Central retinal vein occlusion
- Incidence: 35.00 cases per 100,000 person-years
- Most commonly see in infants
- Sex ratio: 1:1
- Both thrombus formation in the lumen of the central retinal vein, and thrombus in the central retinal artery compressing on the adjacent retinal vein, can cause CRVO.
- However, development of retinal vein occlusion has not been shown to be a predictor of subsequent stroke.
- No difference in prevalence of CRVO between men and women has been demonstrated.
- The prevalence of CRVO increases with age.
- Disorders of coagulation and systemic auto-inflammatory conditions (e.g. (Bechet’s disease, polyarteritis nodosa, sarcoidosis) are also risk factors.
- Rarely, retrobulbar compression of the retinal vein can cause compression e.g. from thyroid eye disease, orbital tumour or retrobulbar haemorrhage.
- Thrombosis in the retinal vein causes increased pressure in the vessels draining from the eye
- This causes transudation of blood products into the retina from the venous capillary beds, leading to increased interstitial oncotic pressure that results in macular oedema and capillary ischaemia.
- Retinal ischaemia induces vascular endothelial growth factor (VEGF) and other soluble cytokine production from retinal pigment epithelial cells.
- These factors promote vascular permeability and neovascularization, contributing to macular oedema and further exacerbating retinal ischaemia.
- The degree to which collateral vessels form, allowing for alternative venous drainage routes and the degree to which macular oedema has developed at presentation determines categorisation into ischaemic or non-ischaemic CRVO.
- For example, total CRVO in a patient with well-developed collaterals may present with only mild visual acuity deficits and macular oedema.
- Any patient with CRVO that has developed neovascularization at the angle has by definition already developed ischaemic CRVO.
- Sudden, painless reduction or loss of visual acuity, usually unilaterally
- Non-ischaemic CRVO presents with a less severe reduction in visual acuity
- 90% of patients with ischaemic CRVO have visual acuity of 6/60 or worse
- In the clinical history, thrombotic risk factors that may be present:
- Hypercoagulable disorders e.g. leukaemia, myeloma, Factor V Leiden
- Systemic inflammatory disorders e.g. Behçets disease, polyarteritis nodosa, sarcoidosis
- Clinical examination:
- Poor visual acuity (<6/60 on Snellen chart)
- Relative afferent pupillary defect
- Fundoscopy signs, to a greater degree in ischaemic CRVO versus non-ischaemic CRVO, include:
- Optic nerve head oedema
- Macular oedema
- Flame-shaped haemorrhages
- Cotton wool spots
- Venous tortuosity
- May indicate hyperviscosity, e.g. thrombocytosis
- Lipid profile
- Identification of modifiable risk factors
- A raised ESR prompts suspicious of systemic inflammatory disorder and auto-antibody screen
- Fasting glucose, Hba1c
- Diabetic screen or assessment of glycaemic control
- Fundus fluorescein angiography (FFA) will be done to at presentation measure areas of capillary non-perfusion. This confirms the diagnosis and can assess the severity of the condition.
- Distinguishes between subtypes of CRVO.
- Non-ischaemic CRVO = presence of <10 areas of non-perfusion
- Ischaemic CRVO = presence of >=10 areas of non-perfusion
- Optical coherence tomography (OCT)
- Confirms extent of macular oedema
- Can be used to monitor the response of macular oedema to treatment
Further ophthalmological clinical examination:
- Slit-lamp examination
- To further assess the anterior and posterior segments of the eye
- Neovascularisation of the iris indicates severe ischaemic CRVO
- To evaluate for the angle for glaucoma and neovascularisation
Otherwise, the key ophthalmological differentials are:
- Branch retinal venous occlusion
- A less clinically severe, but far more common variant of central retinal vein occlusion
- Differentiated by clinical examination (macular oedema is infrequently seen on fundoscopy) and imaging (fundus fluorescein angiography demonstrates only single-quadrant non-perfusion areas)
- Treatment goals are similar, monitoring for signs of ischaemic changes warranting anti-VEGF or PRP treatment.
- Retinal detachment
- Sudden, painless, usually central loss of vision
- Patients often experience floaters or photopsia, which are very unusual in CRVO
- Area of detachment seen on fundoscopy
- Diabetic retinopathy
- Key risk factors present in clinical history, higher risk amongst patients with diabetes with suboptimal glycaemic control
- Bilateral signs in diabetic retinopathy, important differentiating factor from CRVO in which unilateral symptoms are far more common
- Fundoscopy demonstrates micro-aneurysms
- Ischaemic optic syndrome (IOS)
- Carotid artery stenosis leads to ocular hypoperfusion.
- Rarer but important differential as risk of visual loss and hypoperfusion of other cerebral areas
- Key differentiating factors on fundoscopy are microaneurysms on (common in IOS), and macular oedema (rare in IOS).
- General measures:
- In ischaemic and non-ischaemic CRVO, risk factor management is essential e.g. smoking cessation, diabetes control, treatment of hypertension and hyperlipidaemia.
- Furthermore, in both categories control of glaucoma if present is essential, as anti-VEGF therapies cannot be administered with high intraocular pressures. This can be managed with ophthalmic beta-blockers, alpha-2 agonists, carbonic anhydrase inhibitors, prostaglandin analogues, or glaucoma surgery.
- Non-ischaemic CRVO
|6/12 or better||Can observe with regular follow up as may spontaneously resolve. However, 30% may convert to an ischaemic CRVO over three years due to an increase in the area of non-perfusion|
|6/96 or better||Intravitreal anti-VEGF therapy indicated. Ranibizumab and aflibercept are two anti-VEGF agents recommended by NICE. Monthly intravitreal injections until stable visual acuity achieved.|
|Less than 6/96||High risk of ocular neovascularisation (e.g. progression to ischaemic CRVO), and improvement with anti-VEGF therapy alone unlikely to produce improvement in visual acuity. Therefore patients should be closely observed for progression to ischaemic CRVO.|
- Ischaemic CRVO
- Urgent pan-retinal photocoagulation (PRP) where neovascularisation is seen, with repeat at 2 weeks if required.
- In the absence of neovascularization, monthly follow-up to monitor. Where this is impractical, prophylactic PRP may be considered.
- Macular oedema managed with anti-VEGF therapy.