Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain. [1]. Damage and death of these nerve cells, or neurons, leads to characteristic features of optic neuropathy. The main symptom is loss of vision, with colors appearing subtly washed out in the affected eye. A pale disc is characteristic of long-standing optic neuropathy. In many cases, only one eye is affected and patients may not be aware of the loss of color vision until the doctor asks them to cover the healthy eye. Optic neuropathy is often called optic atrophy, to describe the loss of some or most of the fibers of the optic nerve. Ischemic optic neuropathy
In ischemic optic neuropathies, there is insufficient blood flow (ischemia) to the optic nerve. The anterior optic nerve is supplied by the short posterior ciliary artery and choroidal circulation, while the retrobulbar optic nerve is supplied intraorbitally by a pial plexus, which arises from the ophthalmic artery, internal carotid artery, anterior cerebral artery, and anterior communicating arteries. Ischemic optic neuropathies are classified based on the location of the damage and the cause of reduced blood flow, if known. Anterior ischemic optic neuropathy (AION) includes diseases that affect the optic nerve head and cause swelling of the optic disc. These diseases often cause sudden rapid visual loss in one eye.
Genetic mutations in mitochondrial DNA, vitamin depletion, alcohol and tobacco abuse, and use of certain drugs can cause derangements in efficient transport of mitochondria, which can cause a primary or secondary optic neuropathy. Nutritional optic neuropathies
A nutritional optic neuropathy may be present in a patient with obvious evidence of under-nutrition (weight loss and wasting). Months of depletion are usually necessary to deplete body stores of most nutrients. Undernourished patients often have many vitamin and nutrient deficiencies and have low serum protein levels. However, the optic neuropathy associated with pernicious anemia and vitamin B12 deficiency can even be seen in well-nourished individuals. Gastric bypass surgery may also cause a vitamin B12 deficiency from poor absorption. Patients who have nutritional optic neuropathy may notice that colors are not as vivid or bright as before and that the color red is washed out. This normally occurs in both eyes at the same time and is not associated with any eye pain. They might initially notice a blur or fog, followed by a drop in vision. While vision loss may be rapid, progression to blindness is unusual. These patients tend to have blind spots in the center of their vision with preserved peripheral vision. In most cases, the pupils continue to respond normally to light. Toxic optic neuropathies
The most recognized cause of toxic optic neuropathy is methanol poisoning. This can be a life-threatening event that normally accidentally occurs when the person mistook or substituted, methanol for ethyl alcohol.