Definition
The bundle of nerve fibers that carries visual signals from the back of the eye to the brain, where those signals are interpreted as an image.
Plain English
The cable that connects the eye to the brain so you can see what the eye is looking at.
Context Anchor
Seen in night vision discussions when learning how the eye receives light and sends visual information to the brain.
Derivation
From Greek 'optikos' meaning 'of sight' and Latin 'nervus' meaning 'sinew' or 'cord.' Together it literally means 'sight cord' — the cord that carries sight.
Why Pilots Care
Clear understanding of this pathway helps pilots recognize why night adaptation takes time and why certain lighting conditions or eye movements affect what they can see.
Analogy
Think of the eye like a camera and the optic nerve like the cable carrying the image to the screen. The eye receives the light, but the brain has to receive the signal before you can make sense of what you are seeing.
Intuition Check
The optic nerve does not detect light by itself. It carries signals from the eye to the brain after light has been detected.
Example Sentence 1
Light hitting the retina is converted into signals that travel down the optic nerve to the brain.
Example Sentence 2
After ten minutes in the dark cockpit, the optic nerve had adapted enough for the pilot to pick out the runway lights without difficulty.