Pathologic angiogenesis of the retina is a hallmark of frequent blinding conditions among the elderly, such as proliferative diabetic retinopathy (PDR) and neovascular age-related macular degeneration (nAMD). The underlying mechanisms are complex. Currently, the approved therapies consist of intraocular injections of antivascular endothelial growth factor (VEGF) agents, laser treatments, and intraocular surgeries to cope with the complications, such as intravitreal bleeding. Although these therapies are the cornerstone of ophthalmological care for the patients, they are far from perfect. There is a clear need for understanding the intricate regulatory mechanisms of different retinal angiogenic conditions and find novel prognostic and therapeutic tools. Investigation of angiogenesis at the gene regulation level grants the possibility of studying angiogenesis within the tissue of origin, finding biomarkers of disease progression, and offering novel targets and therapy modalities, such as gene therapy agents. This thesis provides further insight into the complexity and heterogeneity of retinal angiogenesis by analyzing human endothelial cells from retinal and choroidal vasculature. Furthermore, we show the biomarker potential of specific microRNAs in PDR progression, focusing on recurrent vitreous hemorrhage. Moreover, we show that hypoxia-inducible factor (HIF)-1α, a master regulator of angiogenesis, is upregulated in retinal pigment epithelium (RPE) in hypoxia. HIFs pathologic upregulation can be mitigated by overexpression of prolyl hydroxylase domain (PHD)2, a prominent HIF regulatory protein. In vitro and in vivo experiments with overexpression of PHD2 protein diminished hypoxia-induced molecular and cellular angiogenesis. Gene therapy experiments in the choroidal neovascularization (CNV) mouse model with PHD2 significantly reduced laser-induced CNV lesions. Therefore, we provide a candidate molecule for anti-HIF gene therapy for sustained and balanced inhibition of retinal angiogenic conditions.