29th December 2023

Retinal vein occlusion

Background & Epidemiology

Retinal vein occlusions (RVO) are a common form of retinal vascular disease second only to diabetic retinopathy in frequency.

RVOs can be classified into central retinal vein occlusions (CRVO), branch retinal vein occlusions (BRVO), and hemi-retinal vein occlusions (HRVO), depending on the affected vein(s). RVOs can be further classified into the ischaemic and non-ischaemic forms based on the size of the area of capillary non-perfusion.

CRVOs occur due to central retinal vein thrombosis at the level of the lamina cribrosa. BRVOs occur when systemic hypertension causes sclerosis of the retinal arterioles: as retinal arterioles and venules share a common adventitial sheath, the sclerosed arteriole compresses the lumen of the retinal venule, causing turbulent blood flow and thereby thrombosis.

The risk of developing RVO increases with age, with over 50% of cases occurring in patients aged 65 years and above. Other common risk factors include systemic hypertension, diabetes (for CRVO), increased body weight (for BRVO), renal failure, and hypercoagulable states, including dehydration, multiple myeloma, polycythaemia, oral contraceptive pill use, protein C and S deficiency, Factor V Leiden etc. Inflammatory diseases associated with occlusive periphlebitis, such as Behcet’s disease, sarcoidosis, or systemic lupus erythematosus, may occasionally cause RVOs.

Clinical features

Patients may be asymptomatic or describe a painless blurring of vision, depending on the area of retina affected and whether macular oedema is present. Macular oedema typically occurs when the superotemporal retinal vein or central retinal vein is affected.

The affected vein(s) is dilated and tortuous, with flame-shaped haemorrhages and dot or blot haemorrhages in the area of the retina drained by the affected vein. In CRVO, haemorrhages are present in all 4 quadrants of the retina, thereby producing the characteristic ‘blood and thunder’ fundoscopic appearance. Optic disc oedema may be present in CRVO. Cotton wool spots may be present. Signs of hypertension, such as arteriovenous nipping, may also be visible.

Management

Systemic Management:

Recommended investigations include blood pressure, serum glucose, and blood tests for ESR and CRP. Further assessment of potentially associated systemic conditions should be considered based on the patient’s age and medical history.

Underlying risk factors such as hypertension and hyperglycaemia should be addressed. The decision to continue oestrogen-containing treatments should be considered on an individual basis. It is important to note that there is conflicting evidence on whether patients with RVOs are at increased risk of stroke and cardiovascular disease. It may be that these conditions may share underlying risk factors such as hypertension and diabetes.

Ocular Management:

Patients should be monitored closely for sequelae such as macular oedema, which can be treated by close monitoring (if asymptomatic) or anti-vascular endothelial growth factor (VEGF) injections such as Ranibizumab or Aflibercept, or intravitreal steroid implants such as Ozurdex. Patients with ischaemic RVOs should also be closely monitored for retinal and anterior segment neovascularisation, which may be due to tissue hypoxia and subsequent release of VEGF and inflammatory mediators. Anti-VEGF injections can serve as a temporising measure, but patients will often require panretinal photocoagulation to reduce the VEGF drive. If this is not adequately treated, neovascular glaucoma can result. Intravitreal steroid implants such as Ozurdex are a second-line treatment option.

Image Source: Wikimedia Commons (2012). Branch retinal vein occlusion, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Branch_retinal_vein_occlusion.jpg (Accessed on: 20 May 2022).