Optic nerve

An optic nerve was an organ related to sight. (TV: Flatline) Optic nerves could misfire, resulting in temporary or even permanent blindness. (PROSE: The Door into Bedlam)

The Twelfth Doctor once hacked Clara Oswald's optic nerve using nanotech, allowing him to see whatever she saw, on the TARDIS scanner. (TV: Flatline) When one's optic nerve was "tapped", though, the act could leave behind scars on the supra-orbital ridge, above the eye. (PROSE: War Crimes) In an alternate timeline, the Eleventh Doctor was partially upgraded into the Cyberiad. When he believed Alice Obiefune was safe in the TARDIS, the Cyberiad hacked into his optic nerves to show him that his ship had been drained of power and Alice, surrounded by Cyber-Silurians, could not enter. (COMIC: Supremacy of the Cybermen)

Dream crabs (who were blind and deaf) could see themselves by streaming the visual input from people's optic nerves to their brains. (TV: Last Christmas)

The Half-Face Man burned a dinosaur accidently brought forwards in time by the newly-regenerated Twelfth Doctor, to use her optic nerve to repair the Clockwork Droids' ship, the SS Marie Antoinette. (TV: Deep Breath)