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 monitor. (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)
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 that appeared in the River Thames, to use its optic nerve to repair the Clockwork Droids' ship, the SS Marie Antoinette. (TV: Deep Breath)