Cerebrospinal fluid absorption in the rabbit. Optic pathways.

Fifteen rabbits were intrathecally perfused with horseradish peroxidase at normal cerebrospinal fluid pressures. Horseradish peroxidase was found in the subarachnoid space around the optic nerve; it permeated the pia and penetrated within the nerve, occupying extracellular spaces between myelinated axons and glial cells up to the area of the lamina cribrosa. Horseradish peroxidase also crossed the perineural sclera and the border tissue of Elschnig to spread into the choroid where it was mostly seen within choriocapillaris, venules, and veins crossing through interendothelial spaces. "Bulk" cerebrospinal fluid absorption in the eye appears to occur through venous drainage in the choroid and SAS.