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What Is the Optic Nerve Sheath?

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  • Written By: Christine Hudson
  • Edited By: Lauren Fritsky
  • Last Modified Date: 07 April 2014
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The optic nerve sheath is also called the myelin layer around the optic nerve. Myelin is described as the "white matter" of the brain. It acts as a protector and insulator for the nerves. This particular sheath is responsible for insulating the optic nerve, which is the primary structure that connects the eye to the brain. Although it is called the optic nerve, this structure is actually made of many nerve axons that originate in the retina of the eye and carry visual information from the retina to the primary visual cortex of the brain.

This optic nerve sheath is made of a fatty insulating substance that covers and protects nerves, arranged in the dura, arachnoid, and pia mater. These terms of the layers are specific to the central nervous system. The sheath itself functions much like a conduit in an electrical system. Within its makeup, the sheath intertwines with hydrocarbon chains, which add strength to the optic nerve sheath. The more scientific name for the chemical, biological, and structural makeup of the optic nerve sheath would be described as oligodendrocytes.

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As it is a major contributor to one's vision, it is important to note the injuries and ailments which might befall the optic nerve sheath. Demyelination is one such condition and refers to the destruction or loss of the myelin sheath. Optic neuritis is an inflammation of the optic nerve which can cause severe pressure, pain and headaches and may result in the destruction of the protective myelin sheath that covers the optic nerve. These conditions are usually the result of an autoimmune reaction or disorder in which the body mistakes its own oligodendrocytes for a pathogen and essentially attacks them.

Any time the myelin sheath has been destroyed or severely compromised, the nerve is susceptible to direct damage. Optic neuropathy is a general term used to describe any conditions that result in damage to the optic nerve. Symptoms would include blurred vision in only one eye, double vision, difficulty in coordination and fatigue. Benign tumors can also form in the optic nerve sheath and cause these side effects. Tumor growth may compress the optic nerve and cause loss of vision in the affected eye.

Research has been conducted for many years to develop techniques for detecting these issues early on and repairing the myelin sheaths. One option to patients might be the surgical implanting of oligodendrocyte precursor cells. Other times, the condition is so progressed or acute that there may not be a cure, only medications and treatments to deal with pain or slow the condition's progress.

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