Intended for healthcare professionals

Clinical Review ABC of diabetes


BMJ 2003; 326 doi: (Published 26 April 2003) Cite this as: BMJ 2003;326:924
  1. Peter J Watkins

    Blindness is one of the most feared complications of diabetes but also one of the most preventable. Diabetes is the commonest cause of blindness in people aged 30 to 69 years. Twenty years after the onset of diabetes, almost all patients with type 1 diabetes and over 60% of patients with type 2 diabetes will have some degree of retinopathy. Even at the time of diagnosis of type 2 diabetes, about a quarter of patients have established background retinopathy. Treatment can now prevent blindness in the majority of cases, so it is essential to identify patients with retinopathy before their vision is affected.

    This article is adapted from the 5th edition of the ABC of Diabetes, which is published by BMJ Books (

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    Frequency of retinopathy (any degree) and proliferative retinopathy by duration of diabetes in people with diabetes diagnosed at age 30 or under, according to insulin treatment

    Classification of retinopathy

    Diabetic retinopathy is due to microangiopathy affecting the retinal precapillary arterioles, capillaries, and venules. Damage is caused by both microvascular leakage from breakdown of the inner blood-retinal barrier and microvascular occlusion. These two pathological mechanisms can be distinguished from each other by fluorescein angiography.

    Background retinopathy

    Microaneurysms are small saccular pouches, possibly caused by local distension of capillary walls. They are often the first clinically detectable sign of retinopathy and appear as small red dots, commonly temporal to the macula.

    Haemorrhages may occur within the compact middle layers of the retina and appear as “dots” or “blots.” Rarely, haemorrhages occur in the superficial nerve fibre layer, where they appear flame shaped; these are better recognised as related to severe hypertension.

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    Exudative maculopathy

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    Preproliferative retinopathy with venous bleeding, cotton wool spots, and some hard exudates

    Hard exudates are yellow lipid deposits with relatively discrete margins. They commonly occur at …

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