Fig. 5.

Hypoxic condition: a Hypoxic tissue produces messengers such as VEGF leading to impairment of tight junctions and thereby weakening of the blood-retinal barrier. This leads to increased permeability of the vessels with the development of exudates, retinal edema and leakage in the fluorescence angiography. b Obviously other factors are involved as well. For example MMP-9 can digest the basal membrane which, together with a weakened blood-retinal barrier, even allows erythrocytes to escape the lumen of the vessel