The optic nerve is a special type of nerve that transmits visual information from the back of the eye to the brain.
The eye is made of three parts.
The cornea and lens which focuses light at the front of the eye – it passes light through the hole called the pupil. The light is then focused onto the back of the eye by the lens.
A light sensitive “film” that is at the back of the eye. It is called the retina. Tiny sensitive patches called photoreceptors cover the back of the eye. They collect information about the world – visual information. The covering of these photoreceptors form a thin film known as the retina.
The optic nerve - a large group of communication “wires” to the brain The optic nerve is the collection of all the 'communication' wires (over one million) joining the eye to the brain. The information then travels to many different special 'vision' parts of the brain.
All parts of the brain and eye need to be present and working for a person to see normally.
What is optic neuropathy?
Optic neuropathy refers to damage to the optic nerve. When these nerves get damaged, the protective outer layer or myelin sheath becomes thinner and it is then called optic neuropathy. Due to this the vision gets blurred, and the capability to see anything in a perfect manner is lost. Severe pain may result in the eyes due to this condition.
The main symptom is loss of vision and colors appear washed out in the affected eye. In many cases, only one eye is affected and patients may not be aware of the loss of color vision until someone asks them to cover the healthy eye.
Optic neuropathy is often called optic atrophy. Medical doctors believe that it should be called neuropathy as “atrophy” means “shrunken but capable of re growth”. They do not believe that nerves can be repaired and that neuropathy cannot be fixed.
Causes of optic neuropathy
A rapid onset of optic neuropathy is typical of demyelinating (breakdown of the myelin sheath), inflammatory, ischemic (loss of blood flow to the area) and traumatic causes.
A gradual onset is typical to compressive, toxic/nutritional and “hereditary” causes.
The many causes of neuropathy are also the causes of optic neuropathy. It is the nerve that becomes damaged.
Trauma is the most common cause, but tumors, nutritional deficiencies, toxins (including tobacco and alcohol), infections, blood flow blockage, inflammatory disease, and other disease’s such as glaucoma, stroke, diabetes, high blood pressure and atherosclerosis are also a cause.
Leber hereditary optic neuropathy, is what medical doctors believe is an inherited form of vision loss that affects mostly males in their 20s or 30s. In Leber's Optic Neuropathy the mitochondria in the cells in the optic nerve stops supplying energy, which leads to visual impairment. (Mitochondria are the energy production factories of any cell).
Other risk factors may include obstructive sleep apnea, and use of certain drugs which are used to treat erectile dysfunction.
Nutritional optic neuropathy typically involves deficiencies in vitamin B 12 (cobalamin), vitamin B 1 (thiamine), vitamin B 2 (riboflavin), and folic acid.
Optic neuropathies from pure nutritional deficiencies have been reported in strict vegan patients. Certain weight reduction methods, including gastric bypass surgery, may result in deficits of vitamins and can be complicated by vision loss from bilateral optic neuropathy. Combined with the use of tobacco and alcohol as they deplete the body of these nutrients. Thus nutritional optic neuropathy is clearly more common among tobacco and alcohol users.
In people over 70, the blood supply to the optic nerve can be blocked due to inflammation of the arteries.