Vein occlusion

• Retinal vein occlusion (RVO) occurs when a thrombus forms in the retinal veins and obstructs the venous drainage from the retina.
• The central retinal vein runs through the optic nerve and is responsible for draining retinal capillaries
• RVO can be classified anatomically based on the location of the occulsion:

  • Branch retinal vein occlusion (BRVO): due to obstruction of one of the four retinal veins
  • Central retinal vein occlusion (CRVO): due to obstruction of the main retinal vein, which is responsible for draining all retinal capillaries
• RVO usually occurs unilaterally
• RVO can also be classified as ischaemic or non-ischaemic.
• Risk factors:

  • Age
  • Atherosclerosis: hyperlipidaemia, hypertension and diabetes
  • Open-angle glaucoma
  • Inflammatory causes: sarcoidosis, Lyme disease
  • Hypercoagulable states: smoking, oral contraceptive pill, pregnancy, malignancy, sickle cell disease
  • Myeloproliferative disorders
  • Systemic vasculitis: Behcet’s disease, polyarteritis nodosa
• Symptoms:

  • Sudden, painless unilateral visual loss
  • More gradual than in retinal artery occlusion
  • Partial visual field defect and metamorphosia
  • Can be asymptomatic if the macula is spared
• Examination:

  • Reduced visual acuity: significantly reduced visual acuity is more suggestive of ischaemia
  • Relative afferent pupillary defect (RAPD): suggestive of ischaemia
  • Visual field defect
• Ophthalmoscopy:

  • Dot/blot haemorrhages, vascular dilatation and tortuosity of retinal veins
  • Macular oedema - hard exudate
  • Evidence of ischaemia
  • Neovascularisation and vitreous haemorrhage
• Treatment (macular oedema):

  • Anti-VEGF agents (ranibizumab, aflibercept or bevacizumab): may help reduce vessel leakage
  • Intravitreal steroid implant (dexamethasone): may also help control oedema and blood leakage
  • Macular laser therapy: less common