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Diabetic Retinopathy

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Overview

Diabetic retinopathy (DR) describes damage to the small blood vessels in the retina due to chronically high glucose levels in patients with diabetes mellitus. It is usually bilateral. The progression of retinopathy is associated with the severity and duration of chronically high glucose levels.

It is the most common eye problem secondary to diabetes. Other problems can be:

Diabetic retinopathy can fall into two types:

  • Diabetic retinopathy which can be subdivided into:
    • Non-proliferative DR (NPDR)
    • Proliferative DR (PDR) – more sight-threatening
  • Diabetic maculopathy – more sight-threatening

Epidemiology

  • Diabetic retinopathy is one of the most common causes of sight impairment
  • PDR is more common in type 1 diabetics
  • Diabetic maculopathy is more common in type 2 diabetics

Classification

Non-proliferative diabetic retinopathy

Non-proliferative DR has no neovascularisation and can be subdivided into:

  • Mild NPDR:
    • Haemorrhages
    • Microaneurysms
  • Moderate NPDR:
    • Haemorrhages
    • Microaneurysms
    • Cotton-wool spots
    • Venous beading
    • Intraretinal microvascular abnormalities
  • Severe NPDR:
    • >20 intraretinal haemorrhages in each of 4 quadrants
    • Venous beading in 2 or more quadrants
    • Intraretinal microvascular abnormalities in one or more quadrants

Proliferative diabetic retinopathy

Proliferative diabetic retinopathy is characterised by the presence of new vessels. These vessels are fragile and can haemorrhage leading to vision loss and retinal scarring. This is more common in type 1 diabetics

Diabetic maculopathy

  • Thickening of the retina at the centre of the macula
  • Hard exudates at the centre of the retina
  • Macular oedema may be present
  • More common in type 2 diabetes

Risk Factors

  • Younger age of onset when diagnosed with diabetes
    • There has been a long time for glucose to be chronically high
  • Increased duration of diabetes
  • Poor diabetic control
  • Hypertension
  • Renal disease
  • Pregnancy can cause the progression of existing retinopathy

Presentation

Patients may have normal eyesight or have such small visual impairment that is unnoticeable even in the presence of PDR or diabetic maculopathy. Some features are:

  • Sudden onset of dark floaters if haemorrhages occur
  • Painless visual loss if severe haemorrhages occur
  • Painless and gradual vision loss

Investigations

  • Fundoscopy and photographs of the fundus
    • This allows for a baseline to be established and monitoring for changes
  • Optical coherence tomography
    • May show macular oedema
  • Fluorescein angiography
    • May show macular leakage and neovascularisation
  • Ultrasonography of the eyes

Management

Referral

  • Any patient who is diagnosed with type 2 diabetes should be referred to the local eye screening service
  • Urgent (within 24 hours) referral to an ophthalmologist should be arranged if there are any of the following:
    • Sudden loss of vision
    • Rubeosis iridis (neovascularisation on the iris surface)
    • Vitreous/pre-retinal haemorrhage
    • Retinal detachment 
    • Neovascularisation

All patients

  • 1st-line: improve glycaemic control + modifiable risk factors e.g. blood pressure + observe

Non-proliferative diabetic retinopathy

  • If severe: consider pan-retinal photocoagulation

Proliferative retinopathy

  • 1st-line: pan-retinal photocoagulation + intravitreal anti-vascular endothelial growth factor (VEGF) e.g. ranibizumab, aflibercept, brolucizumab, bevacizumab
  • If severe PDR: vitrectomy

Monitoring

  • Children with type 1 or 2 diabetes are monitored annually, starting at 12 years of age, to assess for early signs of diabetic retinopathy
  • Adults with type 1 or 2 diabetes are screened yearly

Patient Advice

  • Patients should be informed that once vision is lost, treatment is not likely to restore it but stop its progression
  • Patients should be informed that the progression of diabetic retinopathy can be slowed by effective diabetic and hypertensive control
  • Patients should be informed that attending screening allows to identify diabetic retinopathy at an earlier stage and intervene earlier, improving outcomes

Complications

  • Acute angle-closure glaucoma:
    • This is due to rubeosis iridis (neovascularisation on the iris surface) occluding the trabecular meshwork
  • Vitreous haemorrhage
  • Retinal detachment
  • Macular oedema

Prognosis

  • Diabetic retinopathy is chronic and progressive
  • If untreated, 90% of patients risk losing useful vision after 10 years

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