Retinal vascular disorders

  1. Retinal artery occlusion: There are a number of ways in which the retinal artery can become blocked. The most common one is by an embolus. It causes sudden (over a few seconds), unilateral painless visual loss. Damage becomes increasingly lethal and irreversible with time. The optimal treatment window during which something can be done is somewhat controversial but believed to be about 90-100 minutes. This condition is an ophthalmological emergency.
  2. Retinal vein occlusion: Occlusion of the retinal venous system by thrombus formation is the most common cause but other causes include disease of the vein wall and external compression of the vein. The stagnated blood combined with associated hypoxia results in extravasation of blood constituents, causing further stagnation and so on, resulting in the creation of a vicious circle of events. Ischaemic damage to the retina stimulates increased production of vascular endothelial growth factor (VEGF) which in turn may lead to neovascularisation – a process that can result in haemorrhage (as the new vessels are of poor quality) or neovascular glaucoma.