Some of these causes include: diabetes, glaucoma, certain health problems associated with aging, brain tumors, head trauma, infection, multiple sclerosis, radiation, inflammatory blood vessel diseases, sleep apnea, excessive blood coagulation, high cholesterol, genetic disorders, poisoning, malnutrition, and drug side effects.
The optic nerve is the conduit between the retina of the eye and the visual processing center at the back of the brain. It contains 1.2 million nerve fibers that send sight signals to be processed by the brain. It is sheathed in the fatty nerve casing called myelin. Myelin protects nerves from damage and speeds nerve signals along. When it becomes damaged, nerves are exposed. Then they are very vulnerable to damage, much like an exposed electrical wire which can then fray. When the optic nerve becomes damaged, certain symptoms develop. The primary symptom is visual loss accompanied by diminished color vision such that colors appear washed out. Optic neuropathy can occur in one or both eyes. If it occurs in only one eye, the person may not notice the loss of vision until an eye exam, because the other eye compensates. Optic neuropathy can progress to the point of total blindness. It usually cannot be treated or repaired. The underlying cause must be found and treated to prevent further vision loss.
There are many causes of optic neuropathy. The most common cause is loss of blood flow to the optic nerve. This is called ischemic optic neuropathy. This is very common in elderly people. Ischemic optic neuropathy also has many causes. These include inflammatory blood vessel diseases, radiation, diabetes mellitus, glaucoma, sleep apnea, high cholesterol and excessive blood coagulation. A variety of mechanisms operate to inhibit blood flow to the optic nerve but the end result is that neurons die from lack of blood flow and vision loss occurs.
Optic neuropathy can also be caused by optic neuritis or chronic inflammation of the optic nerve itself. The inflammation leads to demyelination of the nerve and damage to the neurons. It can be caused by multiple sclerosis but has other causes as well. Young adult females are the most common population in which this form of optic neuropathy occurs. In this form there is usually also pain upon eye movement, rapid vision loss and a visibly swollen optic nerve.
Trauma to the head is another cause of optic neuropathy. Usually the trauma has to be quite severe to result in damage to the optic nerve. Motor vehicle accidents and falls are the two most common ways this occurs.
Brain tumors that press on the optic nerve are another possible cause of optic neuropathy. Many types of brain tumors can do this. Additionally, the optic nerve can be infiltrated by certain bacteria and viruses. The most common cause of infiltration of the optic nerve is the autoimmune disorder sarcoidosis, but it can also be caused by agents such as herpes and toxoplasmosis.
Additional causes of optic neuropathy include mitochondrial malfunction, usually due to the ingestion of alcohol, tobacco or some other toxic substance or to vitamin depletion caused by sustained malnutrition. Such malnutrition must usually be in existence for a period of several months to result in optic neuropathy. It can also result from ingestion of a variety of drugs and poisons including antifreeze, ethambutol (a TB drug), or amiodarone (an anti-arrhythmia drug).
Lastly, optic neuropathy can be caused by a number of genetic disorders. These disorders include Leber’s hereditary optic neuropathy, dominant optic atrophy, Behr’s syndrome, and Berk-Tabatznik syndrome.
A rapid onset is more likely in cases of demyelinating, inflammatory, ischemic and traumatic causes. A slower onset usually indicates compressive, toxic/nutritional and hereditary causes. The pace of onset can help a doctor narrow the field for finding the underlying cause.
Symptoms of optic neuropathy include a dimmed visual field, faded color vision, an inability to see fine detail and a reduced visual field. As it progresses, the pupil of the eye does not respond as readily to light and may eventually quit responding at all.
Optic neuropathy can be diagnosed with a thorough eye exam. This includes a test for color vision, a pupil light reflex, tonometry and a visual acuity test. If optic neuropathy is found, other tests will usually be required to determine the underlying cause. Depending on what underlying cause or causes are suspected, testing may need to be quite comprehensive.
There is no treatment for optic neuropathy unless the underlying cause is optic neuritis. Then it is usually treated with a combination of oral and IV steroids. Studies have shown such treatment has little impact on the final vision outcome, but it does diminish frequency of attacks of neuritis in certain instances and diminishes the onset of multiple sclerosis when that is the underlying cause. It is very important to find the underlying cause of optic neuropathy. Once the underlying cause is found, treatments to heal or delay the progress of the underlying disease can slow or prevent further vision loss. Some causes of optic neuropathy respond very well to lifestyle management. These include diabetes, high cholesterol, smoking and drinking.
While no formal treatment exists, nutritional supplements that support the health of the optic nerve may be helpful. These include lutein, zeaxanthin, bilberry and supplements that support myelination like omega-3 fatty acids, B vitamins and L-glycine.
Prognosis depends on the ability to treat the underlying condition.
Many of the causes of optic neuropathy cannot be prevented, but some can. If you have diabetes or glaucoma, managing these conditions can prevent optic neuropathy. Being careful of alcohol and tobacco consumption can prevent optic neuropathy related to those substances. Wood alcohol, or methanol, which is often made in home breweries, should never be consumed as it can cause severe optic neuropathy. And, using safety precautions to prevent head injuries can reduce the likelihood of traumatic optic neuropathy. Managing diet and health to minimize the risk of cancer or high cholesterol can also diminish the likelihood of these potential causes of optic neuropathy.
It is important to get regular eye exams to make sure your eyes remain healthy and to catch any problem as early as possible.