The purpose of this study is to assess the efficacy and safety of up to 3 intravitreal injections of ocriplasmin (0.0625mg or 0.125mg), in subjects with moderate to very severe non-proliferative diabetic retinopathy (NPDR), to induce total posterior vitreous detachment (PVD) in order to reduce the risk of disease progression to proliferative diabetic retinopathy (PDR).