The blood-retinal barrier (BRB) performs an vital function in the homeostatic regulation of the microenvironment in the retina. It consists of interior and outer parts, the interior BRB (iBRB) being shaped by the tight junctions between neighbouring retinal capillary endothelial cells and the outer barrier (oBRB) by tight junctions between retinal pigment epithelial cells. Astrocytes,