The blood-retinal barrier (BRB) is composed of an inner and an outer BRB. The former is located in the endothelial cells of the retinal vessels and the latter in the pigmented epithelial cells of the retina. Morphological evidence from electron micrographs shows the existence of tight junctions (Zonula occludence) between these cells. Clinical methods for evaluation of the function of these barriers are, at present, three: 1) fluorescein angiography (quolitative), 2) vitreous fluorophotometry (quantitative), and 3) fluorescein electroretinography (quantitative). The effect of calcium inhibitor on the barrier function in diabetic retinopathy was evaluated by these methods.