Optic nerve
and Lisa Vogel, medical editorEva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.
More about the expertsLisa Vogel studied departmental journalism with a focus on medicine and biosciences at Ansbach University and deepened her journalistic knowledge in the master's degree in multimedia information and communication. This was followed by a traineeship in the editorial team. Since September 2020 she has been writing as a freelance journalist for
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The optic nerve (nervus opticus) is the second of twelve cranial nerves and is not an actual nerve, but white brain matter. It consists of around a million nerve fibers and conducts the electrical impulses from the retina to the visual center in the cerebral cortex. Read everything you need to know about the optic nerve!
What is the optic nerve?
The optic nerve, like the retina, is part of the brain. It is about four to five centimeters long and begins at the papilla in the eye (discus nervi optici). This is a whitish, disc-shaped area on the back of the eye, where the nerve endings of the retina (retina) bundle to form the optic nerve. There, at the posterior pole of the eye, there is an opening about three and a half millimeters in size for the optic nerve to pass through the sclera (white dermis of the eye).
But not only the nerve endings of the retina collect in the papilla (eye) - the retinal vessels also enter and exit here in a depression in the middle. For this reason there is no vision at this point (no photoreceptors). Doctors therefore also speak of the "blind spot".
After passing through the sclera, the optic nerve winds about 2.8 centimeters through the fat in the bony eye socket behind the eyeball. The curvatures create enough leeway so that the eyeball can move in its cavity and even step forward a little (as is the case with "bulging eyes").
The nerve fibers that come from the edge of the retina are also in the edge of the optic nerve. The fibers from the central retinal area and the macula (the area of sharpest vision) run inside the optic nerve. All nerve fibers in the optic nerve are enclosed by protective myelin sheaths (myelin sheaths).
Optic nerve junction
In the cranial cavity in front of the pituitary gland, the optic nerves of the two eyes unite to form an optic nerve junction (optic chiasm). The nerve fibers in the two optic nerves are only partially crossed: the fibers that come from the middle (nasal) halves of the retina are crossed; the fibers coming from the outer (temporal) areas of the retina are not crossed.
This means that after the crossing, the fibers from the left halves of the retina of both eyes pull into the left hemisphere, the fibers from the right hemisphere into the right hemisphere.
When the two optic nerves cross, doctors speak of the “optic tract”.
What is the function of the optic nerve?
The function of the optic nerve is primarily to transmit the electromagnetic (light) impulses that hit the retina to the visual center in the cerebral cortex. There, the incoming information from the eyes is processed into an image.
Some of the fibers of the optic tract are also important for the pupillary reflex: Usually, both pupils are the same size. If stronger light hits one eye, the pupil not only narrows in this eye, but also in the other, non-illuminated eye at the same time.
What problems can the optic nerve cause?
Damage in the area of an optic tract results in a visual field loss (scotoma) in the affected half of the retina in both eyes (homonymous hemianopia). Damage to the optic chiasm results in a heteronymous hemianopia: The visual field loss affects either the lateral half (towards the temple) or the medial half (towards the nose) in both eyes.
The term glaucoma (glaucoma) encompasses various eye diseases, all of which damage the optic nerve and, if left untreated, lead to the patient becoming blind.
Optic neuritis (inflammation of the optic nerve) leads to impaired vision and can also result in blindness.
Optic nerve fibers are lost in optic atrophy - either in just one optic nerve or in both optic nerves. This can happen as a result of an injury or an inflammation of the optic nerve, for example, or the result of medication, nicotine or low-quality alcohol. Increased pressure (e.g. in the case of a tumor or a "water head" = hydrocephalus) can damage the optic nerve in such a way that nerve fibers die.
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