sulcus prechiasmaticus [TA] a furrow on the superior surface of the sphenoid bone, located just anterior to the tuberculum sellae; it lodges the optic chiasm. Called also chiasmatic s., s. chiasmatis, optic groove..

The superior surface of the body of the sphenoid bone is bounded behind by a ridge, which forms the anterior border of a narrow, transverse groove, the chiasmatic groove (optic groove, prechiasmatic sulcus), above and behind which lies the optic chiasma of cranial nerve 2 (the optic nerve).

The groove ends on either side in the optic foramen, which transmits the optic nerve and ophthalmic artery into the orbital cavity.