About 3 mm. to the nasal side of the macula lutæ is the entrance of the optic nerve (optic disk), the circumference of which is slightly raised to form an eminence (colliculus nervi optici).
The optic disc (optic nerve head) is the location where ganglion cell axons exit the eye to form the optic nerve. There are no light sensitive rods or cones to respond to a light stimulus at this point. This causes a break in the visual field called "the blind spot" or the "physiological blind spot".
The optic disc represents the beginning of the optic nerve (second cranial nerve) and is the point where the axons of retinal ganglion cells come together. The optic disc is also the entry point for the major blood vessels that supply the retina.