The optic nerve, the second cranial nerve, is involved in the visual system.

Sensitive Nerf. The optic nerve is a sensory nerve allowing the assimilation and integration of visual perception.

Origin. Like all cranial nerves in humans, the optic nerve is an even nerve. Each optic nerve begins in the ganglion cells of the retina (1).

Path. Fibers from the ganglion cells in the nasal retina and the temporal retina come together and leave the eyeball to form the two optic nerves. Each optic nerve passes through the optic hole of the sphenoid bone and extends medially and posteriorly to the skull. The two nerves meet in front of and above the pituitary gland to form the optic chiasm. At this point, fibers from the nasal retina cross while those from the temporal retina continue in the same path to form the two optic tracts (2).

Termination. The optic tracts continue posteriorly before terminating as synapses within the lateral geniculate body of the thalamus (2).

Role in the visual message. The essential role of the optic nerve is the transmission of information perceived by the retina to the brain. The information is first processed by the thalamus and then transmitted to the cerebral cortex (3).

Optic neuropathies. They correspond to all the pathologies affecting the optic nerve. Their origin may be of infectious, tumor or even genetic origin (4).

Glaucoma. This disease is caused by increased pressure within the eye, which can damage the optic nerve. Glaucoma can affect vision and lead to permanent blindness in more severe cases (2).

Optic neuritis. This optic neuropathy is linked to inflammation of the optic nerve, the causes of which are varied. In the most severe cases, it can cause partial or complete loss of sight (4).

• Multiple sclerosis. This pathology is an autoimmune disease of the central nervous system, causing inflammatory reactions. The immune system attacks myelin, the sheath surrounding nerve fibers, including those of the optic nerve (5).
• Uveitis. This pathology corresponds to an inflammation of the uvea, made up of the choroid, the filar body and the iris. Symptoms are eye pain and redness, as well as decreased vision (6).

Optic nerve compression. Certain pathologies can cause compression of the optic nerve and impair vision. This phenomenon is notably observed in certain cases of brain tumors, aneurysms of the ophthalmic artery or of the supraclinoid carotid artery (4).

Pharmacological treatment. Depending on the pathology diagnosed, certain pharmacological treatments may be prescribed such as eye drops (eye drops).

Drug treatments. Depending on the pathology diagnosed, certain drugs may be prescribed such as corticosteroids or beta-blockers.

Surgical treatment. In the most serious cases, a surgical intervention can be put in place.

Physical examination. The examination of pupillary function is systematically carried out during an ophthalmological evaluation.

Medical imaging exam. To complete the diagnosis, an MRI, or a CT scan can be performed.

A lot of research is being done to cure blindness patients. Some systems such as the bionic eye or the artificial retina have already shown their effectiveness in partially restoring sight to certain patients. These systems pick up light messages and transmit them to the brain via the optic nerve (7). At this stage of research, the patient’s optic nerve must be intact to allow information to be transmitted to the brain.