Optic Nerve Disorders: Causes, Symptoms, and Specialists in Optic Nerve Disorders

The optic nerve is the second cranial nerve and is medically referred to as the nervus opticus. It is part of the visual pathway and connects the eye to the brain. In the retina, light stimuli are converted into electrical signals. These signals are collected by the ganglion cells and optic nerve fibers and transmitted to the brain.

Experts also refer to the optic nerve as the nervus opticus or the second cranial nerve. It forms the central part of the visual pathway, through which the image travels from the eye to the brain.

When light enters the eye, the retina generates electrical impulses. The optic nerve transmits these impulses (electrical potentials) to the brain. The brain interprets the signals as images, which enables us to see our surroundings.

The human optic nerve is approximately four to five centimeters long and consists of bundled nerve fibers. It runs from the lamina cribrosa through the sclera to the optic chiasm. Experts also refer to it as the chiasma opticum.

The optic nerve of the eye is divided into three distinct sections:

• Intraocular portion: The part of the optic nerve inside the eyeball
• Intraorbital portion: The part of the optic nerve within the eye socket
• Intracranial portion: The optic nerve runs through the skull (cranium)

The optic nerve in the eye also consists of approximately one million nerve fibers. These fibers are known as axons. The extensions of the retinal ganglion cells are called optic nerve fibers. The individual axons converge to form the optic nerve.

Visual impressions that we perceive with our eyes are transmitted to the brain via the optic nerve (nervus opticus) @ bilderzwerg /AdobeStock

The retina of the eye consists of several layers:

The outer layer consists of the photoreceptors—the rods and cones—in the eye. This outer layer is followed by several thin layers in the eye that contain what are known as relay cells. These layers of cells are responsible for the electrical signals generated by light in the sensory cells.

The inner cell layer of the retina also contains fibers from the so-called ganglion cells. These fibers form the actual optic nerve in every person’s eye. They all exit the eye together at a specific point, known as the optic disc, as the optic nerve.

Because the optic nerve passes through it, the optic disc is not sensitive to light and is considered the “blind spot” in the visual field.

After leaving the eyeball, the optic nerve passes through fatty tissue within the eye socket (orbit). This tissue is located in the eye socket between the muscles of each eye. 

The optic nerve finally enters the human skull through an opening (canalis opticus). Here, the two optic nerves from the eyes meet and form the optic chiasm. 

The optic chiasm is an area where the fibers cross over one another. Due to the refraction of light at the eye’s lens, the information from the individual hemispheres of the brain is brought together. The optic chiasm is therefore a crucial junction. Without this crossing in the eye, coordinated vision would not be possible.

The optic chiasm is thus located near the pituitary gland. For this reason, the optic nerves that cross here are of particular importance in the diagnosis of a brain tumor.


The optic tract, greatly simplified

1. In the early stage of optic disc edema, the edge of the optic disc is usually blurred, while the optic disc itself is highly vascularized. Vision is rarely impaired at this stage of the disease. 
2. In the acute stage of optic nerve disease, the optic disc swells significantly. Additionally, the edges of the optic disc begin to bleed in a radial pattern. The optic disc now has a reddish to grayish-reddish color and shows gray deposits. The indentation in the eye known as the “blind spot” gradually disappears.
3. Experts also refer to the final stage as the atrophic phase. Here, the optic nerve fibers in the eye gradually die off. It is only now that the first signs of vision loss become noticeable to the affected person.

Inflammation of the optic nerve in the eye occurs quite frequently. Here, too, edema develops at the optic disc. However, this edema usually goes unnoticed when inflammation of the optic nerve occurs outside the eyeball. 

Diagnosis begins with a detailed interview regarding symptoms, their progression over time, and accompanying symptoms. It is important to determine whether the vision loss occurred suddenly, whether only one eye is affected, and whether there is additional pain, headaches, or discomfort in the temporal region.

This is followed by an ophthalmological examination. The ophthalmologist assesses visual function, pupillary response, and color vision. Examination of the fundus is particularly important. The condition of the fundus provides key clues as to whether there is swelling, a hollow, or any other change in the optic disc. In addition, intraocular pressure is often measured, especially if glaucoma is suspected. This is supplemented by an examination of the anterior and posterior segments of the eye using a slit lamp. A visual field test is also part of the diagnostic process. Most of these examinations are completely painless for the patient.

The nature and distribution of visual field defects also help to better pinpoint the location of damage to the optic nerve. If a vascular disease, AION, temporal arteritis, or a tumor is suspected, additional neurological or internal medicine examinations are necessary. This allows for a targeted determination of the exact cause of the symptoms.

Treatment depends on the underlying cause. There are no standard therapies for all optic nerve disorders. The speed at which the diagnosis is made is crucial, as many types of damage to the optic nerve cannot be reversed later on.

In the case of glaucoma, the primary focus is on lowering intraocular pressure. The goal is to prevent further damage to the optic nerve and to preserve visual function for as long as possible. Treatment options include eye drops, laser therapy, or surgical procedures.

In cases of inflammation, anti-inflammatory medications are used depending on the underlying cause. If an inflammatory vascular disease is present, prompt treatment is particularly important. This is an ophthalmic emergency because, if left untreated, permanent blindness is possible.

For AION, treatment depends on whether the underlying cause is non-inflammatory or inflammatory. The goal is always to ensure blood supply, prevent further damage, and protect remaining vision.

If a tumor is the underlying cause, treatment of the underlying condition takes priority. The sooner patients see a specialist, the better the chances of preventing permanent consequences.