Experimental retinal detachment. VII. Intravenous horseradish peroxidase diffusion across the blood-retinal barrier

Intravenous horseradish peroxidase (HRP) was administered to cynomolgus monkeys to study chorioretinal diffusion in eyes with retinal detachment. In control eyes, HRP was contained within the choriocapillaris and did not penetrate beyond Bruch's membrane. In addition, HRP was confined within blood vessels of the sensory retina. In detached eyes, HRP diffused out of the choriocapillaris and through the intercellular spaces of the retinal pigment epithelium (RPE), where it was blocked by zonulae occludentes. Occasionally HRP was found within pinocytotic vesicles of the RPE. It was also confined within retinal blood vessels by their endothelial cells. It is concluded that the blood-retinal barrier remains intact to HRP following long-term rhegmatogenous retinal detachment. However, a slight alteration exists at the choriocapillaris in detached eyes.