The distribution of intravenously administered peroxidase in the optic nerve head of rabbit and monkey.

Peroxidase was used as an histologic tracer to study the permeability properties of the tissues in the optic nerve head of rabbit and monkey. The distribution of the tracer was observed by light microscopy. Within a short time after intravenous injection peroxidase was located extravascularly in the optic nerve head. The present study confirms earlier reports of a defect in the blood-optic nerve barrier in the region of the optic nerve head. The tracer was found to have reached the connective tissue of the optic nerve head, and to a lesser degree the optic nerve tissue proper. The observations made it probable that peroxidase had reached the connective tissue of the optic nerve head by diffusion from the perineural chorid and sclera.