A DEFECT IN THE BLOOD‐RETINA BARRIER IN THE OPTIC NERVE HEAD REGION IN THE RABBIT AND THE MONKEY

The permeability properties of the tissues in the optic nerve head region have been investigated in monkey and rabbit using horseradish peroxidase as an histochemical tracer. Following intravenous administration, the tracer diffused from the peripapillary choroid into the different parts of the optic nerve head region, and also into the receptor layer of the sensory retina adjacent to Kuhnt intermediary tissue. This observation demonstrates a defect in the blood‐retina barrier in this region. The defect in the permeability barrier is most likely located either to the retinal pigment epithelium near the optic nerve head, to the Kuhnt intermediary tissue, or to the junction between these tissues.