Pathologic changes in patients with DR. (A) Microaneurysm is one of the characteristic findings in patients with NPDR, demonstrated by tiny hyperfluorescent spots in the fluorescein angiography. (B) Disruption in neurovascular units and breakdown of inner BRB leads to ME in DR patients. Optical coherence tomography demonstrates cystoid ME. (C) In PDR patients, VH can occur from fragile new vessels. (D) Fibrovascular proliferation from retinal neovascularization forms diffuse tractional membrane, resulting in TRD.