Diabetic Retinopathy
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Introduction

Diabetic retinopathy is a preventable complication of diabetes mellitus (both types 1 and 2). The risk is directly correlated to the patients glycemic control – worse control results in increased risk of retinopathy (and the other complications of diabetes).
Aiming to keep the patients HbA1c level at <7% in the long-term reduces the risk of diabetic retinopathy.
Diabetic retinopathy is a slowly progressive disorder, that if not managed can lead to blindness.
Diabetic retinopathy is the most common cause of blind registration for patients in the UK between 15 and 65 years.
  • Diabetic retinopathy is thought to affect about 10% of patients with diabetes, but this rises to over 80% at 20 years after diagnosis of diabetes
There are several stages of the disorder, which are generally classified by the appearance of the retina. The main differentiation is made between non-proliferative where the vision is generally normal and proliferative where vision is often affected due to macular ischaemia, oedema and new vessel formation.
Patients with known diabetes should have annual screening with an ophthalmologist, that includes retinal photography to assess for the signs of diabetic retinopathy.
Treatment mainly includes factors for the treatment of the underlying diabetes including maximising glycemic control, controlling blood pressure and cholesterol, smoking cessation, a balanced healthy diet and regular exercise. Specific treatment of the  retinopathy intel may involve laser therapy, or injections of steroids or anti-VEGF into the eye.

Pathology

The exact mechanism by which diabetes causes diabetic retinopathy is not well understood.

  • Diabetic retinopathy is a type of¬†microvascular¬†complication of diabetes
  • Development of diabetic retinopathy correlates to the time since diagnosis of diabetes – the longer the duration the higher the chance of diabetic retinopathy (80% have retinopathy after 20 years)
  • Coexisting disease- especially hypertension
  • Smoking
  • Pregnancy– may accelerate retinopathy
Diabetes causes changes in the retina due to
  • the development of microaneurysms which allow plasma leakage into the retina
  • the development of ischaemic retina
  • the development of AV shunts

Presentation

Most patient are asymptomatic. Even in those with visual declines, the onset may be so insidious (slow and variable) that symptoms may not beneficed by the patient.

Haemorrhages may cause acute onset dark spots (‘floaters’). Severe haemorrhage may cause visual loss. Haemorrhages are painless.

Examination

Slit-lamp / ophthalmoscope
  • Assessment and diagnosis is very difficult without the use of a slit lamp and / or retinal photography.
Fluorescein angiography (FFA)- to assess damage
Optical coherence tomography (OCT)- to assess if there is any macular oedema
Features of diabetic retinopathy as seen on the retina include:
  • Microanueysms –¬†weaknesses in the¬†capillary walls leads to small aneurysms
  • Hard exudates –¬†collections of proteins that congregate on the retinal surface
  • Cotton wool spots –¬†shite ‘fluffy’ patches on the retina
  • Haemorrhages –¬†from¬†repute of¬†weakened capillaries. Typically larger in appearance than micoaneurysms
  • Neovascularisation –¬†new blood vessel formation – an attempt by the retina to heal

The main differential for diabetic retinopathy is macular degeneration – which can have some similar exudates on the retina. Late stage diabetic retinopathy however should be easy to differentiate due to the larger number of signs.

Diabetic Retinoapthy
Diabetic retinopathy

Features

Non-proliferative retinopathy (background retinopathy)

  • Microaneurysms
  • Dot and blot haemorrhages
  • Cotton wool spots
  • Hard exudates

The vision is usually NORMAL

Proliferative Retinopathy
  • Macular oedema- gradual reduction in vision
  • New vessel growth (neovascularisation)
  • Retinal haemorrhage
  • Vitreous haemorrhage- sudden loss of vision
Vision can range from NORMAL to SIGHT-THREATENING (patients often describe this as sudden black curtain)

Treatment

Macular oedema=focal laser treatment to seal any leaking microaneurysms
In proliferative retinopathy- pan-retinal photocoagulation reduces vaso-proliferative factors and causes regression of new vessels
Macular Ischaemia: NO TREATMENT
Vitreous haemorrhage- vitrectomy

Screening

Patients should be screened at the time of diagnosis and annually thereafter.
Annual programme of dilated retinal photographs- referred to ophthalmologist if any pathology found. Pregnant DM patients should be examined every trimester.

Prevention

  • Optimal Management of DM
    • Lifestyle factors – diet and exercise
    • Medication
    • Insulin
    • Aim or HbA1c <7%
  • Optimal management of HTN
  • Smoking cessation
  • Encourage to go to screening
Key Points:
  • Most common cause of blind registration in younger patients
  • May be asymptomatic
  • Annual Screening and prevention is key
  • Laser and pan-retinal photocoagulation treatment is available in some circumstance

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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