Preventing blindness due to diabetic retinopathy. Control glycaemia and blood pressure, and monitor the eyes.

If left untreated, diabetic retinopathy can lead to blindness. This review examines available treatments capable of preventing blindness in patients with type 1 or 2 diabetes, based on published reviews identified and analysed using the standard Prescrire methodology. Early-stage diabetic retinopathy does not affect vision. Visual acuity only declines when complicated proliferative retinal disease or macular oedema occur. Prevention of diabetic retinopathy is mainly based on appropriate control of glycaemia and blood pressure. Several randomised trials have shown that the risk of onset or aggravation of diabetic retinopathy is greatly reduced when HbA1c levels are maintained at about 7% and hypertension is treated. In patients with severe nonproliferative retinopathy or with proliferative retinopathy, several randomised trials have shown that panretinal laser photocoagulation reduces the risk of severe loss of visual acuity and blindness by about 50%. Laser therapy is also indicated in some types of macular oedema. A randomised trial has shown that vitrectomy is beneficial in cases of severe proliferative retinopathy with vitreous haemorrhage that severely reduce visual acuity. In patients with minimal visual acuity, a marked improvement was reported in 25% of operated eyes, compared to 10% of eyes in the control group. Antiplatelet drugs have no proven efficacy in the prevention or treatment of diabetic retinopathy. Intravitreal drug injections (corticosteroids, vascular endothelial growth factor antagonists) have a less favourable or less well documented risk-benefit balance than laser therapy. Diabetic patients should be informed that, even when their sight is not affected, regular ophthalmologic examination is needed to diagnose severe diabetic retinopathy that requires laser therapy.