Phase 2a multicenter, open-label, parallel-arm design study to evaluate the safety, tolerability and pharmacodynamics of a single intravitreal injection comparing 2 dose levels (1 mg and 2 mg) of GB-102 on subjects with Diabetic Macular Edema and Retinal Vein Occlusion who have received prior treatment with anti-vascular endothelial growth factor (VEGF)