Aetiology

mechanisms of vitreous haemorrhage

• vitreous haemorrhage may be caused by the following mechanisms:
  • retinal vessels that are vulnerable to bleeding
  • rupture of normal retinal vessels due to stress
  • extension of blood from an adjoining source
• abnormal retinal blood vessels prone to bleeding :
  • occurs as a result of neovascularization in response to ischemia
  • is induced by vascular endothelial growth factor (VEGF), etc
  • is seen in diseases such as:
    • diabetic retinopathy
    • sickle cell retinopathy
    • retinal vein occlusion
    • retinopathy of prematurity
    • ocular ischemic syndrome
  • these newly formed vessels:
    • are fragile
    • are prone to spontaneous bleeding
    • can rupture due to vitreous traction that occurs with usual movements of the eye
• rupture of normal vessels
  • occurs when mechanical force is greater than their structural integrity
    • e.g posterior vitreous detachment with or without a retinal tear or detachment
    • retinal detachment
  • can be caused by direct injury to intact vessels
    • trauma (blunt /perforating)
    • main cause in age less than 40
  • may be associated with Terson’s syndrome
    • a rare cause
    • associated with subarachnoid hemorrhage
    • sudden increase in intracranial pressure can cause retinal venules to rupture
• extension of blood through the internal limiting membrane into the vitreous from an adjoining source
  • these hemorrhages may arise from :
    • macroaneurysms of the retina
    • choroidal neovascularization
    • tumors

Reference:

(1) John P Berdahl, et al, vitreous hemorrhage: diagnosis and treatment,eye net magazine, © American Academy of Ophthalmology, 2007