Table of Contents
Optic nerve definition
Optic Nerve – the second cranial NERVE, which conveys nerve impulses from the EYE to the BRAIN. There are two optic nerves, one from each eye. The fibers that become the optic nerve originate in the occipital lobes of the cerebrum, in an area called the visual cortex. Each extends along structures called the optic tracts that pass through the temporal lobes and the center of the brain, converging in the optic chiasm.
At this point the optic tracts cross, such that the one originating in the left visual cortex goes to the right eye and the one originating in the right visual cortex goes to the left eye. Each optic nerve enters the back of the eye, terminating in the RETINA.
The ophthalmologist can see through the ophthalmoscope the end of the optic nerve, called the optic disk. It appears as a pale circle, about the size of a pencil eraser, against the dark background of the retina. The retina’s network of nerves extends from the optic nerve, gathering nerve impulses from the rods, cones, and other nerve cells in the retina.
Conditions that can affect the optic nerve
|CONDITIONS THAT CAN AFFECT THE OPTIC NERVE|
|ISCHEMIC OPTIC NEUROPATHY||TOXIC OPTIC NEUROPATHY|
|RETINAL DETACHMENT||RETINITIS PIGMENTOSA|
|RETROBULBAR OPTIC NEURITIS||RETINOPATHY|
For further discussion of the optic nerve within the context of ophthalmologic structure and function please see the overview section “The Eyes.”