Anterior ischemic optic neuropathy (AION) occurs when there is not enough blood flow into the eye. This causes damage to the optic nerve, quickly leading to vision loss. There are two subtypes of AION including arteritic (A-AION) and nonarteritic (NA-AION).
NA-AION makes up nearly 85% of all AION cases.
Both conditions arise when there is reduced blood flow within the eye. This causes a restricted oxygen supply, which eventually damages the optic nerve. However, the reduced blood flow develops differently in A-AION and NA-AION.
This article provides an overview of AION, detailing its symptoms, causes, diagnosis, and treatments. It will also discuss the outlook for people with AION, as well as possible preventative strategies.
Symptoms
Victor Dyomin/Getty Images
Since it affects the optic nerve, the main symptom of AION is vision loss. The Genetic and Rare Diseases (GARD) Information Center describes this vision loss as painless.
People typically lose their vision quickly after developing AION. The process can take days, hours, or even minutes. Initially, it may only affect one eye. However, vision loss could eventually develop in both eyes.
Both subtypes reduce a person’s visual field in their central and inferior vision fields.
NA-AION
Vision loss associated with NA-AION is often painless and less severe than with A-AION.
People often report their vision loss upon waking up in the morning. The vision loss may remain stable or progress over the weeks and months before stabilizing.
A-AION
People experience severe vision loss.
A-AION most often occurs as a complication of giant cell arteritis (GCA), which is inflammation of the arteries. When A-AION stems from this condition, vision loss may present alongside the following symptoms:
- headaches, especially over the temples
- pain or discomfort in the jaw, especially during or after chewing
- pain and stiffness in certain muscles, such as those of the shoulders or thighs
- a tender scalp
- fever
- weight loss
- night sweats
- feeling unwell
- depression
GCA is a potentially life threatening condition that increases the risk of stroke, heart attack, and aortic dissection.
An individual with the above symptoms should immediately seek medical advice. This is especially important if the symptoms accompany new vision loss.
Causes
The following are causes of NA-AION and A-AION.
NA-AION
Scientists are unsure about how NA-AION develops. However, they have documented a variety of risk factors for this condition, including:
- diabetes
- high blood pressure
- night-time low blood pressure
- high blood-lipid levels
- hypercoagulable disorders
- sleep apnea
- anemia
- migraines
- smoking
- being male
- being white
Risk factors for NA-AION indicate that someone is at an increased risk of developing this condition. They are not necessarily causes of NA-AION. They also do not guarantee that someone will develop this condition.
A-AION
A-AION occurs due to dysfunction of the short posterior ciliary arteries. These arteries closely follow the optic nerve. A-AION arises when either inflammation or blood clots block them.
Various conditions can bring this about. However, GCA is its most common cause. It often occurs in those aged 70 and over.
Diagnosis
If an individual has symptoms of AION, doctors may use a range of techniques to diagnose it or rule it out.
There are several diagnostic techniques for AION, including:
- a complete blood count test
- visual field tests
- a funduscopic examination, which uses a light and magnifying lens to check the fundus, a part of the eye that includes the optic nerve and retina
- fluorescein angiography, where an ophthalmologist uses a camera to take pictures of the retina
- optical coherence tomography — A type of imaging test that takes a cross-sectional image of the retina
If a doctor thinks an individual might have AION, they will also want to rule out giant cell arteritis. Additionally, doctors might recommend tests for certain AION risk factors.
Treatments
Once doctors diagnose AION, they will recommend treatment.
A doctor’s recommendations will depend upon whether someone has NA-AION or A-AION:
NA-AION
There is no standard line of treatment for NA-AION. This is because scientists have not yet found good evidence for effective treatment options.
Nonetheless, the following treatments may sometimes produce positive effects:
- corticosteroids
- a medication called levodopa
- aspirin
Preventing NA-AION from developing in the other eye is important. This can be done by treating and managing the underlying cause and risk factors that can trigger or aggravate NA-AION.
An individual with NA-AION should discuss treatment options with an eye specialist.
A-AION
In the case of A-AION, intravenous (IV) corticosteroids are the standard line of treatment, followed by long-term oral steroids.
Alongside preventing further vision loss, and possibly reversing it, prompt corticosteroid treatment could also stop A-AION from developing in the unaffected eye.
Treatment with IV corticosteroids will last for 3–12 months. Given the fast-acting nature of A-AION, doctors will sometimes recommend corticosteroids even before completing all of the diagnostic tests.
Without treatment, it is likely that the other eye will quickly develop A-AION.
Prevention
It may be impossible to prevent AION. However, people can take steps to lessen the probability or impact of certain NA-AION risk factors.
These include managing:
- diabetes
- high blood pressure
- sleep apnea
Preventative steps might include regular exercise, eating healthily, and managing stress. For people with an elevated risk of developing these conditions, regular checkups could also help.
Outlook
The outlook for people with AION is unclear. Some research indicates that with treatment, even partial recovery is rare. This research suggests that the majority of peoplece with this condition never recover any vision loss.
However, there is evidence from 2009 that around 40% of people with NA-AION may experience spontaneous improvements in their vision.
The vision loss is more severe for those with A-AION. The amount of vision loss will depend on the location and amount of damage of the optic nerve.
Scientists continue to research the outlook for AION, with and without treatment.
Summary
When there is insufficient blood within the eye, the optic nerve may receive too little oxygen. Anterior ischemic optic neuropathy is a condition that can result from this process. Its primary symptom is vision loss, which can affect one or both eyes.
There is no standard course of treatment for NA-AION.
Corticosteroids provide the main form of treatment for A-AION. By beginning this treatment early, doctors can prevent or even reverse vision loss. However, this treatment is most effective when AION results from either inflammation or blood clotting.
Even with treatment, it may be impossible for some people to regain their vision. However, some preventative measures could make AION less likely.
Leave a Reply