Laser treatment is effective for diabetic macular oedema and proliferative diabetic retinopathy. In focal diabetic macular oedema, laser coagulation of the microaneurisms prevents the leakage of liquid through their walls. In diffuse macular oedema, laser photocoagulation not only destroys the microaneurisms but probably also hereby causes stimulation of proliferation activity of endothelial cells in retinal capillaries and veins. For some patients with diabetic retinopathy there is a progression of retinal findings and complications arise that require surgery within the eye - pars plana vitrectomy (PPV). In general PPV is indicated in diabetic retinopathy in the following cases: vitreous opacity, traction disorders.