The optic nerve is the bundle of nerve fibres that carries visual information from the retina to the brain. Each eye has its own optic nerve, which leaves the back of the eye at the optic disc.
Structure and Role
The optic nerve is formed by the axons of retinal ganglion cells and passes through the orbit and skull to reach the brain. It has no photoreceptors itself, so the area where it exits the eye corresponds to the natural blind spot.
- Contains more than a million nerve fibres in a healthy adult
- Surrounded by a protective sheath continuous with brain coverings
- Vulnerable to pressure, inflammation, and vascular damage
- Appearance of the optic disc is a key part of eye examination
Clinical Importance
Diseases such as glaucoma, optic neuritis, and ischaemic optic neuropathy can damage the optic nerve and lead to visual field loss. Early detection and management of these conditions aim to preserve remaining nerve fibres and vision.
- Visual field testing helps map functional loss related to nerve damage
- Imaging such as OCT can measure nerve fibre layer thickness
- Systemic conditions, including high blood pressure and autoimmune disease, may contribute to optic nerve problems
- Permanent damage cannot usually be reversed, so prevention and protection are critical
