Optic Ischaemic Neuropathy

Optic ischaemic neuropathy is a serious condition that causes sudden vision loss when the optic nerve doesn’t receive enough blood flow. It most commonly affects people over 50 and requires urgent medical attention to prevent permanent damage.

Table of contents

• What is optic ischaemic neuropathy?
• Types of the condition
• Symptoms and warning signs
• Causes and risk factors
• How doctors diagnose the condition
• Treatment and management
• Outlook and prevention

What is optic ischaemic neuropathy?

Optic ischaemic neuropathy, also known as ischemic optic neuropathy (ION), refers to several conditions that cause vision loss because part of the optic nerve (the cable connecting your eye to your brain) doesn’t get enough blood flow. Without adequate blood supply, the affected areas of the nerve stop working properly and can start to die. If the disruption in blood flow is severe or lasts too long, it can permanently damage the optic nerve.^[1]

This condition is not common and generally affects people over age 50. The optic disk at the back of your eye is a circular area where blood vessels and the optic nerve attach to your eye. ION can happen around the center of this disk or farther back along the optic nerve.^[1]

Because permanent vision loss is possible, it’s essential to get medical care quickly to limit the damage this condition can cause.^[1]

Types of the condition

Optic ischaemic neuropathy is categorized into different types based on which part of the optic nerve is affected and whether blood vessel inflammation is present.^[2]

Anterior ischemic optic neuropathy

This is the most common form of ION. It affects the part of the optic nerve just underneath the optic disk or the optic disk itself. This type has two main subtypes.^[1]

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common form overall. It occurs when there is reduced blood flow to the optic nerve without inflammation of the blood vessels. NAION typically happens in people with a small, crowded optic nerve structure, and the exact cause remains unknown.^[2]

Arteritic anterior ischemic neuropathy (AAION) involves inflammation of the arteries. These conditions usually happen with types of vasculitis (blood vessel inflammation), most notably giant cell arteritis. This form typically occurs in people about age 60 and older.^[4]

Posterior ischemic optic neuropathy

This type of ION happens farther back along the optic nerve, away from where it connects to the eye. It is rare and also has arteritic and nonarteritic subtypes. Posterior ischemic optic neuropathy is typically associated with cardiovascular risk factors or conditions following major surgery.^[2]

Symptoms and warning signs

The main symptom of optic ischaemic neuropathy is vision loss. The way it happens and other accompanying symptoms vary depending on the specific type of ION.^[1]

Symptoms of nonarteritic anterior ischemic optic neuropathy

Vision loss from NAION is usually sudden and painless. It often appears as blurring or worsened vision across part of your field of view, usually in the lower half of what you can see in the affected eye. It can also cause weakened color vision.^[1]

Most people first notice they have vision loss when waking up in the morning, either from longer sleep periods or even brief naps. Less commonly, vision loss may develop gradually over about two weeks. NAION usually affects one eye at a time. About 15% of people who have NAION in one eye eventually develop it in their other eye as well.^[1]

The visual loss typically remains fairly stable without getting markedly better or worse once it has occurred.^[3]

Symptoms of arteritic anterior ischemic optic neuropathy

AAION usually causes sudden vision loss that can range from blurring and darkening to complete loss of vision. Vision loss tends to be more severe with this type. AAION generally involves symptoms from the arteritis-related conditions that cause it, including:^[1]

• Headache
• Swollen arteries in the temples of your head, which don’t have a pulse you can feel
• Muscle pain when chewing (jaw pain)
• A general feeling of being unwell and/or unexplained weight loss
• Muscle aches and pains
• Scalp pain when combing hair^[4]

In a small group of affected individuals, an “occult” form of arteritic ION is possible, meaning they have vision loss but no other arteritis-type symptoms.^[1]

Symptoms of posterior ischemic optic neuropathy

Both arteritic and nonarteritic PION cause sudden, painless vision loss. However, PION is usually a progressive condition early on, meaning the symptoms get worse in the initial phase.^[1]

Causes and risk factors

Optic ischaemic neuropathy occurs when the blood supply to the optic nerve is blocked or significantly reduced. The blockage prevents adequate oxygen and nutrients from reaching the nerve, leading to damage.^[2]

Causes of nonarteritic forms

The exact mechanism causing reduced blood flow to the optic nerve in nonarteritic forms is not fully proven. However, several risk factors are known to increase the likelihood of developing NAION:^[3]

• An anatomically crowded or congested optic nerve (certain structural characteristics that can be seen during examination)
• High blood pressure
• Diabetes
• Smoking
• Atherosclerosis (hardening of the arteries)
• Obstructive sleep apnea
• Low blood pressure at night
• Use of certain medications, such as amiodarone and possibly medications for erectile dysfunction^[4]

Some researchers believe that the use of blood pressure medications at nighttime may contribute to lower blood pressure during sleep, which could be a risk factor for NAION, though this remains controversial.^[3]

