Patients were assigned to 1 of 6 retinopathy levels by the worst affected eye: • level 0 - no retinopathy • level 1 - minimal non-proliferative retinopathy • level 2 - moderate non-proliferative retinopathy • level 3 - severe non-proliferative retinopathy • level 4 - photocoagulated retinopathy • level 5 - proliferative retinopathy