Sjóntauginna

Sjóntauginna, known scientifically as the optic nerve, is a crucial part of the visual system in humans and many other animals. It is a bundle of nerve fibers that transmits visual information from the retina of the eye to the brain. Specifically, it carries signals from the photoreceptor cells (rods and cones) in the retina, which detect light and color, to the visual cortex in the brain where these signals are interpreted as images.

Each optic nerve is composed of roughly one million nerve fibers. These fibers originate from the ganglion cells in the retina. As they exit the eye at the optic disc, they form the optic nerve. A unique characteristic of the optic disc is that it lacks photoreceptors, creating a natural blind spot in the visual field for each eye.

The optic nerves from both eyes partially cross over at a structure called the optic chiasm, located at the base of the brain. This crossing ensures that information from the left visual field of both eyes is processed by the right side of the brain, and information from the right visual field is processed by the left side of the brain. After the chiasm, the nerve fibers continue as the optic tracts, which lead to various visual processing centers in the brain, including the lateral geniculate nucleus and the superior colliculus. Damage to the optic nerve can result in a loss of vision, the severity of which depends on the extent and location of the damage.