<prompt> Longest pa of optic nerve -IntraocularIntracranialIntraorbitalIntracranial  <response>: The optic nerve is about 47- 50 mm in length and can be divided into 4 pas : intraocular 1mm, intraorbital 30mm, intracanalicular 6-9mmand intracranial 10mm. Refer comprehensive ophthalmology 6th edition , A K Khurana , page no. 310 