Optic disc

Discus nervi optici

Sensory (eye & ear)OrgansHeadLeft and right

View left in 3D View right in 3D

What it is

The pale, round head of the optic nerve, where about 1.2 million ganglion-cell axons leave the eye and the central retinal vessels enter; it has a central depression, the optic cup.

Function

Carries all visual signals out of the eye; having no photoreceptors, it forms the physiological blind spot.

Size

1.5-1.8 mm in diameter, about 3-4 mm nasal to the fovea and slightly above it; normal cup-to-disc ratio < 0.5.

Clinical note

An enlarging cup signals glaucoma; a swollen disc (papilloedema) signals raised intracranial pressure.