Diabetic Retinopathy

Diabetic retinopathy is a condition where the blood vessels in the retina are damaged by prolonged exposure to high blood sugar levels (hyperglycaemia) causing a progressive deterioration in the health of the retina.

 

Pathophysiology

Hyperglycaemia leads to damage to the retinal small vessels and endothelial cells. Increased vascular permeability leads to leakage from the blood vessels, blot haemorrhages and the formation of hard exudates. Hard exudates are yellow/white deposits of lipids in the retina.

Damage to the blood vessel walls leads to microaneurysms and venous beading. Microaneurysms are where weakness in the wall causes small bulges. Venous beading is where the walls of the veins are no longer straight and parallel and look more like a string of beads or sausages.

Damage to nerve fibres in the retina causes fluffy white patches to form on the retina called cotton wool spots.

Intraretinal microvascular abnormalities (IMRA) is where there are dilated and tortuous capillaries in the retina. These can act as a shunt between the arterial and venous vessels in the retina.

Neovascularisation is when growth factors are released in the retina causing the development of new blood vessels.

Classification

Diabetic retinopathy can be split into two broad categories: non-proliferative and proliferative depending on whether new blood vessels have developed. Non-proliferative is often called background or pre-proliferative retinopathy as it can develop in to proliferative retinopathy. A condition called diabetic maculopathy also exists separate from non-proliferative and proliferative diabetic retinopathy.

These conditions are classified based on the findings on fundus examination.

 

Non-proliferative Diabetic Retinopathy

  • Mild: microaneurysms
  • Moderate: microaneurysms, blot haemorhages, hard exudates, cotton wool spots and venous beading
  • Severe: blot haemorrhages plus microaneurysms in 4 quadrants, venous beating in 2 quadrates, intraretinal microvascular abnormality (IMRA) in any quadrant

 

Proliferative Diabetic Retinopathy

  • Neovascularisation
  • Vitreous haemorrhage

 

Diabetic Maculopathy

  • Macular oedema
  • Ischaemic maculopathy

 

Complications of Diabetic Retinopathy

  • Retinal detachment
  • Vitreous haemorrhage (bleeding in to the vitreous humour)
  • Rebeosis iridis (new blood vessel formation in the iris)
  • Optic neuropathy
  • Cataracts

 

Management

  • Laser photocoagulation
  • Anti-VEGF medications such as ranibizumab and bevacizumab
  • Vitreoretinal surgery (keyhole surgery on the eye) may be required in severe disease

 

Last updated April 2019
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