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Retinal Vein Occlusion

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Overview

Retinal vein occlusions are a cause of sudden and painless vision loss. The central retinal vein can be occluded (central retinal vein occlusion, CRVO), or one of its branches can be occluded (branch retinal vein occlusion, BRVO). BRVOs are more common than CRVOs.

CRVOs are caused by blockages, typically due to thrombi forming in the lumen of the central retinal vein. BRVOs commonly happen at arteriovenous crossings and typically affect a more limited area of the fundus, which is usually one quadrant of retinal tissue. 

Epidemiology

  • Incidence increases with age
  • Most commonly seen in people >65 years
  • Incidence equal in men and women

Risk Factors

  • Increasing age
  • Atherosclerosis
  • Cardiovascular disease
  • Hypertension
  • Diabetes mellitus
  • Hyperlipidaemia
  • Smoking
  • Glaucoma
  • Thrombophilias

Presentation

The main presenting complaint is sudden and painless vision loss which is usually unilateral:

Fundoscopy may show:

  • Flame-shaped haemorrhages
  • Cotton-wool spots
    • Due to damage to nerve fibres and accumulation of material from them
  • Venous tortuosity
  • Optic nerve head oedema
  • Macular oedema

Differential Diagnoses

Central retinal artery occlusion

  • Clinically difficult to distinguish
  • Fundoscopy shows a pale retina with a “cherry red spot”

Vitreous haemorrhage

  • Can also cause sudden visual loss if the bleed is large
  • Small-moderate bleeds can cause floaters or dark spots

Diabetic retinopathy

  • Fundoscopy shows microaneurysms, haemorrhages, and neovascularisation
  • Cotton-wool spots are less frequent

Retinal detachment

  • Flashes of light and floaters followed by a “curtain” coming over the vision
  • Fundoscopy may show detachment

Investigations

The diagnosis of retinal vein occlusion is clinical, based on the history and examination; however, the following tests may be considered:

  • Fluorescein angiography:
    • To confirm diagnosis if fundoscopy inconclusive
  • Optical coherence tomography:
    • To look for macular oedema
  • Full blood count:
    • May show haematological causes of clotting e.g. thrombocytosis
  • Blood glucose:
    • For diabetes mellitus
  • Lipid profile:
    • For cardiovascular risk factors
  • CRP and ESR:
    • For systemic inflammatory conditions

Management

  • Immediate referral (within 24 hours) to ophthalmology
  • Most patients are observed and managed conservatively by optimising their risk factors where possible
  • Some treatment options are considered in certain patients with complications:
    • Macular oedema – intravitreal anti-vascular endothelial growth factor (VEGF) e.g. ranibizumab, aflibercept, brolucizumab, bevacizumab
    • Retinal neovascularisation – laser photocoagulation

Complications

  • Loss of vision
  • Neovascularisation – may cause increased intraocular pressure and further occlusions
  • Macular oedema – may cause central vision blurring
  • Vitreous haemorrhage

Prognosis

Central retinal vein occlusion

  • Most patients have persisting reduced central vision due to macular oedema
  • Non-ischaemic CRVO has a better prognosis than ischaemic CRVO, but only <10% of patients recover to normal visual acuity. 1/3 of patients go on to develop ischaemic CRVO within 3 years.
  • Ischaemic CRVO has a poor prognosis

Branch retinal vein occlusion

  • The prognosis is generally good depending on the amount of neovascularisation occurring. 50% of patients return to having a visual acuity of 6/12 or better.

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