Optic Neuropathy - Symptoms, Causes & Treatment

What is Optic Neuropathy?

Optic neuropathy (ON) is damage or degradation to the optic nerve due to blood flow issues, head trauma, exposure to chemicals, and other underlying conditions. 

The optic nerve is a bundle of nerve fibers that transmit electrical signals from the eye to the brain, enabling you to see. Damage to the optic nerve will affect your ability to see clearly. If left untreated, total vision loss may result.¹

Optic nerve damage due to blocked blood supply is known as ischemic optic neuropathy (ION). ION can occur with or without inflammation of the arteries (arteritis). 

The exact mechanism involved in reduced blood flow to the optic nerve is not well understood. Fortunately, ION usually only affects one eye. 

Nonarteritic Ischemic Optic Neuropathy (NAION)

Nonarteritic ischemic optic neuropathy is optic nerve damage without arterial inflammation. This condition typically causes sudden vision loss in one eye without any pain.² 

According to research, there are about 6,000 new cases of NAION in the United States each year.³ It's common among the Caucasian population and mostly affects those aged 50 or older. 

Symptoms

The following are common signs and symptoms of NAION:

• Flashing or flickering lights
• Blurry vision
• Loss of color vision (dyschromatopsia)

Arteritic Ischemic Optic Neuropathy (AION)

Arteritic ischemic optic neuropathy is caused by inflammation of the arteries supplying the optic nerve. It’s mostly associated with a condition called giant cell arteritis (GCA) or temporal arteritis.⁴ 

AION is uncommon, accounting for only 5 to 10% of all anterior ischemic optic neuropathies, and mostly affects people aged 70 or older.⁵ It’s also more common among women than men.

Unlike NAION, AION is often painful. It can cause blindness if not treated early. 

Symptoms 

The following are signs and symptoms of AION:

• Pain in the eyes or eye socket
• Loss of color vision 
• Decreased visual acuity
• Vision loss, especially peripheral vision
• Swollen optic nerve
• Confusion/disorientation
• General fatigue
• Unexplained weight loss
• Fever
• Blindness, if left untreated

Seeking immediate medical attention will alleviate symptoms and prevent further optic nerve damage.

Causes and Risk Factors

Damage to the optic nerve may result from trauma, increased eye pressure, changes in blood flow, clogged vessels, or underlying conditions. 

While optic neuropathy can affect anyone, the following factors increase the risk:

• Age of over 50 years
• High cholesterol levels
• Sleep apnea (sleep-related breathing disorder)
• Ocular or head trauma (Traumatic optic neuropathy)⁶
• Diabetes (Advanced diabetic retinopathy)
• Heart disease
• Smoking cigarettes
• Narrow blood vessels
• Glaucoma
• Migraine headaches⁷
• Temporal arteritis (swollen arteries in the head)
• Certain drugs such as sildenafil, isoniazid, linezolid, amiodarone, etc.

When to See an Eye Doctor

See your doctor if you experience symptoms of optic neuropathy, including eye pain, loss of color vision, flashing or flickering lights, double vision, or vision loss. They will diagnose the severity of the damage and recommend appropriate treatment based on the underlying cause.

Diagnosing Optic Neuropathy

Diagnosis involves an eye exam (ophthalmoscopy) to look for signs of optic nerve damage. 

Your eye doctor will use dilating eye drops such as mydriatics to enlarge your pupils for easy examination. They will also:

• Test your side (peripheral) vision
• Measure the fluid pressure in the affected eye(s)
• Perform a blood test to look for signs of giant cell arteritis, temporal arteritis, or blood clotting disorders
• Conduct a toxicology test to check for drug or chemical-induced optic neuropathy (toxic optic neuropathy)
• Perform a color vision test to determine your ability to see different colors and how your eyes respond to light
• Order a temporal artery biopsy to check for giant cell arteritis

Your doctor may also refer you to a neuro-ophthalmologist. This specialist will perform a magnetic resonance imaging (MRI) or CT scan of the brain to check for tumors (abnormal growth/swelling). Brain tumors such as optic nerve glioma can affect vision by exerting pressure on the optic nerve.

You may also have to work with your general practitioner to diagnose underlying health conditions such as heart disease and diabetes.

Treatment Options

Fortunately, many cases resolve without treatment. However, quick treatment of symptoms or the underlying cause can prevent disease progression to the other eye. 

The treatment for non-arteritic optic neuropathy aims at controlling blood pressure, relieving headaches, unblocking clogged arteries, and addressing other issues that may cause further damage to the eyes. 

• In the case of drug-induced optic neuropathy, withdrawing from the drug is usually the first line of treatment
• Anti-inflammatory drugs (such as  tocilizumab) to reduce swelling and inflammation
• corticosteroids (prednisone) to relieve pain and ease swelling
• Assistive technology, which includes magnifiers, telescopes, and large-print devices to help manage low vision activities

There's no treatment to improve vision loss from optic neuropathy. However, assistive technology exists to enhance your vision.  

Prognosis and Complications 

Although there's no effective treatment for optic neuropathy, a good number of cases of nonarteritic ischemic optic neuropathy (40%) resolve without intervention.¹¹ Repeat episodes are also rare.

People with arteritic optic neuropathy are at a higher risk of vision loss than those with the nonarteritic type. Prompt treatment may or may not restore vision loss but can prevent progression to the unaffected eye. 

On the other hand, delayed treatment puts you at great risk of complications such as:

• Severe eye pain
• Stroke
• Cerebral aneurysm
• Slurred speech
• Infections
• Blindness
• Death (in case of a serious underlying condition)

Summary

• Optic neuropathy (ON) refers to optic nerve damage due to  trauma, changes in blood flow, or underlying conditions
• ON may occur with or without inflammation of the arteries (arteritis) with symptoms
• Symptoms include vision loss (most common), eye pain, color vision loss, flashing or flickering lights, and double vision 
• Age, cholesterol levels, heart disease, smoking habits, clogged arteries, diabetes, and glaucoma are the common risk factors of ON
• There's no effective treatment for ON, but your doctor can treat symptoms and underlying causes