Anatomy of the eye
Task of the optic nerve
As with all nerves, the basic task of the optic nerve is to transmit electrical signals. The conversion of external light impressions into these electrical signals is done by a series of biochemical processes within the nerve cells of the retina. From there, they are then conducted through the optic nerve to those parts of the brain that are responsible for processing the information they contain – the visual center.
On their way from the sensory organ of the eye to the primary processing areas in the brain, the electrical signals of what is perceived pass through four stations, where they are each switched from one nerve cell to the next. The first two switchovers already occur in the retina of the eye. The information then leaves the eye with the extensions of the third nerve cell.
This is where about one million of these nerve fibers bundle to form the actual optic nerve. The fibers of the right and left optic nerve meet at the intersection of the optic chiasma. This is where the respective nasal part of the fibers crosses over to the opposite side.
From this point on, the information from one half of the face is bundled and sent to the downstream processing centers. By definition, the course of the optic nerve ends with the crossing of the fibers. An injury to the optic tract in this area results in the so-called chiasm syndrome.
The fibers continue to run as the so-called tractus opticus in the direction of the cortex, where they are processed either directly or after being passed on again. The nerve fibers of the optic tract are involved in the function of the pupillary reflex: If strong light enters an eye, the pupil of both the illuminated and the non-illuminated eye narrows. This reflex is realized by a special interconnection of the optic nerve fibers with the muscle responsible for the constriction of the pupil (M. sphincter pupillae).
