Abstract
The zone where the axons of the retinal ganglion cells bypass the retina and choroid in leaving the eye of the rhesus monkey was examined by electron microscopy. It was observed that the connective tissue space containing Bruch's "membrane" reached the astrocytic sheath over the optic axons. This space was also continuous with similar space about marginal capillaries and the latter space likewise reached the glial surface over the optic axons. Finally, the basement lamina associated with the pigment epithelial cells became confluent with the basement laminae of the astroglia at the optic canal. The data suggest potential anatomic defects in the blood-ocular barrier in this region.