Non-Arteritis Anterior Ischemic Optic Neuropathy: Information on Causes, Diagnosis & Treatments
Non-Arteritis Anterior Ischemic Optic Neuropathy (NAION) involves the loss of the flow of blood to the eye's optic nerve that connects the brain to the eye. Patients with the condition typically experienced a sudden loss of vision in an eye usually without pain. Most patients who develop NAION will awake from a night of sleep with a significant loss of vision, usually in one eye. The loss of vision usually remained stable and does not worsen or get better over time.
The condition is idiopathic, meaning science has yet to determine its exact cause. However, it can be caused by an ischemic insult where there is insufficient blood supply, it is characterized as painless, monocular, and acute visual loss that results in swelling of the optic disc.
- Who is at Risk for Non-Arteritis Anterior Ischemic Optic Neuropathy?
- Common Symptoms
- Diagnosing Non-Arteritis Anterior Ischemic Optic Neuropathy
- Treating the Condition
- What Is the Chance of NAION Recurrence?
Who is at Risk for Non-Arteritis Anterior Ischemic Optic Neuropathy?
Medical science has yet to determine the exact cause of non-arteritis anterior ischemic optic neuropathy or any causal relationship with other conditions. However, scientists believe there are specific risk factors that are associated with the condition. These include:
- Sleep Apnea Syndrome – Case studies have revealed a potential association between non-arteritis anterior ischemic optic neuropathy and sleep apnea. The results show that apneic episodes might lead to acute elevated blood pressure, nocturnal hypoxemia (abnormal oxygen-poor blood), or intracranial pressure that could lead to ischemia or optic nerve edema (swelling).
- Drugs – The use of Interferon that has complex anti-tumor, antiviral, and anti-angiogenic properties are thought to lead to acute sequential, bilateral vision loss associated with non-arteritis anterior ischemic optic neuropathy. In addition, sildenafil, an effective treatment for ED (erectile dysfunction) that works by inhibiting PDE5 (phosphodiesterase type 5) to regulate the flow of blood into the penis, might exaggerate physiologic nocturnal hypertension that leads to optic nerve ischemia.
- Optic Disc Drusen – This condition can increase the risk of developing non-arteritis anterior ischemic optic neuropathy.
- Age – Individuals who are 50 years and older have an increased risk of developing non-arteritis anterior ischemic optic neuropathy (77%) compared to men and women younger than 50 (23%).
- Ethnicity – Out of the nearly 6000 new diagnoses of non-arteritis anterior ischemic optic neuropathy every year, approximately 95% of cases are Caucasians (Whites). However, gender does not seem to be a factor because women and men are affected nearly equally.
The most classic symptoms associated with non-arteritis anterior ischemic optic neuropathy involve painless, acute unilateral loss of vision where the patient complains of cloudy or blurry vision. Most patients never experience headaches, pain, or periocular pain in the area surrounding the eyeball.
In some cases, the patient's vision might become darker in one or both eyes, for a few seconds or could last minutes before finally returns to normal. However, this might be the result of a TIA (transient ischemic attack) that can occur before the onset of non-arteritis anterior ischemic optic neuropathy. A primary care doctor or ophthalmologist can more accurately determine the reason for the symptom.
Typically, the first signs of visual loss tend to be noticed when awakening from a night's sleep. Medical scientists believe that this is the result of nocturnal arterial hypotension. However, this is yet to be verified.
Diagnosing Non-Arteritis Anterior Ischemic Optic Neuropathy
Because most cases do not involve any associated pain, doctors often diagnose as non-arteritis anterior ischemic optic neuropathy as optic neuritis. However, upon further examination and a review of symptoms, the doctor can formally diagnose NAION noting that the vision loss developed within hours to days.
As a part of a visual examination, the doctor can detect swollen hyperemic (insufficient blood flow) optic nerves with associated peripapillary area (around the optic papilla) splinter hemorrhages. The doctor will want to rule out temporal arteritis which necessitates immediate medical attention to avoid losing vision in the other eye.
To verify the diagnosis, the doctor may order laboratory tests to rule out other conditions. This might include obtaining a temporal artery biopsy and the presence of inflammatory markers, especially patients 50 years or older who present many of the symptoms associated with non-arteritis anterior ischemic optic neuropathy.
The doctor will also obtain a complete family and personal history of unexplained or early-onset thrombosis. Usually, neuro-images will not be necessary. However, the doctor may order an MRI (magnetic resonance imaging) scan of the eye orbits and brain if the patient complains of specific pain, especially during eye movement. This can rule out or confirm multiple sclerosis and optic neuritis.
The doctor may also conduct a differential diagnosis to rule out other conditions, especially in cases of bilateral vision loss that might be due to a neurological or cardiac complication. A differential diagnosis might also validate that the condition is caused by an optic neuritis associated with secondary multiple growths.
Treating the Condition
Medical science has yet to develop an effective treatment for non-arteritis anterior ischemic optic neuropathy. However, doctors and scientists are continuing clinical trials to test out various therapies, even though there has been no significant improvement in the visual outcome of individual suffering with NAION as of yet.
Some studies have followed the use of prednisone and other corticosteroids where patients have reported mild improvement. However, these trials were not conducted using rigorous scientific methodologies so determining if the steroids provided significant relief is not conclusive.
Using special eyeglasses are not thought to correct the loss of vision caused by non-arteritis anterior ischemic optic neuropathy. This is because eyeglasses help to adjust the focal point where light enters the front of the eye. However, NAION produces a vision loss at the back of the eye at the point where the optic nerve leaves the eyeball before being connected to the brain.
That said, if the patient is suffering from farsightedness or nearsightedness while experiencing non-arteritis anterior ischemic optic neuropathy, then the glasses can provide help in keeping limited vision and focus. However, it cannot help any injury to the optic nerve.
What Is the Chance of NAION Recurrence?
Once a patient has experienced non-arteritis anterior ischemic optic neuropathy in one eye, it is highly rare for the condition to redevelop or recur in the same eye. However, overall there is nearly a 30 percent risk that the condition can develop in the other eye at some point during the patient's lifetime.
The doctor may recommend that the patient make lifestyle changes including regular exercise, consume a healthy diet, and following other proven measures for treating many of the risk factors associated with the development of NAION including sleep apnea, high blood pressure, and diabetes. Some doctors recommend avoiding taking any high blood pressure drug prior to going to bed to minimize the potential of nocturnal hypoxemia from occurring during sleep, which is thought to be a contributing factor to non-arteritis anterior ischemic optic neuropathy.
Instead, the doctor will likely recommend that the patient should take a daily dose of aspirin. However, the treatment has yet to be supported by approvable evidence that it is better than taking high blood pressure medication before going to bed.