Diabetic Retinopathy Overview

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Diabetic retinopathy or eye disease is the commonest cause of visual impairment in people of a working age. There are now effective medical, laser and surgical treatments. Diabetic eye disease is best detected before vision is impaired (Recommendations for a UK national screening strategy : NHS NSC Diabetic retinopathy screening). Diabetes UK gives useful advice for patients and their doctors (Diabetes UK Home page). In Scotland the NHS is developing clinical standards for the way doctors look after diabetes (Clinical Standards board). This work is being done in conjunction with the Health Technology Board for Scotland and the Royal College of Physicians of Edinburgh - SIGN - Scottish Intercollegiate Guidelines Network.

What is diabetic retinopathy ?

Diabetic retinopathy or eye disease refers to the results of higher blood sugars damaging capillaries that supply the retina. Capillaries are small blood vessels that connect arteries taking blood into an organ, such as the eye, to the veins taking blood out. It is at the level of the capillaries that oxygen and various nutrients are released to the organ. In diabetes the capillaries may become damaged and block off. Healthy capillaries next to these damaged capillaries try to grow in new vessels but this process is only partially successful resulting in little balloons or microaneurysms forming on the side of the capillaries. These balloons are not harmful in themselves. They can however bleed or leak fluid leading to swelling up of the retina.

A capillary B early microaneurysm formation C capillary D large microaneurysm F ruptured microaneurysm For more information on specific features see Diabetic Retinopathy: Grading & Burden

This stops it working correctly. If enough of the capillaries are blocked off then a new blood vessel will grow. Normal blood vessels grow within the retina but these new vessels grow on the surface of the retina inside the eye. Unfortunately they do not help the retina and are prone to bleeding and pulling on the retina.

NV new vessel CWS cotton wool spot CE circinate exudates

Bleeding new vessels Blood hides the retina

Bleeding leads to large floaters that prevent the patient seeing. Pulling on the retina can result on the retina being pulled off- a retinal detachment, with more serious damage to vision.

Traction on the retina leading to vertical tractional detachment

Medical Treatment

The most important aspect of diabetic retinopathy is prevention and screening.

Prevention:

1. Tight blood pressure control
   1. bmj.com Abstracts: UK Prospective Diabetes Study Group 317 (7160): 703)
2. Good control of blood sugars
   1. NEJM -- Abstracts: The Diabetes Control and Complications Trial Research Group 329 (14): 977
   2. bmj.com Abstracts: Stratton et al. 321 (7258): 405;
   3. bmj.com Herman 319 (7202): 104
3. Correction of anaemia
4. Treatment of hyperlipidaemia

Where retinopathy is present these aspects become even more important

Screening

1. Diabetic Retinopathy: Grading & Burden
2. Recommendations for a UK national screening strategy : NHS NSC Diabetic retinopathy screening
3. In Scotland the NHS is developing clinical standards for the way doctors look after diabetes (Clinical Standards board)
   1. This work is being done in conjunction with
      1. the Health Technology Board for Scotland
      2. the Royal College of Physicians of Edinburgh - SIGN - Scottish Intercollegiate Guidelines Network.

Laser Treatment

• New Vessels
  • Laser treatment is very effective for dealing with new vessels. It works best before bleeding has occurred. There are Side-effects and complications of laser but compared to total loss of sight in an affected eye these are a lesser of two evils. Most patients do not experience any side-effects. Laser treatment is usually uncomfortable rather than painful. If the eye becomes very sore after treatment, especially if it turns red then you should return to the eye department without delay. If you do find it painful then tell the doctor who is doing your treatment. Many patients are helped by being given codeine phosphate 60 mg orally 30-60 minutes before treatment. If this is not enough then the eye can be anaethetised with a local anaesthetic. This does not mean putting a needle into the eye. Very occasionally patients need a general anaesthetic. The disadvantage is that you have to come into hospital and stay overnight. The laser used in theatre puts on larger burns so there are more likely to be side-effects and you often need more than one treatment. Virtually all patients with new vessels require at least two treatments
• Macular Oedema
  • If there is leakage of fluid at the centre of the retina this is termed macular oedema.. Laser treatment is less effective but can still be worthwhile. The main aim of treatment is to prevent further visual loss. Laser treatment to the macula can ocasionally itself cause visual loss so most people opt not to have laser unless they feel their vision has actually been affected even if the doctors can see a problem. Leakage of fluid causes blurring of vision in the centre. This problem progresses very slowly and therefore careful supervision is a sensible way of managing people until they feel their vision is being affected. Treatment is usually guided by special photographs taken called a fluorescein angiogram. This enables the doctor to work out where the leakage is and direct treatment to those areas. The effect of laser in this situation is slow and a response cannot often be seen for up to 4 months.
  • Ischaemic Macular Oedema
    • In some patients the swelling at the centre of the retina is not because fluid has leaked out but is because the cells at the back of the retina are sick and swollen up. This is usually because the blood supply has been damaged and is determined ischaemic maculopathy. Although laser will not help tightening up blood pressure and gradually improving diabetic control is important to prevent further deterioration.

Surgery

• Bleeding or Retinal Detachment

If the bleeding will not spontaneously resolve or the retinal detachment is threatening sight then an operation is required. This is usually a Vitrectomy. This removes the gelly which contains the blood or is causing the pulling on the back of the eye.