In the Diabetic Retinopathy Study the 4-years rate for severe vision loss in patients with high-risk retinopathy was 20.4 %. In cases of proliferative retinopathy, panretinal (scatter) photocoagulation can reduce the risk for development of high-risk retinopathy by 50% over 6 years. When panretinal lasercoagulation is initiated, about 2000 laser spots are equally distributed in all four quadrants. Since panretinal photocoagulation bares risks like loss of field of vision, central vision reduction and loss of colour vision, this treatment can not be continued unlimited.