Causes of arteritic forms

Arteritic ischemic optic neuropathy is caused by inflammation of the arteries, most notably giant cell arteritis. This inflammation blocks the blood supply to the optic nerve due to swelling within the arterial walls. This form requires urgent medical attention.^[4]

Risk factors for posterior forms

Posterior ischemic optic neuropathy is typically associated with cardiovascular risk factors or occurs as a complication following major surgical procedures, such as heart, spine, or other lengthy operations.^[2]

How doctors diagnose the condition

Diagnosis of optic ischaemic neuropathy involves a careful examination and several tests to determine the type and underlying cause.^[1]

After taking a thorough medical history, the doctor will perform a careful examination that includes measuring visual acuity, color vision, and peripheral visual field. The doctor will examine the back of your eyes using an instrument called an ophthalmoscope, which allows them to see the optic nerve. In most cases of ischemic optic neuropathy, the doctor will see swelling of the optic nerve at the back of the eye.^[3]

If giant cell arteritis is suspected as a cause, blood tests are done immediately, and treatment with corticosteroids is started right away to prevent further vision loss. Blood tests measure the erythrocyte sedimentation rate (ESR), C-reactive protein level, and complete blood count. Results of these tests may indicate inflammation that is characteristic of giant cell arteritis. A biopsy (removal and examination of tissue) of the temporal artery may be performed to confirm the diagnosis.^[4]

If a person has no symptoms of giant cell arteritis, imaging studies such as magnetic resonance imaging (MRI) or computed tomography (CT) of the brain may be done to make sure the optic nerve is not being compressed by a tumor.^[4]

Other tests may be necessary depending on what causes are likely. For example, if people have symptoms of obstructive sleep apnea, such as excessive daytime sleepiness or snoring, a sleep study may be performed.^[4]

Treatment and management

Treatment for optic ischaemic neuropathy depends on the underlying cause and the specific type of the condition.^[1]

Treatment for arteritic forms

Arteritic anterior ischemic optic neuropathy is an ophthalmic emergency. If giant cell arteritis is suspected, immediate treatment with high-dose corticosteroids (such as methylprednisolone or prednisone) is essential to prevent further vision loss in one or both eyes. Treatment does not restore vision that has already been lost, but it can help protect the unaffected eye.^[2]

The typical steroid regimen involves starting with a high dose and gradually reducing it over several months, depending on the patient’s response and blood test results. Monthly monitoring of inflammation markers is important to guide treatment adjustments.^[11]

Treatment for nonarteritic forms

Unfortunately, there are no treatments for NAION that are proven to be consistently effective. Many clinical trials have studied over a dozen different therapies, but none have convincingly improved visual outcomes in patients with NAION.^[3]

Some studies have investigated the use of corticosteroids and suggested mild improvement, but these studies did not use rigorous scientific methods, and it remains unknown whether steroids are actually helpful. One long-term study suggested that NAION patients treated with systemic corticosteroids during the acute phase had significantly better visual outcomes than untreated patients, but this remains controversial.^[11]

Eyeglasses do not correct the vision loss caused by NAION, as the problem is in the optic nerve at the back of the eye, not in the focusing structures at the front.^[3]

For posterior ischemic optic neuropathy, some patients treated with high-dose systemic steroid therapy during the very early stages showed significant improvement in visual acuity and visual fields compared to untreated patients.^[9]

Managing risk factors

Management of underlying health conditions and risk factors is essential for preventing further problems. This includes:^[3]

• Controlling blood pressure
• Managing diabetes
• Regular exercise and a healthy diet
• Treating sleep apnea if present
• Stopping smoking

These measures may help reduce the risk that ION occurs in the other eye.^[3]

Outlook and prevention

Once NAION has occurred in one eye, it is very rare for it to occur again in the same eye. However, there is approximately a 30% chance that it can occur in the other eye over one’s lifetime.^[3]

The visual loss from NAION typically remains fairly stable after the initial event. Vision can range from almost normal to complete blindness in the affected eye. Some patients experience gradual improvement over weeks to months, but significant recovery is not common.^[1]

People with giant cell arteritis tend to be older, and their loss of vision tends to be more severe. Without prompt treatment, there is a high risk of vision loss in the other eye.^[4]

To try to reduce the risk of developing ION or having it occur in the other eye, doctors recommend controlling cardiovascular risk factors, maintaining a healthy lifestyle, and treating conditions such as high blood pressure, diabetes, and sleep apnea. For patients who have already experienced NAION, it may be advisable to avoid taking blood pressure medications at nighttime to prevent excessively low blood pressure during sleep, though this approach should be discussed with a healthcare provider.^[3]

Early detection and prompt medical evaluation are crucial. If you experience sudden, painless vision loss, especially upon waking, seek immediate medical attention. Quick diagnosis and treatment, particularly in cases involving arteritis, can prevent further vision loss and protect the unaffected eye.^[1]