Nonarteritic Anterior Ischemic Optic Neuropathy (NAION) is one of two main types of Anterior Ischemic Optic Neuropathy (AION), a condition in which insufficient blood supply to the optic nerve damages it, resulting in loss of vision. NAION results from a combination of certain cardiovascular risk factors in a patient with crowded optic discs. Arteritic Anterior Ischemic Optic Neuropathy (AAION), the other main type of AION on the other hand, is a less commonly occurring inflammatory condition of medium-sized blood vessels that occurs in those generally slightly older than in those who get NAION.
NAION mostly develops in adults over the age of 50. With 1,500 to 8,000 people developing NAION annually in the U.S., it is the most common acute optic neuropathy among older adults in the nation. About half of the patients get 20/64 vision or worse. Vision subsequently improves in about 30-40 percent of patients, worsens in 12-22 percent, and remains unchanged in about 45 percent of them.
NAION occurs suddenly upon awakening. Sight in one eye is obscured by a shadow, usually just in the upper or lower half of vision. There is no pain and only a few cases result in almost complete loss of vision, but there is a significant risk that NAION will affect the fellow eye within the next few years. When evaluated by a doctor, symptoms of AAION must be excluded, which include painful jaw muscle spasms, loss of appetite, unintentional weight loss, scalp tenderness, fatigue, and muscle pain.
While the mechanism behind what causes the condition is not fully understood, neuro-ophthalmologists generally agree that the convergence of two problems is to blame. In most people, the diameter of the hole in the eye wall through which the optic nerve penetrates through is 20-30 percent larger than that of the optic nerve. The first of the two problems in those who tend to develop NAION is that they do not have this 20-30 percent margin of error. The second problem involves cardiovascular risk factors that lead to a poor blood supply, or ischemia, to the optic disk, which is in the forward portion of the optic nerve. The disc swells as a result, and since there is no room for this, the resulting compression of the optic nerve leads to more ischemia.
The most common of these cardiovascular risk factors include diabetes, hypertension and high cholesterol levels. There are genetic factors at play in the potential for developing these risk factors. There is evidence that other genetic factors may also play a role in the potential for developing NAION.
Several studies have correlated the use of Erectile Dysfunction (ED) drugs like Viagra, Cialis and Levitra to NAION. In July, 2005, the U.S. Food and Drug Administration (FDA) directed the manufacturers of these drugs to add warnings on their package insert labels. But these warnings merely indicate that some users of these drugs have developed NAION. A causal link has been difficult to prove because people who are likelier to take ED drugs also tend to have the very medical risk factors that make them susceptible to developing NAION. Additional legal BLOG addressing the connection between NAION and Viagra, Cialis and Levitra can be found at the following web pages –
While some rare causes of NAION are treatable, there is no accepted treatment to reverse NAION in the vast majority of cases once it happens. Attempting to control the cardiovascular risk factors may help prevent NAION from occurring in the second eye. In any case, an ophthalmologist should be consulted in the event of sudden vision loss. If NAION is suspected, a neuro-ophthalmologist should also be consulted.
There is currently some research being conducted to find ways to protect the optic nerve and even to regenerate new fibers within it.