Blood-Retinal Barrier (None)

The blood-retinal barrier (BRB) is a critical physiological structure that maintains the specialized environment of the retina, essential for proper visual function. It acts as a selective barrier, regulating the movement of solutes, nutrients, and fluids between the bloodstream and retinal tissue while preventing potentially harmful substances from entering the retina. The BRB consists of two main components: the inner blood-retinal barrier (iBRB), formed by non-fenestrated endothelial cells lining retinal capillaries, and the outer blood-retinal barrier (oBRB), composed of retinal pigment epithelial (RPE) cells joined by tight junctions. Disruption or breakdown of either component leads to increased vascular permeability—an underlying factor in several sight-threatening diseases.

Therapeutic strategies often target pathways involved in barrier breakdown to restore integrity or modulate it for drug delivery purposes, e.g., by inhibiting VEGF.