BRVO cases, the standard golden treatment is intravitreal agents, anti-VEGF, and steroids. Numerous studies proved the efficacy and safety of both types of drugs.(26-31) The grid macular laser may be an option in macular oedema secondary to BRVO.



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26 Campochiaro PA, Heier JS, Feiner L, Gray S, Saroj N, Rundle AC, Murahashi WY, Rubio RG, BRAVO Investigators. Ranibizumab for macular edema following branch retinal vein occlusion: six-month primary end point results of a phase III study. Ophthalmology. 2010 Jun 1;117(6):1102-12.

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