in·ter·vag·i·nal subarachnoid space of op·tic nerve
[TA] the spaces within the internal sheath of the optic nerve, between the arachnoidal and pial layers, filled with cerebrospinal fluid and continuous with the subarachnoid space. Synonym(s): spatium intervaginale subarachnoidale nervi optici [TA], intersheath spaces of optic nerve, Schwalbe spaces