Retinopathy

Diabetic retinopathy is the commonest cause of visual loss amongst working age people in the UK. However, it is almost completely preventable with good glycaemic control and regular retinal screening. Diagnosis is usually made on retinal screening. Management is by laser photocoagulation, good glycaemic control and there is also some role for ACE inhibition and possibly fibrate therapy.

Prevention

What are the main strategies for prevention of retinopathy?

The mainstay of prevention of retinopathy is still good glycaemic control as judged by an HbA1c of less then 7.5% (58 mmol/mol).

The importance of this strategy was convincingly demonstrated by the original and DCCT and UKPDS trials for T1DM and T2DM respectively. Numerous subsequent investigations have supported these findings.

What other strategies for retinopathy prevention are there?

More recently, some evidence supporting the use of fibrates (specifically fenofibrate) has emerged for the prevention of retinopathy. These data mainly relate to the prevention of retinopathy in T2DM. It should however be emphasised that this has not yet become widely accepted practice and has not as yet been incorporated into the major national guidelines.

For patients with T2DM, control of blood pressure has been shown to be an effective way of reducing the risk of retinopathy. There is also some evidence that treatment with ACE inhibitors and with angiotensin receptor blockers has beneficial effects on retinopathy.

Other research has shown that a combined approach of intensive simultaneous control of hyperlipidaemia, blood pressure and glycaemia in T2DM also produces a modest risk reduction of retinopathy.

Management

Retinal screening

The mainstay of retinopathy management is retinal screening.

This should be performed annually with fully dilated pupils by an accredited retinal screening programme. These usually use digital retinal cameras and off-site grading of photos by ophthalmologists or by trained retinal graders. Grading is reported on a scale or R0 (no retinopathy) to R3 (proliferative retinopathy), with the addition of various other codes such as M1 (diabetic maculopathy) to add further specificity.

The system triggers automatic referral to an ophthalmologist when specific retinal grading criteria are exceeded.

What treatment modalities do ophthalmologists use?

Laser therapy

Laser photocoagulation is the commonest modality of treatment. Conventionally this is used when signs of pre-proliferative retinopathy are present, in a pan-retinal pattern, to arrest progression to full blown proliferative retinopathy.

Focal laser therapy is also used to treat specific areas of the retina, especially when hard exudates are threatening the fovea, or to photo-coagulate fragile vessels that are threatening to bleed.

Vitreal sugery

If there have been extensive retinal or intra-vitreal heamorrhage in the past, then vitrectomy may be used to restore some visual acuity. This type of surgery works by either removing the haemorrhage itself, vitreal scar tissue or even retinal scar tissue.

During surgery the vitreous is replaced with a liquid or a gas implant, to keep the retina stable and this is slowly absorbed as new vitreous gel is formed.

Steroid therapy

Intra-vitreal triamcinolone therapy involves the injection of a potent synthetic gluco-corticoid into the vitreous and can be a very effective treatment for macular oedema in association with maculopathy.

However, the published evidence base for this treatment is relatively sparse and the effects only last a maximum of three months, necessitating repeat treatments.

Medical therapy

Good glycaemic, blood pressure and lipid control are all essential adjuncts to the management of patients with retinopathy in order to help prevent its progression.

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