Diabetes mellitus is still one of the commonest causes of blindness worldwide. The ophthalmic complications of diabetes include diabetic retinopathy (DR), cataracts, primary open angle and neovascular glaucoma, and cranial nerve palsies. Retinovascular disease, including retinal vein and artery occlusion, and non-arteritic ischaemic optic neuropathy are more common in diabetic subjects. DR occurs in approximately 30–35% of diabetic subjects with ethnic differences. The primary abnormalities of DR are capillary basement membrane thickening, such that it becomes porous, and capillary occlusion with resultant retinal ischaemia. In Type 1 diabetes, DR is almost invariable after 15 years of disease duration. In Type 2 diabetes, 20% have retinal signs at diagnosis of diabetes, rising to a prevalence of 60% after 15 years of known disease duration. Major modifiable risk factors for DR include poor glucose and blood pressure control, and increasing lipid levels. In broad terms, Type 1 diabetes is associated with proliferative retinopathy, and Type 2 diabetes with maculopathy.