Endothelial tight junctions (TJs) in the retina are potential therapeutic targets for diabetic complications such as retinopathy. TJs primarily determine the endothelial barrier, regulating vascular permeability to maintain tightly closed circulating homeostasis. Our recent study has demonstrated that glial cell-derived cytokines limit vascular permeability by modulating the TJ function of retinal capillary endothelium and eventually attenuate the breakdown of vascular integrity in diabetic microangiopathy. In addition, suppression of deregulated protease activity in lens cells results in dramatic inhibition of the development of murine diabetic cataracts. We believe that pharmacological modulation of the ocular tissue microenvironment such as that regulated by endothelial TJs may be a feasible strategy for reducing the development of diabetic complications in the eye.