Diabetic patients with established diabetic eye disease are at risk of visual loss from vitreous haemorrhage, traction retinal detachment, macular oedema, cataract and eventually posterior capsule opacification. If there is an effective screening service, timely adequate photocoagulation should minimise visual loss from vitreous haemorrhage, traction retinal detachment and macular oedema. Vitreoretinal surgery should only be required in exceptional cases. Extracapsular cataract surgery and intraocular lens insertion can be followed by a dramatic worsening of pre-existing diabetic macular oedema. This can be prevented provided the severity of the retinopathy is recognised pre-operatively and treated appropriately by photocoagulation either before surgery or shortly afterwards. Neovascular glaucoma can follow YAG laser capsulotomy if the retina is very ischaemic. This likewise can be prevented provided the severity of the retinopathy is recognised and treated adequately by scatter photocoagulation.