The intraorbital (post-laminar) portion of the optic nerve is approximately how many millimeters in length?

• A. 15 mm
• B. 20 mm
• C. 30 mm
• D. 40 mm

Answer: (C)

The length of the intraorbital (post-laminar) optic nerve is about 30 millimeters. This segment runs from the lamina cribrosa, at the back of the eye, to the optic canal in the orbit. In most individuals it measures roughly 25–30 mm, so using a round figure of 30 mm matches common anatomical references. Choosing a value much shorter or longer would not fit the typical course of the nerve through the orbit. This length helps explain why the intraorbital portion is longer than the intraocular part but shorter than the canalicular segment, and it’s useful for imaging and understanding orbital trauma or surgical planning.